GEI41042 Rev O - Washing-Cleaning PDF
GEI41042 Rev O - Washing-Cleaning PDF
GEI41042 Rev O - Washing-Cleaning PDF
GE Energy
These instructions do not purport to cover all details or variations in equipment nor to provide for
every possible contingency to be met in connection with installation, operation or maintenance. Should
further information be desired or should particular problems arise which are not covered sufficiently for
the purchaser's purposes the matter should be referred to the GE Company.
© 2005 General Electric Company
GEI 41042o Gas Turbine Compressor Cleaning
I. SCOPE
The scope of this document is to present the methods of compressor cleaning offered by GE. The two types
of cleaning are liquid and solid compound cleaning. Two methods of liquid cleaning are employed — on
line and off line. On-line cleaning is the process of injecting cleaning solution into the compressor while
running at full speed and some percentage of load. Off-line cleaning is the process of injecting cleaning
solution into the compressor while it is being turned at cranking speed. The advantage of on-line cleaning
is that washing can be done without having to shut down the machine. On-line washing, however, is not as
effective as off-line washing; therefore, on-line washing is used to supplement off-line washing, not replace
it.
The second type of cleaning is solid-compound cleaning. Solid-compound cleaning is done at full speed
and reduced load. Most deposits can be removed with liquid cleaning, but for those that cannot, solid-com-
pound cleaning may be necessary. It is to be noted that some blade surface deterioration may be attributed
to solid-compound cleaning.
This document applies to all heavy duty gas turbine models offered by Gas Turbine Division, which do not
have Dry Low Nox combustion systems. Refer to GEK 103623 for liquid washing recommendations for
those units.
II. INTRODUCTION
A loss of gas turbine performance is indicated by a decrease in power output and an increase in heat rate.
Often a loss of performance is a direct result of fouling of the axial flow compressor. Fouled compressors
result in reduced air flow, lower compressor efficiency and a lower compressor pressure ratio.
Compressor cleaning will remove fouling deposits and restore performance. Compressor cleaning may
also slow the progress of corrosion, thereby increasing blade life and reducing the contribution of corrosion
products to the formation of fouling deposits.
The type and rate of fouling of an axial compressor depends on the environment in which it operates and
the filtration present.
Experience has shown that fouling deposits consist of varying amounts of moisture, oil, soot, water-soluble
constituents, insoluble dirt and corrosion products of the compressor blading material. Fouling deposits are
probably held together by moisture and oil. If corrosion of the blading is occurring, the corrosion products
will promote and stabilize the deposit.
It is important to minimize fouling deposits by reducing oil leaks and the ingestion of oily constituents
(lube oil fumes). Good filtration may greatly reduce fouling. Moisture formation cannot be reduced in
humid environments. Moisture is formed in the compressor inlet when humid air is cooled below its dew
point as a result of being accelerated to about Mach = 0.5. GER 3601, “Gas Turbine Compressor Operating
Environment and Material Evaluation,” discusses the factors influencing compressor fouling and corrosion.
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Gas Turbine Compressor Cleaning GEI 41042o
There are two basic methods for determining the cleanliness of the compressor. Visual inspection and
performance monitoring are described below.
A. Visual Inspection
The best method for detecting a fouled compressor is visual inspection. This involves shutting the
unit down; removing the inlet plenum inspection hatch; and visually inspecting the compressor inlet,
bell-mouth, inlet guide vanes and early stage blading.
If any deposits, including dust or filmy deposits, can be wiped or scraped off these areas, the compressor
is fouled sufficiently to affect performance. The initial inspection also reveals whether the deposits are
oily or dry. For oily deposits, a water-detergent wash is required. Location of the source of the oil and
correction should be accomplished before cleaning to prevent recurrence of the fouling.
B. Performance Monitoring
A second method for detecting a fouled compressor is performance monitoring. Performance monitor-
ing involves obtaining gas turbine data on a routine basis, which in turn is compared to base line data
to monitor trends in the performance of the gas turbine.
The performance data is obtained by running the unit at steady-state BASE load and recording output,
exhaust temperature, inlet air temperature, barometric pressure, compressor discharge pressure and
temperature, and fuel consumption. The data should be taken carefully with the unit warmed up.
GEK 28166, “Field Performance Testing Procedure,” can be used as a guide for assessing machine per-
formance both before and after cleaning the compressor. The purpose of this particular document is to
establish the performance of generator drive machines. The appropriate portions can, however, also be
used for all machines, both generator drive and other applications, for assessing cleaning effectiveness.
Output and heat rate can be corrected to a standard condition using the turbine performance curves, and
an analysis can be made of compressor pressure ratio and efficiency. The current performance levels
can be compared to base line data and will aid in determining the problem area.
