VGB-Standard
Recommendations for the
Inspection and Overhaul
of Steam Turbines
VGB-S-115-00-2016-01-EN
(formerly VGB-R 115)
Publisher:
VGB PowerTech e.V.
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VGB-S-115-00-2016-01-EN
Preface to the third edition
After many years of favourable experience in the use of VGB Guideline VGB-R 115,
a revision became necessary on the occasion of the transposition of the Guideline
into a VGB-Standard, especially due to the changed framework conditions on the
energy market.
The necessity and usefulness of inspections and overhauls of steam turbine plants is
undisputed. Based on long-term experience, the most diverse strategies have been
developed and criteria used during recent years for optimal scheduling of turbine
inspections and to minimize the time required for the implementation of inspections
and overhauls. The efforts of turbine owners therefore focus on achieving optimum
performance with the objective of lengthening the intervals between required
inspections and overhauls. The recommendations for the inspection and overhaul of
steam turbines provided in this standard cover a variety of different aspects.
Essen, January 2016
VGB PowerTech e.V.
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Authors
The following contributors were involved in the transposition of the former VGBGuideline into a VGB-Standard:
Dipl.-Ing. Klaus Blomeier, VGB PowerTech e.V.
Dipl.-Ing. Dipl.-Wirtsch.-Ing. Hans-Günter Busch, HDI Global SE
Wolfgang Daum, VGB PowerTech e.V.
Dipl.-Ing. Albert Harrer, Harrer Turbine Consult
Dipl.-Ing. Heiko Höhne, Uniper Kraftwerke GmbH
Dipl.-Ing. Peter Richter, VGB PowerTech e.V.
Dipl.-Ing. Thomas-Michael Scholbrock, BASF SE
Dipl.-Ing. Hartmut Strangfeld, RWE Power AG
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Contents
1
1.1
1.2
Introduction ............................................................................................... 6
Object ......................................................................................................... 6
Scope ......................................................................................................... 6
2
2.1
2.2
Basic considerations for the inspection and overhaul of steam ............
turbines ..................................................................................................... 7
Theoretical considerations in scheduling inspections and overhauls .......... 7
Practical considerations in scheduling inspections and overhauls .............. 9
3
3.1
3.2
3.3
Types of inspections and overhauls ..................................................... 10
Minor overhaul or inspection ..................................................................... 10
Intermediate overhaul ............................................................................... 10
Major overhaul .......................................................................................... 11
4
Inspection and overhaul considerations .............................................. 12
5
5.1
5.4
5.5
5.6
Scheduling inspections and overhauls ................................................ 14
Initial service period (< 25,000 EOH), until minor overhaul/inspection ..........
(see 3.1) ................................................................................................... 16
Second service period (between 25,000 and 50,000 EOH), .........................
until intermediate overhaul (see 3.2)......................................................... 16
Third service period, until major overhaul (between 50,000 and ..................
100,000 EOH) (see 3.3)............................................................................ 16
Unplanned inspections and overhauls due to irregularities ....................... 16
Unplanned inspections and overhauls due to damage ............................. 17
Summary .................................................................................................. 18
6
6.1
6.2
6.3
Planning for inspections and overhauls ............................................... 19
Spare parts planning................................................................................. 19
Planning for intermediate and major overhauls ........................................ 19
Marginal conditions for implementing inspections and overhauls ............. 21
7
Tests and inspections during overhauls .............................................. 23
8
8.1
8.2
8.2.1
8.2.2
Results of overhaul, conclusions.......................................................... 27
Documentation.......................................................................................... 27
Conclusions drawn from overhauling results ............................................ 29
Conclusions for further operation .............................................................. 29
Conclusions for next inspection/overhaul ................................................. 29
9
Literature ................................................................................................. 30
10
Appendix ................................................................................................. 34
5.2
5.3
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1
Introduction
1.1
Object
Steam turbine plants are used in industry and in utility power plants in various ways
to generate electrical energy, to drive compressors and pumps, and to provide costeffective heating or process steam at various pressure levels.
The turbine design data are determined by the specific requirements and needs of
the different user groups. This means that the steam turbines have to be adapted to
the process conditions of each specific application and that a differentiated approach
to maintenance has to be adopted accordingly.
The prevailing economic boundary conditions of steam and electricity generation
make great demands on the thermal efficiency and on the availability and reliability of
steam turbine plants.
In the past, an inspection and overhaul strategy tailored to the specific plant has
proved to be an important tool for ensuring optimal and reliable operation. To permit
an overall assessment of the condition of steam turbines and their auxiliaries, a factfinding inspection after opening of plant components is required in addition to the
usual monitoring routines, inspections and additional measurements.
These recommendations provide guidelines for scheduling inspections and
overhauls, taking into account the type of turbine, the design, the monitoring and
diagnostic equipment, the operation regime, the duty and the age of the unit.
1.2
Scope
These recommendations apply to:
 utility superheated steam turbines,
 utility saturated steam turbines,
 industrial steam turbines,
 steam turbines in refuse / RDF incineration plants and biomass fired plants,
 steam turbines for mechanical drives
and their ancillary and auxiliary systems, such as gear units, condensers and oil
supply systems.
Generators are covered by VGB Guideline VGB-R 167.
The present standard does not cover instrumentation and control systems, for which
other considerations apply.
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2
Basic considerations for the inspection and overhaul of
steam turbines
Inspections and overhauls are necessary in order to maintain steam turbines. Their
purpose is to
 maintain/improve safety, availability and economic efficiency during the
forthcoming service period,
 determine the present condition of the unit,
 detect and avert impending failures,
 eliminate defects,
 refurbish worn parts,
 obtain information for assessing the remaining life and thus indications of future
inspection and overhaul requirements, and
 enable improvements and upgrading measures.
2.1
Theoretical considerations in scheduling inspections and overhauls
A turbine is a system consisting of numerous parts. Even if the reliability of the
individual components is relatively high, the probability of a failure of the complete
system increases with the number of component parts, a significant factor being the
number of operating hours. An increased number of starts and shutdowns, and lowload operation, can cause component stresses that are different from those faced in
the past, which likewise have an impact on the inspection/overhaul date.
The service time of a steam turbine unit can be divided into three phases:
Phase 1:
Initial service period: at its end, minor inspections/overhauls will
typically be carried out.
Phase 2:
Second service period: at its end, an intermediate inspection/overhaul
will be carried out, with mainly foreseeable maintenance requirements,
for instance due to wear and tear of highly stressed components such
as valves, and control and safety equipment.
Phase 3:
Main service period
The main service period is the period from commencement of initial
commissioning until the first major inspection/overhaul, or the period
between two major inspections/overhauls, as the case may be.
These service periods can be graphically represented in a kind of bathtub curve, as
shown in Figure 1.
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Time-independent influences are predominant in the left-hand part of Figure 1 while
time-dependent influences prevail in the right-hand part. Time-independent
influences can recur after each overhaul.
Fig. 1.
