METHOD STATEMENT
FOR FIELD ERECTION STORAGE TANKS
Owner
: CAZ (THAILAND) COMPANY LIMITED
Project Name
: COLD WATER GENERATION PLANT
PROJECT
Location
: MAPTAPHUT,THAILAND
CERTIFIED
1
4150001554-L-PC&KO-A-007
REV.
DOCUMENT NO.
PROJ.
DATE
MGR
DATE
6-May-14 OWNER
BY
CHK.
APPR.
DATE
PAGE 1 OF 21
DATE
CONTENTS
Page
1.
Scope………………………………………………
3
2.
Related Documents………………………………..
3
3.
Tank Erection Procedure………………………….
3
4.
Inspection Test Procedure ………………………..
8
5.
Nondestructive Examination (NDE)……………...
18
6.
Repairs of Weld……………………………………
19
7.
Hydrostatic Testing and Settlement Check………..
19
8.
Painting Inspection ……………………………….
19
9.
Tank Calibration………………………………….
19
10.
Submittal of Inspection and Test records…………
20
11.
Safety Precaution………………………………….
20
12.
Erection work –flow chart
22
13.
Appendix………………………………………….
23
1.
Scope
1.1
This method statement shall be applied for field erection of miscellaneous carbon
steel and stainless steel vertical storage tanks .
1.2
Items to be supplied
.ON
METI
NTITPMREMNO
EPRT
.IRTT
PTIAPEI
2. Related Documents
2.1
Applicable Codes and Standards
1)
API 650 11th Edition,2007 Add :
Welded Steel Tanks for Oil Storage.
2)
ASME II-2004 Part A
:
Ferrous Materials Specifications
3)
ASME II-2004 Part C
:
Specifications for Welding Rods, Electrodes
andFiller Metals
4)
ASME Section V-2004 Ed
:
Nondestructive Examination
5)
ASME VIII – Div. 1-2004 Ed.
:
Rules for Construction of Pressure Vessels
6)
ASME Section IX-2004 Ed.
:
Welding and Brazing Qualifications
3. Tank Erection Procedure
3.1 General Sequence of Work

The planned sequence of construction and completion involves the erection of
the vertical storage tanks in accordance with the approved construction
schedule.

Deliveries of pre-fabricated materials are scheduled to satisfy the erection
sequence and mobilization of manpower, equipment and facilities.
3.2 Foundation

Prior to tank erection activities, through its civil sub-contractor shall turn-over the
foundation to PC&KO.

The following items of foundation shall be checked prior to tank erection work.
a) Dimension, levelness and surface condition of the foundation.
b) Dimension, location and orientation of the anchor bolts.
c) Tolerance shall be in accordance with field and test procedure.
3.3 Erection Sequence

Lifting plan which also stated the number of workers involved shall be
submitted to prior to erection activities. Job Safety Analysis (JSA) must be
submitted and approved.

Designated area for the storage of pre-fabricated materials shall be approved.
3.3.1 Bottom and Annular Plates

Sequence of annular and bottom plate erection shall be as follows:
Lay-out of location  installation of annular plates inspection
prior to welding  welding of annular platesvisual inspection
RT on butt joint (shell location)  installation of bottom plates 
inspection prior to welding  welding of bottom plates  visual
inspection and vacuum box test on all welded joints
Note: The distribution of the final welding line shall be determined prior to bottom plate
arrangement.
1) Three plate laps shall be welded as shown in figure 1
KNOCK DOWN
Fig. 1
2) General welding sequence is as follows : (See Figure2)
1 1
Annular butt joint with
backing strip. *
2 2
1st course shell butt joint
3 3
4 4
Bottom to bottom
short side line
5 5
Bottom to bottom
long side line
Annular to shell
6 6
Annular to Bottom
Closing seam
Annular
Plate
FitupJig
(Typ)
Shell Plate
3
2 2
1 1
6 6
Backing Strip
Bottom Plate
4 4
5
5
Fig 2


