IM/07
(Restricted Circulation Only)
POWER STATION
ERECTION
CENTRAL TRAINING RESOURCES UNIT
CORPORATE TRAINING DEPARTMENT
CONTENTS
S. NO.
DESCRIPTION
PAGE NO.
1.
Methods & Techniques used in Power Station Erection
1
2.
Methods and Techniques of Erection
9
3.
Erection of Boiler
12
4.
Boiler Drum Erection Procedure
14
5.
Steam Generator Package
19
6.
Erection of Boiler Auxiliaries
21
7.
Erection of Steam Turbine
24
8.
Boiler Feed Pump Erection
43
9.
Field Erection Procedure
46
10.
500 MV Generator Erection
61
11.
Guidelines For Alignment of Rotating Machinery
66
12.
Hot and Cold Alignment
74
13.
Grouting of Machinery
80
14.
Erection, Alignment, Pre-Commissioning
and Commissioning
84
15.
Precautions to be taken during Erection, Alignment &
Grouting
90
16.
MW Tools and their Applications
92
17.
Effect of Misalignment
99
18.
Introduction to Alignment of Static Equipment
102
1. Methods & Techniques Used In Power
Station Erection
The Process of erection of a 500 MW unit is a very complex process. Work involved in the
erection of a 500 MW unit are very large and the Techniques are so varied that it is quiet
difficult to discuss them all in details. The following figures will give an idea of the work
involved and are to be completed for the commissioning of one unit of 500 MW.
1.
Earth Work
approx. 10 lacs M3
2.
Concreting Work
1.1 lac M3
3.
Structural erection
120000 tons
4.
Mechanical and Electrical equipments
18000 tons
5.
Length of piping
approx. 130 krns.
6.
Length of cabling
350 to 400 krns.
7.
Brick work
40,000 to 50,000 sq. mtrs.
Here we will discuss only the erection of major mechanical equipments and some of the
important electrical equipments. To facilitate the discussion we can further sub divide the
erection activities into specific areas such as
i)
Structural
ii)
Steam Generators & Auxiliaries
iii)
Turbine and its auxiliaries
iv)
Inter-connecting piping
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v)
Special equipments such as boiler drum, generator stator and generator
transformers.
vi)
Miscellaneous piping and cabling
vii)
Coal handling plant.
Since we have to cover the erection techniques and activities only \ we will not be discussing
the techniques used for civil construction. This may be covered separately.
ORGANISATION
Before we undertake any project work it is necessary to identify the requirements of
manpower, define the organisational structure in which this manpower will work and then to
clarify the role of each member of the team. In NTPC we have more or less standardised
such requirements and the organisational structure. As you see the erection organisation at
the project level is headed by a Additional General Manager. At the next level of the
organisation it is divided into 2 Section Mechanical and Electrical each headed by DGM.
Further sub division is done on equipment basis of specialisation for example we may have
a Manager/Sr. Manager heading group responsible for the erection of turbo generator and
auxiliaries and also have Dy. Manager who is responsible for welding and non destructive
testing a very specific area of specialisation in the power house erection work. Similarly on
the electrical side we have groups responsible for cabling 6.6KV switchgear and separate
group for electrical testing.
ERECTION PLANNING AND SCHEDULING
Before taking up such a large size work it is necessary to calculate and establish the inter
relationship of the large number of erection activities to be completed so that the end result
is achieved in a co-ordinated manner. The details of erection scheduling, are being covered
separately, but we can discuss a broad relationship between major erection activities. As
you will see that first activity to be started is the erection of power house structures, what we
mean by power house structure is the turbine hall known as AB Bay. The equipment bay i.e.
BC and the mill bay. This is followed by start of erection activities of steam generator
structures, pressure parts and auxiliaries. After a time interval of 8 to 10 months follows the
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erection work of turbine, turbine auxiliaries and later on the inter - connecting piping. At
about this time the erection activities on mechanical and electrical auxiliaries are taken up.
This is a very broad based bar chart. In actual practice the entire activities are broken up
package wise at three tier of planning and planning and monitoring. This detailing will be
covered separately.
ERECTION EQUIPMENT
Although hundreds of tools and plants are used for erection work. The major erection
equipments now in use at the project sites are as follows.
Cranes
We have 2 types of cranes available in the country - one type is tyre mounted and the 2nd
type is crawler mounted. The tyre mounted cranes are generally in low capacity ranges, say,
upto about 25 tons because of the limitation of the indigenous availability of tyres. The
cranes above 25 ton capacity are all of crawler mounted type. In the higher range we have
only 2 manufacturers in the country i.e M/s. Telco and M/s Hind Motors. The highest
capacity crane is the 90 tons capacity no. 1055 BLC manufactured by Telco manufactured in
India but now a days for 500MW Boiler, Froc Crane is used for structural work and ceiling
Girder at capacity 285 MT on Ringer and 150 MT capacity cranes are also used. In the lower
ranges i.e. upto about 25 tons capacity, a number of manufacturers have introduced cranes
with
hydraulically controlled collapsible boom. These hydraulic cranes are yet to prove
themselves in the field and the manufacturing process has also to be established since so
far the cranes supplied by these manufacturers have been only assembled in India.
Derrick
This is perhaps the oldest fixture used for lifting of loads higher levels. The simplest derrick
is the one used by workers for hoisting the electrical poles. However, the designing and
fabrication of derrick has become sophisticated and at some of the projects derricks upto
200 tons capacity have been used for erecting heavy weight vessels.
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Winch
A winch is nothing but a contraption to provide mechanical advantage. Hand winches upto
about 1.5 ton capacity are still in use for small works but electric winches presently being
used at project site may have as high capacity as 2500 tones. The limitation on size comes
due to size of the rope and the rope drum, Electric winches are extensively used in
combination with derrick for erection of mechanical and electrical equipments in a power
house.
STRUCTURAL ERECTION
The structures are either fabricated completely or partly at site and partly at the works of the
contracting agency. In case part of the fabrication work is done at the works of the vendor
pre-assembly work is done at site. In power house structures the main items are columns
connecting beam trusses and the platforms. For a 500 MW unit the single columns lengths
can be as much as 50 mtrs. and a single column may weight upto about 45 tons. The cross
section through a typical power house indicating the location of the columns the height and
approx. weight can be shown in the erection drawing.
The erection of the A & B row columns, can be done by using either a derrick or a mobile
crane. The choice depends on the number of units to be done, for example, if only one unit
is to be erected the use of crane becomes uneconomical as it calls for high initial investment.
In such a case ordinary high capacity derricks are made use of. The columns may be lifted in
a single pc., or in 2 pcs. depending upon the capacity of the derrick or the crane. The trusses
which weight about 25 to 30 tons are lifted in single pc, after completing ground assembly,
by using either 2 derricks or 2 cranes, two point lifting is preferred so as to avoid deformation
during erection. Sometimes the physical position of the civil works may also necessitate the
use of 2 cranes/ derricks.
The columns in the BC & D row have unnecessarily to be lifted in pcs. because of the length
and the weight of single pc. This is necessitated because we do not have the cranes of
adequate capacity to handle single column piece. As pointed out earlier the highest capacity
crane manufactured is by Tata P&H is of 90 ton capacity at the minimum radium. The inter
connecting tie beams are generally lifted one by one with the help of electric winches. This is
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a time consuming process but use of a crane for lifting the small weight beams and tracing
works out to be uneconomical.
ERECTION OF STEAM GENERATOR
The steam generator is the main and central equipment for the power house. It is also the
most difficult and complicated from the erection point of view. A 500MW steam generator
means an assembly of approx. 80,000 to 90,000 different sub-assemblies adding upto a
sizable 24,000 tons of equipments. The equipments may be as rough as structures going up
in sophistication of a furnace control cubical. The erection starts with the positioning of boiler
structures. Since the height of the column may be as much as 90 mtrs., with the single
column weight may be 100-110 tons. The use of higher capacity crane is essential.
However, the structures can also be erected using a set of 2 high capacity derrick in case
only one unit is to be done since the deployment of heavy capacity crane for one unit alone
will call for high investment. The erection of the pressure parts systems follows the erection
of structures this is a sophisticated work from the view point of technology of welding. For a
500 MW steam generator as many as 25,000 high pressure, welds have to be made at site,
radiographed and tested at high pressure, before the steam generator declared ready for
light up. High technology proccsass are used to ensure quality welding since failure of a
single weld will result in the shut down of unit resulting in heavy loss in generation. As
pointed out earlier the erection time span is about 48 months requiring deployment of 600 to
800 persons and of sophisticated high capacity erection equipment.
TURBINE AND ACCESSORIES
The 500 MW turbine is in 3 parts i.e. low pressure, intermediate pressure and high pressure
casing. For the thermal stations in India we have 2 types of turbines under operation and
erection. The units installed till 1982 mostly have turbines of Russian design and whereas
German design of M/s KWU has been used for stations installed after 1982. From erection
point of view both these turbines are very much different from each other. In case of Russian
designs complete assembly has to be done at site for all the 3 casing, where as in case of
KWU turbines IP casing and LP casing are assembled at site and other 1 casing are
completely shop assembled. However, in both the designs the condensers is completely
assembled at site.
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The erections are generally started with the assembly of the conde nser either in site or out
side the turbine hall. After completing the assembly of the shell, it is aligned and leveled in
position and then the turbine work is started. This process takes about four months. The
erection of the turbine is started with the placement of LP casing followed by IP and HP
when the work on the main turbine is going on simile tenuously the erection of auxiliary
system like oil system cooling system auxiliary steam system etc. starts. After the turbine is
boxed up the final connection of the auxiliary systems are made and thereafter the work on
instrumentation is taken up to make the turbine ready for starting the pre-commissioning
tests in the unit.
INTER CONNECTED PIPING
There are many many piping systems connecting the main equipment of steam generator
and turbo-generator and these main equipments to the auxiliary systems. These piping
system carry water, air, condensate, steam etc. from one point to another point as per the
flow diagrams. Although there is no work of heavy lifting as the piping pcs. are of prefabricated lengths and have such weights which can be erected with the use of electric
winches. There is extensive work of welding, stress relieving and non destructive testing a
special induction heating m/c is used for X-20 material (High thickness) pipe joints. The
normal process followed in erection of piping systems is to lift them to position piece by
piece place them on temporary supports, level and align maintaining suitable slopes, and
then carry out the welding. After completing the welding the permanent supports and
hangers are installed, adjusted and the piping load is released. The systems are then
hydraulically tested to supplement the non destructive testing and also to specify the
statutory requirements. After the completion of these stages some of the piping systems are
insulated depending upon the service conditions. Erection of valves is the one which needs
close attention. If the valves are not properly erected they can cause very serious operation
problems. The valves should be completely serviced before erection, they are to be installed
in the correct direction of flow and it should be seen that they are accessible for operation.
Each valve should have tag no. properly identified and direction of opening and closing
normally marked on the hand wheel with suitable platform for access.
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ERECTION OF SPECIAL EQUIPMENTS
There are 3 critical equipments in the power house erection. They are boiler drum, generator
stator and generator transformers. We will briefly discuss the erection of these 3
equipments.
Boiler drum
For 500 MW unit BHEL design the boiler drum is about 24.5 meter long has a diameter of
2.2 mtrs. and weight approx. 234 tons. This heavy mass has to be hoisted to a height of 22.5
mtrs. on the front side of the boiler and is to be suspended from the roof beams. For the
erection of boiler drum, a temporary structure is erected on top of the boiler structures and 2
sets of pulley blocks of 150 tons capacity each are hoisted from this structure. A similar set
of pulleys is tied to the boiler drum and a steel rope of 25mm & 23mm dia is taken to four
electric winches each of 15 & 10 tons (2 each) capacity. This arrangement is sufficient for
lifting a 300 tons load (boiler drum is weighing 247 tons). The extra provision in lifting
capacity is to be made to absorb shock loading during lifting of the boiler drum.
Generator Stator
This piece of equipment, to be installe d on the turbine floor, weight about 265 tons has a dia
of approx. 4 mtrs. and a length of 8.5 mtr. depending upon the power house design and lay
out the stator may be lifted by portal cranes temporarily errected in turbine hall. In some of
the power stations another method has been used by which the stator has been placed on
the turbine floor using a temporary gantry crane. Under this arrangement, a gantry crane is
placed over the structures which lifts the stator placed directly under its hook, moves to the
actual position of the stator and stator is lowered on to the foundation. This is a simpler and
less costly method and has now been adopted for our 500 MW unit under erection.
Generator Transformer
This transformer again is in the region of 130 tons weight, is about 4.5 mtrs. high and 10 to
11 mtr. long. This is erected on the outside of the turbine hall on a row side and is to be
placed on foundation which has got embedded rails. Normally the transformer is literally
dragged to position by the use of a set of rollers and the rollers are then tied to the
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foundation franc of the transformer. Occasionally used of heavy duty mobile cranes has to
be made where there are problems of access to the foundation. Although the erection
activity is simple, extensive work has to be done after the transformer has been placed. After
placement of the transformer on the foundation the work on the other auxiliaries such as
cooling system, oil system and fire protection system is take up.