Failure probability of a unit as a function of its operating hours.
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2.2
Practical considerations in scheduling inspections and overhauls
For the scheduling of inspections and overhauls a time-based approach or a
condition-based approach can be adopted. For the latter, it must be possible to
assess the condition of the turbine generator.
In scheduling inspections and overhauls, two factors are significant:
a)
Time-independent influences, such as:

deficiencies related to planning, design, calculation and/or construction,

faults during manufacturing, installation and/or repair,

material defects or confusion of materials (quality assurance),

damage,

faulty operation and faulty maintenance.
Time-independent influences are frequently due to human failures. They depend on
the knowledge, skill, experience and diligence of the manufacturers and owners. It is
known from experience that these influences mainly have effects during the initial
service period after first installation and must in some cases also be anticipated after
inspections and overhauls.
b)
Time-dependent influences, such as:

wear and tear, corrosion and erosion damage, deformation,

changes in the blading,

life expenditure, relaxation,

starting and load spectra,

deposits of any kind, including consequential damage,

poor maintenance,

experience with comparable units.
Time-dependent influences are due to stresses experienced by individual
components in relation to the design levels during the service life of the unit,
especially as a result of start-up and shutdown procedures, load changes and special
modes of operation or operation at off-nominal conditions. Frequent starts and
shutdowns and more frequent low-load operation need to be considered in particular.
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3
Types of inspections and overhauls
DIN 31051 and DIN EN 13306 define and distinguish between maintenance
measures as follows:
Servicing: Measures for maintaining the function and for delaying the consumption of
the existing wear reserve.
Inspection: Measures for determining and assessing the actual condition, including
determination of the cause of wear and derivation of necessary measures.
Repair: Measures performed to restore the function.
On the basis of the DIN standard, the present standard defines the types of
inspections and overhauls as follows:
 Minor overhaul or inspection
 Intermediate overhaul
 Major overhaul
Note: Servicing measures are carried out continuously.
The safety equipment covered by VGB-R 103, “Guideline for monitoring, limiting and
protection devices on steam turbine plants” is to be given special consideration.
3.1
Minor overhaul or inspection
A “minor overhaul” should be performed as necessary during an outage caused by
other plant components or during a failure-induced or planned outage of the unit. In
the case of new plants, it is useful to also carry out a minor overhaul prior to expiry of
the warranty period.
The primary objective is to prevent forced outages by systematic inspection. No
casing parts are opened. Information can be obtained for an “intermediate overhaul”
or a “major overhaul” (for scope of work, see Sheets 1 and 2 of Appendix 1).
3.2
Intermediate overhaul
An “intermediate overhaul” is performed during a planned outage of the unit. If
required, a turbine section and/or major turbine components, such as valves,
bearings or couplings, are opened and overhauled; in addition, other parts of the unit
can be subjected to boroscopic inspection. The measures taken also focus on smallscale repair work in the surroundings of the steam turbine installation.
Intermediate overhauls also serve to obtain detailed information for the next “major
overhaul” (for scope of work, see Sheets 1 and 2 of Appendix 1).
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3.3
Major overhaul
A “major overhaul” is performed during a planned outage of the turbine generator and
allows thorough checking and a fact-finding inspection and repair of all components.
Within the scope of a major overhaul, the casings are opened.
The duration of the outage depends on the rating and design of the turbine
generator, the scope of restoration work and the number of staff assigned (for scope
of work, see Sheets 1 and 2 of Appendix 1).
An event of failure or damage can be used to bring forward an upcoming overhaul,
see section 5.5.
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4
Inspection and overhaul considerations
Once the steam turbine unit has been carefully designed, engineered and installed,
and upon successful commissioning and handover to the owner, the owner is
responsible for the proper operation, monitoring and maintenance of the plant.
Constant monitoring of all operating parameters reduces the risk of malfunctions and
can in many cases prevent damage.
As a matter of principle, malfunctions and failures cannot be completely ruled out in
machines of any kind. With this in mind, inspections and preventive measures are
carried out during scheduled outages in order to reduce the amount of damage and
number of malfunctions.
Monitoring of the long-term service performance of the steam turbine likewise
contributes to knowledge of the plant condition and thus permits longer intervals
between inspections/overhauls and shorter duration of inspections and overhauls.
Inspections and overhauls are planned according to safety and economic
requirements. In addition to the cost of the overhaul proper, the non-availability of the
unit is an important factor. It is determined by the outage duration due to
malfunctions or damage. Hence, lengthening the inspection intervals is expedient
only if this does not result in increased non-availability.
A forced outage due to damage will normally result in a longer downtime than a
planned outage for inspection and overhaul. An outage due to a breakdown always
occurs unexpectedly, i.e. normally at an unsuitable time.
It the plant is operated in accordance with the principles set out in VGB Guideline
VGB-R 105 and with the manufacturer’s operation manual, service life issues should
not be a determinant during the first main service period.
Inspections and overhauls on steam turbines may become necessary earlier than
scheduled, due to more frequent starts and shutdowns, extreme low-load service or
poor quality of oil or feedwater.
Experience has shown that issues of material fatigue and remaining service life
become more important once 100,000 equivalent operating hours have been
accrued.
From this time on,
 it is absolutely necessary to consider these influencing factors in the scheduling of
inspections and overhauls, because certain components, e.g. components in the
superheated steam section, can only be dismantled with significant effort once a
high number of operating hours has been accrued;
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 signs of fatigue and creep, such as the formation of cracks in casings and/or the
deflection of diaphragms, must be specifically monitored and measured over an
extended period in order to draw conclusions about the remaining service life;
 turbine-internal superheated steam carrying pipes that are operated in the creep
range must be subjected to periodic inspections;
 once 200,000 equivalent operating hours have been accrued, statements
regarding the remaining life are possible only on the basis of findings from
inspections and overhauls. A computational assessment is not always possible,
because sometimes no complete documentation of the operation mode over the
entire service life of the turbine is available.
For turbine plants of an older design, further aspects have to be considered
(drawings no longer available, casting patterns already destroyed, etc.).
The above instructions are applicable only to steam turbine plants that are operated
and serviced in accordance with the technical rules and codes of practice.
Further aspects and the considerations in scheduling of inspections and overhauls
specified in section 2 hereinabove are:
 the inspection needs of associated major components (steam boiler, generator),
 owner‘s operating experience,
 manufacturer’s recommendations for inspection and overhaul,
 exchange of experience with other owners,
 expected operation regime,
 conditions agreed with the insurer,
 literature.
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5
Scheduling inspections and overhauls
Planned inspections and overhauls, both preventive and condition-based, are
scheduled on the basis of the inspection and overhaul strategy.
Unplanned inspections and overhauls result from irregularities in the unit or from
malfunctions requiring a shutdown of the unit.
There is a smooth transition between planned preventive maintenance strategy and
condition-based maintenance strategy.
