GEK 116862 Inspection and Maintenance Instructions for 7FA.05 Gas Only and Dual Fuel Gas Turbines
H. Pipe Couplings
Check the couplings for oil leakage due to aging and heat. Replace seals as needed.
Lubricate seals prior to each assembly of seals.
X. COOLING WATER SYSTEM
A. Cooling System Checks
Cooling system fouling, with consequent performance degradation, must be checked periodically,
even though the system is properly rust inhibited. Fouling of the fin-tube heat exchangers will
probably be the most severe, since the tubes are the smallest in the system.
A maximum of ten percent of the tubes in each heat exchanger can be plugged to eliminate water
leaks. The leaks in the water-to-air heat exchanger may be repaired at an authorized field service
repair center. This method is preferred to plugging the tubes, since the system performance is not
seriously affected. Plugging the heat exchangers will reduce system performance and result in more
frequent cleaning. If excessive corrosion is found in the cooling water heat exchangers, the heat
exchangers shall be cleaned and flushed according to the heat exchanger supplier’s maintenance
instructions. It may be necessary to flush the entire system to drain after heat exchanger cleaning to
ensure the contamination has been removed from the system.
After the system has been properly cleaned, refill with pure water and the recommended amount of
corrosion inhibitor or anti-freeze mixture. Refer to the Fluids Specification section of this Operation
and Maintenance Manual for appropriate mixture composition.
B. Flow Checks
The closed cooling water system has several sharp-edged orifice plates mounted in the orifice
flanges. These orifices are used to balance the pressure drop in parallel flow circuits. They also may
be used to measure system flow rates. Measurement of system flow rates is extremely important for
troubleshooting, if problems develop. Design flow rates for the water circuits with the temperature-
actuated valves in the open position are listed on the Cooling Water Schematic Piping Diagram, in
the Operation and Maintenance Manual. When the flow check is made, it is suggested that a single
delta pressure gauge/transducer be installed across the orifice for accuracy. This procedure will
eliminate measurement errors, which could occur when two separate gauges are used. Runs of
pressure lines should be as short as possible.
Use of a mercury manometer is not recommended. Mercury will react destructively with copper and
brass in system components under certain conditions, if it were accidentally injected into the cooling
water system.
C. Flow Versus Pressure Drop
Water (or coolant) flow versus pressure drop curves may be prepared for any orifice* size by using
the equation:
gpm
P
KA =
Δ
= 300Q
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