TECHNICAL CHECKS DURING ERECTION
Proper erection of any equipment plays a vital role in the ultimate performance of that
equipment and the system as a whole. It has been observed that even an equipment which
has been very well designed, manufactured under strict quality control can be a failure in
operation if it is not correctly erected. This important aspect must be clearly understood by
those who want to make a career in erection. Unfortunately this aspect of the work has not
got the proper attention it needs and it is wrongly thought in may organizations that erection
is any body’s job, but it is not so.
To ensure proper, quality of erection work, a system of check and measures must be
developed, check lists for the proper logging of the completion of stages of erection should
be
developed
in
consultation
with
the
suppliers.
These
check
lists
should be verified by an independent agency such as field quality assurance group at site.
Various techniques are being used at site for checking the quality of welding, which is a very
important aspect of field work. The methods are:
i)
Dye penetration test
ii)
Radiography
iii)
Ultrasonic testing.
The results of all these tests have to properly recorded and preserved for approval by the
boiler inspector of the state where the unit is being installed.
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2. Methods & Techniques Of Erection
Methods & techniques for certain part of erection activities are commonly applied whereas
for certain equipment exclusive in nature, erection personnel are required to be educated
thoroughly before proceeding with the erection.
In fact the erection activity is very broad in nature and does cover some peripheral activities
which are not directly connected with actual erection job but are desirable in order to have a
systematic output. These activities along with the erection activities are tabulated in the
sequence it is required to be followed.
1.
TRANSPORTATION, INSPECTION & STORAGE
This activity forms the input for next activity. Once the material is received at site all parts are
checked with the help of packing list 1\2 slip sent with the consignment and relevant drawing
if necessary. Missing\shortage\damaged items are listed under respective heads and action
is taken to replenish\repair the same. Nearly 30,000MT, materials are installed in one unit at
500 MW Boiler.
After inspection is carried out, the components received are stored/stocked properly in order
so that their life is not reduced due to prolonged storage and retrieval at the time of
requirement is also easy. Long storage is done with specific preservation methods which is
time dependent. Storing may be done outside or inside depending on the nature of the
component. Preservation methods which are commonly adopted are,
a)
Rust Preventive
b)
Corrosion inhibitor
c)
Sillicagel application
d)
Spray reel application etc.
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2.
PREPARATION FOR ERECTION
The following details shall be thoroughly studied with the individual contracts reg. size, range
application, and scope of supply with reference to the product offered.
Preparation for erection:
i)
System lay out
ii)
Assembly drugs. of various equipment
iii)
Performance drugs/manuals
iv)
Installation drawings
v)
Foundation plans
vi)
Scope of supply of the contracts
vi)
Scope of supply of the contracts
vii)
Shipping lists with respect to erection drawings
After ensuring the above, following are to be observed.
1)
Before proceeding with erection adequate arrangements for safe handling of
equipment is to be made at work site. This may include tools, tackles rigging and
handling facilities required for erection. Special attention is to be paid for the
shape/size/wt. of the components as well as the space limitations while proceeding
with installation.
2)
In line with the construction management philosophy erection department is required
to be actively involved in the checking of foundation before it is cast and after it is
cast for any defects which maybe detrimental for the equipment. Performance in the
longrun as well as cause difficulty during the course of erection.
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This is achieved by paying special attention to the dimension of the foundations to be
cast by keeping a close touch with the civil department. Also after casing of
foundation it is checked immediately for any abnormality as regards centre line shift
and other mistakes.
3)
The material received earlier at stores and stocked properly are to be retrieved as
per the sequence of erection to be done with ref. to drawings/manuals etc.
4)
The preservatives used during storage purposes are to be cleaned thoroughly and
the item be made ready for assembly/erection.
5)
Finally foundations is taken over with all respective dimensions properly checked with
limits / tolerance specified in the drawing.
Attention should be paid to presence of match marks for components. For large
components which require pre-assembly separate area is identified where such
activities can be carried out. After pre-assembly the components are transported with
care to the foundation for erection.
6)
For placing any equipment/column structure on the foundation a base plate is first
erected on to the foundation on packing plates which takes care of matching of base
plate with the foundation as well as for alignment of the equipment/column structure.
This matching is achieved by matching the pack or plates or blue matching as may
be the level of requirement.
7)
Once the first part of the equipment is erected and leveled / aligned, the equipment is
grouted i.e. the space below the base plate and the foundation is filled with suitable
grout mixture to have a compact filling with good bounding with the foundation.
8)
The next step is to go ahead with further erection as per the standard erection
procedure as laid out and as per the sequence predicted boiler drum lifting is given
as a typical example.
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3. Erection Of Boiler
The following will illustrate a brief outline on boiler erection emphasising on the key technical
requirements to be fulfilled. As stated earlier, having assimilated the assembly drawings,
detail drgs, bill of materials, quality documents and other relevant information sequence,
stepwise erection activity is taken up.
1.
COLUMN ERECTION
The boiler presently in use are hanging type i.e . these are supported at the top in order to
allow free expansion of the boiler during hot condition without any hinderance whatsoever.
However the anchor point called ceiling girder on the top of the boiler is adequately
structured on top of support columns called ceiling girder on all the sides of the boiler so that
the load transfer could take palce to the foundations. Hence the importance of columns is
immense.
In order to have a strong and safe structural footing, the columns are to be erected very
carefully. Since the columns are very tall it can not be transported and erected in one piece.
So the columns are broken up during manufacture into several pieces and transported to site
where it is pre-assembled in two or three pieces and erected. Now a days Pre-assembly is
being done in shop & column design has changed from (H) section to (T) section.
Utmost care is taken in the pre-assembly stage to maintain the matching of the column end
faces and to achieve a verticality well within the tolerance limits prescribed. Verticality is the
single most important factor and is given top priority as the columns are vertical and a small
error at the base level may reflects a severe inclination at the top which is dangerous from
loading the columns with associated boiler component. This is achieved by ensuring
verticality at every level of the column and by bracing the columns with another in order to
reduce the slenderness of the columns as a single piece. The column vertically is allowed 1
mm/metre & max. of 20 mm.
Once the column erection is. over up to the full height, the cross beams are placed securely
over the columns which support the main boiler. In order to carry out this job special erection
tools like cranes with extra long boom to carry heavy loads at that height are deployed.
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When this cross beam erection is over the entire structure so erected is adequately braced
so that sufficient rigidity and strength is obtained for further loading these structures by
erecting the boiler drum, headers and subsequently the pressure parts. Nearly 46000
(HSFG) High strength friction bolt are used for erection & to strengthen the main structure.
2.
PRESSURE PARTS
The pressure parts are composed of headers which are having numbers stubs welded on to
it on one plane and collector pipe stubs (relatively larger in size) on the other plane, or on the
same plane depending on the requirement. After these headers are supported from the
overhead beams the water wall panel erection is taken up. These panels are tubes joined in
one plane by fusion welding up to a required length. One side of boiler water wall may
require 35 to 40 such panels to be welded with one another. During the formation of these
boiler walls with panels the verticality of the wall and its axis with respect to boiler centreline
marked earlier with reference to drum position is maintained. The walls so erected are
temporarily supported with the structure in a continuous manner. After the four walls are
completed alongwith their bottom headers in position the furnace is floated i.e. the temporary
supports are cut and removed so that the entire load of the furnace is passed on to the
support hangers at the top. Subsequent to this the axis of the furnace is checked for the shift
and corrected if required. The hangers which has been loaded with the furnace are then
checked individually for its proper loading. In order to avoid differential loading the hangers
are adjusted to their required value. Total Boiler pressure parts is divided in two passes
name as First Pass, Second pass & weight of pressure parts are nearly 5,000 MT.
3.
MISCELLANEOUS
After the erection of pressure parts is over other erection activities; like, insulation, soot
blowers, and other peripheral activities connected with the boiler light up is taken up
alongwith the above jobs. The finishing activities of the boiler is taken up with an emphasis
on the safety and operational aspects. This is most important.
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4. Boiler Drum Erection Procedure
Procedure
2X500 MW STEAM GENERATOR ERECTION
1.
INTRODUCTION
Boiler drum lifting is one of the milestone in 500 MW Boiler Erection. In fact after 1st column
erection the time given is 9 months, during which 3600 MT structural erection is to be
completed for activity. This includes Main Columns, Aux. Columns, all Bracing upto level,
Ceiling Girders, Welded Beams & Rolled Beams.
The Auxiliary preparation work for drum lifting includes welding of cat head structure at the
roof level, making ready of winches with anchoring arrangements, fixing of main pulleys,
auxiliary pulleys and guide pulleys.
Here we will discuss about the salient features of drum and its lifting procedure.
2.
TECHNICAL DETAILS
a)
Drum
i)
Over all length
:
24216 mm
ii)
Size (Bithikness)
:
R 874 x 195, R 889 x 165
iii)
Weight (without internals)
:
234 MT
iv)
Elevation (drum centre)
:
72508 mm
v)
Distance from girder B
:
6257 mm
vi)
No. of lifting lungs
:
2 (for stage I lifting)
2 (for stage II lifting)
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b)
Suspension Rod
i)
No. of Suspension rod
:
2
(U type)
c)
ii)
Over all height
:
13518.5 mm
iii)
Weight (2 Nos.)
:
14 MT
iv)
Dist. between U-rod arms
:
2350 mm
v)
Dist. between U-rod
:
13412
:
Between A&B Girder on
Supporting Structure for drum
i)
Location of drum
Suspension beam
ii)
Elevation of drum
WB3 & WB4
:
83155 mm
:
26000mm
Suspension
iii)
Centre line distance of
side column (S7L to S7R)
3.
SALIENT FEATURES
Since the Boiler Drum length 24216 is within the clearance available between two columns
26000 mm; the drum had to be lifted in horizontal position.
Also, since the column S14L & S14R has to be erected and all interconnections completed
upto 68 M, the drum has to be lifted initially at a height of 68 M from front row of columns
between SSLR & S9LR.
After crossing the structure at 68 M, the drum has to be shifted to the final position (i.e 2993
mm from front row of columns).
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4.
LIFTING ARRANGEMENT
The equipments required for drum lifting purpose has been given in a separately for
reference.
The pulley blocks are approximately 700 mm wide & 1700 mm in length and the distance
between the lifting lugs provided on the drum is only 915 mm since both the pulleys have to
be attached to the drum, the lugs on the drum for stage I & Stage II lifting are kept at right
angle to each other:
The pins used on drum lugs are of 512 mm and those used with pulley block are of 225 mm.
ROUTING THE ROPES THROUGH GUIDE PULLEYS
All four winches of 15 T & 10 T are positioned between Boiler & ESP. The first guide pulley
of the 15T will be attached to the Wbs at the ceiling and the rope is to be brought down to
515 columns base and then to the 15T winch.
The first guide pulley of l0T will be attached to Wbs at the side blacing in column 510 at 79.9
Mtr. and it comes to 10T winch to 516 column.
ANCHORING OF WINCHES
All the winches are placed on a plain wooden mat then anchored to Tower crane parking
block concrete blocks.
After the load test of all winches, interconnection is done between all the 4 winches to
minimise vibration and dislocation during operation.
Suitable guide pulleys with pulling M/ C are to be arranged for guiding the rope winding on
winch drums.
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AUXILIARY WINCHES & ITS CONNECTIONS
The first set of rigs (15T) are attached to the drum at ground level and the second set of the
rigs (10T) will be brought upto 68 Mtr. and temporarily anchored at this level. 3 ton winches
are attached to the (10T) rigs for holding the bottom pulley blocks to facilitate attachment to
the drum at 68 M before Stage II Lifting.
The U-Rods will be kept lashed on to the boiler drum in slanted position. The distance
between the U-Rod ends is to be maintained by attaching channels bol ted on either end. 5T
winch is employed along with 2 sheave pulley blocks for lifting either of the U-rods after the
drum reaches its final position. The top guide pulleys will be anchored on to a temporary
beam kept on top of drum suspension beams.
MISCELLANEOUS
The Boiler Drum (with U-rods lashed on) is to-be lifted 1 mtr. initially and pulley block and
guide pulley are checked for proper orientation and to ensure smooth passing of ropes.
Also the structural members are to be checked for any possible deformations.
The Drum is allowed to remain in this position for approx. half an hour to verify the break
hold of winches.
LIFTING
1.
The drum is brought between column no. 8LR & 9LR and then it is lifted uniformly
until it reaches 68Mtr. with the 1st set of pulleys and using 15T winches.
2.
There upon the 10T second set of rings are to be attached to the drum lifting lugs.
10T winches operated for keeping the rope fully taut. Afterwards the first ring (15T) is
to be gradually released so as to allow the drum to drift towards final position after
the first stage pulley are released (by 15T winches), the second stage of pulleys are
tightened (10T winches) for maintaining the drum centre elevation approx. 73 M.
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3.
The U-rods lifting pulleys are attached at this stage, to either of the U-rods and then
U-rods are made vertical and gradually lifted to the required height. After the U-rods
passing through the holes of the rocker plate, nuts are screwed until the projected
length is maintained.
At this stage, the U-rods bottom is held by rope so as to ensure that the U-Rod is
properly placed at the distance of 13.412 mm and also that the U-rods are on the
inner of the stopper lugs.
Thus after ensuring that all four lugs of U-rods are properly positioned and nuts
tightened keeping the required projection. The drum is to be gradually lowered on to
the rods until the wire rope is slack and load is transferred on the U-rod.