Even in the case of the planned preventive or condition-based maintenance strategy,
checks and inspections should be carried out at certain intervals, which can help to
use forthcoming outages and overhaul shutdowns more effectively.
There is a general interest in extending the time between overhauls, which are
sometimes performed at fixed and comparatively short intervals. Efforts should be
made to attain greater flexibility in establishing inspection intervals and to lengthen
the service periods between overhauls in relation to the condition of the unit
(condition-based maintenance).
Besides the design, the available monitoring and protection equipment and the
operation regime, the in-service behaviour of the unit and any changes as compared
to its normal condition are of crucial importance.
The aspects resulting therefrom for the scheduling of the overhaul/inspection are
 proper operation of the steam turbine unit, and
 equivalent operating hours, also accounting for the number of starts.
These are impacted by the design type, operation and maintenance, ambient
conditions, steam parameters, and fleet experience.
Equivalent operation hours (EOH) are defined by the following relationship:
TEOH  Tact  ns  T s
where:
TEOH =
equivalent number of operating hours,
Tact =
actual number of operating hours,
ns =
number of starts, without differentiating between hot and cold starts,
Ts =
number of additional operating hours to be considered for one start.
According to the present state of knowledge, each start incurs a penalty
in terms of an equivalent number of 20 to 30 operating hours.
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Further findings and insights must be considered:
 Turbine design
e.g. split casing turbines or barrel type turbines, condensing turbines with great
exhaust steam wetness, high-temperature turbine sections of austenitic materials,
geared turbines
 Mode of operation
e.g. continuous duty, off-nominal conditions, starting and loading modes,
temperature transients and resulting material stresses, variable-pressure/
constant-pressure operation
 In-service observations
e.g. running smoothness, bearing and casing temperatures, alignment conditions,
stage pressures and temperatures, expansion and thrust data, leakage steam
flow rates, terminal temperature difference of condenser, signs of wear and tear,
leakages, changes in service fluids such as turbine oil, lubricants, feedwater,
cooling water
 Special measurements
e.g. internal efficiency, vibration analysis, heat consumption
 Boroscopic inspection of plant parts
 Deformation of foundations
 Evaluations/changes in the steam pipework system and the resulting forces and
torques acting on the turbine inlet connections
 Oil analyses (see VGB-S-416),
 Feedwater analyses (see VGB-S-010)
 Functional checks
e.g. protection and control equipment (see VGB-R 103)
 Life assessment calculations
 Turbine life expenditure
 Coast-down times, shape of the coast-down curve
 Valve closing times
 Casing temperature measurements for determination of insulation condition
 Inspection intervals of other power plant components, e.g. steam boiler and
generator
 Manufacturer’s and/or insurer’s recommendations
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 Exchange of experience with other turbine owners, e.g. information on known
weaknesses or damages
 Influence of downtime (see VGB-S-016).
5.1
Initial service period (< 25,000 EOH), until minor overhaul/inspection (see
3.1)
It is advisable to check the unit for defects and deficiencies prior to expiry of the
warranty period (warranty inspection). A specific inspection, supported by videoboroscopic inspection without time-consuming disassembly of components is suitable
for this purpose. Casings are normally not opened after such a short service period.
In the case of turbines of new design, suitable arrangements in this regard should be
agreed between the manufacturer and the owner.
5.2
Second service period (between 25,000 and 50,000 EOH), until
intermediate overhaul (see 3.2)
If no irregularities are detected by process monitoring or other in-service
measurements and if no negative experience with comparable units has become
known, it is recommended to carry out an intermediate overhaul after the end of the
second service period.
5.3
Third service period, until major overhaul (between 50,000 and
100,000 EOH) (see 3.3)
Planning for the major overhaul is determined by the inspection findings and test
results obtained during the intermediate overhaul and the minor inspection. The first
major overhaul is performed between 50,000 and 100,000 EOH.
If the major overhaul reveals no serious findings, the same interval time between
major overhauls can be kept for future overhauls.
Findings, a changed operation regime, life expenditure, and operating experience
from comparable turbines may indicate the need for shorter intervals.
5.4
Unplanned inspections and overhauls due to irregularities
The intervals indicated in sections 5.1 to 5.3 hereinabove are applicable to the
condition that process monitoring and other specific measurements (e.g. efficiency,
heat consumption or stage pressure measurements) and the inspection findings
reveal no irregularities.
However, if process monitoring of the turbine generator reveals irregularities
(deviations from nominal conditions) which are substantiated by additional checks
(e.g. measurements), it may be necessary to advance the date of the next overhaul
(see Appendices 3.1 and 3.2).
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Moreover, information provided by the manufacturer, by other turbine owners or by
the insurer on incidents experienced with similar units can lead to an unplanned
inspection or overhaul. If findings and results of inspections indicate the need for
extended plant downtime, advancing the date of a planned major overhaul may be
contemplated for economic reasons.
5.5
Unplanned inspections and overhauls due to damage
Bringing forward the date of a planned overhaul may be expedient for economic
reasons, not only in the case of damage to the turbine generator, but also in the case
of a failure experienced by a non-redundant plant component (steam boiler, pressure
vessel, generator transformer etc.).
In contrast to an unplanned inspection/overhaul due to irregularities, which in most
cases does not necessitate an immediate shutdown of the turbine generator, damage
may require an immediate shutdown. If the time necessary for repair of the damage
results in extended downtime of the turbine generator, the date of a planned (major)
overhaul may be advanced.
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5.6
Summary
A basic inspection schedule for the entire service life of the turbine taking into
account the above considerations is shown in Figure 2.
Typical basic inspection schedule for the entire service life of a turbine
Service life
Initial service period
Minor overhaul/inspection
Minor overhaul/
inspection
Minor overhaul/
inspection
Second service period
Minor overhaul/inspection
Inspection
Intermediate overhaul
Major overhault
Fig. 2.
~ 2 to 3 days
~ 1 to 4 weeks
~ 6 to 8 weeks
Main service period
Major overhaul
Typical basic inspection schedule for the entire service life of a turbine.
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6
Planning for inspections and overhauls
It is the goal of inspection and overhaul planning to find a favourable time/cost ratio
for a defined scope of overhauling activities. This includes spare parts planning,
implementation planning and consideration of the necessary marginal conditions.
6.1
Spare parts planning
The spare parts considered necessary by agreement between the owner and the
contractor should be available in the number required prior to commencement of the
inspection/overhaul.
The decision on the purchase of spare parts mainly depends on the following criteria:
 significance of the turbine generator/the plant for the company,
 cost of outage due to unexpected/extended downtime,
 probability of failure,
 delivery time of spare parts,
 operation of several identical units by the company, and
 consolidated spare parts inventory shared by several companies.
Certain spares should be purchased in due time so as to be prepared for life
expenditure of the original parts.
Delivery time / availability of spare parts
The spare parts must be stocked in such a way as to be protected against corrosion
and damage and to be easily found. Any parts withdrawn from stock should be
replaced in due time either by ordering new parts or by reconditioning parts removed
from the unit. In the event of the design of the turbine generator being changed, the
spare parts have to be examined for their fitness for use.
