Tipologías de pavimentos musivos y generalidades 2.2
2.2.3 El opus tessellatum
must reduce water or steam injection to 3% maximum of compressor inlet flow.
(3.) Operation
The on-line water wash is initiated from the turbine control panel. The operator selects the WATER WASH manual control display on the panel CRT and then presses the ON-LINE WATER WASH ON Softswitch. From that point on, the wash cycle is totally automatic. The normal sequence of events which occur are as follows:
(a.) Operator selects ON LINE WATER WASH ON.
(b.) Water pump, 88TW–1, turns on.
(c.) Solenoid valve 20TW–3 begins to open 3 seconds after the water pump turns on.
(d.) Flow switch 80WW–1 indicates that water has begun to flow and it starts the wash peri-od timer, L2WWP. The message COMP WATER WASHING is displayed on the nor-mal CRT display.
(e.) L2WWP times out typically after 30 minutes, and 20TW–3 begins to close.
(f.) 88TW–1 turns off 10 seconds after L2WWP times out.
The wash period time, L2WWP, is initially set for 30 minutes. The operator, though, should measure the effectiveness of the wash at various timer settings and adjust it accordingly.
At sites where there are multiple turbines, one water wash skid is shared by all the turbines.
The controls are designed so that only one turbine compressor can be washed at a time. If a compressor is being washed, either on-or off-line, and a request is inadvertently made to wash another compressor, the request will be blocked and the alarm WATER WASH SKID IN USE will occur on the turbine control panel.
The operator must be aware of the position of the two selector switches on the ANNUNCIA-TOR/CONTROL PANEL which is located on the water wash skid. One switch is the WA-TER TEMP SETPOINT, 43WK–1, and the other is the OPERATION SELECTOR SWITCH 43WK–2. These switches are used when performing an off-line wash and they need to be returned to their proper positions when the off-line wash is completed.
The WATER TEMP SETPOINT switch has two positions, HOT and COLD. In the COLD position, the temperature setpoint for the water tank heaters, 23WK–1, –2, –3 is 65°F (18.3°C). This is the correct position for on-line washing. In the HOT position, the tempera-ture setpoint is 178°F (81°C). This is the correct position for off-line washing. When the op-erator decides to perform an off-line wash, he should select the HOT setpoint around the same time he gives the turbine a shutdown command. This will give the water time to heat up while the turbine is shutting down and cooling down. When the off-line wash is com-pleted, he should select the COLD setpoint again.
The OPERATION SELECTOR SWITCH also has two positions, MANUAL and AUTO-MATIC. The operator should select MANUAL whenever he selects HOT on the WATER TEMP SETPOINT switch. When the switch is in the manual position, all turbines are blocked from performing an on-line wash. This is done to prevent inadvertently using up
System Description Gas Turbine
12
the hot water for an on-line wash instead of the off-line wash it was intended for. When the off-line wash is completed, the operator should select AUTOMATIC again. This is the cor-rect position for on-line washing.
(4.) Permissives
In order to perform an on-line compressor wash, certain permissives must be satisfied. These permissives can be divided into two groups; turbine permissives and water wash skid per-missives.
There are two turbine permissives:
(a.) The turbine must be operating at full speed and not in the process of shutting down.
(b.) The compressor inlet air temperature must be greater than 50°F (10°C).
If either of these permissives are not satisfied when an on-line wash is requested, the alarm WATER WASH INHIBITED will occur on the turbine control panel.
The water wash skid permissives are:
1. Only one compressor can be washed at a time.
2. All alarms on the annunciator control panel must be reset.
3. The water temperature must be above 50°F (10°C).
4. The water in the tank must be above a minimum level.
5. After the water pump, 88TW–1, is turned on, the pump inlet and discharge pressures must be satisfactory.
6. The flow switch relay, 83WW, must indicate water flow exists.
The logic elements for all of the skid permissives are contained in the ANNUNCIATOR/
CONTROL PANEL which is located on the skid. If one or more of the skid permissives are not satisfied, the appropriate alarm will occur on the ANNUNCIATOR/CONTROL PANEL and also the alarm WATER WASH SKID TROUBLE: TRIP will occur on the turbine control panel. If the latter alarm occurs, the operator must go to the water wash skid, investigate and correct the problem, and then reset all alarms on the ANNUNCIATOR/CONTROL PANEL.
Then he can attempt to initiate the wash again from the turbine control panel.
GEK 110220a Revised May 2002
GE Power Systems
Gas Turbine
Gas Turbine Compressor Water Wash System
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.
© 2002 GENERAL ELECTRIC COMPANY
GEK 110220a Gas Turbine Compressor Water Wash System
I. GENERAL
Gas turbines can experience a loss of performance during operation as result of deposits of contaminants on internal components. This loss is indicated by a decrease in power output and an increase in heat rate.
The deposits of atmospheric contaminants on compressor parts occurs with the ingestion of air.
The ingested air may contain dirt, dust, insects, and hydrocarbon fumes. A large portion of these can be removed before they get to the compressor by inlet air filtration. The dry contaminants that pass through the filters as well as wet contaminants, such as hydrocarbon fumes, have to be removed from the compressor by washing with a water-detergent solution followed by a water rinse.