4.
The level of the drum centre is to be verified by water level at this stage to ensure
exact elevation 72.508 M + 3mm.
© PMI, NTPC
18
5. Steam Generator Package
1.
T & P REQUIRED FOR DRUM LIFTING (500MW)
WINCHES
S.No. Item
Qty.
Remark
1.
2 Nos.
For stage I lifting
2 Nos.
For Stage II lifting
2 Nos.
For ‘U’ Rod lifting
2 Nos.
For side pulling of drum at 70 M
Electric winch of 15T cap with
wire rope 28 mm; 2800 Mtr.
2.
Electric winch of 10 T cap. with
wire rope 26 mm; 1200 Mtr.
3.
Electric winch of 5 T cap. with
wire rope of 1”
4.
-do-
Level
5.
Electric winch of 3T cap with
2 Nos.
3/4” or 7/8” rope
Pulling stage II lifting pullies for
conn. with drum before stage II
Lifting
PULLEYS
1.
300 T - 15 shieve pulley block
2 sets
For Stage I lifting
(4Nos.)
2.
300 T-15
-do-
2 sets For Stage II lifting
(4 Nos.)
3.
30 T - single shieve pulley
(Guide)
12 Nos.
For guide pulleys
in Stage I & II
lifting.
© PMI, NTPC
19
4.
10T - 2 shieve pulley block
4 Nos.
‘U’ Rod lifting
5.
50/40 T-3 shieve pulley
2 Nos.
For side pulling
of drum block
(with 5-2 Col.)
6.
25/30 T - 2 shieve pulley
2 Nos.
-do
Block (withS-I col.)
7.
10T-2 shieve pulley block
4 Nos.
For pulling the
bottom pulley of
Stage II lifting
towards rear
8.
5T chain pulley block
2 Nos.
For alignment of
Stage II lifting
pulley block while
inserting the pin
with drum lug.
9.
D-shackles dog clamps of various
sizes for the above
MISCELLANEOUS
1.
Walkie - Talkie
2.
Telephone at ‘O’ M & 72 M.
3:
Colour flags & whistles
4.
Flood, light arrangements.
5.
Cameras & video camara etc.
© PMI, NTPC
20
6. Erection Of Boiler Auxiliaries
Among the auxiliaries which require utmost care during erection are Fans, Mills and Air Pre
heaters. Only one case of fan will be dealt which itself will be sufficient to envisage the
complex nature of the activity and carefulness to be adopted during erection stage. In
general, the same technique will be applied for other rotating machines also.
1.
INSTALLATION OF BASE PLATE
As discussed elsewhere the correctness of foundation in case of rotating machines is
very important. Once the correctness of the foundation has been ensured the
foundation bolts of the equipment is mounted in the pockets made in the foundation
for the purpose. The locking of the foundation bolts with anchor provided inside the
foundation is ensured thereafter.
2.
GROUTING
After the locking has been achieved, grouting of the pockets is to be done with a
suitable grouting mixture either by preparing at site or readily purchasing from the
market. Once the grout is set the packers are set into their position by blue matching
the surface in contact to ensure proper contact for effective load transfer.
The base plate is then placed on the packers and the bolts temporarily tightened and
relative elevation of the base plate at different locations is observed by employing a
water level gauge, straight edge etc. Each base plate is leveled to the required
accuracy along and perpendicular to the fan axis. To achieve this, micro adjustment
stainless steel shims of various thickness are used.
3.
MAIN FAN ERECTION
The impeller and the other related housings diffusers are then placed on the
foundation base plate. These are then aligned with the centre line of the foundation.
The elevation as per the requirement is also ensured. The important alignment
© PMI, NTPC
21
parameter to be checked and maintained at this stage is the verticality of the impeller
or the horizontality of the shaft. This is achieved with a master level gauge and it
should be within O.4mm/M. The above exercise is to be carried out by tightening all
the foundation bolts properly so as to avoid any stress induction in parts due to
physical distortion.
4.
MOUNTING OF COUPLING
The shaft end and coupling bore dimension are measured and recor ded and then
should comply with the product drgs. The coupling is shrunk fit on to the shaft. In
order to mount the coupling it is heated in a oil bath by maintaining a temperature of
150 0 C approx. in the bath.
5.
ASSEMBLY OF IMPELLER BLADES
The blades of each impeller are identified by an alphabet series alongwith a serial
number. One such set of blades (for axial fans only) are taken and mounted on to the
impeller hub starting from any one location and proceeding in the serial order as
market on the blades and these may be done in clockwise or anti clockwise direction
as found convenient.
6.
INSTALLATION OF MOTOR
As applicable for the fan erection, the motor has to be erected on the base frame and
then aligned with respect to the fan. This is necessary as the fan housing is rarely
removed from position and hence it may be considered as fixed. Whereas the motor
is removed as a total unit several times for maintenance purposes.
7.
ALIGNMENT
The alignment of one equipment with respect to the other is very important. For
carrying out the alignment job, precision tools are required. Dial gauges of least
count of 0.001mm is required. These instruments are mounted on both the ends of
the shaft connecting the equipment and the shaft is rotated. The rotation of the shaft
© PMI, NTPC
22
gives the misalignment reading at various angular position of the shaft which later is
corrected by adjusting the motor on the base frame.
8.
INSTALLATION OF OTHER MISCELLANEOUS EQUIPMENTS
The fans, air preheaters, mills will necessary require a lubrication system which may
be internally mounted or externally mounted. For externally mounted lub oil system
unit certain precaution is to be observed while erection. As the oil supplied by the oil
unit is directly going to the bearings so the oil should be totally clean. The oil piping
which is connected to the fan with the oil unit is cleaned thoroughly by acid to remove
rust and scales, then washed with caustic soda and finally preserved with oil and
installed thereafter.
9.
GENERAL
While the erection of rotating machines are in progress cleanliness of the internals of
the equipment is to be ensured. Running clearances required as per the documents
is to be documented properly in the format supplied. This is the history card of the fan
and will be the base document for future reference.
The applicability of the requirements what has been discussed may vary with the
type of equipment supplied but in general the principle adopted is similar.
I.D. FAN
A special type of I.D. fan installation is being started with V.F.D (variable frequency
drive) arrangement where ID fan started with zero speed & picks up the speed as per
requirement of system.
© PMI, NTPC
23
7. Erection Of A Steam Turbine
Of the various types of prime movers available today viz. Electric motors, Steam turbines
and gas turbines, steam turbine is widely used in Chemical, Petro-chemical, power, fertiliser,
and other industries owing to its low cost of operation and dependability.
AUXILIARY UNITS
Normally steam turbines will consist of a lub oil circulating unit, gland steam condenser and
vaccum pumps, a condenser and condensate pump are the other units if it is a condensing
type of turbine.
COMPONENTS OF A TYPICAL STEAM TURBINE
The following are the important components of a typical turbine.
1.
Turbine Casing (in two halves).
2.
Diaphram & nozzles.
3.
Rotor.
4.
Journal Bearing.
5.
Thrust Bearing.
6.
Governor.
Erection
Like any other equipment care should be taken regarding the orientation and elevation of the
turbine. It is needless to say that precautions taken for a rotary equipment should be taken
for a steam turbine also.
© PMI, NTPC
24
We can divide the erection into various activities listed below:1.
Initial leveling.
2.
Pocket grouting
3.
Tightening of anchor bolts and re-leveling.
4.
Final grouting.
5.
Centering the rotor and leveling.
1.
Initial Levelling
The machined levelling surfaces provided on the base frame are used for this
purpose. Usually the initial levelling is done either on the jack bolts or on the liner
plates, within tolerance specified by the manufacturer.
2.
Pocket Grouting
Either epoxy materials or any non shrinking grout is used for grouting the machinery.
Care should be taken to keep the anchor bolts vertical at the centre of the hole during
the grouting.
3.
Tightening the Anchor Bolts and Relevelling
After the grout is sufficiently cured, the anchor bolts are tightened and the level is
checked again with master levels. If there is any deviation it is relevelled shimming
between the sole plate and the liners.
4.
Final Grouting
Once this is accomplished the equipment is released from the jack bolts and loaded
on the liners. While carrying the final grouting under the base frame care should be
taken to avoid air getting trapped. Some manufacturers ask for a recheck in the level
© PMI, NTPC
25
after the grout is cured to detect any change in level due to the shrinkage of the
grout.
5.
Centering the Rotor and Levelling
After the equipment is grouted the clearances between various components are
checked and the results are compared with that obtained at shop. They are:
1.
Clearance between the rotor and the casing.
2.
Clearance between the rotor and the bearing
3.
Clearance between the rotor and the seal.
4.
Rotor level.
5.
Lateral position of the rotor which respect to the thrust bearing.
If the shop values are different from the site values, the rotor is then centered again
as per the protocol.
1.
Casing Centering
A dial gauge is mounted on the rotor with the plunger touching the surface of the
casing near the seal axially. The rotor is then rotated and dial gauge reading noted at
3 0’ clock 6 0’ clock and 12 0’ clock position. If the readings are not the same as the
shop values then the rotor is lifted with the help of jack bolts and the casing shifted by
jack screws. The movement is monitored by fixing dial gauges.
2.
Bearing Housing Centering and checking the lateral position of the rotor
Centering of the rotor with respect to the bearing housing and position of the rotor
with respect to the thrust bearing are two vital points to be taken care of.
© PMI, NTPC
26
The gap between the thrust collars on the rotor and the thrust bearing is measured
and the position is set with the help of jack screws. After the lateral position of the
rotor is fixed, the journal bearing is removed and two dial gauges are fixed on rotor.
At both the active and inactive side. The readings are noted at 3 O’ clock, 6 O’clock
and 9 O’clock positions. The bearing housing is shifted with the help of jack screws if
there is any change in the readings.
Sometimes the clearance between the bearing and rotor is checked with the help of a
lead wire. In this case the top half of the bearing is opened and a thin lead wire
placed on the shaft. The bearing is replaced then and tightened. It is reopened again
and by measuring the thickness of the leadwire the clearance is measured.
3.
Rotor Levelling
The rotor should be at a redetermined level depending upon the cut of various blades
mounted on it. This is checked with the help of a master level and any change from
the shop value is corrected.
After all these exercises are completed the machine is said to be initially aligned.
Then various piping connections are given without introduction any strain in the
system which will affect the level of the equipment to a very greater extent. All the
flange connections should be parallel to each other and all the pipes are to be
properly supported.
We carry out these centering checks once again after all the piping connections are
made to find out whether these have introduced any strain on the machine. Any
adverse change leads to the rectification and re-work of turbine.
© PMI, NTPC
27
TURBO GENERATOR 3X500 MW
Erection activities of TG are classified into the following main categories:
1.
Condenser
+ LP heater No. - 1
2.
Turbine
i)
HP Turbine
ii)
IP Turbine
iii)
LP Turbine
iv)
HP & IP stop cut control valves
i)
Generator
ii)
Excitor
iii)
Terminal Bushings
iv)
H2 coolers
v)
Excitor coolers
i)
Lub oil equipment (oil tank, aux. oil
3.
4.
Generator
Auxiliaries
a) Turbine
pumps,
coolers,
jacking
oil
oil
pumps,
centrifuge,
oil
vapor
exhausters, & Duplex oil filter).
ii)
Control fluid equipment (CF tank, CF
pumps,
Mechanical
filters,
Earth
filters, Accumulators, supply units).
iii)
Governing Rack
iv)
LP by pass Rack
v)
Condenser on load tube
cleaning system.
vi)
© PMI, NTPC
Vacuum pumps
28
vii)
HP by pass system
i)
Stator water unit
ii)
Seal oil unit
iii)
Gas system
iv)
Excitation equipment
i)
UCB
ii)
Relay & Turbovisory panels
iii)
Local JBs and instruments
iv)
Cabling.
i)
Main steam piping
ii)
Hot Reheat piping
iii)
Cold Reheat piping
iv)
LP bypass piping
v)
TG cycle drains
i)
Lub oil piping
ii)
Control fluid piping
b) Generator
5.
6.
Control & Instrumentation
Piping
a) Critical Piping
b) Turbine Integral piping
© PMI, NTPC
29
iii)
Gland steam piping
iv)
Condenser Air Evacuation
v)
TG drains
i)
Seal oil piping
ii)
Stator water piping
iii)
H2 gas piping
i)
Condenser cooling water
c) Generator Integral piping
d) External piping
piping
7.
Interface
ii)
Aux. cooling water lines.
i)
Foundation checking for all
equipment
ii)
Terminal points take over/
hand over.
8.
Customer Inputs
© PMI, NTPC
iii)
Electrical checks interface
iv)
C&I interface
i)
Safety Inputs
ii)
Civil foundations
iii)
Floors, ‘O’ M, 8.5 M & 17.0 M
iv)
Approaches
30
v)
Lighting
vi)
EOT cranes
vii)
Power Supply
viii)
All associated pkgs. required
for synchronisation and
running of the units.
ix)
Construction Power
that
it
CONDENSER ERECTION
1.
Inspect
foundation
and
check
conforms
to
the
drawing.
(Level, dimensions, pockets, identify longitudinal & transverse centre lines.)
2.
