Steam seal regulator

[Billthethrill]

Commissioning a rebuilt 1950s GE turbine with orginal steam seal regulator. Apparently working fine for 2 weeks, now gauge on it shows no pressure. No steam leaking at the seals. I suspect the guage is bad. How can I check while online?

 

[TheBlacksmith]

Some turbines are self sealing at higher loads; enough steam enters to sealing system from the high pressure end to supply the low pressure end seals. Has the load been increased over the two weeks? If the turbine is lightly loaded or the gland exhaust has a good vacuum, you may not see steam outside, but are you seeing higher DO? That would indicate a loss of sealing. Your gauge line may just be plugged with debris. Can you safely isolate the gauge with a root valve and change it?

 

[byrdj]

Is this a condensing unit, If so and if there was insuficient sealing steam you would loss vacuum.

There should be a least a couple taps (with isolation valves availabe to to you. More than likely the gauge you use to look at will have an isolation, then a plugged tee for installing a test guage for calibration ( or as a check guage.

You didn't say if MSTG or LSTG regulator, but in either case the feed and dump valve are operated by one summing lever. If that lever is level, then both are closed.

while off line or below minimun load the lever will be tilted to open the feed and supply main steam to the seal header.

Once on line and above minimun load, the HP gland leakage will back flow into the header, the regulator will sense the increase seal pressure and close the feed and open the dump valve and the lever will be tilted with the other end up.

For the LSTG, the dump valve opens with the hydrualic actuator piston down. For the MSTG, with the actuator piston up.

IF you have any other questions related to those MHC controls, please ask

 

[byrdj]

OH...DO NOT isolate the sensing line from the header to the regulator belows while on line. there may (or should be) a high point condensing pot in that line.

If the regulator fails it will NOT be with both feed and dump closed, it will be with one wide open. Thus a full dump of the header, or an over pressure feed condition

 

[rmw]

What load were you running at during this condition? Look at your heat balances and see what the steam seal regulater output pressure should be for the load that you were or are carrying. Sometimes at low loads the steam seal pressure goes below atmospheric.

We chased a condenser air leak for years until it was noticed that the problem was intermittant happened only at minimum (overnight) loads (which didn't necessarily happen every night) and upon examining the heat balances looking for what piping went under vacuum only at low loads, the SSR piping was found to operate under vacuum at the lowest heat balance, and lo and behold, there was a loose flange that I had seen mentioned in an outage report several years previously but that had never been tightened. At higher loads it leaked steam, but at low loads it sucked air. There were enough serious steam leaks around that unit that the low pressure SSR output didn't get much attention.

Tightened the flange and the problem went away.

rmw

 

[byrdj]

Sorry, the SSRs I discribed maynot be what have.

I did a little research and the LSTG isobar regulator was not introduced till 1951. I just can't remember working on a LSTG SSR pre 1951's design.

As far as the MSTG, while it is not a true isobar, it should have had a very narrow regulation, but I don't know when they were introduce or the vintages I've worked on but all Lynn's looked old to me anyway

 

[Billthethrill]

Thanks for the replys. It is a 15MW MSTG condensing unit. The turbine/generator and condensor was relocated and rebuilt. We are operating at 14-15MW for the last two weeks (on and off with trips). We have been unable to take our hogger offline. Did the helium checks for leaks and fixed those. Running both ejector sets on the I/A and vacuum will range from 1.5 to 3.0 "HGA. Nothing is consistant with regards to vacuum. The SSR is just a recent occurance that made me nervous because of the lack of pressure on the gauge.

I have worked 37 nights straight and have convienced them to let me go to a 4 & 4 rotation. This is my last night and I really don't care right now. I will check back with yall on the 8th.

 

[byrdj]

Good luck if it requires any adjustment...
I believe you will have the "door spring" set point adjuster. And the regulation is a function of spring load at set point and its gradiant. with a higher header pressure required to open the unloader with higher load.

I believe design regulation was 2psig at NL and 4 psig at FL,with an acceptable operation of 0.5 psig at NL and 8 psig at FL

IF the manual control handwheel works down and makes contact with the cover it will prevent the unloader from pinching down as load is reduced and cause a header pressure drop


Boy that brings back unpleasant memories bent over under the deck flooring on the right side

 

[rmw]

If you are on the side of the globe where it is summer right now, 3.0" of back pressure sounds pretty good and 1.5" sounds fantastic. I suspect that your SSR problem and your vacuum fluctuation are related.

rmw

PS to byrdj-the SSR section was my only "F" during my FEP.

 

[byrdj]

to rmw
...have you found

http://turbinecowboy.com/...

jfb, FEP 1979

 

[rmw]

No I hadn't. Thanks for that. I just took a glance and came back to say thanx. I'll go back now and dive in.

rmw

 

[unclesyd]

Just curious, is there any amount of steam flowing through the regulator?