Table of Contents
Advertisement
Inspection and Maintenance
Inspection and Maintenance Procedures
With lock washers installed, verify that the servovalve mounting screws are long enough to provide 1
to 1.5 times the screw diameter of thread engagement.
If longer servovalve mounting screws are required to meet minimum thread engagement, verify that the
replacement screw does not bottom in the threaded hole. Rework the screw if required.
Torque all servovalve mounting screws to 17–19 inch pounds.
Check Valves, Orifices and Orifice Check Valves
During a shutdown period, the system has to be drained and the valves and orifices have to be removed
to check for evidence of erosion, corrosion, or component deterioration. Check the orifices for plugging,
size and sharpness of the hole. Check the valve seat for leakage. Check the condition of the seals, "O"
rings, or gaskets, and replace them if there is any indication of wear.
Lube Oil Filters
The lube oil system filters should be changed once a year, regardless of the pressure drop. The pressure
drops must be checked under turbine operating conditions, with the lubricant at normal operating tem-
perature, and at rated flow through the filter. In most gas turbine lube systems, the main lube filter, which
filters the lubricant to the main bearing header, can be checked for clogging by the pressure drop indica-
tion. Here, the pressure downstream from the filter is maintained by a pressure regulating valve, and the
difference in the pressures shown on the gauges before and after the filter will provide a reliable indica-
tion of the filter condition. The condition of other filters in the lube system, such as the control fluid filter
or hydraulic control pump filter, cannot be determined as reliably by the pressure drop indication since
the flow through these filters may be very low under steady-state conditions. It is unlikely, however, that
these low-flow filters will foul before the recommended annual changeout of the filter element.
On gas turbines that are expected to run continuously over long periods of time, dual filter arrangements,
with a transfer valve, are usually incorporated into the lube system to facilitate the servicing of the filters
without turbine shutdown. Systems with single filter arrangements require that the turbine be shut down
to service the filters.
Hydraulic Supply Filters
The hydraulic supply system filter should be changed when the pressure drop across the filter is 60 psig
(4.14 bars), or once a year, regardless of the pressure drop.
The pressure drop must be checked under turbine operating conditions, with the hydraulic fluid at oper-
ating temperature and at rated flow through the filter. The rated flow can be assumed to be realized during
maximum transient conditions, such as at the instant of hydraulic tripout of the gas turbine. Under
steady-state conditions, there will be only a small flow through the filter and any differential pressure
indicated on the system gauge will probably be small and not a true indication of the condition of the
filter. It is unlikely, however that these low-flow filters will foul before the recommended annual change-
out of the filter cartridge.
On gas turbines that are expected to run continuously over long periods of time, dual-filter arrange-
ments, with a transfer valve, are usually incorporated into the hydraulic supply system to facilitate serv-
icing of the filters without turbine shutdown. Systems with single-filter arrangements require that the
turbine be shut down to service the filters.
IMP–5
Advertisement
Table of Contents