A. On-Base Supplied Equipment
The on-base turbine equipment supplied with this compressor wash system consists of piping from the purchaser's connection on the base, air operated water injection valve(s), and the appropriate spray manifold(s). Drains from the inlet plenum, combustion area, exhaust frame, and the exhaust plenum are also provided. In addition, there are purchaser connections in these drain lines. The schematic for this on-base water wash equipment is located in the Reference Drawing sections of this manual.
B. Off-Base Equipment
The off-base portion of the water wash system, known as the water wash skid, contains both a water tank and a detergent tank. The water tank is equipped with temperature sensors and electric heaters to maintain proper water temperatures. The skid is equipped with a centrifugal water pump motor (88TW-1) and a venturi used with the water pump to mix detergent solution. Also included on the skid are the various control panels to initiate wash and to manually start/stop the appropriate devices. All equipment is made of corrosion resistant material. The schematic for the water wash skid is included in the Reference Drawings section of this manual.
All devices are set to give proper temperature, pressure, and flow. The settings for these devices can be found in the device summary for the corresponding system.
C. Functional Description
During the washing operation, water or wash solution is delivered through customer piping to the gas turbine in the proper mix ratio. The wash water solution is delivered to the turbine unit at the proper pressure, temperature, and flow rate to wash the gas turbine compressor. Refer to the system schematic in the Reference Drawing section for proper pressure(s), temperature(s), and flow rate(s) for this gas turbine.
1. System Requirements
Water used for washing turbine parts should be reasonably clean so that it does not cause fouling or corrosion in itself. Distilled or deionized water is recommended. Water quality requirements are listed in Table 1 of GEK-107122 (Latest Revision). Oily or varnished oil deposits on internal gas turbine parts require that a detergent solution be used during the washing operation. The detergent shall meet the requirements of GEK-107122 (Latest Revision), Appendix 1.
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Gas Turbine Compressor Water Wash System GEK 110220a
2. Compressor Washing Frequency
The frequency of compressor washing depends upon the severity and type of atmospheric con-tamination that fouls the compressor and reduces performance. The recommended method for establishing the frequency is to monitor gas turbine performance, comparing the routine perfor-mance with the baseline perforperfor-mance to observe the perforperfor-mance trends.
If the performance has fallen significantly, and compressor fouling is suspected, it must be verified by visual inspection. This visual inspection should include the compressor inlet, bellmouth, inlet guide vanes and the first and, possibly, the second stage of the compressor blades.
NOTE
Inspection should be made for the source of the oily deposits. If possible, correc-tive action should be taken.
D. Washing System Operation 1. General
a. Off-line Water Wash
Off-line water washing should be scheduled during a normal shutdown, if possible. This will allow enough time for the internal machine temperature to drop to the required levels for the washing. The time required to cool the machine can be shortened by maintaining the unit at crank speed. During this cooling of the turbine, the wash water may be heated to the proper level.
Refer to GEK-107122 (Latest Revision) for gas turbine compressor liquid washing recom-mendations
b. On-line Water Wash
The period between off-line water washes can be extended via frequent on-line washing.
When the compressor is suspected of being heavily fouled, an off-line wash should be per-formed.
The on-line compressor wash system allows an operator to water wash the turbine compres-sor without having to shut down the turbine. The method of washing is similar in many ways to the off-line system. Both systems use the same pump, 88TW-1, and piping to supply high quality wash solution to the compressor. When the supply pipe reaches the vicinity of the turbine base, it splits into two branches, one for the off-line system and one for the on-line system. Each branch contains a stop valve, flow control orifice, manifold(s) and spray noz-zles.
There are significant differences, though, between the two systems. GE recommends against the use of detergents during on-line washing, while the use of detergents during off-line wash-ing are encouraged. The on-line wash water requirements differ from that of off-line wash solution and must meet the requirements of Table 1 of GEK-107122 (Latest Revision) for on-line washing. Finally, the on-line system proceeds automatically after it is manually initi-ated; whereas, the off-line system requires operator intervention before and after the wash.
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GEK 110220a Gas Turbine Compressor Water Wash System
NOTE
When using a detergent solution for on-line washing, it is recommended that the wash be followed by enough rinse water to remove the detergent residue from the wash nozzles at the spray manifold. This will prevent the detergent solutions from drying and clogging the nozzles.
2. Mandatory Precautions
Before water washing of the compressor begins, the turbine blading temperature must be low enough so that the water does not cause thermal shock.
CAUTION
The differential temperature between the wash water and the interstage wheelspace temperature must not be greater than 120F (67C) to prevent thermal shock to the hot gas parts. The maximum wheelspace temperature as per TIL 1196–1 must be no greater than 150F (65.5C) as measured by the digital thermocouple readout system on the turbine control panel.
To reduce this difference, the wash water may be heated and the turbine kept on crank until the wheelspace temperatures drop to an acceptable level. The wheelspace temperatures are read in the control room.
CAUTION
If, during operation, there has been an increase in exhaust temperature spread above the normal 15F to 30F (8.3C to 16.6C), the thermocouples in the ex-haust plenum should be examined. If they are coated with ash, the ash should be removed.
Radiation shields should also be checked. If they are not radially oriented relative to the turbine, they should be repositioned per the appropriate drawing. If the thermocouples are coated with ash, or if the radiation shields are not properly oriented, a correct temperature reading will not be obtained.
If neither of the above conditions exists and there is no other explanation for the temperature spread, consult the General Electric Service Engineering representative.
***WARNING***
THE WATER WASH OPERATION INVOLVES WATER UNDER