Make sure the backing strip has tight and good contact with annular plate
before welding the annular joint.
In case of the tanks have internal painting coating , weld bead and plate
edges shall be ground smoothly.
3.3.2 Columns

Column location shall be inspected. Columns can be installed before or after
welding of bottom plates. Guy lines shall be installed on the column upon
installation.
3.3.3 Shell Plates

Sequence of shell plates erection shall be as follows:
Inspection of shell location  installation of first shell ring  fit-up of no.1
vertical seam  fit-up inspection and welding of no.1 vertical seam 
visual, and peaking check of shell first ringRT on first vertical seamfitup of corner weld seam  fit-up inspection and welding inside  oil test 
welding outsideroundness, levelness and plumbness inspection 
installation of second ring  fit-up of no.2 vertical seam  fit-up inspection
and welding of no.2 vertical seam  visual and peaking checkfit-up ring
no.1 and ring no.2 horizontal seam  fit-up inspection and welding 
visual and banding checkRT of weld seam ( the same procedure shall
be followed up to the last shell course )  installation and welding of top
angle  visual and plumbness check  installation and welding of wind
girders (if any) rafters, shell platform, nozzles, stairway and other
attachment
Note: Shell plates shall be erected completely during the day at each level
and guyed from the third ring due to the strong wind.

Prior to erection of the 1st course shell plate, following marking shall be performed on
the annular plate as shown in Figure 3.
1
The radius marking for shell plate erection shall be larger than
specified diameter in drawing considering the gap of vertical
joints.
2 2
The radius marking for checking roundness of shell plate.
3
The marking of vertical joints of the 1st course shell plate.
1
2
2
2
3 3
100
mm
Annular joint
Annular Plate
Fig 3
 The 1st course shell plate shall be erected on the annular plate, adjusting the
required gap and plate alignment of vertical joints.
 Level, roundness and verticality shall be checked before and after complete welding
the 1st course shell plate to annular plate. (See Figure 4)
Measure
1st Ring Shell Plate
3 2
Reference Marking
1 1
24 3
Plumb Bob
Annular
Plate
Bottom Plate
Fig 4
Level
Instrument
3.3.4 Manholes & Nozzles
 Sequence of manhole and nozzles shall be as follows:
Lay-out and inspection of manhole or nozzles  cutting of hole  fit-up of
pre-fabricated reinforcing pad plates, manhole or nozzles  fit-up
inspection and welding  visual and air leak test
3.3.5 Roof Plates
 Sequence of roof erection shall be as follows:
Inspection of roof location  installation of roof plates  fit-up and welding
of roof weld seam  vacuum box test  installation of roof nozzle, platform
and attachments
Note: For Dome Roof Tank, roof shall be ground assemble. After inspection,
roof shall be air raised on its final location.
3.3.6 Scaffolding (BS Standard)

During erection, the scaffolding shall be provided properly and inspected by
qualified personnel.
4. Inspection Test Procedure
4.1 Welding

Welding Procedure and Specification (WPS) and Procedure Qualification Record
(PQR) shall be prepared for approval. Welding operators and welders shall be
qualified prior to welding works.

The parts to be welded shall be clean, free of oil, grease, paint, rust and foreign
materials.

Before the start of welding, the surface must be free from slag, welding spatter or
defects. Undercut and cracks shall be completely removed before the succeeding
weld.

All joints shall be checked and inspected before start welding
4.2 Welding Qualification Test
4.2.1 Welding Procedure Qualification

The welding procedure specification shall be supported by the records of
procedure qualification test (PQR), that have been performed in accordance
with ASME Section IX. It shall be approved customer prior to
commencement of production welding.
4.2.2 Welder Performance Qualification

The welders who weld pressure parts and join non pressure parts, such as
all permanent and temporary clips and lugs, to pressure parts shall be
qualified in accordance with ASME Section IX.

The qualified welder list and welder’s previous qualification records shall be
submitted to the purchaser’s inspector for review prior to commencement of
any production welding work.