6.2
Planning for intermediate and major overhauls
Approximately one to two years before the start of the overhaul, the owner should
send a detailed specification of supplies and services to the manufacturer and/or to
potential service companies. If the turbine unit is covered by insurance, the insurer
should be informed in time about the date and scope of the planned overhaul.
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In addition to the definition of the scope of the overhaul by means of the specification
of supplies and services, other aspects also need to be clarified, such as:
 estimated spare parts requirements,
 delivery times of spare parts,
 time needed for oil flushing to VGB-S-030,
 completeness and condition of spare parts kept on stock by the owner. Orders for
replacement of missing or unserviceable spare parts must be placed immediately,
taking into account any design modifications to date,
 availability of tools and fixtures (items kept available by the owner, items to be
provided by the contractor).
The following requirements depend on the kind, duration and scope of the overhaul:
 Owner and contractor should jointly compile a preliminary manpower and
overhaul time schedule.
 A work schedule is to be compiled showing the work to be performed in
workshops (owner, manufacturer and outside contractors).
 A clear division of responsibility must be agreed upon for any ancillary work
required, such as disassembling and reassembling of instrumentation and motors,
including their re-commissioning.
 Both the contractor and the owner must consider in their plans the availability of
the necessary workshop and machine tool capacity.
 Special attention should be devoted to balancing facilities that may be necessary.
 Blocking of the spring packs of the turbine foundation is to be considered, where
applicable.
 The mode of transport, transport permit, transport insurance and the provision of
transport facilities must be agreed upon between the owner and the
manufacturer.
In good time prior to the start of the overhaul, the actual condition of the turbine
generator is to be determined by measurements (e.g. pressures, efficiency, vibration
levels, foundation displacements) and compared with the nominal condition.
No later than four months before the start of the overhaul, a further pre-overhaul
meeting should be held, focussing on the following additional requirements:
 Project managers are to be designated.
 The results of the measurements should be evaluated to determine the need for
additional inspection/overhauling activities.
 The manpower and work schedules must be updated.
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 The required manpower qualification levels as well as the composition of the
overhaul crews should be finalized.
 Working hours should be agreed upon.
 The time schedule for the entire overhaul period requires updating. Note that
disassembling without delay enables a fact-finding inspection to be performed by
the owner and the contractor at an early date and thus facilitates attending to
unexpected damage.
 The areas of activities under control of the contractor and owner during the
overhaul at the power plant are to be agreed upon.
All documents required for the overhaul should be on hand before the start of the
overhaul (as-built documentation, drawings, installation records etc.).
It is recommended that all parties involved in the overhaul should meet for an
exchange of experience as soon as the turbine has been restarted.
6.3
Marginal conditions for implementing inspections and overhauls
Planning should include wash rooms and locker rooms for outside contractors’
personnel, and an adequate number of toilets and parking spaces.
The availability of accommodation and catering facilities near the power plant outside
working hours and of rooms for having meals at the power plant should be clarified.
Good lighting and electric power at the required supply voltages for the connection of
the necessary electrical appliances must be available.
The supply of compressed air to the jobsite must be ensured.
Heating and welding equipment with an adequate supply of oxygen and gas cylinders
must be provided.
Inductive preheating is to be considered, if necessary.
Necessary special tools and fixtures are to be kept available, e.g. bolt heaters,
special hoisting equipment, alignment shaft with inductive transmitters etc.
A cleaning/abrasive blasting contractor and a thermal insulation contractor should be
informed about and contracted for the scope of work to be performed.
A layout plan of the turbine house indicating the permissible loads must be available.
Crane availability and use must be clarified.
Work benches, racks, supporting trestles, transportation skids, hoisting equipment
etc. are to be provided.
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Racks, cases or containers for small items should be provided at the job site for
dismantled small items, such as, for instance, shaft glands, valve stems, casing and
bearing seal rings, bolts, etc., in order to ensure an orderly laying down of the parts
and to avoid confusion of parts manufactured from different materials.
An adequate number of wooden planks, beams and trestles for the laying down of
components should be made available and inspected for their fitness for service
before being used. Covers and means for blocking off are to be provided for the
protection of working areas.
Provision of a lockable container for storage of special parts may be advisable in
some cases.
It is recommended to set up a tool and material crib in the vicinity of the steam
turbine generator in order to eliminate long distances.
An office room/container with communication facilities for the overhaul personnel
should be provided.
Before the start of the overhaul, the working time regulations and the rules of conduct
at job site must be handed out to all persons involved. The accident prevention rules
must be laid out for perusal, and the staff must be instructed in these rules and
practices.
Lists of all ropes and slings required and of all loads to be lifted must be available. It
is advisable to store all ropes and slings in a proper manner in a single location. It is
It is recommended to provide tags with details of safe load capacity, description and
length. Ropes and spreaders allowing for adjustment of length must be made
available. After use, the ropes and slings must be inspected for their condition and, if
necessary, replaced.
Collecting pans and containers for oil to be drained and oil-absorbing substances
must be kept available in adequate numbers.
The Water Resources Act and the Ordinance on Hazardous Substances must be
observed.
Consumables and auxiliary materials, such as non-linting cleaning rags, solvents,
lubricants, sealing materials, shims etc. are to be made available.
After completion of the overhaul, all tools and appliances used must be checked for
fitness for reuse and for completeness.
It should be ensured that an efficient nearby workshop will be available for use at any
time.
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7
Tests and inspections during overhauls
The following principal techniques, identified by code numbers, are available for
inspecting steam turbine generator components. Details on their application are
given in Appendix 2.
