We have a GE frame 7EA gas turbine controlled by the mark V redundant control system RST. our problem start after major inspection when we try to put the unit on ratchet. the hydraulic pump not start on auto because the the switch 63QTX-1 is open. my question is, when we jumper the contact the pump start on auto without any problem and the pressure reach about 1490psi and the ratcheting sequence start normally. but when i try to find the pressure switch in the field i couldn't find it. so where is this switch?

or maybe there is different name for it

 

Yeah, GE kind of did a "bad" thing recently with the permissive for the Aux. Hydraulic Pump....

The physical contacts of an actual physical pressure switch, measuring L.O. header pressure (since the Aux. Hydraulic Pump suction is "fed" from the L.O. header), used to be physically wired in to the Aux. Hyd. Pump motor starter control circuit.

Someone then decided it would be a "better" idea to use a contact of a relay output of the Speedtronic as that L.O. pressure permissive instead of a pressure switch, and, then to make the "better" idea complete they decided to "name" the signal L63QTX1 (that's the typical name; some applications used some variation of that name) to drive a relay output called 63QTX-1. And that relay output contact is wired in series with the Aux. Hyd. Pump motor starter output of the Mark V.

So, you're probably not looking for a switch; more likely you're looking for a relay output that's in series with L4HQZ.

The permissive is necessary because if there's no L.O. pressure feeding the suction of the Aux. Hyd. Pump the pump will be damaged. (And, the hydraulic pump is not capable of drawing a suction from the tank so it's suction needs to be pressurized.) And, since the Speedtronic has multiple contact inputs to tell it when there is L.O. Header pressure (think 63QT-2A & -2B and 63QA-1) someone thought it would be okay to use those signals to drive an output for the Aux. Hyd. Pump permissive. Sort of makes sense, but the signal name confuses a lot of people.

Hope this helps!

 

Thank you very much

you know this is a new info to know about it. and you make every things clear cos you make me stop looking for this 63QTX-1 in the field and try to find the real problem which it was the porting valves for the 63QT-2A&2B. those valves found open which make the discharge pressure very low. so when we close the valves every thing return back to normal.

again thank you for your respond,
have a great day.

 

Happy to have been of some help!

Thanks for the feedback!