V. CLEANING METHODS
There are three methods used for compressor cleaning: off-line, on-line and solid-compound cleaning.
There are two types of cleaning agents: solid compounds and liquids. Liquids are the preferred cleaning
agents for reasons stated below.
A. Liquid-Compound Cleaning
It is recommended that on-line water washing be addressed in the facility’s operating air permit. Reg-
ulators may interpret this as an additional short-term emissions source, requiring an exemption similar
to that provided for start-up, shutdown and transient conditions.
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GEI 41042o Gas Turbine Compressor Cleaning
Liquid cleaning involves washing the compressor with water and/or detergents. This can be accom-
plished while the turbine is on line or off line. As the on-line washing practice has been found to be
most effective when carried out daily, the specification on the liquid must be more restrictive for on-line
washing than off-line washing. The water specifications for off-line and on-line cleaning are given in
Table 1.
Except for the pH, the restrictions in these specifications are concerned with deposits and corrosion
of the hot gas path. The pH restriction is concerned with corrosion in the water-handling system.
High-purity demineralized water after contact with air will have a pH in the range of 5.0 to 6.0. Thus,
allowance has been made in the pH provided this is the reason for the low pH.
If a detergent is used, additional restrictions are required to ensure no harm will result to turbine com-
ponents. These are given in Appendix 1.
In general, deposits will contain some water-soluble material and oils. The latter will be more amenable
to removal by detergent, but the deposit may be removable by water washing alone, depending on the
amount of water-soluble material present. Hot water at 150 to 200°F (66-93°C) is generally more
effective than cold water.
There are a number of detergents commercially available for this purpose, some of which, along with
the deposits that have been removed, may constitute a hazardous solid waste (as defined by the US
Environmental Protection Agency) when used for an off-line wash. Because of this possibility, local
regulations should be considered for the storage, handling and treatment of the water wash effluent
when the drain and containment system is designed.
B. Solid-Compound Cleaning
There are two types of solid compounds used: organic — nutshells and rice; and inert — catalyst
supports, spent catalysts and polishing powders. Combustible compounds are preferred to inert com-
pounds. The organics will burn up in the combustion process while the inerts will not and may cause
erosion or blocked cooling holes.
Recent experience in the use of rice for compressor cleaning suggests that solid-compound cleaning can
be detrimental to compressor blade coatings and to compressor blade surface finish. Shallow impact
craters of several mils in diameter and tenths of mils in depth have been found on clean number 1 rotor
blading upon inspection immediately after solid-compound cleaning. Furthermore, an increase of sur-
face roughness from 20 microinches to 100 microinches has been observed on this blading. When one
considers that the relative velocity of a particle to a number 1 rotor blade is in the range of 500 to 1,000
feet per second (152 to 305 m/s) during solid compound cleaning, such damage is not unreasonable.
In the past only solid-compound cleaning was performed at full speed; but with the advent of water
washing at full speed, solid-compound cleaning no longer holds this singular advantage.
If dry, hard deposits were present, past practice was to remove them using a solid compound cleaner.
However, unless deposits have dried out, they will usually contain significant moisture and water-
soluble material, which can be removed using a liquid compound.
Perhaps some deposits cannot be removed except by abrasive cleaning, but it must be appreciated that
some deterioration of the blade surface may accompany fouling deposit removal.
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Gas Turbine Compressor Cleaning GEI 41042o
Presently, under most conditions, liquid-compound cleaning is the preferred method. Solid-compound
cleaning may be necessary in certain instances. In cases where blading is corroded over time and
surface roughnesses are well above OEM values (25 microinches), solid-compound cleaning should
not be harmful.
1. Preparation
a. Off-line washing solution must meet the requirements of both Table 1 and Appendix 1.
b. Piping to the atomizing air compressor must be opened and blocked off to prevent water
from entering this area. All air-extraction lines from the compressor should be blocked
off.
c. If a unit is equipped with off-base atomizing air compressor, the compressor should be
deenergized during the wash and rinse cycles.
e. Make sure all drains are open and diverted to suitable areas.
f. Close flame detector valves. Water will foul the flame scanners and make starting diffi-
cult.
g. When regenerators are present, the gas-side face must be covered and kept dry during
compressor washing to prevent wetting regenerator deposits. These deposits may change
form when wet and become extremely difficult to remove. Leave access doors open while
cranking to provide an air exhaust path.
h. For off-line water wash the operator must take appropriate precautions to prevent freezing
in the compressor inlet, gas turbine, exhaust and drain system. Off-line water washing
should not be done at compressor inlet temperatures, CTIM, less than 40°F (4°C), mea-
sured while cranking..
2. Washing Procedure
Washing can be accomplished using a permanent system (a series of nozzles or a spray ring
mounted in the inlet plenum) or with a manual system (a hand-held hose and spray nozzle).