If a new qualification test for welders are to be taken, the welder performance
qualification test shall be performed in accordance with Section IX of ASME
Code.
4.3 Foundation Inspection

Prior to commencement of erection work, tank foundation shall be checked as
follows:
4.3.1 Cleanliness of foundation surface.

There shall be no steel scrap, concrete block or any other rubbish left on
the surface of the foundation.
4.3.2 Levelness of foundation

Measurements shall be taken at every 3.0 m of total circumference.
1) Where a sloping foundation is specified, the elevation differences about
the circumference shall be calculated from the specified high point.
Actual elevation differences about the circumference shall be determined
from the actual elevation of the specified high point, the actual elevation
difference shall not deviate from the calculated differences by more than
the following tolerances.
(a) Where a concrete ring wall is provided, ±3.0 mm in any 9 meter of
circumference and ±6.0 mm in the total circumference.
(b)
Where a concrete ring wall is not provided, ±3.0 mm in any 3 meter
of circumference and ±13 mm in the total circumference.
Measurements shall be taken at every 3 meter, minimum 8 points on
the circumferential length and at every 5 meter or minimum 2 points
on the radius axes of the tank as shown in Fig. 5 below.
0°
90°
270°
180°
Fig. 5
4.3.3
Orientation and Center Marks on the foundation surface
1)
The datum points of 0°,90°, 180° ,270° which are divided equally into four
parts shall be marked on the periphery of concrete ring wall as shown in Fig.
6 below, and shall be confirmed against the reference bench mark
established for civil work.
0
°
l
4
2
7
0
°
r
1
r
4
Check
point
l
1
r
2
r
3
l
3
9
0
°
l
2
1
8
0
° Fig. 6
 r1, r2, r3, r4, l 1, l 2, l 3, and l 4 to be measured.
2) Location of anchor bolts on the foundation (concrete ring wall) where anchor
bolts for tank are installed in foundation, the location of anchor bolts shall be
checked. The radius measured horizontally from the center of tank towards
anchor bolt shall be within ± 5 mm and also the spacing between the top of
anchor bolt and the top of anchor bolt shall be within ±5 mm. See Fig. 7 for
reference.

The elevation of anchor bolt shall be within –0, + 10 mm and the
verticality of anchor bolt shall be within ± 3.
0
°
d
r
2
7
0
°
9
0
°
1
8
Fig. 7
0
°
4.4
Material Identification
 The mill-marking or coded number of the plates stamped on the pressure retaining
parts such as shell plates, bottom plate, annular plates and compression ring plate
shall be checked before erection and recorded on as-built sketch just after
erection.
4.5 Dimension Inspection
4.5.1 Radius of bottom annular
 The radius of the bottom annular shall be measured at the middle of each
annular plate before welding, and it shall be within + 20 mm, -0 mm than
the specified radius.
4.5.2 Dimensional inspection of 1st course (before welding)
 Before commencement of welding for vertical joints of 1st course, the
following dimensional inspection shall be carried out and the tolerances for
1st course shell plate are as follows in table 1 below.
Table 1
Tank
diamete
r
(m)
<12
(1)
Plumbne
ss
(mm)
H/200
(2) Level (mm)
A*
±3
B **
± 6/13
(mm)
± 13
12 to < 45
H/200
±3
± 6/13
± 19
Note *
**
(3) Roundness
***
Differences in any 9 m for concrete ringwall and in any 3 m if concrete ringwall
is not provided.
Max. difference in total circumference. (6 mm for concrete ringwall and 13
mm if concrete ringwall is not provided.
***
Difference from the reference marking in radius.
1) Levelness
 After erection of the lowest shell course, the levelness of the shell shall
be measured at the center of each shell plate, the top of the lowest
shell course shall be within tolerance in paragraph 6.2. See Fig. 8 for
reference.
S
c
Shell
Plate
Marking
For measurement
A
Bottom plate
Fig. 8
2) Plumbness
 After welding of the lowest and the last number shell courses, the
plumbness of the tank shell shall be measured at eight points which
are equally divided at 0°, 45°, 90° to 315° in the circumference of tank,
and the maximum out-of-plumb of the top of the shell relative to the
bottom of the shell shall not exceed 1/200 of the total height before
commencement of welding and after completion of welding. See Fig.
9 for reference
A
(TOP)
Shell
Plate
B
(Bottom)
Plumb
bob
30
0
Bottom
Plate
Fig. 9
3)
Roundness
 After welding of the lowest shell course, radii of the tank shall be
measured at the same positions as levelness and 300 mm above the
bottom corner, it shall not exceed the following tolerances after corner
welding. See table 2 and Fig. 10 for reference.
Table 2
Tank Diameter (m)
Radius tolerance (mm)
<12
±13
From 12 to < 45
± 19
Reference mark
For measurement
Shell
Plate
Measuring value
30
0
Bottom
Plate
Fig. 10
4.5.3
Local deviations after completion of vertical & horizontal welding.


