Dear All,

I am working with Frame 6 machine, 32MW.
While going through P&ID of lube oil, trip oil and hydraulic oil circuit, I have noticed that Trip oil regulator valve's position is after 88QA discharge line and then after 88QE discharge is added to header.
VPR1 valve's setting is 4.75 Kg/cm2.

As far as i understand from reading manual, initially during turbine start-up when 88QA runs, as VPR1 (Normally closed valve) remains closed and first trip oil circuit charges and then after when trip circuit charged fully and VPR1 set point reaches and VPR1 starts opening and further lube oil circuit charges.

Am i correct till now?

Now my question is suppose in case of black start up (No power at all, Neither from grid), If we are going to start machine with 88QE (as AC power is not available to run 88QA) how it will charge trip circuit as, 88QE discharge is connected to header after VPR1.
And until unless trip circuit is not built, SRV will not open.

Kindly correct me and through some light here.

 

Is your machine black start capable? It's a long time since I've worked on a black start machine with a VPR-1. Is it possible you could post a copy of your Lube Oil P&ID for us to have a look at?

 

> Is your machine black start capable?

That I am not sure about it, but the panel Mark IV has the black start inverter in it.

Surely i will post P&ID of my lube oil system.

 

Black start of GT - Interesting question , I have not seen a GT black start (fortunately) and am just summarising what all drives are needed at a min.

No , you cannot start the plant with EOP , EOP is meant as the last ditch attempt to save the turbine shaft and bearings , it is not designed as a startup

tool. you need to have AC power for a black start. some of the important drives which are used in startup need AC power

1. DM water pumps - for warren LO cooling (if you have a dry pump like IMO then it is not needed) , atomising air cooling (there is no trip as such for a high atomising air temp , and when the machine reaches FSNL it will be around the 250-280 assuming that the CTD will be the atomising air temp)

2. Fuel pumps (well if you have a gas then perhaps you will get the supply from elsewhere and you do not need it)

3. cooling water pumps - you need to have a LO cooling water supply to maintain LO temp , diesel engine cooling and DM water cooling.

4. warren LO pump - needed only if you have a warren shaft driven fuel pump

5. AHOP - needed for IGV , LFBV , GCV/SRV working (i am told that not every design has a AHOP. so perhaps at firing speed the MHOP might develop required pressure i guess. someone who has worked on such design can perhaps clear the point)

6. LO mist eliminator - well, you need to maintain a active vacuum to prevent LO fumes from bearing (a significant fire hazard)

so, i guess just with DC supply you cannot start the machine, you need a AC power source of at least 100-150 KW for starting the GT.

and yes you are correct about the VPR1 part. as for SRV opening, though i have not tried it yet, i think i might open with 2 kg pressure but the discharge of EOP is given after VPR1 which only opens when when the pressure on the upstream is greater than 4.75 kg. so with just the EOP the 2 kg pressure might not be there in the trip oil circuit.

 

Process Value,

There are MANY GE-design heavy duty gas turbines designed for black-start applications. They usually have diesel starting motors, and they do use the ELOP for developing Trip Oil pressure (in addition to bearing L.O. header pressure) during starting.

Some have special transformers and dedicated AC circuits for cooling water pumps and cooling water fans. The generator is flashed at a low speed during acceleration and generator terminal voltage (at less than rated frequency) is used to drive the cooling water pump and -fan.

To the original poster, the presence of a black start inverter would seem to indicate the machine is capable of a black start. But, one would need to examine the sequencing running in the Mark IV, as well as the auxiliaries, to be sure. There were a couple of Mark IVs that were supplied with "black start inverters" simply to power the CRT and printer in the event of loss of AC to the Mark IV. (The CRT and printer in the Mark IV require AC to operate.)

 

Thanks for reply.
Now i need to check, that where my machines are capable of Black start up or not.

I will get back to here in case of any query.