With either system, take care to cover the full circumference of the bellmouth. The inlet
plenum and bell-mouth should be cleaned first to prevent these deposits from being washed
into the compressor during the cleaning.
Washing with water or detergent should be done at crank speed or slower. This provides more
effective washing near the hub of the rotor. Flow rates are given in Table 3.
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GEI 41042o Gas Turbine Compressor Cleaning
CAUTION
b. Apply the solution at crank speed for three to five minutes, shut unit down, continue
spraying during coastdown until the solution is no longer drawn into the compressor inlet.
Crank speed is considered to be approximately 350 rpm for the MS-7001; 300 rpm for
the MS-9001; 600 rpm for the MS-3002, 5001, 5002 and 6001.
c. Allow the detergent to soak for 20 minutes and rinse with water at crank speed for 15 to
20 minutes following the recommended flow rates of Table 3.
3. Rinsing Procedure
The effectiveness of the wash and the rinse can most easily be evaluated by observing the
runoff from the drains during the rinse and visual inspection of the compressor inlet at the
end of a wash cycle.
a. The compressor should be rinsed until the drain water appears clean.
b. The runoff water may also be checked for the amount of impurities it contains by mea-
suring its electrolytic conductivity. The conductivity value will decrease as washing con-
tinues and the runoff water contains fewer dissolved impurities.
NOTE
The detergent wash may need to be repeated depending on the amount of fouling
and detergent effectiveness.
4. Restoration
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Gas Turbine Compressor Cleaning GEI 41042o
The intent of on-line washing is to keep the gas turbine compressor clean through frequent wash-
ings of short duration. When the compressor is suspected of being heavily fouled, an off-line wash
should be performed.
Adding water for wash will increase the compressor pressure ratio and thus reduce the surge mar-
gin. Under normal circumstances, there is ample surge margin to allow for washing and steam or
water injection for NOx control or power augmentation. However, the following steps are recom-
mended prior to performing an on-line wash.
1. Preparation
a. On-line washing solution must meet the requirements of both Table 1 and Appendix 1.
b. Turbine must be running at full speed and not in the process of shutting down.
c. Compressor inlet temperature, CTIM from the Speedtronic panel, must be greater than
50°F (10°C).
2. Washing Procedure
3. Solid-Compound Cleaning
1. Preparation
a. Solid-compound cleaning is done at full speed and reduced load. This keeps internal tem-
peratures down and eliminates possible damage by cleaning material due to hot corrosion
in the turbine section. Nutshells are recommended over rice and both over the inerts.
b. Make sure turbine has been running for at least 30 minutes before solid-compound clean-
ing to ensure dryness.
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GEI 41042o Gas Turbine Compressor Cleaning
d. Evaporative coolers must be shut down one half-hour before solid-compound cleaning to
make sure surfaces are dry.
e. Make sure that any separators that are installed on compressor air extraction lines (i.e.,
cooling and bearing sealing air lines) are functioning, and that any blowdown valves
installed on these separators are open.
2. Cleaning Procedure
a. The solid compound can be applied to the compressor either through an injection ring
permanently installed in the bellmouth for that purpose or by a manual method.
b. When the solid compound is injected manually, a location should be used to allow time
for good dispersion in the airstream. There is no mixing within the compressor; therefore,
if the solid compound is not dispersed when it enters the compressor, only portions will
be cleaned. A hopper or other device may be helpful in establishing an even injection
rate.
CAUTION
Solid compound injection may cause fouling of flame scanners and a possible trip.
Following the injection rates in Table 3 will help prevent this.
NOTE
Use only inert cleaning compound for units equipped with GARRET regenerators.
CAUTION
Too rapid injection of solids may lead to an accumulation of solids in the cooling
and sealing air lines and the No. 2 bearing housing. The even injection rates shown
in Table 3 should be followed.
c. To determine the effectiveness of solid compound cleaning, set load to 20% and make
note of the exhaust temperature and compressor discharge pressure.
a) Inject solid compound and maintain constant load. Use 20-pound (9-kg) increments of
solid compound at the proper rates. If the cleaning is effective, the exhaust temperature
will drop and the compressor discharge pressure will increase.
b) Inject solid compound until no further effect is seen. At this point, solid-compound
cleaning is finished.
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Gas Turbine Compressor Cleaning GEI 41042o
3. Restoration
If applicable, return the evaporative coolers to normal service. Normal operation may be
resumed.