Place on the foundation spring elements the springs are placed in locked condition
with heights adjusted to give the required slope.
3.
Pre-fabricate/assemble condenser bottom plate and hot well.
4.
Place bottom plate with hot well on springs.
5.
Pre-fabricate side walls.
6.
Pre-fabricate water box tube plates.
7.
Place tube plate and side plates on the bottom plate, align and weld.
8.
Pre-fabricate Dome walls.
9.
Install tube support plates & weld.
10.
Install stiffening structure, air evacuation zone.
© PMI, NTPC
31
11.
Install Dome walls and LP Heater 1 supporting structure.
12.
Install LP Heater No.1
13.
Clean condenser steam space.
14.
Insert condenser tubes and expand.
15.
Weld condenser neck (dome walls) with LP Turbine exhaust hood.
16.
Hydro test of condenser steam space and leak test, & drain.
17.
Assemble water box covers and hinge assembly.
18.
Hydro test water side.
19.
Release condenser springs and adjust to operating valves.
20.
Drain water box and remove hydro test flanges.
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN
L. P. TURBINE - ENSURE SAFE WORKING CONDITION
1.
Check and prepare foundation w.r.t. drawing and plant bench marks and identify long
and transverse centre lines.
2.
Place and level LP outer casing base plates, IP and LP rear bearing base plates and
grout with non shrink cement.
3.
Install LP longitudinal girders, and LP casing lower front and rear walls.
4.
Install longitudinal fixed points for front and rear walls.
5.
Place LP inner casing lower half section and make preliminary alignment.
© PMI, NTPC
32
6.
Place lower half of divisor sections.
7.
Place LP inner casing upper half and the diffuser sections and align.
8.
Assemble LP outer casing and weld match the parting planes.
9.
Remove LP outer casing and inner casing upper half and prepare LP rotor for
placement.
10.
Place LP rotor and do final alignment of LP in casing and shaft seals.
11.
Fix axial and radial keys of LP outer casing.
12.
Weld internal piping of LP casing.
13.
Checks steam flow path clearances.
14.
Box up, LP inter casing and outer casing.
15.
At this stage it is expected that HPT and IPT are erected and aligned w.r.t. LPT.
16.
Centre LP glands and install compensator.
17.
Install seal rings for hearing casing and align.
18.
Prepare pedestals for OIL flushing.
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN.
I. P. TURBINE - ENSURE SAFE WORKING CONDITION
1.
Along with the placement of pedestals of IP rear and LP rear bearings the remaining
IP front and HP front bearing pedestals sole plates are also erected, levelled.
2.
Respective pedestals are placed on position and aligned w.r.t. turbine centre line and
transverse axes.
© PMI, NTPC
33
3.
Pedestals are then grouted.
4.
Cleaning and preparation of lP turbine for erection.
5.
Place IPT in position, centre and level it.
6.
Align IP rotor with LP rotor.
7.
Fix IP front bearing position axially.
8.
Final centering of IP casing.
9.
Rolling test.
10.
Honing of coupling bolts of IP and LP rotors.
11.
Cross around piping from IP to LP turbine is parallel done.
12.
Erection of barring gear.
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN
H.P. TURBINE - ENSURE SAFE WORKING CONDITION
1.
Prepare HP turbine for erection.
2.
Place HP turbine in position, centre and level it.
3.
Aalign HP rotor with IP rotor.
4.
Final centering of HPT.
5.
Align main oil pump with HP rotor.
6.
Rolling test.
© PMI, NTPC
34
7.
Honing of coupling bolts of HP and IP rotors.
8.
Final alignment of HPT, IPT &. LPT with respect to the coupled rotor.
9.
Carry out horn drop test of HPT and IPT.
10.
Check final oil clearance of bearings and box up bearing pedestals. This applies to all
the bearings of HPT, IPT & LPT.
11
Prepare for oil flushing.
12.
Oil flushing.
13.
After completion of oil flushing normalise bearings and box up.
14.
Insulate HPT & IPT.
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN
STOP CUM CONTROL VALVE
ENSURE SAFE WORKING CONDITION
1.
Check elevation and centre lines for the structure at 17M floor on which the
suspension frames for stop cum CVs are to be placed.
2.
Place suspension frames on the structure and blue match it.
3.
Remove the suspension frames and attach valve suspensions to the frames.
4.
Prepare the stop cum CVs for erection.
5.
Lower the frame with suspensions over the valves and assemble the valves to the
suspension.
6.
Install the complete assembly on the structure and fasten it.
7.
Level the stop cum CV in x,y & z directions by means of tie-rods in the suspensions.
© PMI, NTPC
35
8.
Repeat the procedure for 4 Nos. HP valves and 4 Nos. IP valves
9.
Procedure is more or less similar for LP bypass valves (2 Nos.)
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN
GENERATOR - ENSURE SAFE WORKING CONDITION
1.
Check foundation and make logitudinal and transverse centre line. Check levels w.r.t.
bench mark.
2.
Place cross beams and mount terminal box.
3.
Place pedestals sole plates, level and grout.
4.
Check pedestals for PORTAL CRANE.
5.
Install and commission portal crane, along with load testing.
6.
Place the generator stator special wagon with the stator adjacent to the generator
foundation outside the ‘A’ row.
7.
Lift stator and place it on the foundation.
8.
Align the stator w.r.t centreline and the LP rotor.
9.
Place bottom end shield LPT side.
10.
Insert rotor.
11.
Place bottom end shield exciter end and align.
12.
Install and align blower.
13.
Attach seal ring carrier and align.
© PMI, NTPC
36
14.
Position top end shields and tighten.
15.
Install hydrogen coolers.
16.
Align generator rotor w.r.t. LP rotor and tighten anchor bolts.
17.
Install seals.
18.
Couple generator rotor with LP rotor.
19.
Check exciter foundation and place sole plates.
20.
Place exciter on sole plates, level and align.
21.
Align exciter rotor with generator rotor and tighten anchor plates.
22.
Couple exciter rotor with generator rotor.
23.
Prepare for oil flushing.
24.
After completion of oil flushing control fluid flushing, seal oil flushing and stator water
flushing the unit is ready for putting on barring.
Note: PROTOCOLS ARE TO BE MADE AS PER THE FIELD QUALITY PLAN
G.
Ensure all other inputs are established as follows;
a.
Boiler
b.
Piping (including hydrotest and steam blowing)
c.
Auxiliaries
d.
Instrumentation
e.
Other packages
The unit can then be rolled and prepared for synchronization.
© PMI, NTPC
37
© PMI, NTPC
38
3 X 500 MW TG PACKAGE NTPC INPUTS
(REF PERT NETWORK SH. 1 OF 2)
S. No.
Input
Description
1
D
1. Condenser Foundation
2. EOT crane
3. Area for labour/staff quarters
4. Project railway siding and Rail track up to TG hall.
5. Approach road to TG hall.
6. Power & water supply.
7. Storage / office area
8. TG hall with approach side walls roof. & lighting
2
E
1. TG foundation
2. TG 17 ‘m’ floor
3. TG 8.5 m floor
4. TG ‘0’ m floor
3
F
1. LT Power
2. Cable for Oil pumps.
3. Instrumentation.
4
G
© PMI, NTPC
1. Complete Instrumentation
39
S. No.
Input
Description
5
H
1. Readyness of main boiler.
2. Completion of Regenerative system equipment e.g.
Deacrator, LP heaters, HP heaters piping, BFPs,
condensate Ext. pumps.
3. Unit aux. Transformer
4. Complete UCB with instrumentation.
5. Generator Transformer
6. Switch yard & control room
7. Power evacuation system/grid.
6
I
1. Stator unloading track.
2. Portal crane foundation
7
J
1. All auxilliaries foundation.
2. Pipe supporting stracture
3. Auxilliary platform & approach stair cases.
4. DM water.
5. Instrument / Plant air.
© PMI, NTPC
40
© PMI, NTPC
41
© PMI, NTPC
42
8. Boiler Feed Pumps 3 X 500 MW
MW
STEPS INVOLVED IN ERECTION
The erection activities are broadly classified into the following categories:
A.
B.
C.
Main equipment
Auxiliaries
Piping
© PMI, NTPC
i)
Main Pump
ii)
Booster pump
iii)
Drive Motor (for MDBFP)
iv)
Voith coupling (for MDBFP)
v)
Drive Turbine (for TDBFP)
vi)
Gear Box (for TDBFP)
i)
Lub oil coolers
ii)
Working oil coolers (for MDBFP)
iii)
Lub oil tank (for TDBFP)
iv)
MOPs/AOPs and EOP (for TDBFP)
v)
Gland drain tank
vi)
Emergency seal water pump
i)
Feed water suction/discharge
ii)
Lub oil/control oil
43
D.
E.
F.
Instrumentation
Interface
Customer Inputs
© PMI, NTPC
iii)
Steam lines - HP/LP, gland steam
iv)
Seal water
v)
Cooling water
i)
Control panels
ii)
UCB consoles
iii)
Field panels, instruments, junction boxes
iv)
Cabling
i)
Civil foundation take over
ii)
Equipment terminal points take over/hand over
iii)
Cable termination checks
i)
Safe working area
ii)
Foundations
iii)
floor - ‘O’ M, 8.5 M & 17 M
iv)
Lighting
v)
Approaches to TG hall and fans
vi)
EOT crane
vii)
Construction power
viii)
Equipment power supply
44
TURBO – DRIVEN BOILER FEED PUMP
A.
Main Equipment
The TDBFPs are located at 17M operating floor of TG Hall. There are two TDBFPs of 50%
capacity. Unlike MDBFP the TDBFPS are delivered to site as separate units comprising of
main pump, turbine, and Gear box + Booster Pump in a common frame. They are located on
top of the concrete condition deck.
(The concrete foundation deck is freely supported on springs which are placed on steel
structure raised from pipe foundation. This is done to achieve high degree of vibration
isolation
which
prevents
transmission
of
vibration
from
BFPs
to
the
adjacent
structure/equipment and vice versa).
1.
The erection procedure is given broadly in the enclosed sheets FE to FE4.
© PMI, NTPC
45
9. Field Erection Procedure
1.
Install all parts below the turbine floor which can be easily installed now, before the
turbine is put in place.
2.
Install the oil unit.
3.
Check foundation dimensions and location of the foundation bolts before starting
erection. Check Position of pipe connections against customer elevation plan. Mount
the sole plates to the turbine supports.
4.
Refer to drawing, fit the jack bolts and the foundation bolts in the holes, which have
been provided in the sole places of the turbine.
5.
Place steel plates, approx. 100 x 100 x 10 mm on the foundation, so that these plates
will take the thrust of the levelling screws.
6.
Lower the turbine on to the foundation and level it transversely and longitudinally
using the jacking bolts. Adjust the distance between the top of the concrete
foundation and the bottom of the sole plates to 20-25 mm. Forms or dams around the
sole plates are required.
7.
Mount all steam and oil piping to the turbine.
8.
Mount the sole plates to the boiler feed pump supports. Fit jack bolts and foundation
bolts in the holes which have been provided in the sole plates.
9.
Place steel plates, approx. 100 x 100 x 10mm on the foundation, so that these plates
will take the thrust of the levelling screws.
10.
Lower the boiler feed pump on to the foundation and level it transversely and
longitudinally using the jacking bolts to align the pump shaft with respect to the
turbine shaft. For alignment data see the alignment protocol in the last section of this
book. Forms or dams around the sole plates are necessary.
© PMI, NTPC
46
11.
Fit the jacking bolts and foundation bolts in the bottom flange of the booster pump
bedplate. Tighten the bolts of the levelling pads.
12.
Place steel plates, approx. 100 x 100 x. 10mm on the foundation, so that these plates
will take the thrust of the levelling screws.
13.
Lower the baseplate, with the booster pump and gear box in place but the coupling
disconnected, on to the foundation. Using the jack bolts, level it transversely and
longitudinally to align the couplings between the booster pump and gear box and
between the gear box and turbine. For alignment data see the alignment protocol in
the last section.
14.
Mount all water and oil piping to the booster pump and gear box, and check the
coupling alignment.
15.
Fill the holes of the booster pump foundation with grout, in such a way that the half of
the shim thickness is in it. See detail “A” below. Use a non-shrinkable flowable grout.
Make provisions that the levelling screws stay free of the grout.
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16.
Allow the Grout to dry (according to the manufacturer’s prescription).
17.
Loosen the leveling screws and tighten the foundation bolts and keep checking the
alignment. Tightening of the foundation bolts should have no effect on the alignment
of the set. If it is necessary to make a correction in the leveling of the booster pump
bedplate, handle as follows:
Loosen the foundation bolts, loosen the tap bolts of the shims, level the bedplate by
means of the leveling screws, fit between the shims and the supporting pads the
required liners, loosen the leveling screws, tighten the tap bolts, tighten the
foundation bolts and check the alignment again.
18.
Grout the turbine and the boiler feed pump to the foundation in such a way the half of
the sole plate thickness is in the grout. Use a non-shrinkable flowable grout. Make
provisions that the leveling screws stay free of the grout.
19.
Allow the grout to dry (according to the manufacturers prescription).
20.
Loosen the leveling screws and tighten the foundation bolts and keep checking the
alignment. Tightening of the foundation bolts should have no effect on the alignment
of the set. Make any required correction.
