Mark 5 fuel leak

Hi
we run a dual fuel mark 5 gasturbine. our GT was Isolated but when we went to check the oil level again there was a huge amount of fuel in the oil sump . any suggestions
 
Bobby,

Why do you suspect the turbine control system? (Could it be you are confusing a Mark V and a GE-design Frame 5 heavy duty gas turbine (which might be controlled by a Mark V)?)

Does the turbine have a diesel starting means and is there a diesel fuel tank directly under the diesel, and above the L.O. reservoir?
 
I corrected my hasty reply mistakes in the response above.... SORRY FOR ANY CONFUSION!!! A Frame 5 can be controlled by a Mark V (the Frame series uses the "Arabic" numerals, and the Mark* turbine controls use the Roman numerals).
 
I corrected my hasty reply mistakes in the response above.... SORRY FOR ANY CONFUSION!!! A Frame 5 can be controlled by a Mark V (the Frame series uses the "Arabic" numerals, and the Mark* turbine controls use the Roman numerals).
Hi I did post it wrong it is a frame 5 gas turbine with mark6 speedtronics. The GT was off and wasn’t on ratchet . When it was switched off it was checked and checked the following day the oil level was ok. After about 10 days there was probably about a ton of diesel in the oil sump the fuel pump has been checked and seems ok.
 
Bobby,

One problem solved--it's a GE-design Frame5 heavy duty gas turbine. With a Mark VI Speedtronic turbine control system.

Many people believe that all Frame 5s are like all other Frame 5s, and that's just not true. Yes, they all suck and squeeze and burn and blow, but they do so with very different auxiliaries. The starting means for a Frame 5 could be an expander turbine, or an electric motor, or a diesel engine. WHAT STARTING MEANS DOES THE FRAME 5 WITH OIL IN THE SUMP HAVE? AN ELECTRIC MOTOR OR A DIESEL ENGINE?

You say the fuel pump has been checked and seems ok. ARE YOU REFERING TO THE FUEL FORWARDING PUMP FROM THE TURBINE DIESEL FUEL STORAGE TANKS? OR ARE YOU REFERRING TO THE HIGH-PRESSURE LIQUID FUEL PUMP IN THE ACCESSORY COMPARTMENT?

Any by "...seems ok...." what do you mean? No visible signs of a fuel leak? If you're referring to the Liquid Fuel Forwarding Pump (there's usually two, for redundancy) do you mean they start and run without any noises? If you're referring to the high-pressure liquid fuel pump in the Accessory Compartment, it is turned by an output shaft of the Accessory Gear, through an electric clutch. To test the high-pressure liquid fuel pump it would be necessary to START the unit, with liquid fuel selected, and observe the pump pressures (using the selector valve and gauge on the liquid fuel flow divider).

Finally you keep talking about a "sump.' I have been taking sump to mean the turbine L.O. reservoir, which is the main part of the Accessory Compartment base. Are you referring to a gas turbines drains tank--which is usually mounted underground (so compartments and equipment drain down into the tank). What--and where--is this sump you speak of?

If you are referring to an underground gas turbines drains tank (sometimes called a "sump tank") it is used to prevent leaks of diesel fuel and/or L.O. from running onto the soil around the gas turbine and contaminating the soil and resulting in a big, expensive clean-up and possibly fines. If that's where you're finding this "ton" of diesel fuel, there aren't too many places where it can come from. Especially if the turbine hasn't been running. I suppose fuel filter drain valves left open accidentally could cause turbine diesel fuel to run by gravity from the storage tanks to the unit and into the underground gas turbine drains tank. BUT, the fuel forwarding stop valve, 20FL-1, would have to be failed in the open direction. Or, the Mark VI would have to have turned on the fuel forwarding pumps AND opened the fuel forwarding stop valve. That's not outside the realm of possibility, but it would be necessary to review the application code (program) running in the Mark VI to know if that's possible.

But, we need to know if the unit has a diesel engine starting motor in the Accessory Compartment, AND what is the "sump" you refer to. Without that, we're blind.



If the Frame 5 you are working on has a diesel engine starting motor, it is almost always located in the Accessory Compartment, above the turbine L.O. reservoir. Between the bottom of the starting diesel motor and the top of the turbine L.O. reservoir there is usually a fuel tank for the starting diesel engine--it's long, and wide, and flat (meaning it's not round, but flat and not very tall (six or eight inches at most). Fuel for the diesel starting motor is usually kept in the tank below the engine, which is above the turbine L.O. reservoir. Usually, the fuel for the diesel starting motor comes in a smaller tank truck and is pumped directly into the starting diesel engine's fuel storage tank under the motor. (In other words, the fuel for the starting diesel motor DOES NOT USUALLY come from the large storage tanks which hold the fuel to be burned in the turbine.) The starting diesel motor has its own fuel pumps, one to draw from the its fuel storage tank below the motor and one to raise the fuel pressure high enough to be injected into the diesel engine's cylinders. And this only happens when the diesel starting motor is running. All of this is above the turbine L.O. reservoir, and usually, if all of the access covers to the L.O. reservoir tank are tightly closed (as they should be) there would be visible puddles of fuel around the top of the L.O. reservoir.