B. Results of Cleaning
OFF-LINE WASHING
ON-LINE WASHING
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GEI 41042o Gas Turbine Compressor Cleaning
Machine flow rate lb/min Press Temp Flow Press Temp Flow
(psig) (°F) (GPM) (psig) (°F) (GPM)
MS3001, 3002 0.72 115 150-180 15 100 50-180 3.5
MS5001, 5002 1.75 85 150-180 35 100 50-180 8
MS6001 2.3 85 150-180 42 100 50-180 10
MS7001EA 3.5 85 150-180 50 100 50-180 18
MS7001F/FA 5.0 85 150-180 81 100 50-180 26
MS9001E 5.0 85 150-180 72 100 50-180 26
MS9001F/FA 7.2 85 150-180 117 100 50-180 38
1. Dispensed at a uniform rate over the cleaning period. The
1 rate should not be higher than that shown above.
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Gas Turbine Compressor Cleaning GEI 41042o
APPENDIX 1
I. SCOPE
1. This specification is for cleaning compounds for use in compressor washing. It is required that these
compounds will not cause harm to gas turbine components. Thus, their purity and composition must
be such that they do not cause aqueous corrosion or stress corrosion of compressor materials. Also,
it is required that they do not cause hot corrosion in the turbine. Furthermore, they must not lead to
compressor fouling. With regard to the cleaning agents themselves, they must be chemically stable
in themselves and in their mixtures with water. Also, they must not form combustible mixtures and
they should satisfy all local codes relative to health and safety requirements. Compliance with this
specification does not imply a cleaning compound improves the cleaning of a compressor over and
above what can be obtained from water alone.
II. REQUIREMENTS
1. The cleaning compound when mixed with water in the manufacturer’s prescribed concentration shall
satisfy the water washing specifications for on-line and off-line water quality given in Table 1. In the
pure state it shall satisfy the specification given in Table A1.
2. The residue or ash content of the cleaning compound shall not exceed 0.01%. See test 4.1.
3. The storage stability of the cleaning compound shall show no marked color change, shall not separate
and shall not corrode or stain the steel specimen when tested as specified in test 4.5.16 of MIL-C-
85704A. This test is given in 4.2.
4. The cleaner and its mixtures with water shall not form gums under compressor conditions.
5. The Pensky-Martens flash point of the cleaning compound shall be above 140°F (60°C) (ASTM D93).
1. Use of the cleaning compound shall not have adverse effects on engine system materials such as com-
pressor or turbine materials.
IV. TESTS
Approximately 10 g of cleaning compound shall be weighed to the nearest 0.1 mg in a tared porcelain
crucible. The crucible shall be heated at 221° ± 2°F (105° ± 1°C) for 24 hours, then heated at 464° ±
4°F (240° ± 2°C) for the next 24 hours. Following this, the crucible and its contents shall be carefully
ignited over a Bunsen-type gas burner. The crucible shall then be placed in a muffle furnace at 1,900°F
(1,040°C) for 2 hours. The crucible shall be transferred to a desiccator, cooled and weighed until con-
stant weight. The ash content shall be calculated as the percentage of the initial weight of cleaning
compound.
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GEI 41042o Gas Turbine Compressor Cleaning
Preparation of test sample.A 150-ml portion of a well-shaken cleaning compound shall be poured into
each of two chemically clean 250-ml pressure-resistant clear glass bottles which shall be approximately
9.5 inches (24.1 cm) in height and 2.5 inches (6.4 cm) in outside diameter. One bottle shall be capped
and stored in the dark for at least six days at room temperature. A strip of steel 6 by 0.5 by 0.02 inches
(15.2 x 1.3 x 0.05 cm) conforming to MIL-S-7952 shall be polished to remove surface contamination
and then cleaned by boiling for one minute in chemically pure isopropyl alcohol and one minute in
mineral spirits. The steel strip shall be placed in the other test bottle and the bottle shall be capped.
The capped bottle containing the steel strip shall be thoroughly shaken for one minute.
Procedure. The capped bottle containing the steel strip shall be placed in a water bath and heated at
a uniform rate to a temperature of 140° ± 4°F (60° ± 2°C) over a period of five hours. It shall be held
at this temperature for three hours. No heat shall be applied to the bath overnight. The above heating
procedure shall be repeated each day for five days. (This test need not necessarily be attended if an
interval time is used to regulate the temperature automatically. The test may be started on a Wednesday,
Thursday or Friday and still have the pressure bottle removed on a normal workday.) On the morning
of the sixth day, the bottle shall be removed from the bath, uncapped, examined for separation and the
steel strip carefully withdrawn from the cleaning compound. Separation into layers shall be cause for
rejection. The portion of the steel strip which had been immersed in the compound shall be examined
for evidence of pitting, corrosion and uneven darkening. The open bottle shall be capped and the two
bottles shall be thoroughly shaken for one minute, then allowed to remain undisturbed for one hour
at room temperature and then examined. Any marked change in the color and uniformity of the aged
sample shall be considered as showing unsatisfactory stability properties.
GE Energy
General Electric Company
www.gepower.com
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