Our unit 2 is a Frame 6B, MKV, Capacity 30MW, commissioned 1984, dual fuel system, gas pressure at GPRS 21 bars, Gas Separator 19 bars. Dual operation mode open cycle (OC) and combined cycle(CC).
Unit 2 was shut down to rectify gas leak at Gas Pressure reducing station (GPRS). Unit 2, however, failed to start up on gas (OC) with alarm of failure to ignite (4 attempts).
Immediately the following works were done.
1. Hard Reset mkv
2. Check condition supply to ignition ok
3. Tested spark plug ok
4. Verify lvdt and servo current and voltage for Gcv, found servo
Unit 2 still failed to start up on Gas with the same alarms ( >4 Attempts)
1. Tested Flame scanner reading more than 1k,
2. Tested spark plug, ok
3. Verified solenoid dumb valve, ok
4. Transducer 96fg verify using beamex, ok
5. Stroking gcv, open close ok
6. Stroking srv, open close ok
7. Change Mark V card tcqa <R>, reading voltage/actual position, ok
8. Check terminal Mark V and local connection gcv/srv, terminal
transducer 96fg, ok
Unit 2 still failed to start up on Gas with the same alarms ( >3 Attempts)
1. replace LVDT's for SRV
Test firing, found that the gas pressure @SRV is a bit low at 1 barg instead of 1.7 barg
Further investigation on SRV opening found that before starting up the value for RST (fully closed) is at -97.10 for all, while during start up/firing mode it differs at -0.05 , 4.56 and 2.91
1. We adjusted FSR firing from 16.5% to 18%
2. Auto/manual calibrate SRV
Reading on each card now showing similar values with slight variation.
Unit 2 was able to reached FSNL but failed to synch to GRID due to CPD fluctuating and TNH speed drop to 95% only.
Unit was shut down and found that T Core has no supply, we replaced it.
Test firing, back to the old problem failure to ignite with 2 attempts
Upon checking, 2 diagnostic alarm pops up for <C> & <Q>, we check and replaced again.
Once verify all parameters is as it supposed to be, Unit 2 is start again but still failed to start on gas due to failure to ignite.
During the successful firing and reach FSNL, the CPD was a bit low at 3.8 bar which we think it should be around 7 bar.
Any ideas what to do next? We can just replace all the cards but that would be too expensive. Your help is greatly appreciated its been 8 days since the normal shutdown.
Thanks in advance.
Most of the data you have given seems OK but the CPD at 3.8b at FSNL is at least a starting point to look at something.
Are Compressor Bleed Valves operating properly, is IGV angle OK, is it possible anything is partially blocking Inlet Air flow? Can you just crank again then switch to fire and record P1,P2 & P3 pressure, CPD and check SRV & GCV position? This will give us some simple baseline data to try and establish why no flame.
"Further investigation on SRV opening found that before starting up the value for RST (fully closed) is at -97.10 for all, while during start up/firing mode it differs at -0.05 , 4.56 and 2.91"
Just an update, I read your post again. -97.10 on SRV at shutdown is OK, this is a hard close signal on the valve. At operation, all servo currents should be roughly the same at slightly positive to overcome the null bias. Yours are not (but could work). Have you tried changing this servo? Are wiring polarities OK? Have you tried stroking the valve with one coil at a time?