Code number
(see Appendix 2,
Sheets 1 to 3)
Functional tests
1
Visual inspection (outside/inside)
2
 naked eye, good lighting and optical aids
 boroscope (rigid and flexible;
accessories: TV camera, monitor, video recorder)
 magnifying glass
 inspection of surface microstructure (e.g. roughness)
 blueing check
Surface crack examination
3
 liquid penetrant testing
(note: thorough precleaning of surface may be required,
e.g. for component surfaces affected by scaling)
 magnetic particle testing
note: not applicable to austenitic materials)
 eddy-current testing
Ultrasonic testing
Phased array
4
Radiographic testing
5
 X-ray
 gamma-ray (isotope)
Determining crack depth
6
as far as practicable by means of potential probe or ultrasonic
method; possibly drilling and/or grinding of cracks
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Code number
(see Appendix 2,
Sheets 1 to 3)
Ring test
7
mainly for assessing tightness of blade seating
Determining natural frequencies of components
8
 primarily to detect changes in natural frequencies for
moving and stationary blades
 holographic inspection and test methods
Detecting permanent deformations
9
 length measurements, e.g. to determine clearances,
ovality, deformations, gaps
 runout tests, e.g. to determine distortions
 geodetic measurements, e.g. foundation, machine base,
bearing pedestals
Wall thickness measurements
10
by means of calipers or ultrasonic testing
Non-destructive tests
11
 on-site examination of surface microstructure by means of
optical microscope or replica methods after etching of the
surface, film or lacquer replica, VGB-S-517-00-2014-11DE-EN
 hardness test, e.g. Brinell, Rockwell, Vickers
 material identification test, e.g. by means of hand
spectroscope
Material tests using test specimens
12
 tensile test for determination of yield strength, tensile
strength, elongation after fracture and reduction of area
 notched-bar impact test
 chemical analysis
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Code number
(see Appendix 2,
Sheets 1 to 3)
Determining residual stress
13
 strain gauges
 ring core method
 X-ray goniometer
Leakage test by
14
 filling
 pressurizing
 evacuating (e.g. by means of a test gas)
Electrochemical examination of protective coatings
15
 e.g. on condenser tubes of copper alloy materials, by
potential/resistance measurement
Resistance measurement to check shaft earthing system
(shaft currents)
16
Quality control of service fluids
 e.g. lubricating and control fluids, anti-seize agents, grease
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The scope of tests and inspections should be agreed between the manufacturer and
the owner in due consideration of experience available from comparable units and
new findings derived from failures. The manufacturer should indicate highly stressed
areas of the components requiring inspection.
The scope of tests and inspections should be specified in checklists, taking into
account the type of turbine, the operation regime and the age of the machine.
In many cases it is advisable to subject a particular component to several different
test procedures, since the results partly complement each other.
Appendix 2 lists a number of recommended test procedures classified according to
steam turbine components, to be applied during overhauls. They relate to tests on
the turbine, condenser, heat exchangers, internal piping system of the turbine and
auxiliary systems of the steam turbine unit.
The test results should be recorded and kept for the entire lifetime of the turbine (e.g.
reports, sketches, drawings, photographs, radiographs and recalculation records).
Planning of overhauls should take into account the extra time and additional expense
for the tests and inspections. Moreover, the long intervals between overhauls make it
necessary to include in the test programme a considerably larger number of items
than previously.
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8
Results of overhaul, conclusions
8.1
Documentation
Detailed documentation of the results is an integral part of any overhaul or inspection
(see also VGB-S-029). It is recommended that this documentation be compiled in
cooperation between the contractor and the owner, in due consideration of the needs
and requirements. The following headings are intended as a recommendation for the
set-up and contents of the documentation. The order in which they are mentioned
does not imply any ranking in priority.
Implementation of overhaul
Manpower and work schedules. Logging of each day’s activities, their sequence and
the required number of working hours together with a statement of qualifications. Bar
charts, critical-path diagrams, minutes of meetings, assessment of overall condition
on the basis of the operating data recorded.
Inspection findings should be described in detail and supported by photographs,
video recordings, sketches, etc. Significant leads can already be found in the process
of disassembling the turbine and its components.
The inspection findings report is compiled by the contractor. In case of
disagreements, the owner and/or the expert have the right to have their comments
recorded in this report.
Restoration and repair work
Kind and scope of the restoration and repair work performed.
Upgrading and modification work
Kind and scope of the work.
Spare parts
List of spare parts used. Modifications to spare parts are to be specially recorded.
Service fluids
Information on quantities replenished and material designations.
Test records for component parts
Test records and factory assembly records for replacement parts and components
reconditioned at the manufacturer’s workshops, material test certificates.
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Settings records and functional test records
Settings and tests of control, monitoring, limiting and protective equipment, oil
throttles, oil pressures, shaft lift oil pressures.
Assembly records
Records of all measurements taken.
Plant records
Drawings, piping diagrams, operating instructions, etc. should be checked for
continued validity and revised as necessary.
Operating records
Operating data should be recorded under comparable steady-state conditions before
and after the overhaul and checked for any departure from their nominal values. Data
to be recorded include, but are not limited to: live steam conditions and valve positions,
stage pressures and temperatures, casing temperatures, oil pressures and
temperatures, cooling water inlet temperature and temperature rise in oil cooler,
terminal temperature difference of oil cooler, bearing temperatures, expansions,
vibrations, data of gland steam sealing system, data of vacuum test, terminal
temperature difference of condenser.
As a prerequisite for acceptance of the contractor’s inspection and overhaul services
by the owner, the assembly and commissioning records (also preliminary and/or
handwritten records) must have been submitted to the owner. Prior to the closing of
the turbine casing, the clearances set should have been approved in writing by
engineering department of the contractor.
The commissioning procedure is to be discussed and agreed between the contractor
and the owner.
Special measurements
Efficiency, heat consumption, foundation distortion, intercept valve test.
Costs
Recording of total cost of overhaul, broken down by personnel, material and outside
contractor costs.
Planned/actual comparison
Comparison of planned data with the actual overhaul process.
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8.2
Conclusions drawn from overhauling results
8.2.1
Conclusions for further operation
Normally, no restrictions need to be observed for future operation if the components
 were left in the condition as found due to the absence of deficiencies,
 were replaced by spare parts (e.g. parts subject to wear and tear, such as valve
stems; typically small items which are kept on stock), or
 were reconditioned at site, at manufacturer’s works or at an outside contractor’s
facility.
If damaged components (e.g. casings with cracks) have to be left in the condition as
found, it should be decided whether operation can be continued, if necessary with a
change in the operation mode. This decision may result from:
 re-analysis of component stress levels,
 envisaged remaining service life of the unit,
 duration of repair work, or
 non-availability of replacement parts.
The condition of the damaged components must be monitored and documented.
If necessary, additional monitoring facilities should be provided. Any required spare
parts should be ordered.
8.2.2
Conclusions for next inspection/overhaul
The findings, if possible supplemented by a life expectancy calculation and operating
and overhauling experience available from other units of the same type, may prompt
a change in the current periodic inspection intervals established for a particular
turbine generator.
Shortening of the time between overhauls is always recommended when there are
indications of particular components approaching their expected end-of-life, while
replacement does not yet appear absolutely necessary.
An analysis of the procedure details of the preceding overhaul can provide important
hints for planning the next overhaul.
Problems frequently recurring during an overhaul include difficulties during
disassembly, unexpected findings, unavailability of replacement parts, delay in repair
of damaged components, and difficulties in procurement of material and special
fixtures.