There have been a couple of cases reported where some welds of the diesel engine fuel storage tank (between the bottom of the starting diesel motor and the top of the turbine L.O. reservoir) have cracked and allowed diesel fuel to flow down into the turbine L.O. reservoir.

All of the turbine diesel fuel lines are run OUTSIDE of the turbine L.O. reservoir--for two reasons. First, so that if there are any leaks they are visible during walk-downs/rounds. And, two, so if there are any leaks the oil won't go into the turbine L.O. reservoir. The liquid fuel to be burned by the turbine coming from the forwarding pumps into the Accessory Compartment flows through the Liquid Fuel Stop Valve (a hydraulically-operated valve) and then through the high-pressure liquid fuel pump and then through the liquid fuel flow divider and out of the flow divider it flows through 10 individual tubes under the turbine inlet and into the turbine compartment to the check valves directly in front of the fuel nozzles. It requires 100 psig of liquid fuel pressure to open the check valves and let fuel flow into the fuel nozzles (which is usually provided by the high-pressure liquid fuel pump; liquid fuel supply pressure up to the Accessory Compartment is supposed to be approximately 60 psig--less than 100 psig so it shouldn't be able to open the liquid fuel check valves at the fuel nozzles).

So, we need to know the following to be of any further help:

1) What kind of starting means (device; motor; engine; expander turbine; etc.) does the Frame 5 have at the site where you are working?

2) What is the "sump" you are referring to--the turbine L.O. reservoir, or the gas turbine drains tank, or--possibly the diesel starting motor's fuel storage tank (under the diesel starting motor and above the turbine L.O. reservoir)?

SOME, but not very many, sites have a black start diesel engine-generator which is NOT mounted in the turbine Accessory Compartment. When there is no electricity available from the grid, this black start diesel engine-generator starts and provides electricity to the site--including the electric starting motor in the Accessory Compartment used to start the gas turbine. But, generally, Frame 5s provided with diesel starting motors are capable of starting without any AC power at all; sometimes they are called "black-start" units (meaning the gas turbine can be started without any AC power from the grid using the diesel starting means mounted in the Accessory Compartment).
 
Hi
Yes the turbine is started by a Diesel engine.
The sump is intact the lube oil resoviour.
The fuel pump is the high pressure fuel pump in the compartment . I haven’t spoken to our technicians but I have been told the pump checked out good . I noticed that when the problem was discovered there was a drip from the false start drain . Thin to me would indicate fuel getting to the firing can.
 
Bobby,

Thank you for getting back to us with some answers.

The P&IDs really hold the information you need, but I'll try to summarize here.

But, first, I have a question: Did the Mark VI annunciate an alarm "L.O. LEVEL HIGH"? (or something to that effect)

Most sites have some diesel storage tanks where the liquid fuel for the turbine is stored. There is usually a small skid with two pumps which draw fuel from the storage tanks, through a strainer, and pump it to the turbine Accessory Compartment. On the fuel forwarding skid there is usually a solenoid-operated stop valve, 20FD-1, and a pressure regulator to limit the pressure downstream of the skid and upstream of the turbine Accessory Compartment. That pressure regulator is usually set for approximately 55-60 psig. (Some AEs (Architect-Engineers) or EPCs (Engineering Procurement Companies) provide their own skid for forwarding fuel from the storage tanks to the turbine, and sometimes there is a pressure regulator and sometimes there is not.

The fuel, on its way to the turbine Accessory Compartment, usually passes through one low pressure liquid fuel filter. Sometimes, on newer units there is a second low-pressure liquid fuel filter in the Accessory Compartment. The fuel, at a pressure of around 55-60 psig then goes to the Liquid Fuel Stop Valve, I think the device number is VS1-1, which is controlled by a solenoid-operated valve, 20FL-1. This liquid fuel stop valves requires hydraulic oil pressure to open the stop valve, and there is a limit switch to indicate when the valve is closed (it has to be closed in order to be able to START the turbine initially). And, usually there are alarms to say if the valve is open when it should NOT be open, too, but not always.

After the liquid fuel leaves the stop valve is then passes through the high pressure liquid fuel pump, which is driven by an output shaft of the Accessory Gear through and electric clutch. So, in order for the high-pressure liquid fuel pump to rotate the turbine shaft has to be turning AND the electric fuel pump clutch has to be energized.

Depending on the age of the turbine there is usually a liquid fuel bypass valve around the high pressure liquid fuel pump, and by controlling the opening and closing of this bypass valve the fuel flow-rate to the turbine is controlled. The bypass valve is usually OPEN when the unit is at rest, so there is a path for fuel to flow AROUND the high pressure liquid fuel pump and towards the fuel nozzles/combustors.

After the fuel flows through the high pressure liquid fuel pump it then passes through the liquid fuel flow divider, whose function is to equally divide the fuel flowing out of the high pressure liquid fuel pump into ten equal flows to each of the 10 fuel nozzles/combustors. There is a gauge and a manual selector valve which can be used to check the liquid fuel pressures to each of the 10 fuel nozzles/combustors, as well as the output pressure of the high pressure liquid fuel pump and the inlet pressure to the high pressure liquid fuel pump.