Local deviations from the design shape of the shell shall be measured by
using sweep board 900 mm long.
Peaking at vertical weld joints and banding at horizontal weld joints shall
not exceed ±13 mm. See Fig. 11 for reference
Banding
Peaking
Check point (inside view)
Fig. 11
4.5.4
Nozzle, manhole, draw off sump and other attachments

Before cutting the opening of nozzle and manhole, orientation & elevation
of them shall be checked with the latest revision drawing.

The nozzle, manhole, draw off sump and other attachments of the tank shall
be within the following allowable tolerance after completion of welding. See
Table 3 for reference.
1) Nozzle, manhole and draw off sump ;
Table 3
Tolerance, mm
Draw off sump,
Items
Nozzle
manhole
Elevation from bottom : A
Orientation from reference centerline :
B
± 9.5
± 9.5
±5.0
±25.4
Projection : C
-0, +5
-0, +10
± ½° or 2.0, (*1)
±1°
Max. 1.5
-
Inclination of flange face : D
Rotational orientation of bolt hole
Distance from roof or bottom center to
nozzle, manhole and draw off sump :
F
Note (*1) : Whichever is greater.
± 9.5
± 9.5
2) Clips or similar structural attachment for platform, ladder or pipe support. See
table 4 and Fig. 12A and 12B for reference
Table 4
Items
Tolerance, mm
Location from support
Orientation from reference
centerline
± 9.5
± 14.3
F
C
B
C
F
D
A
B
Fig. 12A
Fig. 12B
3) Verticality of gauge well (gauge pole)

If the roof will be provided with gauge well that complies with the design, the
verticality of each gauge well shall be checked and shall not exceed the
tolerance of instrument manufacturer specified in the purchaser order.
4.6 Fit-up Inspection

The surface of joints to be welded shall be free from rust, scale and any foreign
material which may be harmful to weld properties within at least 13 mm from the
joint.

Tolerance for misalignment of plates of butt welded joint plates to be joined by butt
welding shall be fitted property and shall be maintained in position during the
welding operation.
4.6.1 Misalignment of the center line of the plates shall not exceed the following.
1) Misalignment in completed vertical joints for plate thickness greater than
16.0 mm thick shall not exceed 10% of the plate thickness or 3.2 mm,
whichever is less ; misalignment for plates less than or equal to 16 mm thick
shall not exceed 1.5 mm.
2) In completed horizontal butt joints, the upper plate shall not project beyond
the face of the lower plate at any point by more than 20% of the thickness of
the upper plate, with a maximum projection of 3.0 mm. ; however, for upper
plates less than 8.0 mm thick, the maximum projection shall be limited to 1.5
mm.
3)
See Fig. 13 for reference.
UPPER
PLATE
LOWER
PLATE
Fig. 13
4.6.2 Unless the configuration and dimension of the joints are specified in the drawing
or welding procedure specification (WPS), they shall be prepared as shown in
Fig. 14.
Fig. 14
Note: 1. Back gouged second side and welded except horizontal joints welded by SAW
process.
2. Applicable only for annular to annular plate joints (Not applicable for shell
joints.
3. Back chipped surfaces shall be inspected by visually, and shall be free from
any visible defects. In case of any doubt of the inspector during visual
inspection, further grinding or PT will be carried out to identify defect.
4.7 Welding Control