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9
Literature
DIN 1943
Thermal acceptance tests of steam turbines
(VDI standard for steam turbines)
DIN 31051
Grundlagen der Instandhaltung (Fundamentals of maintenance)
DIN 31661
Gleitlager-Begriffe; Merkmale und Ursachen von Veränderungen
und Schäden (Plain bearings; terms, characteristics and causes
of changes and damages)
DIN 51515, Part 1 Lubricants and governor fluids for turbines – Minimum
requirements – Part 1: Turbine oils TD for normal service
DIN 51515, Part 2 Lubricants and governor fluids for turbines – Minimum
requirements – Part 2: Turbine oils TG for high temperature
service
DIN EN 13306
Maintenance – Maintenance terminology
DIN ISO 7919
Mechanical vibration of non-reciprocating machines –
Measurements on rotating shafts and evaluation
DIN ISO 10816
Mechanical vibration – Evaluation of machine vibration by
measurements on non-rotating parts
VGB-M 101
Empfehlung zum Vermeiden von Schäden an Dampfturbosätzen
(innere Verschmutzung) (Recommendations for the avoidance of
damage to steam turbine generators (internal fouling))
VGB-M 108
Ausrichtkontrolle an Turbosätzen (Alignment checking of turbinegenerators)
VGB-M 109
Recommendations for control and lubrication systems of steam
and gas turbine installations
VGB-M 110
Fast cooling-down of steam turbines
VGB-M 111
Maßnahmen zur Lebensdauerverlängerung und Ertüchtigung
von Dampfturbinenanlagen (Service life extending measures and
upgrading measures for steam turbine units)
VGB-M 114
Wirkungsgradänderungen an Dampfturbinen-Ursachen und
Gegenmaßnahmen (Changes in steam turbine efficiency –
causes and countermeasures)
VGB-M 120
Vermeidung von Fremdkörpereintrag in geöffnete Systeme/
Komponenten von Kraftwerken (Avoidance of foreign body
ingress into opened systems/components of power plants)
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VGB-M 305
Umgang mit wassergefährdenden Stoffen im Kraftwerksbereich
(Handling of substances hazardous to water in power plants)
VGB-M 633
Aufgaben der Vermessung bei Planung, Bau und Betrieb von
Kraftwerken und anderen Industrieanlagen (Surveying tasks in
the planning, construction and operation of power plants and
other industrial plants)
VGB-M 634
Präzisionshöhenmessungen an Turbosatzanlagen (Highprecision levelling for turbine generator units)
VGB-R 103
Guideline for monitoring, limiting and protection devices on
steam turbine plants
VGB-R 105
Thermal behaviour of steam turbines
VGB-R 106
Tubes for condensers and other heat exchangers for the
operation of steam turbine plants – Copper alloys
VGB-R 108
Fire protection in power plants
VGB-R 113
Tubes for condensers and other heat exchangers for the
operation of steam turbine plants – Stainless steels
VGB-R 114
Tubes for condensers and other heat exchangers for the
operation of steam turbine plants – Titanium
VGB-R 118
Anleitung zum Überwachen von Dampfturbinen durch Messen
des inneren Wirkungsgrades (Guidelines for the monitoring of
steam turbines by measurement of internal efficiency)
VGB-R 121
Supverision-, Limiting- and Protection Devices on Gas Turbine
Systems
VGB-R 126
Recommendations for design and operation of vacuum pumps at
steam turbine condensers
VGB-R 167
Overhaul recommendations for turbo-generators
VGB-R 503
Guideline for the internal pipework of turbo-generator sets
VGB-R 505
Guideline for the use of high-temperature bolting
VGB-R 512
Guideline for the inspection and evaluation of in-service rotors
and casings of steam and gas turbine generator sets
VGB-S-010-T-00;2011-12.EN
(formerly VGB-R 450)
Feed water, boiler water and steam quality
for power plants/industrial plants
VGB-S-016-2014-08-EN
Turbine internal drains
VGB-S-029-S-00;2012-03-EN
Maintenance-compatible documentation
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VGB-S-030-00-2013-06-EN
Oil system cleaning for gas and steam turbine
plants
VGB-S-416-00-2014-08-EN
(formerly VGB-M 416)
Part A: In-service monitoring of turbine oils
in steam and gas turbines
Part B: In-service monitoring of fire-resistant fluids
for steam and gas turbines
VGB-S-504-00-2013-12-EN
(formerly VGB-R 504)
Inspection and testing of large forgings and
castings for steam and gas turbine generator sets
VGB-S-517-00-2014-11-DE-EN Richtreihen zur Bewertung der Gefügeausbildung
(formerly VGB-TW 507) und Zeitstandschädigung
warmfester Stähle für Hochdruckrohrleitungen und
Kesselbauteile und deren
Schweißverbindungen
Guidelines
for
rating
the
microstructural
composition and creep rupture damage of
creep-resistant steel for high pressure pipelines and
boiler components and their weld connections
VDMA 4315-ff
Turbomaschinen und Generatoren – Anwendung
der Prinzipien der Funktionalen Sicherheit
(Turbomachinery and generators – Application of
the principles of functional safety)
VDEW-Empfehlungen zur Verbesserung der H2-Sicherheit wasserstoffgekühlter
Generatoren. 1. Ausgabe 1989 (VDEW Recommendations for the improvement of
H2 safety of hydrogen-cooled generators. 1st edition 1989)
VGB Technisch-wissenschaftlicher Bericht VGB-TW 112: Auslegung und Betrieb von
Dampfturbosätzen in Kraftwerken unter sicherheitstechnischen Gesichtspunkten.
1. Ausgabe Juni 1992 (VGB Technical Scientific Report 112: Safety aspects to be
considered in the design and operation of steam turbine generator sets in power
plants)
Höxtermann, E.: Schaufelschäden an Dampfturbinen. VGB KRAFTWERKSTECHNIK
59 (1979), H. 12, S. 952 bis 964 (Blade damage in steam turbines. In: VGB
KRAFTWERKSTECHNIK 59 (1979), issue 12, pp. 952-964)
Höxtermann, E.: Erfahrungen mit Schäden in Form von Anrissen und Brüchen an
Dampfturbinenwellen, Radscheiben und Generatorläufern. VGB-TW 107, 3. ergänzte
Ausgabe, Mai 1992 (Experience with damage in the form of incipient cracks and
fractures in steam turbine shafts, rotor discs and generator rotors. VGB Technical
Scientific Report 107, 3rd edition May 1992)
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Schäden an Gleitlagern. Allianz-Druckstück Nr.: TI-DE-28/1990 (Damage to plain
bearings. Allianz publication no. TI-DE-28/1990)
Verordnung für gefährliche Stoffe (Gefahrstoffverordnung – GefStoffV) vom 26.
August 1986, (BGBI. I, S. 1470), zuletzt geändert durch Verordnung vom 23. April
1990 (BGBI. I, S. 790) (German Ordinance on Hazardous Substances)
Gesetz zur Ordnung des Wasserhaushaltes (Wasserhaushaltsgesetz – WHG).