21.
If it is necessary to correct the radial coupling alignment, this, should be done by
changing the thickness of the shims under the supports of the respective
components.
22.
Remove the boiler feed pump inner assembly in accordance with the instructions
given in the maintenance section.
23.
Weld the pipes to the respective pump nozzles in such a way that no forces and / or
moments are exerted on the nozzles.
24.
Connect the other water and oil pipes to the boiler feed pump. Also without exerting
forces and / or moments by the piping.
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25.
Remove the booster pump inner assembly in accordance with the instructions in the
stork instruction manual.
26.
Remove the inlet filter inner assembly in accordance with the manufacturer’s
instruction.
27.
Prepare the set for pickling by blanking off the relevant openings.
28.
It is strongly recommended by Delaval Stork that the pickling is done by a company
which is a specialist in this field. Such a company will have the necessary equipment
available and possesses the technical knowledge. Pipes that have been furnished by
Delaval-Stork with the unit, have been pickled before leaving the shop.
29.
After pickling, remove all blanking plates and reinstall the boiler feed pump inner
assembly, the booster pump inner assembly and the inlet filter assembly.
30.
Check the alignment .of the couplings. Make any required corrections.
31.
Flush the oil system in accordance with the flushing instructions given in the
operation section.
32.
Prior to the initial start, make an overall inspection to make sure that all accessories
have been properly installed.
33.
Make sure that the coupling between the boiler feed pump and turbine is disengaged.
Make sure that the coupling between turbine and gear box is connected so that the
mechanical over speed trip can be tested during the test run.
34.
Before starting the turbine remove the transport rings items.
35.
Blow down the steam inlet line before allowing steam to enter the turbine. Make sure
that the steam pipes are reasonably clean and do not contain sand, welding beads or
other harmful material.
36.
The turbine should be isolated in accordance with drawing and Technical
Specification.
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37.
Check and, if necessary, adjust all the relevant control and safety device settings and
start the turbine for a test run.
38.
After the turbine test run, stop the turbine and engage the coupling between the
turbine and boiler feed pump. Make up the coupling between the gear box and
booster pump.
39.
Start the complete unit in accordance with the instructions given in the operating
section.
40.
If there are objections against the coumping alignment at operating conditions, a hot
alignment check can be made as follows: couple up the unit and run it with indicators
mounted on a bridge tupe bracket as shown on the attached sketch to check the
alignment under operation condition. Indicators should be zeroed when the machined
is cold and read and recorded after normal conditions have stabilized. Before shut
down, the indicators should be reset at zero and readings should be recorded after
the unit has cooled. Make any required correction. Record coupling alignment on
drawing for adjusting data.
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B.
Auxiliaries
Auxiliaries for MDBFP are lub and working oil coolers. Gland drain tank and DC emergency
seal water pump.
Lub and working oil coolers are located at ‘O’ M level on the floor.
Gland drain tank is located at minus 2.5 M level.
1.
Check foundation pockets for the cooler with respect to drawing.
2.
Place the coolers on the foundation correctly w.r.t. x, y & z planes.
3.
Grout the cooler with ordinary grout mix.
MAKE PROTOCOL FOR TERMINAL POINTS
4.
After curing for 3 days piping work on the equipment can be taken up.
5.
Gland drain tank is placed at ‘O’ M level on insert plates on the floor at the
designated location after ensuring its level and then tack-welded.
MAKE PROTOCOL FOR TERMINAL POINTS
6.
Steps 1 to 4 are identical for DC emergency seal water pump.
MAKE PROTOCOL FOR TERMINAL POINTS
C.
PIPING
a.
Feed water piping
1)
All the piping has to be erected in position in totality before it is connected to the
booster pump or the main pump this means
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i)
All welding joints/flanged joints other than the one with the pump are
complete in all respects i.e. radiographed, stress-relieved, permanent gaskets
installed, all flanged bolts tightened.
ii)
All hangers are installed.
iii)
All spring hangers are delocked and adjusted to their cold values.
iv)
All restraints are installed.
v)
Insulation and cladding has been completed.
vi)
There are no temporary supports or lifting or pulleying tackles attached to the
pipeline.
vii)
In the above condition the joint with the pump is fully in alignment within the
welding tolerance/flanged joint tolerance. Usually the ID of the pipe should be
within ± 1mm of each other.
The line should be free to swing if forced and then return to the original
position. This is called a FREE JOINT.
MAKE PROTOCOL OF THESE CONDITION i) to vii).
2.
Mount dial gauges to the coupling hubs of the equipment involved in the final weld
joints to monitor if any undue forces are transmitted to the equipment during welding
which might disturb the equipment during welding which might disturb the equipment
alignment. Same applies for flanged joint.
3.
Allow final joint to be welded / bolted.
4.
If any appreciable deflection is observed on the dial indicators then change the
welding sequence 1800 out of pahse in order to compensate the distortion.
5.
The above procedure is valid for all the feed water piping connected to the pumps.
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Note:
1.
Ensure that all piping are clean on the inside and free of rust, sealed and debris. For
this purpose pipes are acid pickled and then neutralised. Alkali flushing of the pipes
may be carried out for suction lines before the suction strainer and feed lines going
out of the pump. Oil should Not be applied to the internals of the non oil lines to
prevent rusting.
2.
Hydro test of lines is ensured at an appropriate tage.
b.
Cooling water, seal water lines:
1.
Lines are connected from one terminal point to the other as per the drawing.
2.
Seal water lines are acid pickled to ensure that water supplied to the pump seals is
free from scales and dirt.
3.
Flushing of the seal water lines and cooling water lines is done to ensure removal of
all debris and free matter.
c.
Oil lines
1.
Lines are pre-fabricated and erected in the normal manner
2.
If not already acid pickled then suitable sections are then made to remove the
complete piping for acid pickling and cleaning.
3.
Lines are reassembled.
4.
Pressure test of the lines is carried out according to the drawing requirements (15
times the design pressure).
5.
Oil Flushing:
The purpose of oil flushing is to achieve completely clean internal surface of oil pipelines
before oil can be supplied in such lines to bearings, gears, control valves etc.
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i)
Remove the bearing half from main pump, booster pump and motor and replace
them with auxiliary bearings.
ii)
Install bypass lines in the control oil circuits for all servo devices.
iii)
Fill Voith coupling oil tank with oil up to the specified level.
iv)
Ensure that the filter element on the Voith coupling inlet are in position and in clean
condition.
v)
Keep the oil incirculation by auxiliary oil pump of the Voith coupling.
vi)
Thermal shocks are given to the pipelines by heating the oil to 75°C holding it for 30
mms and then suddenly cooling to 35°C. This is repeated several times to loosen all
scales etc. And until no more dirt comes into the filters.
Heating of oil can be achieved by admitting hot water into the oil cooler by suitable
arrangement which can be interrupted to supply cold water.
vii)
All lub oil lines are then normalized according to the drawing taking care that no
foreign material enters the lines.
ix)
Flushing oil is then drained and fresh oil is charged into the system.
x)
Oil system is now ready for pre-commissioning and commissioning.
Motor Driven BFP
A.
Main Equipment:
1.
Ensure approach to the main BFP foundation at 8.5 M floor
2.
Ensure SAFE working conditions
3.
a.
Check completeness of foundation and measurements as per the civil and
mechanical drawings.
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b.
Check levels of foundation w.r.t. drawings and plant bench mark
c.
Ensure cleanliness of foundation
MAKE PROTOCOL OF a) AN]) b) WITH DIMENSIONS FOR TAKING OVER THE
FOUNDATION
4.
Dress/chip foundation pedestal tops to make it even and free of debris/loose cement.
Also ensure foundation pockets/bolt holes are free of loose cement and concrete.
Foundation is now ready for placing the equipment.
The Motor driven BFP is delivered to site on a common steel skid the main pump,
booster
pump
and
Voith
coupling
are
already
mounted
on
the
skid.
The drive motor for BFP is delivered separately to site.
5.
Place steel plates 100 x 100 x 10mm thick on the foundation at location where
levelling bolts /jacks bolts on the skid are located so that the complete skid can be
placed on its jack bolts on top of these plates.
6.
With the help of lifting beam and the slings (as per the relevant drawing) left the total
skid and place it on the foundation.
7.
Lower the Drive motor on the skid and secure it with the bolts provided.
8.
Level the skid w.r.t plant bench mark within ± 1 mm.
9.
Adjust the levelling screws so as to achieve parallelism of all the coupling faces with
± 0.02 mm.
10.
Remove rotor locking device (transport device) from all equipment and check
complete alignment of the respective equipments in accordance with drawing. Adjust,
if necessary, by using SS shims under the feet of the equipment to within the
tolerance limits given in the drawings. It is customary to take ‘Voith Coupling’ as the
reference point and align the other equipment w.r.t it. The skid is now ready for
grouting.
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MAKE PROTOCOL FOR ALIGNMENT BEFORE GROUTING
11.
Keep the foundation pockets (42 Nos.) and its surroundings wet by water atleast 3
hours before grouting. Place foundation bolts in position.
12.
Make wooden frame work around the bolts and grout with non shrink grout mix.
13.
After 3 days of curing remove the framework. Loosen all the jackbolts and tighten all
foundation bolts.
14.
Check alignment of all equipment at the couplings. Adjust/correct if required.
MAKE PROTOCOL FORALIGNMENT AFTER GROUTING & BEFORE PIPING
15.
Hand over the terminal point for Feed Water piping after checking its location.
MAKE PROTOCOL FOR HANDLING OVER OF PIPING TERMINAL POINTS
16.
Equipment is now also released for instrumentation and electrical jobs.
17.
After completion of all piping work check the alignment of all the equipment again
Make corrections, if necessary.
MAKE PROTOCOL OF ALIGNMENT AFTER ALL PIPING
18.
All the equipment are then dowelled as per the drawing.
19.
Place coupling spacer between main pump, voith coupling, Motor and Gear box and
tighten to the specified torque.
20.
Equipment is now ready for other pre-commissioning and commissioning activities.
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10. 500 MW Generator Erection
The various stages involved in the erection of a 500 MW Generator Stator are its
transportation from the manufacturers works to site, unloading and placement on foundation.
TRANSPORTATION
The dimensions of the Generator Stator are:
Length
8830 mm
Width
4100 mm
Height
4020 mm
Weight
265 MT
The stator is transported on a special wagon consisting of 24 axles i.e. 8 bogies (4 on each
side of stator) of 3 axles each with facility to swiral. These two sets of bogies are connected
by a carrier beam and the beam is pivoted to the bogies.
The procedure of handling of generator stator on receipt of same at site comprises of the
following two major activities.
1.
Unloading of Generator Stator from the special wagon in the unloading bay outside
the TG hall.
2.
Erection of the portal crane and shifting of Generator stator from unloading bay into
its foundation using portal crane.
UNLOADING
Before the unloading is done, the following inputs are to be ensured.
1.
Availability of EOT crane in TG hall.
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2.
Completion of civil foundation for unloading of stator, placement of fabricated
pedestal and placement of jacks.
3.
Rail track should be ready for stator shifting.
4.
There should be an easy access to mobile crane of 75 T capacity around the
unloading bay.
After ensuring the above inputs, the unloading of generator stator is carried out in the
following manner.
1.
Position the special wagon so that the transverse centre line of the stator coincides
with
the
extended
transverse
axis
of
Tg
stator
on
the
rail
track
(See fig. 1)
2.
Insert packing plates between the stator and pedestal behaving a gap of
2-3 mm.
3.
Adjust the position of the hydraulic jacks (4 Nos. each of 175 MT capacity).
4.
Dismantle the support beam on both front and rear end of the stator.
5.
Pressurise all the jacks simultaneously and insert the packer plates and transfer the
load of stator from the carrier beam wagon on to the pedestral by lowering the jacks.
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6.
De-couple the vacuum pipe assembly of the rear end as well as front end of the
wagon bring the roller block on the carrier shield on rear side in engaged position so
that the beam can be raised up while lifting the stator by jacks.
7.
Slowly raise the stator slaotingly by pressurising rear side jacks so that the carrier
beam is off the rear side bogie assembly and sufficient gap between the carrier beam
and bogies is available to facilitate movement of the rear set of bogies independently.
Insert the packers and lower the jacks.
8.
Move the rear set of bogies towards the rear end approx. to a distance of
25 metres. By doing so the carrier beam gets released off the rear set of bogies and
is left supported on the roller blocks on the carrier shield at the rear end.
9.
Move the front set of bogies alongwith the carrier beam slowly till the rear end of the
carrier beam has just reached upto the rear carrier shield of the stator.
10.
Adjust the stator by means of the jacks so that the carrier beam is being supported
now by the guide roller device of the front. Carrier shield cover and the roller device
at the rear end carrier shield cover is getting free. Remove the carrier beam carefully
out of the stator until a position is reached, when the jacking trolley can be put
underneath the beam.
11.
Place the jacking trolley on the front side between stator and bogies and support the
carrier beam closes to the stator. When changing load this way, the guide roller
device at the front shield cover must become free of load.
12.
Move the front set of bogies further till the carrier beam is moved out of the front and
carrier shield of the stator.
13.
Dismantle and remove the front as well as rear end carrier shields.
14.