Welding control shall be performed in accordance with “Welding Procedure
Specification”.
4.8 Visual Inspection
4.8.1 All welds shall be visually inspected and meet the following requirements.
4.8.2 All welds shall be free from crack, overlap, spatter, slag and other deleterious
defects.
4.8.3 Undercutting
 The edges of all welds shall merge smoothly with the surface of the plate
without a sharp angle. For vertical butt joints, the maximum acceptable
undercutting is 0.4 mm of the base metal. For horizontal butt joints,
undercutting not exceeding 0.4 mm in depth is acceptable. For welds that
attach nozzles, manholes, cleanout openings, and permanent attachments,
undercutting shall not exceed 0.4 mm.
4.8.4 The frequency of surface porosity in the weld shall not exceed one cluster (one
or more pores) in any 100 mm of length and the diameter of each cluster shall
not exceed 2.5 mm. Surface defects shall be removed.
4.8.5 The height of weld reinforcement in all butt joints on each side of the plate shall
not exceed the following as shown in table 5.
Table 5
Max. height of
reinforcement, mm
Vertical
Horizont
joint
al joint
Plate thickness, mm
Up to13, incl.
2.5
3.0
4.8.6 The size of each shell-to-bottom fillet weld shall not be more than 12.7 mm and
shall not be less than the nominal thickness of the thinner of the two plates joined
(that is, the shell plate or the annular plate immediately under the shell) or less
than the following values as shown in table 6.
Table 6
Nominal thickness (T) of shell plate,
mm
5
> 5 - 20
Minimum size of fillet weld,
mm
5.0
6.0
4.8.7 The roof shall not have dimples that will permit accumulation of water.
5. Nondestructive Examination (NDE)
 The extent of NDE as shown in table 7 below shall be carried out in accordance with
the NDE procedure
Table 7
1. Shell to Shell (CS/ES)
Weld
Type
Butt
Applied Exam.
Type
Degree
RT
Per API 650
3. Shell to Bottom (CS/ES)
Fillet
PT
Per API 650
4. Annular Butt joints (CS/ES)
Butt
PT
Per API 650
5. Bottom to Bottom /Annular (CS/ES)
Lap
VBT
Per API 650
Lap
VBT
Fillet
LT / PT
Butt
PT
No.
6.
Welds of
Roof to Roof /Compression Ring/Top
Angle
Nozzle neck to Shell including pad
7.
plate (CS/ES)
8.
Flange to manhole / nozzle neck
Manhole /Nozzle neck to shell / roof
9.
/reinf. pad
10.
Tee/Fille
t
Other (Shell, Bottom, Roof)
Attachment
Fillet
PT /LT
PT
Per API 650
Per API 650
Per API 650
Per API 650
Per API 650
Abbreviation
RT
VBT
PT
LT
:
:
:
:
Radiographic examination
Vacuum box test
Liquid Penetrant Examination
Air leakage test
6. Repairs of Weld
 When defect appears to be removed, repair welds shall be made in accordance with
approved welding procedure specification, and repaired area shall be re-examined
by the same method originally taken.
7. Hydrostatic Testing and Settlement Check

The hydrostatic testing and settlement checking of the tank shall be taken in
accordance with the approved hydrostatic test procedure.
8. Painting Inspection