Bundesgesetzblatt (German Water Resources Act)
Verordnungen der Länder über das Lagern wassergefährdender Stoffe (z. B. NRW:
VO über Anlagen zum Lagern, Abfüllen und Umschlagen wassergefährdender
Stoffe) (Ordinances on the German federal state level on the storage of substances
hazardous to water)
Verordnung über Gefährlichkeitsmerkmale von Stoffen und Zubereitungen nach dem
Chemikaliengesetz (ChemG Gefährlichkeitsmerkmale – VO) (German Ordinance on
hazard characteristics of substances and mixtures under the Chemicals Act)
Unfallverhütungsvorschriften: Schutzmaßnahmen beim Umgang mit
krebserzeugenden Arbeitsstoffen (VBG 113) (German Accident Prevention
Regulations: protective measures in the handling of carcinogenic substances)
Gesetz über die Vermeidung und Entsorgung von Abfällen (Abfallgesetz-ABfG)
(German Waste Management Act)
Gesetz zum Schutz vor gefährlichen Stoffen (ChemG) (German Act on protection
against hazardous substances)
Schönebeck, G.: Eine allgemeine holographische Methode zur Bestimmung
räumlicher Verschiebungen. Dissertation, TU München (1979) (A general
holographic method for the determination of 3D displacement. Doctoral thesis, TU
Munich, 1979)
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10
Appendix
Minor overhaul /
inspection
Intermediate overhaul
Major overhaul
Appendix 1/Sheet 1
Open couplings, measure preloads of coupling bolts, check axial and radial
alignment, runout and displacement (external measurement of actual
dimensions).
O
X
X
Check alignment of turbine casings and bearing housings.
---
O
X
Disassemble bearings, check bearing metal, measure clearances, check
bearing seats in bearing housings.
O
X
X
Examine, overhaul and, if required, replace seal rings of bearing housings.
O
X
X
Inspect bearing housing and casing guides for contamination (carbonized oil);
if binding is detected, remove, clean and overhaul keys.
O
X
X
Examine sliding behaviour, remove and overhaul lubrite plates inserted below
bearing housings.
O
X
X
Lift off bearing housings as far as practicable for overhaul of sliding surfaces
and guides. Check condition of grout.
---
O
X
Check spacer bolts at bearing housings and casing brackets and, if required,
correct clearances.
X
X
X
Check anchor bolt preloads.
---
X
X
Check emergency stop valves, control valves and bypass valves on their
actuator and steam sides; if required, replace wearing parts.
O
X
X
Remove steam strainers; check for foreign objects and damage and, if required,
repair or recondition strainers.
---
X
X
Examine shutoff valves of exhaust steam pipes and of automatic and nonautomatic extractions on their actuator and steam sides. Replace gaskets and, if
required, replace parts subject to wear and tear.
X
X
X
Inspect pipes and fittings of drainage system, open and clean silt traps.
O
X
X
Open turbine casings, measure casing distortion, check joints for erosion,
perform crack testing.
---
O
X
Inspect steam inlet elements in turbine casing for oxide scale, wear and free
movement.
---
O
X
Check inner casing guides for free movement and wear.
---
O
X
Measure permanent elongation of high-temperature joint bolts and inspect bolts
for embrittlement. Inspect all bolts for cracks.
---
O
X
Scope of inspection and overhaul activities
as dictated by condition assessment
O = as necessary
X = required
--- = not required
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VGB-S-115-00-2016-01-EN
Minor overhaul /
inspection
Intermediate overhaul
Major overhaul
Appendix 1/Sheet 2
Check shaft glands and balance pistons for wear, oxide scale and deformation.
Examine springs of spring-loaded segments.
---
O
X
Check rotors for runout, rub marks, scoring of journal areas and cracks. Check
couplings.
---
O
X
Clean blades as necessary and inspect blades for damage. Perform crack
testing and vibration testing on free-standing LP moving blades.
---
O
X
Visually examine last stage of condensing turbine for erosion (crack testing as
necessary).
X
X
X
Check seal strips for wear and oxide scale.
---
O
X
Examine earthing brushes and contact faces on shaft, including proper
functioning
X
X
X
Open main oil pump, check bearings, seal rings, shafts, impeller, etc.
Open auxiliary oil pumps only if necessary.
O
O
X
Examine control and protective equipment, including automatic test facility,
giving particular attention to parts subject to wear and tear and to parts
susceptible to contamination. Replace parts as necessary.
X
X
X
Perform functional testing of monitoring equipment (mechanical, electrical,
hydraulic and pneumatic). Recondition and recalibrate equipment as necessary.
X
X
X
Inspect condenser interior, tubes and water boxes for fouling and damage.
Perform leakage tests on cooling water and steam sides.
O
X
X
Check evacuation system.
O
X
X
Inspect turbine-internal steam pipes and expansion joints for cracks, distortion
and deformation.
---
O
X
Inspect drain pipes for free passage and proper function (condensate traps and
drain valves).
---
O
X
Inspect main steam pipes (external).
---
O
X
Inspect anchors, pipe hangers and supports.
---
O
X
Inspect spray water system (HP, LP bypass station and gland steam and
exhaust steam desuperheaters).
O
X
X
Drain lubricating and control fluid tanks. Separate and, if necessary, change
fluids, inspect tanks, clean strainers.
---
O
X
Inspect filters. Remove and clean filter elements and examine for damage
X
X
X
Remove tube bundles of coolers, examine tubes for mechanical damage and
chemical attack. Clean.
---
O
X
Inspect fluid pipes for damage. Eliminate leaks.
X
X
X
Inspect and clean fluid vapour extraction and conditioning systems.
X
X
X
Carry out oil flushing to VGB-S-030, “Oil system cleaning for gas and steam
turbine plants”
X
X
X
Scope of inspection and overhaul activities
as dictated by condition assessment
35
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Minor overhaul /
inspection
Intermediate overhaul
Major overhaul
VGB-S-115-00-2016-01-EN
Inspect gear couplings (multi-tooth and multiple-disc couplings, jackshafts, etc.)
O
O
X
Inspect turning gear equipment for wear and for proper function
O
O
X
Inspect gear units (tooth contact pattern, seating of thrust collars, surface crack
testing, ultrasonic testing of gearing etc. as necessary.
Observe manufacturer’s instructions and recommendations.