Place and assemble the temporary end covers on both end of the generator stator.
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SHIFTING AND PLACEMENT ON FOUNDATION
Before actual shifting operation, the following should be ensured.
1.
Portal crane erection is complete.
2.
Foundation plates are positioned and grouted.
3.
Positioning of Terminal bushing box of the Generator has been completed.
4.
The actual shifting and placement on foundation has the following activities.
1)
Check and ensure that the stator has been placed under the hook of portal
crane, exactly at centre of crane whose beam extends outside the TG hail
and is covering the distance upto the Rail Track where stator is unloaded.
2)
Lower the lifting hook of the portal crane.
3)
Fix the stator lifting slings in the portal crane hook and also the lifting lugs of
the stator.
4)
Fix a manilarope at the diagonal end of the stator in order to facilitate
maneuverability of rotary movement of stator.
5)
Slowly raise the hook of the crane and arrest the swinging and swaying
movements of stator with the manila rope.
6)
Lift the hook to its full height i.e. 21.576 M
7)
Turn the stator body by 90 deg. to its final position of placement. Arrest the
swaying of the stator.
8)
Move the tolley and hook of the portal crane and take the stator into the TG
hall.
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9)
After reaching the stator above its foundation in the TG hall, turn the stator by
90 deg. so that it is parallel to the foundation axis.
10)
Lower the generator stator onto its foundation and insert the packers
underneath the stator.
11)
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Slowly release the lifting slings and hook of the portal crane.
65
11. Guidelines For Alignment Of Rotating
Machinery
Correct alignment is necessary for the successful operation of rotating machinery as
misalignment may cause severe problem such as reduction of bearing life, coupling life,
failure of seals, vibration and decreased production capacity etc. Thus for maintenance free
operation of rotating machinery correct alignment plays a vital role.
The alignment operations for complex machines is to be performed in compliance with the
instruction of the machine supplier.
The alignment of two pieces of equipme nt to be coupled is performed by correcting the radial
and axial deviations to be coupled in the desired position, within the prefixed limits of
tolerance.
TYPES OF MISALIGNMENT
It will be easier to understand if we consider misalignment (shaft axis not being colinear).
Misalignment occurs in following ways:
i)
Centre Offset: If the shaft axis are parallel to each other, then this type of
misalignment is called centre offset Fig. 11
ii)
Angular Offset: If the shaft axis are not - co - linear and they intersect each other, it is
called angular offset. Fig. 12
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Generally misalignment occurs in the combination of above two types and in xyz plane. In
the following discussion misalignment and its measurements are considered in one place
and a little consideration will show that same principles and methods are applicable for xyz
planes. For this purpose, it is necessary to prepare three dial indicators with the suitable
outfits, as shown in (fig. 13).
The Following points should be taken care while taking the readings of misalignment.
i)
Check the dial gauges or measuring instruments to the used for checking alignment.
ii)
Alignment bracket should be mounted firmly check it for any deflection. Ensure that it
is secured firmly.
If the distance between shaft ends (or coupling hubs) is not much, fix the alignment
bracket and set the dial indicator on the rim of the same coupling hub set the dial
indicator to zero when it is at top. Turn the shaft by 180’. The dial indicator reading
will show the amount of deflection or displacement of the bracket.
If the distance between two shaft ends is larger, then a fixture made of steel plate
and a thin pipe can be used. Fix this fixture to coupling and mount the alignment
bracket on it as shown in the fig. 14.
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Set dial indicator to zero when it is at top and turn the coupling through 180 0 , the
indicator readings will show the amount of deflection.
iii)
Dial gauges must be secured solidly to the alignment bracket. Ensure the cover of
the dial gauges is secured properly to its body. If not, tighten the fixing screws.
iv)
Dial indicator is generally set at the top and twined in the same direction as that of in
which the machine is operated. It is very important that left side and right side of the
machine should be decided so as to confirm that no mistakes are made during
correction of misalignment.
v)
Shims for the adjustment should be made generally of SS and contact surfaces
should be kept smooth, free of burrs and cleaned thoroughly before placing in
position.
vi)
The rim and face on which the dial indicator is to be mounted should be check for
any eccentricity and surface imperfections. There should not exceed the tolerances
recommended by the manufacturers.
METHODS FOR MEASURING THE DATA FOR RADIAL MISALIGNMENT
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When the two shaft axis are parallel & collinear, as shown in fig. (15) and when the dial
indicator is set on top of coupling of shaft B and rotated, printer of the dial gauges will not
show any deviation. But if the shaft axes are as shown in fig. (16), measure the data by
rotating through 360 0 .
The algebraic sum of the values read on the horizontal plane (90 0 & 2700) will be equal to
(except for small errors) the value read on the vertical plane 1800).
If x=y+z, the difference (considered error) shall not be greater than 1/100 mm.
Axial Misalignment = y-z/2 (In Horizontal Plane)
Axial Misalignment = x/2 (In vertical plane)
METHOD FOR MEASURING THE DATA FOR AXIAL ALIGNMENT
Axial alignment means to check the relative position between the axes perpendicular to the
axes of rotation of the two items to be coupled. In other words, it must be checked that the
axes of rotation are parallel or have the divergence/convergence on top or bottom.
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Two dial indicators Al & A2 are used for measuring the data for axial misalignment. The
necessity to use two dial indicators is due to the fact that axial displacement of the two items
to be coupled may occur during the rotation of two flanges.
By the use of two dial indicators, the possible displacement along the axis are annulled
whereas the face displacement of the two flanges remain unaltered.
The value of axial misalignment on the vertical plane will be the algebraic half difference of
the readings (considered with their signs) made on the dial indicators.
Al & A2 after a rotation of 1800, that is.
V= c – a
;
V = Vertical misalignment on the vertical plane.
2
If the result has a minus sign, the flanges are open downwards; if the result has a plus sign,
the flanges are open upwards. The normally accepted limit is 4/100 mm. for the compressors
and 5/100mm for the pumps. Different values shall be specified by the manufacturer for
these machines.
The value of axial misalignment on the horizontal plane will be the algebraic half
- difference of the readings (considered with their signs) made on the dial indicators Al & A2
after rotation of 90° & 270°, that is;
Or = (b-d) - (h-f)/2
Or = Axial misalignment on the horizontal plane.
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If the result has a minus sign, the flanges are open to the left, if the result has a plus sign,
the flanges are open to the right.
ALIGNING GEAR AND FLOATING TYPE COUPLING
Various Steps
1.
Push coupling covers out of the way. Measurements are then made on coupling hubs
as shown
2.
For floating type of couplings, the jack shaft between the pump and driver must be
removed and a bracket as in (b) must be made. It must be long enough torch from
one coupling to another when fastened to one.
3.
Fasten the bracket to one coupling and a dial gauge type indicator to the arm, so that
the indicator contacts the rim of the other coupling half.
4.
Revolve the left coupling slowly so that the indicator turns about the right hand one.
Check readings. Adjust as required.
5.
For shaft and play check with a micrometer (inside one) as shown in (b).
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6.
When one coupling is aligned, reverse the bracket and perform the same steps on
other coupling.
7.
When alignment is completed, insert the jack shaft and bolt the coupling halves.
ANOTHER METHOD OF COUPLING ALIGNMENT
a.
Check angular alignment using tapered gauge between the coupling faces at each
900 around the faces.
b.
Use straight edges and feeder gauges to check the axial alignment at each 900 of
rotation.
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ALLOWABLE TOLERANCE COUPLING ALIGNMENT
A.
OFFSET MISALIGNMENT
Dimensions in mm.
SPEED
B.
OUTPUT OF ROT. M/c KW
COUPLING
rpm
BELOW 400
400-1000
OVER 1000
FLEXIBLE
2500-4000
0.01
0.02
0.03
COUPLING
1300-2500
0.025
0.04
0.06
BELOW 1300
0.04
0.06
0.10
RIGID
2500-4000
0.01
0.02
0.03
COUPLING
BELOW 2500
0.015
0.03
0.04
ANGULAR MISALIGNMENT
Dimensions in mm.
SPEED
OUTPUT OF ROT. M/c KW
COUPLING
(r.p.m.)
BELOW 400
400-600
OVER 600
FLEXIBLE
2500-4000
0.02
0.03
0.04
COUPLING
1300-2500
0.06
0.07
0.10
BELOW 1300
0.08
0.10
0.15
RIGID
2500-4000
0.02
0.03
0.04
COUPLING
BELOW 2500
0.03
0.04
0.05
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12. Hot And Cold Alignment
COLD ALIGNMENT
It is the procedure that involves positioning of shaft in relation to each other. In a train of
equipments consisting of driver machines, driven machine, reduced or intermediate shafts,
couplings etc. one of the machines is set first as the reference unit and others are aligned in
accordance with ‘position of this reference unit. Generally the largest and the heaviest
machine which is difficult to reposition is set as the reference machine.
If thermal effects on the machine casing, rotating parts or supports are neglected then cold
alignment is the procedure by which we make the shaft axes of the equipment train collinear.
HOT ALIGNMENT
When operating temperature of the machine is much higher than ambient temperature there
will be thermal growth of casing rotating parts and supports. Generally the construction of
machines is such that despite these effects, thermal growth of the parts shaft axes of the
machine will not be allowed in lateral direction (Horizontal Plane) even at very high
temperatures - But due to linear expansion of support in vertical direction, though the
machines are aligned very well within tolerances, the position of shaft axes will be altered
during normal operation. Hence shaft position will not be the same during operation as it was
at ambient temperature. This thermal growth at the supports can be calculated theoretically
and also during test run in shop and can be practically measured also. During cold condition
shaft axes can be aligned in such a relative position to each other than during normal
operating conditions, the shafts will be collinear.
Sometimes in case abnormal vibrations alignments is done immediately after shutdown
when machines are still at a temperature nearly equal to their normal operating temperature.
To Measure misalignment, two methods are usually adopted.
They are:
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1)
Rim and Face method
2)
Reverse Indicator method
This method is a preferred alignment procedure when distance between the shaft end is less
than half of the coupling diameter. The procedure is explained in figure (22) and (23).
Step 1
Fix the alignment bracket to the coupling hub of the reference machine shaft
as shown in fig (IX) and set the two indicators to coupling hub of the second
machine one on the rim and second on the face.
Step 2
Rotate the reference shaft and second shaft by equal amount and record the
reading of both dial indicator at four points i.e. at 00, 90°, 180°& 270°. Make
sure that dial indicator reading is zero at top and after rotating the 180°, it
returns to zero.
Chech R1 + R3 = R2 + R4
and F1+ F3 = F2 + F4
Step 3
To know the corrections necessary for cold alignment, draw the alignment
graph as follows:
a)
Plot vertical line Rec. representing reference coupling face and plot
vertical line Seg representing second machine coupling hub at a
distance D = coupling Diameter from Re G. Plot Line FF and RF
representing front foot and Rear foot recording to actual distances
measured from second coupling hub face.
b)
To plot points RV, S V, R II and SII obtain values
RRV = R3/2
RRII = R2 -- R4
2
SSV = R3/2 + F3
SSH = (R2 -- R4)
+ (F2 -- F 4)
2
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Plot these points on the graph. Graph for vertical plane and horizontal
planes are drawn separately. Note that positions of these points on
graph i.e above or below zero offset line are decided by the sign of
these values (-ve or + ve) + ve values to the plotted below the zero
offset line and -ve values to be plotted above the zero offset line.
c)
Joint points RV and SV, and extend line RV SV to interest line FF and at
RF, Al and B1 respectively. Similarly joint the points RH and SH and
extend line RII SII to interest lines FF and RF at points A2 respectively.
d)
Similarly alignment graphs for AV BV and AII BII for planned (required)
reading can be obtained.
e)
Measure distances Vm Vn and Hm Hn as shown in map, which shows
the-amount by which second machine is to be shifted in vertical or
horizontal directions at front foot and rear foot respectively.
f)
Make adjustments at front foot and rear foot accordingly to the values
obtained in (e) to get second machine in required position in relation to
reference machine.
NOTE:
Alignment bracket can also be mounted on second shafts and dial indicator
set on reference shaft. In this case the values are:
RRV = R3/2
RRII = R4 - R2/2
SSV = R3/2 + F3 SSII
R4 -- R2
+ (F2 -- F 4)
2
REVERSE INDICATOR METHOD
“Reverse Indicator Method” is a preferred alignment procedure when distance
between shaft ends is greater than half the coupling diameter. This method is
explained in (X) and (XI).
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Step 1
Fix the alignment bracket to the hub of the reference machine and dial
indicator on the rim of the second machine coupling hub.
Step 2
Rotate the reference shaft and record dial indicator reading at four points.
Check sum of the side readings is equal to sum of the readings at the top and
bottom.
i.e B1+ B3 = B2 + B4
Step 3
Remove the alignment bracket and fix it to the coupling hub of the second
machine and set the dial indicator on the coupling hub of reference machine.
Step 4
Take readings, as per step 2
Check that A1 + A2 = A2 + A4
Step 5
To know the corrections necessary to be done for cold alignment, plot the
alignment map as described below:
a)
Plot axial position of coupling hub of reference machine i.e. ReG.