Painting Inspection requirement is as follows
1) The brand name and Munsel no. of Paint to be applied shall be checked.
2) No painting operation shall be done in the following weather condition of the
working area.
(a)
(b)
(c)
(d)
(e)
Rain, fog, mist
Relative Humidity is greater than 85%
Dust effects adversely due to high wind
Ambient temperature below 5°C above dew point
Metal Surface temperature is less than 3°C above dew point.
3) At each step of painting work, number and dry film thickness of coats shall be
confirmed whether it meets the required thickness in the painting procedure. At
least one spot of dry film thickness (DFT) shall be checked in every 9.0 square
meter area approximately.
4) Drying time and dryness of previous paint shall be checked by touching with
fingertip and by the manufacturer’s instruction before subsequent coating.
5) The film shall be visually inspected for defects such as in adequate curing, runs
and lack of adhesion.
6) After completion of painting work, the final color shall be visually checked with the
standard of color, whether it meets the specification one.
9. Tank Calibration
 Calibration by third party.
10. Submittal of Inspection and Test Records
 The results of inspection and test shall be properly recorded and shall be submitted
to the purchaser inspector for review and signature immediately after the inspection
and or test.
 The following inspection and test records shall be submitted to the purchaser after
completion of final inspection.
(1)
Letter of acceptance
(2)
Material identification record
(3)
Foundation inspection record
(4)
Dimensional inspection record
(5)
Nondestructive examination report
(6)
Hydrostatic test record
(7)
Settlement check record
(8)
Painting inspection record
(9)
Photograph or rubbing of name plate
11. Safety Precaution
 All the personnel and work activities involved in the construction, painting and
testing of the tanks shall be governed by project safety requirements.
11.1
Requirements of confined space
 The following requirements shall be followed when entering confined
space.
1)
2)
3)
4)
Apply for the confined space entry permit.
Conduct risk and hazard assessment and personnel training.
Test the air before entering confined space.
Designate watch men inside and outside prior to the entrance to
confined space.
5) Conduct pass-in and pass-out signing system. The construction
person shall sign his name before and after entering confined
space.
6) Possess operable emergency plans and schedules.
7) Erection method install course by piece.
Fig. 15
12. Erection Work-Flow Chart
FOUNDATION
CHECK
ANNULAR PLATE
LAY DOWN / WELD
FORM
ITP
BOTTOM PLATE
LAY DOWN /
WELD
FORM ITP
FORM ITP
PEAKING
CHECK
PEAKING
CHECK
1-st COURSE
INSTALL
ROUNDNESS
CHECK
FORM ITP
1-st COURSE
1-st COURSE
VERT-WELD
PLUMNESS
CHECK
FORM ITP
2ndPLUMNESS
COURSE
INSTALL
PLUMNESS
CHECK
FORM ITP
2nd COURSE
VERT-WELD
3nd COURSE
INSTALL
FORM ITP
PEAKING
CHECK
PEAKING
CHECK
PEAKING
CHECK
PLUMNESS
CHECK
FORM ITP
PLUMNESS
CHECK
FORM ITP
PLUMNESS
CHECK
FORM ITP
4th COURSE
VERT-WELD
5th COURSE
INSTALL
FORM ITP
FORM ITP
3nd COURS
VERT-WELD
4th COURSE
INSTALL
FORM ITP
PLUMNESS
CHECK
5th COURSE
VERT-WELD
6th COURSE
INSTALL
PLUMNESS
CHECK
FORM ITP
PEAKING
CHECK
6th COURSE
VERT-WELD
7th COURSE
INSTALL
FORM ITP
PEAKING
CHECK
PLUMNESS
CHECK
FORM ITP
7th COURSE
VERT-WELD
1-st TO 2-nd COURSE
PLUMNESS CHECK
FORM ITP
1-st TO 2-nd COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
3nd COURSE
INSTALL
PLUMNESS
CHECK
FORM ITP
2-st TO 2-nd COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
4th COURSE
INSTALL
PLUMNESS
CHECK
FORM ITP
