Alstom Typhoon Gas Turbine Off Skid Gas Fuel Vent Valve Failed Open Fault

A P&ID might be useful. When is the gas fuel vent valve supposed to be open/closed, and what could happen if it is wrong in either way? How does the control system sense the status of this valve?

Actually, this valve is normally closed whether the turbine is running or standing idle. It opens when there is gas or fire detection inside the enclosure or there is any fault at the on package vent valve. Watever is causing this valve to open should also be indicated in the annunciation window but in our case nothing is happening, turbine is getting tripped on this particular fault.

What did the manufacturer say when you described the problem to them?

Could be a sensor fault, wiring fault, programming glitch or something else is causing it.

Try locating the valve and reproducing the fault to see if you can figure out which one of these it is.

How could a programming glitch cause this? i mean it happened thrice in 6 months and there are 300 inputs & outputs...y this particular input?

I only mentioned this as a possibility, which is not unreasonable but probably the most unlikely (and hardest to trace) of the things it could be.

If everything else appears to check out it could be a software glitch (which can be caused for example by a voltage spike due to lightning, internal hardware tolerance or component failure in the protection relay (or similar), etc).

Ya probably, after the last tripping we changed the solid state relay & a PCB. i hope this will rectify the problem but will be confirmed in next few months.

Did you:

1. read the manual?

2. understand the manual?

3. read the trouble shooting guide?

4. go to the company website for help?

5. contact the company directly for help?

6. call a service technician?

Or, did you just want a bunch of total strangers, who know nothing about the installation or how it is used, or the competence of the operators using the equipment, or your personal competence to describe the problem to total strangers who probably have never seen this piece of equipment, to divine an answer out of thin air?

Dude thanks for the suggestion but i think there are lot professionals who have worked on similar machines and i believe they can point me in the right direction.

So, that would be no, to all of the above?

Dude, that would be a no. Didn't you know that CR4 users are more qualified then the manufacturer to help in this situation. Come on Lyn, do you have to ask?

He has posted same question on other sites as well, he'll get the professional help he needs.

http://www.control.com/thread/1359289991

I have tried first three things what u have suggested but last three are invalid in my case because the manufacturer company doesnot exist anymore and now the maintenance is done by another company which lacks competent personnel as the instrumentation & control system (Rustronic Mark II) are getting obsolete.

Company doesn't exist? Who is this then?

http://www.alstom.com/power/

We are not trying to be mean, but you really should be talking to someone intimately familiar with your particular gas turbine. You will get a lot of guesses here, but who knows, one of our esteemed users may be familiar with it.

@ JPool, i am talking about Typoon gas turbine. Its not manufactured by Alstom anymore neither is the maintenance is done by them.

The company still makes gas turbines, they have installed 740 such turbines worldwide. Are you sure they can't help you?

http://www.alstom.com/power/gas-power/gas-turbines/

<edit>

Ok, one of those deals where 2 companies where merged then split?

I did a search for "Typhoon Gas Turbines" and it returned over 18 million results, surely one of those can help you.

I am 100% sure because as i said the support services for this machine is provided by another company.

And there is nobody at this other company with any competence, right, you did say that. Well then I wish you luck finding someone that knows about your turbine. Are you sure they are all incompetent, or just the ones you talked to?

I've gotta go. You take it from here.

I'm done too. I know next to nothing about said turbine, just trying to point OP in the right direction.

As to whether this applies to your situation or not, I haven't a clue, but it represents one use of a fuel vent valve for other large consumers of fuel gas.

Boiler and furnace regulations in many countries require double block and bleed (DBB) valves on the fuel line that are used as Safety Shut-off Valves (SSOV) with a Normally open (NO) vent valve installed between the double block valves. The vent valve is typically energized to a closed position during normal operation when the block valves are open, supplying fuel to the burners.

When the block valves are dropped out for any reason, power to the vent valve is turned off and the valve goes to its normally open position, venting any fuel that leaks by the upstream block valve to atmosphere, rather than letting it bleed past the downstream block valve where it could accumulate.

A vent valve that fails and won't close on a call for fuel, as it should, vents a large amount of fuel up the vent, which can create light-off problems due to low fuel pressure/delivery.

As to how an indication of an open vent valve is deduced, vent valves can a limit/stop switch.

You might investigate the fuel delivery end of your process.

Without knowing:

• The make of the valve
• The size of the valve
• The age of the valve
• The number of intended swings per unit time for the valve in comparison with the manufacturer's recommended upper limit
• The design transit time from open to closed
• The design transit time from closed to open
• The wiring diagram for the valve at "as built"
• The configuration of the control system alarm table
• The Control Philosophy for the installation, which should be documented at "as built" status
• The Functional Design of the system, which should be documented at "as commissioned" status, with commissioning records attached thereto as part of site acceptance testing
• The default position of the valve according to the "as built" P&ID
• The amount of standby equipment available
• The location of the valve on the planet/country/district/site/unit/x-y-z co-ordinates
• The ambient temperature and humidity at the valve's location in comparison with the manufacturer's limits on these parameters

etc., it becomes a game of "20 Questions" to some readers, trying their patience. After all, it could be any of the following:

• Incorrect transit time selected in the alarm configuration software
• Inadequate lubrication of the valve drive, resulting in extended swing times
• Mechanical obstruction either inside or outside the valve
• Other mechanical problem with the valve motor
• Low control system supply voltage/current
• Loose connection on the valve wiring
• Incorrectly-aligned limit switch inside the valve
• Low control air pressure (at this moment, the forum does not know whether the valve is electrical, electro-pneumatic or something else)
• Blown fuse in the control wiring, which is a symptom, not a cause
• Rainwater in the control wiring
• Failed conductors in the control wiring
• Something else
• Some combination of the above

So here's a return question: if the company that supplied maintenance for the system is seemingly unable to diagnose and rectify the fault, why persist with its contract and why not take maintenance in-house instead?

I can relate to what you are going through. An intermittent trip can be very difficult to troubleshoot sometimes.

I had a turbine that would trip at almost the same time in the afternoon during the summer. Turns out at a little after 2:10 in the afternoon the sun had been shinning directly on the side of the control cabinet long enough for the PLC power supply to trip off on a thermal. It would trip off cool down reset and when the operator got out to it all was normal and ready to start.

On another turbine an expander/compressor unit in a air seperation plant we had intermittant trips that would activate an interlock that resulted in a total plant trip.

This would happen very infrequently sometimes many months between trips. Turns out it was a break inside the insulation of a small gage wire on a limit switch on the quick closing valve. The wire was a capable of handling the low voltage and current but not mechanicaly robust enough for the loacation, someone had probably stepped on it while loooking at the trip valve. The limit switch wiring would indicate a turbine trip when it was really still running this would then activate an interlock that resulted in a turbine trip.One of those circular logic things.

Look for every piece of information you can, does it happen when it rains maybe something is shorting out, does it happen when another piece of equipment is started or stopped,power dip or surge, does it always happen to the same shift operator.

The next option is see what directly activates the trip and start to change out one piece at a time, if you suddenly have two problems reverse what you just did.

For a fire eye detector, is the tube it is installed in purged with clean air or nitrogen to keep it clean. They can be very sensitive sometimes all it takes is a small flake of rust that falls off the lens as soon as you disturb it when removing it.

Just some ideas good luck.

Thx for sharing ur experience!!! Actually we did everything i.e., inspected cabling,replaced limit switches, checked grounding etc. wat i think its something to do with electronic cards that are installed. The cards are multi layered PCBs and cannot be troubleshot. there is one Solid state pepprl & Fuch relay and one is Mark II control system switch input module (Muti layer PCB). this could be also software glitch but i am not sure.

I have encountered I/O board failures, but in a ratio of about 50:1 for wiring issues or field sensors/output device (valves) issues. It's not that a failed I/O board can't happen, but statistically, in my experience, faults lie in the things that physically move in the field or in the connecting wiring, not in the boards that just see electrons move about.

The description of the fault (gas fuel vent valve failed open) sounds like the vent valve shown in a generic turbine fuel train below (ignore the liquid fuel side):

As PWSlack asked, in effect with his 20 observations, "What kind of valve is this fuel vent valve?", yet we've had no description of the type of valve, its power source, the logic used to drive it nor the logic conditional on its operation.

Until you find and inspect the fuel vent valve and its wiring, cycle it multiple times and observe its operation and the logic it produces; it's wishful thinking. For instance, if it is a solenoid vent valve, dirt inside the solenoid will cause erratic operation as the solenoid mechanically sticks or jams.

thx Iris...jus for your info i list down the activities that we did to rectify this fault before the last tripping:

1. Replaced limit switches

2.checked solenoid valve

3.checked the actuator seal kits for air leakage & any other wear & tear.

4.inspected cabling & grounding

5.Checked instrument air pressure & air lines

But in the last tripping we replaced solid state relay & Rustronic Mark II PCB.

The fault "Off skid gas fuel vent valve failed open" means vent valve has failed because the close feedback from limit switch has been lost and now the valve is open even if it is not actually but the limit switch has malfuntioned thats how the controller reads it and initiates the shut down.

When I see your first action I remember the problems we had. A false trip from a limit switch that activated an interlock that made things much worse.

In our case the limit switch was fine but the wiring from the LS was broken inside the insulation and proved to be intermittant.

Does the LS prove open or infer open by not being closed.On the LS when you have a failure is the feedback from the limit switch going to a zero or going to a one state.

Each condition points in different troubleshooting directions short verus open.

Is the limit switch a mechanical physical contact lever type or a proximeter type.

The failure of the circuit board is less likely but still possible.

The solenoid operated vent valve is engergized to close and its normally open.It has two limit switches, one for close feedback & other for open feedback. Each switch has two contacts normally open & normally close. The close limit switch uses normally close contact to give the close status of vent valve. When the solenoid is de-energized, the cam rotates and disengages the close limit switch and engages the open limit switch. This means normally close contact of close limit switch changes to normally open contact. Similarly, normally open contact of open limit switch changes to normally close contact. Thats how the open status of valve is communicated to Mark II control system.