Draw the vertical line SeG representing second machine coupling
face. FF and RF according to distance obtained by measuring their
distance either physically or from drawing.
b)
Obtain values:
RRV =
A3
RRH
2
SSV =
B3/2
A3 -- A4
2
SSH
B3 -- B4
2
Plot these points on the graph. Maps for vertical and horizontal planes are
drawn separately. Note that position of these points on the graph is above or
below zero offset line are decided by sign (-ve or + ve) + ve values for RRV
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and RSII are plotted above the zero offset line but + ve values for SSV and
SSII are plotted zero offset line.
Step 6
Compare the maps with planned alignment graph and find values Vm Vn and
Hm Hn . The values are the amount of correction to be made at front foot or
rear foot in vertical or horizontal directions so that second machine can be
positioned in relation to reference machine in desired position.
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13. Grouting Of Machinery
Grouting is the process of pouring thin mortar (a cement, sand, and water mixture) around
and under the machine base after it has been wedged shimmed and aligned. Grout takes up
any unevenness in the concrete and equipment base and prevents shifting of the unit after it
is bolted tightly to the foundation. Now a days invariably for it is better qualities over
conventional cement, used in earlier days for grouting of rater TG - M/C.
Various types of grouts available in market can be classified as under:
i)
Grouts containing ordinary portland cement and an expanding agent like aluminum
power, which generates gas bubbles and compensate for shrinkage of the fresh
grout.
ii)
Grouts containing iron granules and a rust promoter like calcium chloride. These
grouts expand due to rusting of iron and the expansion takes place after the grout
has been set. (e.g. Ferro grout).
iii)
Grouts containing polymer resins, which give rise to high strength but no shrinkage.
iv)
Grouts based on calcium sulphoaluminates (e.g. shrinkomp). Such grouts contain
ordinary portland cement, a plasticizer to make the grout flow at a low water content,
gypsum and calcium aluminates. Usually the product is supplied as a ready to use
grout mix i.e. it contains sand and aggregates also, so that only water has to be
added at site.
NON SHRINK MORTAR
A non shrink mortar based on calcium sulpho-aluminates (CSA) has following advantages
over ordinary portland cement.
i)
Ordinary portland cement shrinks while drying up while as non shrink mortar expands
just enough to cancel the shrinkage of a hardened grout at seven days. This property
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is by virtue of the expanding agent added to make non shrink mortar. This property
ensures a positive grip while grouting bolt holes of machinery.
ii)
It has less tendency to separate from water added and therefore water does not
bleed to the surface. Thus, the contact between the top of grout surface and bottom
of machine base plate is ensured.
Before using non-shrink mortar we would ensure that it has been packed in air tight
polythene bags. Another important precaution is regarding storage and shelf life.
Non shrink mortar should generally be used within three to four months to get the best
results.
GROUTING PROCEDURE
Before the machinery is grouted into place, it is extremely important to ensure that it is
properly wedged and shimmed. It is advisable to check alignment of the equipment before
grouting.
a)
Cleaning & Surface Preparation: Concrete surface should be roughened, all
rubbish and unwanted materials should be removed. If the foundation is less than 28
days old, soak it in water for atleast 12 hours, before pouring grout. If it is older than
28 days, soak with water for at least 24 hours. The aim of wetting down the
foundation is to reduce the amount of water it can absorb from the grout giving a
solid bond between it and the bedplate of equipment.
b)
Framework and reinforcements: The hardened grout should not be allowed to
expand freely. If this is allowed, the grout will crack due to disruptive expansion. To
provide enough resistance against expansion, the formwork should be braced
against firm ground or other immovable surfaces. The entire formwork should be
implies for seven days. All reinforcements and metallic inserts should be checked
with respect to size, position, spacing and cover, so that they are positioned
accurately.
c)
Mixing and Placing: A mechanical mixer should be used. The quantity of water
should be measured in a calibrated bucket and only the amount of water specified by
the manufacturer should be added. To ensure maximum advantage the quantity of
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water should be commensurate with workability, compaction, and filling of the grout
in all corners and crevices. Mixing should be done for a minimum of three minutes to
obtain fluid grout of uniform consistency.
The grout should be placed with minimum possible delay and compacted either by
ramming manually or by light vibration incongested places. Compaction should be
stopped as soon as water begins to rise to the surface.
d)
Curing: Curing is of utmost importance in aerating. Soon after initial set, the exposed
surfaces should be covered with wet gunny bags and kept moist. Where external
restraint is provided in the form of formwork, the top opening and all stray openings
should be covered with wet sacks for at least seven days. The formwork should be
removed only seven days after grouting.
e)
Serviceability: Normally erection of machinery on the base plate can begin after
seven days of laying the grout, however, it is advisable to consult the design
engineer prior to loading the foundation.
IMPORTANT PRECAUTIONS TO ENSURE ADEQUATE BONDING
Due to carelessness following defects may occur in the grout:
1.
Lack of contact between, top surface of grout and the base plate.
2.
Crack in the grout.
Lack of contact with a large surface such as the base plate is revealed by a hollow sound
when the plate is struck by a hammer. This can be eliminated by following steps:
a)
Check whether the grout mix has been stored properly and has not exceeded its
shelf life.
b)
Review the placing conditions and check whether grout is of fluid consistency and
has been worked into place by tamping, rodding or vibration.
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c)
Check whether too much of water or too much of vibration has been used. In this
case, the bleed water would have risen to the surface, thereby giving rise to lack of
contact.
Crack in the grout can be detected readily only in a few cases. In a majority of the
cases their presence can only be suspected when the heavy machinery starts giving
vibration problems, at which time no remedial action can be taken. Therefore, the
grouting operation much be carried out to the best prescribed standards. On the few
occasions when the cracks are detected and reported, review the following points:
a)
Check whether the grout has been stored properly and that it has not
deteriorated due to storage.
b)
If the cracks are noticed at early stage, say within 24 hours or so, they may
be ascribed due to plastic shrinkage, the remedy is to cover the grout surface
with wet gunny bags till ponding is commenced after 24 hours.
c)
If the cracks appear after say 3 to 4 days or after still a longer period, the
reason may be either inadequate water or disruptive expansion.
Eliminate the possibility of inadequate water by ensuring thoroughly wetted
surfaces before grouting and by complete curing for seven days with water.
Eliminate the possibility of disruptive expansion by robust formwork with rigid
supports. If all the above possibilities are eliminated and still cracks are
observed the cause of cracking may be assigned to restrained drying
shrinkage. This occurs with ordinary cements and therefore, the grout mix
should be sent for testing to check whether it has enough expansion potential.
LIST OF MANUFACTURERS AND THEIR SPECIFICATIONS
1.
Associated Cement Companies Ltd.
Shrinkkomp - N
Shrinkkomp - H
2.
Fazroc Chemicals (P) Ltd.
Conbextra - GP1
Conbextra - GP2
3.
Ferrosite
Ferrogrout
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14. Erection, Alignment, Pre Commissioning &
Commissioning
ERECTION
We have dealt in depth about the erection procedures and precautions in other sections. So
we can briefly list out the important points to be taken care of in erection.
1.
Orientation and elevation of the foundation including that of the pockets.
2.
Defects of the foundation.
3.
Lifting procedure.
4.
Safety aspects.
5.
Erection sequences.
ALIGNMENT
We discuss here only the alignment of rotary equipments as comparatively aligning a static
equipment does not give much problems.
Temporary Alignment
The total train comprising the driver and the driven with intermediate speed reduction
devices are placed on foundation and temporarily levelled. After routing the pockets the
equipments are finally levelled and based frame grouted. If the driver is a motor, power
connection is given and its direction of speed and critical speed are checked.
If it power connection is given and its direction of speed and critical speed are checked. If it
is steam turbine as we have discussed in the other session, the rotor level, bearing
clearances, lateral movement of the rotor etc. are measured and compared to the protocol.
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Then the driver and the driven are aligned for paralled and angular offsets. Here the
manufacturer’s recommendations and guidelines are meticulously followed:
Final Alignment
After temporary alignment is completed the piping connections are made. The pipes are
supported properly and welded in position to avoid introduction of stress in the system. The
alignment is checked once again and the piping is modified if the alignment is found altered.
Some manufacturers recommend checking the bearing clearances once again.
PRE COMMISSIONING
Pre Commissioning activities can be broadly classified into
1.
Supporting of pipes.
2.
Hydro testing and flushing.
3.
Air blowing/Steam blowing.
4.
Cleaning the bearings and replacing seals.
5.
Oil flushing.
6.
Activating the auxiliary systems.
SUPPORTING
After the piping is completed, they are to supported at the specified points with the specific
type of support. An improper support will introduce stress in the train and will cause
vibration.
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HYDRO TESTING AND FLUSHING
Then the piping system is hydrotested to check the soundness of welds. After testing, the
pipes are flushed with chemically clean water to remove foreign particles.
1.
Air blowing/Steam blowing/De greasing/chemical cleaning
Some critical lines are blown with air or cardboard blasted to completely remove the
dust, welding slag etc. degreasing is done to remove oil and dust. Chemical cleaning
is done to remove seales, welding glass and other impurities. After that steam
blowing is carried out. Finally the blowing is done with a target plate to ascertain the
clean lines.
2.
Cleaning of bearing and replacing seals
Most of the times this activity is carried out during the final alignment stage. The
bearings are washed with diesel and oil and replaced. Temporary seals installed for
transportation purpose, if so, are replaced with permanent seals.
3.
Oil Flushing
The entire lub oil circuit is flushed with the lub oil or flushing oil. This is done in two
stages, the first without the bearings and the second with bearings.
a)
Primary Oil Flushing
The pipes supplying oil to the bearings are disconnected and temporary jump overs
are made. Oil is circulated for a determined time. The temperature of the oil is raised
to the working temperature or a point recommended by the manufacturer and ‘cold
shots’ are given. Temporary stainers are placed on the return lines and are cleaned
periodically.
b)
Secondary Flushing
Once the system is temporarily flushed, the jumpovers are removed and the oil
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circulated through the bearings. Temporary stainers are installed and cleaned
periodically during flushing.
4.
Activating the auxiliary systems
Following are main systems to be activated for the commissioning of an equipment.
1.
Lub oil system.
2.
Various trip systems.
3.
Condensing systems.
4.
Vaccum Pumps, if the driver is a steam turbine
5.
Gland steam condenser
COMMISSIONING
1.
Solorun of the driver
If the driver is motor it is energised and its critical speed, vibration and direction of
rotation are checked.
It is a steam turbine all the auxiliary systems are activated. Once everything is clear,
steam is taken in slowly and the turbine is rolled. Speed is gradually increased and
the performances of various tripping devices are checked.
After the solorun is successfully completed the alignment is checked once again and
required re alignment is done.
2.
No load running of the Machine
The driver is coupled to the driven and the machine is started slowly. Manufacturer’s
recommendation is followed while stepping the speed up.
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3.
Full load running
Then the equipment is run to full load and the performance is studied.
The following points are checked.
1.
Inlet and outlet pressure
2.
Lub oil temperature and pressure
3.
Vibration.
4.
Instrument out pressure.
5.
Speed.
1.
Over speed trip test
2.
Check the lateral critical speed
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3.
Plots showing vibration amplitude and phase angle versus speed for acceleration.
4.
1 percent below the trip speed (about 12818 rpm)
5.
Speed setting device test
6.
Maximum continuous speed running, speed governing device test
7.
Recording the vibration amplitude versus frequency.
8.
Noise level test
9.
Plots showing vibration amplitude and phase angle versus speed for deceleration.
10.
Operation test of T & T valve control valve and turning gear.
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15. Precautions To Be Taken During Erection
Alignment And Grouting
I.
ERECTION
1.
Lifting procedure should be finalised.
2.
All the lifting tackles should have the safe working capacity.
3.
Manufacturer’s recommendations should be strictly followed.
4.
Always the load lifted should be balanced and in level. Use of chain pulley blocks
where ever possible should be made to achieve this.
5.
Cranes should be used within their capacity and proper signals are to followed.
II.
ALIGNMENT
1.
Before erection, elevation of the foundation, orientation and various other aspects
like no. of bolts, height of the bolts above the foundation etc. should be checked.
2.
Foundation of equipments should be checked for any cracks, air pockets.
3.
All the alignment tools should be in good working condition.
4.
Technicians should be well trained in using these equipments.
5.
Packing plates or liners should be ground properly and there should be no gap
between two liners.
6.
Jack bolts should be of proper shape and molycote of grease should be applied
before grouting.
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III.
GROUTING
1.
The grouting area should be cleaned thoroughly to remove oil, great dust etc.
2.
Wetting should be done in case of cement mortar or non shrinking grout.
3.
When grouting pockets, the straightness of the bolts should be ensured.
4.
There should be no air pockets which will cause a phenomena called ‘spring foots.
5.
Proper curing should be done after grouting for a period of 7 days.
6.
In case of epoxy grouting the ratio of the mixture should be strictly adhered.
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16. M.W. Tools & Their Applications
MW tools are the precision instruments which we use for aligning various equipments. They
are manufactured with a great degree of accuracy so as to give a reliable performance. We
classify the tools under the following types depending upon their usage.
1.
Levelling Instruments
2.
Linear Measuring Instruments.
3.
Precision Instruments.
4.
Alignment tools.
5.
Hand tools for a M.W. Fitter.
6.
Overhauling/Commissioning tools.
