Gas Turbine Heat Exchanger and Filters

Lube Fluid Heat Exchanger

The heat exchanger system is required to dissipate the heat absorbed by the lubricating fluid and to maintain the fluid at the proper bearing header temperature. This is accomplished by circulating cooling water through the cooling tubes of the heat exchanger as the lubricant flows over the tubes. Cooling water flow through the heat exchanger is controlled by temperature sensitive flow regulator valve VTR 1, that maintains the correct bearing temperature.

(See Cooling water system for information on this regulator valve). The lube fluid heat exchanger system uses a fluid-to-water cooler of the shell and tube bundle design. There is one heat exchanger, flange mounted in the lube reservoir in a horizontal position. A U-tube bundle extends into the center of the shell through which the cooling water is passed. The lube fluid flows in and out of the shell ; passing over the cooling tubes of the tube bundle. Cooling water connections are made at the external steel bonnet that bolts to the shell mounting flange through the tube sheet that supports the tubes of the tube bundle.

Filters

Main lube filtering system - Filtration of all lube oil is accomplished by a 5 micron, pleated paper filter installed in the lube system just after the lube oil heat exchanger.

One (duplex) filter is used with a transfer valve installed between the filters to direct oil flow through either filter and into the lube oil header.

The dual filters arranged side by side, are installed on the tank and connected into the pump discharge header through a manual transfer valve. Only one filter will be in service at a time, thus cleaning, inspection, and maintenance of the second one can be performed without interrupting oil flow or shutting the gas turbine down. By means of the manually operated, worm-driven transfer valve, one filter can be put into service as the second is taken out, without interrupting the oil flow to the main tube oil header. The transfer of operation from one filter to the other should be accomplished as follows:

1 -Open the filler valve and fill the standby filter until a solid oil flow can be seen in the flow sight in the filter vent pipe. This will indicate a "filled" condition.

2 -Operate the transfer valve with a wrench to bring the standby filter into service.

3 -Close the filler valve.

Filters should be changed when the differential pressure switch 63 QQ-1 indicates a differential pressure of 15 psig (i.e. about 1.03 bar). Refer to the "Gas turbine maintenance guide chapter" for inspection schedules. An alarm from 63 QQ-1 signals when the differential pressure exceeds 15 psig.

NOTE: For the detailed drawing of the lube oil system circuit and the settings, see "Gas turbine operation guide chapter”: Piping systems schematic.