3nd TO 4th COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
PLUMNESS
CHECK
FORM ITP
5th COURSE
INSTALL
4th TO 5th COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
6th COURSE
INSTALL
PLUMNESS
CHECK
FORM ITP
5th TO 6th COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
BENDING
CHECK
7th COURSE
INSTALL
PLUMNESS
CHECK
6th TO 7th COURSE
HORIZ-WELD
BENDING
CHECK
FORM ITP
PEAKING
CHECK
TOP COURSE
INSTALL& WELD
FORM ITP
PEAKING
CHECK
TEMP.CENTER
COLUMN
FORM ITP
AIR LEAK TEST
FORM ITP
FORM ITP
TOP COURSE
VERT-WELD
ROOF PLATE SECMENTS
INSTALL AND WELD
FORM ITP
BOTTOM
VACCUMN TEST
FORM ITP
PT SHELL TO
BOTTOM
FORM
ITP
FINAL
INPECTION
PAINTING
HYDRO
TEST
FORM ITP
CHECK FOUND
SETTELMENT
FORM ITP
Appendix 1
Table A : Permissible variations from flatness for carbon steel plates
Permissible variations from a flat surface for specified widths (W), mm
Specified
Thickness
(T), mm
1524 < W <
1829
1829 < W < 2134
2134 < W <
2438
2438 < W <
2743
6.4 < T < 9.5
23.8
28.6
31.8
34.9
9.5 < T < 12.7
12.7 < T
<19.1
19.1 < T <
25.4
25.4 < T <
50.8
15.9
19.1
22.2
25.4
15.9
15.9
19.1
25.4
15.9
15.9
15.9
19.1
14.3
14.3
15.9
15.9
Note :
1)
Flatness variations for length - the longer dimension specified is considered the
length, and permissible variations in flatness along the length should not exceed the
tabular amount for the specified width in plates up to 3658 mm (12 ft) in length, or in
any 3658 mm (12 ft) of longer plates.
2)
Flatness variations for width - the flatness variations across the width should not
exceed the tabular amount for the specified width.
Table B : Permissible variations in waviness for plates
Flatness
tolerance
mm
14.3
15.9
19.1
22.2
23.8
25.4
28.6
31.8
34.9
Waviness tolerances, when number of waves in 3658 (12 ft) is, mm
1
2
3
4
5
6
7
14.3
15.9
19.1
22.
2
23.
8
25.4
28.6
31.8
34.9
11.1
12.7
14.3
17.5
7.9
9.5
11.1
12.7
6.4
6.4
7.9
9.5
4.8
4.8
6.4
6.4
3.2
3.2
4.8
4.8
3.2
3.2
3.2
3.2
17.5
12.7
9.5
7.9
6.4
4.8
19.1
22.2
23.8
27.0
14.3
15.9
17.5
19.1
11.1
12.7
12.7
14.3
7.9
9.5
9.5
11.1
6.4
6.4
7.9
7.9
4.8
4.8
6.4
6.4
Note : The waviness tolerance is a function of the flatness tolerance as obtained from
table A as appropriate.
5. ASSEMBLY OF THE BOTTOM
The bottom plates have been arranged and laid down in the longitudinal direction these
shall be left free to prevent distortion, They shall be temporary fitted with dog plate. Before
start welding the distortion-restraint jigs and reinforce channel shall be installed in order to
minimize field work shop assembly of bottom plates might be trial fitted and welded some
pieces together accept the annular plate. The vacuum test shall be done when complete
weld at site.
6.ASSEMBLY AND WELDING OF THE TANK SHELL PLATE
6.1) Assembly of the first shell course.
6.1.1 The horizontality of the drawn circle line will be measured by using the
Y-.Level and be adjusted properly, if necessary to get a correct level.
6.1.2 Tank shell plates will be fitted on circle line with each other using
Strong back, key plate, spacer and key wedge.
6.1.3 Adjust the aberration of rolling curve of the tank inside and outside
Based on the drawn line by the piece wedge. The drawn circle line
Shall be concentric having the radius of the tank age designed radius
Added with shrinkage allowance due to welding on the well vertical
Joints. Do not tack weld the tank shell to the tank bottom.
R=RC + 3N/2 ¶
R: Inside wall radius for erection
(Actual marking line on the bottom plates )
RC: Designed inside radius (After completion)
N: Number of vertical joints.
3. shrinkage rate (mm.) of each joint
6.1.4 Plate to be jointed by butt welding shall be matched accurately and