O
O
X
Scope of inspection and overhaul activities
as dictated by condition assessment
O = as necessary
X = required
--- = not required
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VGB-S-115-00-2016-01-EN
Appendix 2/Sheet 1
Test procedures to be applied to steam turbine components during inspections and
overhauls
Component
Inspection findings
Test procedures*
Remarks
Rotors
Radial/axial rub marks
Deformation of blade grooves
Surface cracks
Mechanical damage
Erosion, corrosion
Internal defects
Permanent deformation
Damage to shaft journals
2, 3, (4), (11), (13)
2, 3, 9
2, 3, (4), 6, 11
2, 3, (9)
2, (3)
4, 5
9, 11, 13
2, 3, 9
Including central and
radial bores as well
as welds
Radial/axial rub marks
Deformation of blade grooves
Loose shrink fit
Surface cracks
Mechanical damage
Erosion, corrosion
Internal defects
2, (11)
2, 3, 9
2, (4), 7, 9, 13
2, 3, (4), (6)
2, 3, (9)
2, (3)
4, 5
Radial/axial rub marks
Mechanical damage
Deposits
Erosion, corrosion
Surface cracks
Change in blade attachment
and preloading
Permanent deformation
2, 3, 7, (11)
2, 3, (9)
2, 11, 12
2, 3, (8)
2, 3, 4
Rigid couplings
Looseness
Eccentricity
Permanent deformation
Cracks
2, (4), 7
9
9, 11
2, 3
Flexible couplings
Looseness
Eccentricity
Tooth flank damage
Cracks
Flow of damaging currents
Changes in clearances
2,7
9
2, 3, 9, 11
2, 3
2, 16
2, 9
Nozzles,
stationary blades,
diaphragms
Radial/axial rub marks
Mechanical damage
Deposits
Erosion, corrosion
Surface cracks
Change in blade attachment
and preloading
Permanent deformation
2, 3, 7, (11)
2, 3, (9)
2, 11, 12
2, 3, (8)
2, 3, 4
Discs
Moving blades
*
2, (4), 7, 8, (9)
2, 9
2, (4), 7, 8, (9)
2, 9, (11)
Primarily in disc bore
Blade roots, airfoils,
damping elements,
lacing wires,
shrouds,
tenons,
pins of pinned fork
blades
Also check for
possible damage to
bolt holes
Blade roots, airfoils,
damping elements,
lacing wires,
shrouds,
tenons,
pins of pinned
fork blades
Code numbers according to Section 7
Test procedures in parentheses should only be applied if the preceding tests have revealed a defect or
if recommended by the manufacturer.
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VGB-S-115-00-2016-01-EN
Appendix 2/Sheet 2
Test procedures to be applied to steam turbine components during inspections and overhauls
Component
Inspection findings
Test procedures*
Non-contacting seal
elements
Restriction of free movement
Mechanical damage
Fracture
Erosion, corrosion
Permanent deformation
Embrittlement of labyrinth sheet
metal
Mechanical damage
Deformation
Surface cracks
(inner/outer surface)
Erosion, corrosion
Internal defects
Permanent deformation
Mechanical damage
Surface cracks
Erosion, corrosion
Mechanical damage
Surface cracks
Permanent deformation
Erosion/corrosion
Deposits
Changes in clearances
Functional impairment
Mechanical damage
Corrosion
Deposits
Changes in clearances
1
2, 3, (9)
2
2
2, 11
Mechanical damage
Deformation
Cracks, leakage
Corrosion
Internal defects
Mechanical damage
Surface cracks
Corrosion
Cavitation
Flow of damaging currents
Deposits
Bond failures (white metal lining)
Seat contact pattern
Changes in clearances
Functional impairment
Surface cracks
Abrasion marks
Permanent deformation
Erosion, corrosion
Changes in cold pull
Leakage
2, 3, 9, (11)
2, 9
2, (3), 9, 14
2
4, 5
2, 3
2, 3
2, 3
2, 3
2, 3, 16
2, 12
2, 4, 7
2, (9)
2, 9
1, 2
2, 3
2, 3, 10, (11)
2, 9, 10
2, 9, 10
2, 9
2, 14
Outer casings,
inner casings,
stationary blade
carriers,
steam chest,
valve bodies
Flange and
joint bolts
Valve internals
Monitoring,
limiting and protective
equipment;
control system
components,
automatic test facility
Bearing housings
Bearings
Steam pipes (internal),
connecting elements
expansion joints;
drainage system
*
Remarks
Oxide scale, if
applicable
2
2, 3, 9 (11)
2, 9
Sealing, fitting and
sliding faces
2, 3, (6)
2, (3)
4, 5
2, 3, 9
2, 3
2, 3, 4 (12)
2, (3)
2, 3
2, 3, 6
2, 9
2, 3
2, 12
1, 2, 9
1
2, 3
2, 3
2, 12
1, 2, 9
Sealing, fitting and
sliding faces
Especially in elbow
areas and at
welded joints
Code numbers according to Section 7
Test procedures in parentheses should only be applied if the preceding tests have revealed a defect or
if recommended by the manufacturer
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VGB-S-115-00-2016-01-EN
Appendix 2/Sheet 3
Test procedures to be applied to steam turbine components during inspections and
overhauls
Component
Inspection findings
Test procedures*
Steam pipes
(external),
e.g. HP and IP
steam pipes
Surface cracks in weld joints
Permanent deformation
Changes in support
2, 3, 10, 11, (12)
Steam strainers,
including housings
Surface cracks
Mechanical damage
Permanent deformation
2, (3), 11
2, 3
2, 9
Including
embrittlement of
materials and solidparticle erosion
Lubricating and
control fluid pipes
Leakage
Abrasion marks
Surface cracks
Deposits
Corrosion
2, 14
2, 3, 10, 11
2, 3
2, 12
2, 12
Primarily at welds
Condenser,
coolers,
spray water system
Disturbed flow path
Surface condition
Mechanical damage
Cracks
Erosion, corrosion
Leakage
1, 2
2, (3), (10), (15)
2, 3
2, (3), (12)
2, 10
2, 14
Gear
Tooth contact pattern
Surface cracks
Mechanical damage
Deposits
Flow of damaging currents
Changes in clearances
2, 3, 11
2, 3
2, 3
2, 12
2, 16
2, 9
Evacuation system
Malfunction
Erosion
Wear
Leakage
1, 2, 14
2
2, 9
2, 14
*
2, 9, 11, (12)
2, 9
Remarks
For assessing forces
and torques acting
on the turbine
For instance,
protective coating,
deposits
Code numbers according to Section 7
Test procedures in parentheses should only be applied if the preceding tests have revealed a defect or
if recommended by the manufacturer
39
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VGB-S-115-00-2016-01-EN
Appendix 3
Recommended actions on detection of off-normal conditions
Appendix 3.1
Recommended measurements and checks
Off-normal conditions detected by
in-service measurements and checks
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VGB-S-115-00-2016-01-EN
Appendix 3.2
Examples of actions on detection of off-normal conditions
Example 1
Casing temperature difference, top/bottom
(possible causes, for instance: internal casing leaks, damaged thermal
insulation)
Item
in Appendix 3.1
2.2
Measurements and checks required:
Interstage temperature
Shaft, bearing housing, bearing vibrations
Absolute and differential expansions
Efficiency l
Noise/rubbing
Drains
Thermal insulation
Rundown time
1.2
3
4
11
12.1, 12.2
13
14
15
Additional checks recommended:
Gland sealing system
Heat consumption
6
11
Example 2
Thrust bearing temperatures rise
(possible causes, for instance: higher axial thrust due to change in
extraction steam flow, deposits, damage to blading, binding of casing
supports)
5.2
Measurements and checks required:
Stage pressures
Absolute and differential expansions
Lubricating oil system
1.1
4
10
Additional checks recommended:
Behaviour of casing temperatures
Vibrations
Casing supports
Efficiency
Noise/rubbing
Rundown time of turbine
Foundation
2
3
7
11
12.1, 12.2
15
17
41
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