7.
Others.
1)
LEVELLING INSTRUMENTS
As we saw earlier level of any equipment with respect to a standard and established
level is the primary criteria in alignment. We use a variety of instruments to achieve
this. Four types of levelling instruments are:
a)
Theodolite
b)
Transit level or Dumpy level
c)
Water tube manometer.
d)
Water level micrometer
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a)
Theodolite
Theodolite has got a telescope which can rotate about both the vertical and
horizontal axes and has scales to measure the amount of rotation. It is mounted on a
tripod and resting on three levelling srews
It is used for (1) establishing a straight line. (2) Finding the distance between two
points in the vertical and horizontal planes.
b)
h
=
Xxtan Q
h
=
Heigh of a building
X =
distance between the theodolite and the building
Q =
inclination of the telescope with horizontal axis.
Transit level or Dumpy level
It has got a telescope resting on three levelling screws and is mounted on tripod. It
has got only one axis of rotation viz vertical axis. It has got a scale with a vernier to
measure the angular movement of the telescope. This equipment is used to (1)
Compare two different levels (2) Transfer a level from one point to another.
c)
Water tube manometer
This is the simplest of all the instruments and so can be used by all. This is based on
the U-tube manometer principle that the level of a continuous liquid on the two arms
of an U tube will be the same. When using this one should ensure that there is no
trapped inside since this, will make the liquid (usually water) discontinuous.
d)
Water level micrometer (Sketch)
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1)
a)
INSTRUMENTS USED FOR LEVELLING ANY GIVEN AREA
Spirit level
It has got an air bubble trapped in spirit and it is mounted on a machined frame. The
bubble should be at the centre when the surface is perfectly horizontal. These are to
be calibrated periodically. The accuracy we can get with these levels are 0.2 to
0.5mm/m.
b)
Precision level or master level
The principle is same as that of the spirit level out the frame is machined to a much
greater accuracy. Using sophisticated machining techniques. Least count of these
instruments are 0.01 mm/ mtr. or 0.02 mm/m. They are made either in straight type or
box type to suit different places.
c)
Stright Edges
These are machined blocks and are used to compare levels. Normally they are used
in combination with precision levels.
d)
V-Blocks
Though V blocks may have other uses, we are mentioning here because they are
used with master level to measure the level of any cylindrical objects like shafts and
places where the master level can not be placed directly.
2)
LINER MEASURING INSTRUMENTS
Following are the liner measuring instruments which need no explanation.
1.
Steel rule.
2.
Measuring tapes.
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3.
Dividers.
3)
PRECISION INSTRUMENTS
a)
Vernier Caliper
In simple terms it is a steel scale with a movable vernier fixed on it. Nine divisions of
the main scale are divided into ten divisions on the vernier scale. Thus the least
count of the instrument is 0.1mm and the measurement is no of main scale divisions
+ 0.1 x No of vernier scale divisions which is coinciding with the main scale division.
The vernier has got a depth gauge also fixed to it.
b)
Micrometers (Inside and Outside)
As the names imply they are used to measure the inside and outside dimensions of
any two points or surfaces. In simple words the micrometers have long nut with a
screw moving inside where (pitch is 0.5mm). The head of the screw has got a vernier
scale with 50 divisions marked on it. When it completes two revolutions, it moves by
100 divisions, so the reading will be main scale divisions + 0.01 x No. of auxiliary
scale divisions. The least count of these instruments are 0.01 mm. Both the
instruments will have distance pieces suit various distances.
c)
Depth gauge/height gauge
This is similar in principle to the vernier calipers except that it is used to measure
depths or heights. The least count of this is 0.01mm.
d)
Thickness gauges
i.
Feeler gauges:
These are finely machined leaves with thicknesses ranging from 0.03 mm to
1mm. These leaves will be inserted in the gap to be measured and the value
is directly read from the inscription on the leaf
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ii.
Taper gauges:
These are used to measure comparatively longer gaps say 1 mm or more.
Distance is marked on an angular scale and the gap is read directly after
inserting it in the gap.
4)
ALIGNMENT TOOLS
a)
Dial gauges
Dial gauges are mainly used to detect the misalignment of the shafts in the parallel
and angular directions. In the dial gauges the linear movement of the plunger is
converted into circular movement of a needle by mechanical means. The pointer
moves on a scale divided into 100 divisions and is read directly. The sizes of the
dials and the position of the plunger with respect to the dial vary depending upon the
usage and requirement. L.C. of the dial gauges range from 0.01mm to 0.001mm.
b)
Alignment fixtures
When the coupling gap is less, we use either of the following fixture.
1.
Clamps.
2.
Fabricated pipe clamps.
3.
Magnetic Gauges.
If the distance between the coupling• hubs are high we use sturdy fixtures fabricated
from plates and structural members to avoid defection of the fixture.
5)
HAND TOOLS FOR A MW FITTER
A good MW fitter should be in possession of the following tools.
1.
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Steel tape.
96
6)
2.
Steel square - to check the squarness of two adjacent sides.
3.
Files - (Triangular, Flat, half round, round, needle files).
4.
Hammer - (Wooden mallet, Nylon hammers Copper rods).
5.
Marking Chalk.
6.
Shim cutter.
7.
Chisel.
8.
Set of spanners, slogging spanners.
9.
Set of allen keys.
10.
Screw driver.
11.
Pliers.
12.
Wrenches - pipe wrench adjustable wrench.
13.
Scriber, Scribing needle.
14.
Emery paper - (rough and smooth).
OVER-HAULING/COMMISSIONING TOOLS
Though these can not be strictly classified as MW tools they are very much required
while overhauling a machinery and when doing• commissioning activities.
1.
Scrappers - Flat, half round and triangular.
They are used to remove metal in very small thickness mainly from bearings.
2.
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Punches- Letter punch, number punch, hole punch & pin punch.
97
3.
Lapping tool, Lapping paste:
Lapping is a process of fine machining. Lapping paste made of abrasives like
silicon carbide is applied on the mating surface and lagged to remove minor
aberrations.
7)
4.
Carborandum stone (oil stone)
5.
Prussian blue.
6.
Cleaning agents, like carbon tetra chloride, Tri-Chloroethane, cleaning cloth.
OTHER TOOLS
Some of the tools are not classified under any of these headings and they are given
here.
1.
Pitch gauge
For measuring the pitch of the given thread.
2.
Surface Plate
For checking the level of any surface.
3.
Custom built tools
Like snpa ring plier, bearing pullers etc. They are made to satisfy any
particular need and are custom built.
CONCLUSION
This does not cover the entire range of tools available in the market. Researches are carried
out and every day and more and more new tools are manufactured to cater to the needs of
various industries.
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17. Effects Of Misalignment
A.
WHAT IS MISALIGNMENT?
When two or more equipments in a train do not come under co-liner axis in Hot
condition, the axis of each equipment lies away either parallely or angularly or in both
ways with respect to the other equipment. This condition is called misalignment.
B.
TYPES OF MISALIGNMENT
1.
Vertical misalignment
2.
Horizontal misalignment
Again, both can be subdivided into:
C.
1.
Parallel misalignment
2.
Angular misalignment
3.
Both parallel and Angular misalignment
NEED TO AVOID MISALIGNMENT
To have longer maintenance free, and smooth running of the equipments. Almost
60% of the breakdowns caused are because of misalignment.
D.
RESULTS OF MISALIGNMENT
1.
Vibration
2.
Coupling failure
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3.
Bearing failure
4.
Seal failure
5.
Shaft breakages.
CONSEQUENCES OF THE ABOVE SAID FAILURES
1.
Vibration
The equipment may have vibration due to misalignment, imbalance, surging, inlet
and outlet pr. and temperature differing from the design parameters, improper
bearing clearances, excessive Lub Oil, pr., oil whirls, loose bolts and. keys etc.
But each defect has its own characteristics and can be identified by the frequency of
vibration.
For example imbalance will cause vibration having a frequency equal to the rpm.
The frequency will be half on the rmp. if there exists oil whirls. Like wise the
misalignment, due to jammed coupling, bearing defects and bent shaft will give a
frequency range of two times that of the rpm.
The vibration will be transmitted through coupling to the connected equipments.
The vibration will cause the equipment to have other problems like bolt loosening,
fatigue of the shaft, etc. Which will result in the production loss.
2.
Coupling failure
A flexible coupling does not mean the coupling can accommodate the misalignment.
A misalignment would cause the membranes in these membrane coupling and
diaphgram in the diaphgram couplings to have more fatigue causing the failure of the
flexible members ultimately.
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A coupling failure may cause serious personnel injury as well a equipment damage
resulting in production loss etc.
3.
Bearing failure
The seating of the shaft of the bearings is disturbed due to misalignment and if the
shaft is not seated properly, the bearing will have excess load causing a rise in
temperature of the oil and the failure of the bearings.
4.
Seal failure
In the mechanical seal, the rotating seal carbon ring would be fixed in the shaft and
the stationary seal on the casing. Misalignment would cause uneven force in the seal
against the stationary seal and the rotating seal will go off quickly resulting reduction
of pumping fluid.
In the floating ring seal, the rings are assembled in close clearances with the shaft
enough to have the oil film to seal the gases.
The misalignment causes uneven or zero clearance in the floating ring resulting in
uneven oil films and rubbing. This causes the immediate failure of the seal.
5.
Shaft failure
Finally the misalignment subjects the shaft to uneven stress and torsional load.
There are cases where the shaft gets twisted out of shape due to the torsional load.
Following are the outcome of the misalignment.
1.
Damage to the equipments.
2.
Production loss due to shut down.
3.
Injury to workman and loss of life.
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18. An Introduction To Alignment Of Static
Equipments
Broadly speaking, equipments used in process plants can be categorised under two heads:
i)
Static
ii)
Rotary/moving machinery
STATATIC EQUIPMENTS
Static Equipments can be defined as the equipments which during their operation do not
transmit a dynamic load to the foundation e.g. Tanks, Heat Exchangers, Towers, Columns,
etc. Various steps for aligning such equipments can be summarised as under:
a)
Foundation Check
This check involves following steps:
i)
Checking of centre lines and marking the same
on foundation.
ii)
From a reference bench mark, transfer level on
to the foundation Compare this level with the
equipment level from the drawings.
iii)
Check number of bolts, their pitch circule
diameter and pitch. Check bolt height to ensure
that after erecting the equipment sufficient
thread length is available to tighten the nut.
iv)
Chip off foundation to make it rough. Adjust
shims and check level on shims with a dumpy
level. While using taper shims ensure that
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effective contact area is more than 2/3rd of the
entire contact area.
b)
Orientation checking
After the equipment has been successfully
erected,
its
orientation
with
foundation
is
checked. This check involves following steps:
i)
Select main nozzles on the equipment and find
out their orientation from the drawings.. From
the nozzle centre drop a plumb bob and match it
on the foundation.
ii)
Match a nozzle 900 to the above on with the
foundation.
Allowable
tolerances
for
orientation
are + or 5 mm max. on the plot plan.
c)
Verticality/Liveliness check
This check and the orientation check should
preferably be carried out simultaneously for a
faster and accurate results. This check involves
the following steps.
i)
Mark the punch marks on equipment with paints
at bottom and top of equipment on two axis-90°
apart.
ii)
Set theodolite in centre line with the axis being
checked.
iii)
Match cross lines of theodolite with punch mark
on equipment at top and by vertical axis
movement of theodolite match the bottom punch
mark. Note down the difference in verticality.
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iv)
Repeat above procedure for on 90 0 to above
axis.
v)
Level the equipment with taper shims to bring it
within acceptance limits.
Allowable limits for verticality are 0.5 mm/mtr. subject to a maximum of 10 mm.
Liveliness check is done for horizontally mounted equipments. This can be accomplished by
a dumpy level.
After the equipment has been aligned, tighten the anchor bolts (not very tight) and prepare
the foundation for grouting. Ensure that foundation is wetted thoroughly before grouting;
make a sound formwork and grout the foundation.
ROTARY/MOVING MACHINERY
It can be defined as the one which while operation transmits a dynamic load to the
foundation e.g. pumps, compressors, turbines, generators, etc. one of the biggest factors in
successful operation and maintenance of such machinery is the correct installation. Longer
life of the machinery is ensured by correct installation. Correct installation reduces the
vibrations considerably thereby fewer overhauls and repairs are needed.
Various steps for alignment of such equipments can be briefly summarised as under
i)
Foundation Checking
:
This is to be done in the same way as is done
for static equipments.
ii)
Orientation Checking
:
This is done on similar lines to static
equipments, e.g. in pumps orientation can be
checked, taking suction and delivery piping
flanges as reference.
Some equipments are supplied separately with base plates. For such equipments, align
base plate with foundation. Grout the pockets for anchor bolts with non shrink mortar. Erect
driver and driven on the base plate. Use shims (min. 2 mm) for aligning. Fix the driven parts
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as basic reference guide and check on the driver. The various checks on the couplings are
as under
a)
Angularity check
-
To check axial alignment
b)
Parallelism check
-
To check radial alignment
c)
Coupling gap
-
Check with an inside micrometers of
taper gauge.
In those rotary equipments, where a gear box is also mounted, check level on the machine
surface as recommended by supplier. Check bearing clearance with a feeler gauge.
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