Retained in position during the welding operation.
Misalignment in completed vertical joints shall not exceed 10 percent
Of the plate thickness, or 1.6 mm which is larger
( refer AP1 650 SEC.PAR.5.2.3.1)
6.1.5 Incomplete horizontal butt joints. The difference between the center
Line of the upper and lower plates shall not exceed 20% the
Thickness of the upper plate. With a maximum allowance of 1/8 inch
Except that projection of 1.6 mm is except for upper plate than 8 mm
Thick. (PREFER API 650 SCE. 5 PAR.5.2.3.2)
6.1.6 After completed installation of the tank shell first course.
The horizontal and the vertical will be measured at topedge of the
Course. The second course will be arranged and installed only after
The adjustment of the horizontality and the verticality of the
First course is completed.
6.2) Assembly and installation of the remaining shell courses.
6.2.1 Welding and installation of the second course shall follow the same
Sequence as for the first shell course, After the vertical welding joints
Are completely welded the second shell course to the first shell course
6.2.3 The assembly, setting and installation of the third course of the tank
Shell will be carried out after the horizontal welding of the second
Course is completed.
6.2.4 The assembly, setting and installation of the remaining course will
Follow in row only after the horizontal welding of the immediate lower
Course is totally finished.
6.3) Dimensional tolerances
6.3.1 The maximum out of plumpness of the the shell relative to the Bottom
Of the shell shall not exceed 1/200 of the tank height.refer: API 650
SEC.5 PARA 5.5.1)
6.3.2 The out of plumpness in any single shell not exceed 6.4mm
6.3.3 Radius measured at 1 foot above the bottom corner
Weld shall not exceed the following tolerances.
Diameter range
0 TO 12m Exclusive
12 TO 45m Exclusive
Radius tolerance
±1/2 Inch (13m)
±1/2 Inch (13m)
(REFER:API 650 SEC. 5 PARA 5.5.2)
7. WELDING
Welding shall be performed manually by certify welder in accordance with the
Welding procedure specification. Welding shall be performed in such a manner
As to ensure complete fusion with base metal.
7.1) Commentary of welding
7.1.1 The back chipping will be carried out on the inside after welding from the
Outside the back chipping will be carried out by grinding method.
7.1.2 The thickness of the the reinforcement of the welds on all butt on each
Side of the plate shall not exceed the following thickness.
Plate thickness: maximum thickness of reinforcement
(Inch)
Vertical Joints
Horizontal Joints
Up to ½ Inclusive
….3/32 (2.5mm)
1/8 (mm)
3.2 mm
4.8 mm
Over ½
(Refer: API 650 SEC.5 PARA.5.2.1.5)
7.2) Repair Welding.
When any defects in welder parts will be found by radiographic
Inspection, visual and other tests. Defects shall be repaired by
Chipping or required and rewarding with welding procedure
7.3) Radiographic examination
7.3.1 Radiographic examination method shall be in accordance with
The same boiler and pressure vessel code. Section V. “NON
Destructive Examination” Article2.
7.3.2 The radiography examination will be carried out on API 650
The same time after welding of shell joints.
8.WELDING SEQUENCE OF 1st COURSE AND BOTTOM
.
Fig-5
9. WELDING SEQUENCE OF BOTTOM PLATES
Fig-6
NOTE: START WELD FROM CENTER PLATE.
10 ASSEMBLY AND WELDING OF DOME ROOF, SELF SUPPORT CONE ROOF.
Roof plates shall be assembled at shop on the jig with or without nozzle manhole
Attached. All plates shall be fitted to a completed unit. Then by a partial welding,
Roof Plates shall be separated to suitable segments for transportation and site
Erection.