All three processors of MARK V R,S,T are reading liquid fuel flow even when GT is selected on gas fuel. checked for flow divider rotation but found not running, checked for passage through false start drain valves, but no fuel.

so please comment on what to be checked from sensors, mark v side.

 

Can you tell us what the turbine is (frame size) and who the OEM/packager is?

How long has this problem been occurring?

Does it occur only during start-up?

Does the unit have an electric motor for starting?

Noise on the flow divider speed pick-up wiring causes this problem. Usually, it is caused by poor wiring practices during the installation (incorrect shield drain wire termination; signals run in close proximity to "noisy" electrical wiring; cables not properly segregated in conduits or wire trays; etc.).

This is NOT a Mk V problem; it IS a wiring, cabling, routing problem.

markvguy

 

Hello,

I'm more familiar with MKIV than MKV, so my thoughts may not be exactly correct...
Hopefully it will be of some help and not send you down a futile path in your search;

Signal path from the mag pick ups first goes to the AIO card, ( 1 mag PU for each of the processors) then to the HPRB in each processor. Are any of the other pulse rates ( turbine speed, and diesel speed, NOx water flow if you have black start and Nox water injection) registering any values when the device is not running?)

Our HPRB cards have a single on-board pot for adjustment of the Ref speed., althought your particular card may be different.

Mag Pick up to AIO module to HPRB: That's the ciruit in it's rendered down form.

Hope this helps..

Ralph TK

 

We have dual fuel units, but no gas line to site so run on liquid fuel only. My question: when running on 100% gas, does the high pressure fuel pump have a clutch (or something ) to disengage it - or put another way -> is the HP fuel pump rotating or "shut down" when on Nat gas?

Seems I have not provided much of a answer -
just added to the question...

 

Yes; on most units there is an electromagnetic clutch between the high-pressure liquid fuel pump and the output shaft of the accessory gear which drives the high-pressure liquid fuel pump.

If your units were packaged by GE you will have a set of drawings commonly referred to as "Piping Schematics"--what the rest of the world generally refers to as P&IDs (Piping and Instrumentation Diagrams). Even if your units were not packaged by GE, the packager should still have provided some form of P&ID or Piping Schematic diagram, which shows the components of each system--including the Liquid Fuel System. The high-pressure liquid fuel pump, and the clutch which connects it to the accessory gear (presuming your H.P liquid fuel pump is driven off the accessory gear and not by an electric motor...) should be shown on the drawing/diagram. The clutch is usually shown with the device mnemonic 20CF-1 ('20' is the device number for a solenoid-operated device--an electromagnetic clutch coil could loosely be considered a "solenoid", 'CF' for Clutch, Fuel).

markvguy

 

> Can you tell us what the turbine is (frame size) and who the OEM/packager is?

ANS : GE Frame 6FB, GE is the supplier
>
> How long has this problem been occurring?

ANS : For last 5-6 mONTHS
>
> Does it occur only during start-up?

ANS : OBSERVED DURING THE STARTUP.
>
> Does the unit have an electric motor for starting?
>
ANS : NO ELECTRIC MOTOR , WE HAVE DIESEL ENGINE FOR STARTING MEANS

> Noise on the flow divider speed pick-up wiring causes this problem. Usually, it is caused by poor wiring practices during the installation (incorrect shield drain wire termination; signals run in close proximity to "noisy" electrical wiring; cables not properly segregated in conduits or wire trays; etc.).

ANS : WE ALREADY LAID NEW CABLE FROM FLOW DIVIDER JB TO MAIN TERMAINATION JUNCTION BOX AT FIELD.

NOW PENDING IS CABLE TO CHANGED FROM MAIN JB AT FIELD TO MARK V BUT ITS A JACKPIN CONNECTOR TYPE, SO PLAN TO LAY DIRECTLY TO MARK V PANEL DURING NEXT SHUTDOWN.

 

Remember the shield drain wire grounding practices--even when you run wire outside of the conduits and plug-connected cables. The shield drain wires are to be connected to ground ONLY IN ONE PLACE. And that is usually defined to be the control system cabinet. So, even with a single TSP (twisted, shield pair) cable for each speed pick-up run from the junction box closest to the flow divider all the way directly into the Mk V panel, the shield drain wires should ONLY be terminated in the Mk V control cabinet (i.e., they should NOT be terminated in the JB at the flow divider).

You should be able to check the shield drain wire all along it's length. If there are breaks in the drain wire (as there usually are when two or more cables are used between the control system and the device), each length of TSP should have it's drain wire terminated to ground in ONLY ONE PLACE. This author has seen where the drain wires were terminated to ground in EVERY JB for every length of shielded wire--and that caused a LOT of noise problems!

When you say "Observed during the start-up" do you mean during the original start-up/commissioning, or only during unit starts during the last 5-6 months of operation?

One respondent has suggested trying to connect each of the flow-divider speed pick-ups in parallel to an unused speed pick-up input point. It's not certain how this would help--or hurt--the situation, but it's worth a try. Use the Signal Flow Diagrams in App. D of the Mk V Application Manual, GEH-6195 to locate spare flow divider inputs (look for '<Q> Core - Pulse Rate Inputs on QTBA Terminal Board').

Also, there was a card/PROM revision combination many years ago that required jumpering UNUSED speed pick-up inputs to eliminate nuisance Diag Alarms, but that was usually done for the emergency overspeed pick-up inputs on the PTBA card of <P> core, not on the QTBA card.

markvguy

 

Dear all,

Please support me below question:

Our plant is refinery, we are using gas turbine Frame 6FA - Mark VIe. Can you tell me what conditions to running water injection liquid fuel? What values and parameters to consider and compare when starting up with water injection.
What is the value of WIPDP, WIPPR then accept?

Thank for your support.

 

All three processors of MARK V R,S,T are reading liquid fuel flow even when GT is selected on gas fuel. checked for flow divider rotation but found not running, checked for passage through false start drain valves, but no fuel.

so please comment on what to be checked from sensors, mark v side.

If you sure no liquid fuel flow,pls force this variable L3lfbsq =0.