After the fuel leaves the flow divider in 10 individual tubes it then has to flow through a check valve which requires 100 psig oc pressure (sometimes it's only 90 psig)--but the check valve cracking pressure is supposed to be at least 50% or so higher than the liquid fuel pressure from the forwarding pumps at the fuel storage tanks. This should prevent flow which might get through the liquid fuel stop valve and around the high pressure liquid fuel pump (through the open liquid fuel bypass valve) from getting into the fuel nozzles and combustors.

I was at one site in the late 1980s where the AE used 300 psig pumps to send the fuel from the storage tanks to the turbine Accessory Compartment--without any pressure regulator. When the turbine tripped due to high exhaust temperature the 300 psig fuel pressure would not let the liquid fuel stop valve close--and fuel flow to the turbine fuel nozzles and combustors did NOT stop. We had to close the manual isolation valve at the edge of the turbine Accessory Compartment to shut off the flow of fuel to the turbine and prevent an overspeed and worse....

There is another check valve which the liquid fuel has to get past on it's way to the fuel nozzle, and that's the liquid fuel purge check valve. These have been known to leak and allow liquid fuel to flow in the reverse direction (back towards the Atomizing Air Compressor), but there is a three-way valve which should direct any leakage to the gas turbine drains tank through what's identified on the Liquid Fuel Purge P&ID as the 'Tell-Tale Leakoff'--so named because any flow out of this drain would be an indication that at least one of the 10 atomizing air check valves was leaking in the reverse direction.

So, under typical conditions and a typical design, even if the liquid fuel forwarding pumps were started by the Mark* AND the liquid fuel forwarding stop valve, 20FD-1 was energized to open the valve, liquid fuel would flow towards the turbine Accessory Compartment up to the liquid fuel stop valve (VS1-1). To open the liquid fuel stop valve, there would have to be L.O. pressure and hydraulic pressure--from either the Aux. Hyd. Pump (if present) OR the unit would have to be spinning (from the diesel starting means). IF the liquid fuel stop valve was open liquid fuel could flow around the high-pressure liquid fuel pump to the flow divider and to the 10 liquid fuel check valves at each of the fuel nozzles/combustors. BUT, the liquid fuel pressure would have to be greater than 90-100 psig in order to open the liquid fuel check valves and allow the liquid fuel to flow into the fuel nozzles and combustors. With no flame or no air flow (I'm presuming the unit was NOT spinning), the fuel would puddle in the bottom of the combustion wrapper, and the lower combustors and would flow out of the normally open false start drain valves and into the gas turbine drains tank.

The Frame 5 is a two-bearing machine, so I don't know how liquid fuel would get from the combustion wrapper and into the L.O. reservoir--there's no path I'm aware of for that to occur. The bearings are basically "sealed" (covered) so the turbine would have to "fill up" with liquid fuel to even get into the bearing enclosures past the labyrinth seals to get into the bearing drains and make its way back into the L.O. reservoir.

On all of the GE-design heavy duty gas turbines I've seen all of the liquid fuel piping is OUTSIDE of the L.O. reservoir, to prevent any leaks from getting into the L.O. reservoir.

What I have also heard of (I wasn't at the site where this occurred) was that the diesel fuel supplier who provides the diesel fuel for the diesel fuel starting motor was new and no one was around when he arrived to fill the diesel starting motor fuel tank in the turbine Accessory Compartment. He mistook the L.O. reservoir fill line for the diesel starting motor fuel tank fill line and pumped a whole bunch of liquid fuel into the L.O. reservoir before someone realized the L.O. LEVEL HIGH alarm had been annunciated and went out to investigate. A little bit of paint would have saved a LOT of oil and work (two different colors for the two different fill lines, which are sometimes located close to each other and look an awful lot alike).

I simply can't imagine any other way for fuel to get into the L.O. reservoir--with the exception of the diesel starting motor fuel tank (which, again, is usually under the diesel motor and above the L.O. reservoir) having a leak. Again, if enough fuel leaked into the L.O. reservoir there should have been a L.O. LEVEL HIGH alarm. And, the level in the diesel starting motor fuel tank would be very low. The diesel starting motor has it's own "forwarding" pump from its own fuel storage tank, and it has its own high-pressure fuel pump for the injector--all outside of the L.O. reservoir, though directly above it.

If the fuel did in fact get all the way to the fuel nozzles/combustors and then through the false start drain valves and into the gas turbine drains tank, there's usually an alarm to warn of a high gas turbine drains tank level (either on the gas turbine control system, or the plant DCS or balance-of-plant control system). But, it's not clear to me how liquid fuel would get from the combustion wrapper and lower combustion cans into the L.O. reservoir.

So, it would be VERY MUCH APPRECIATED if you would keep us posted on what you find!!! Because this is pretty strange. And a LOT people read these threads, and will for many years, so you would be helping a lot of people avoid a similar problem.
 
Also, the false start drains do not go to the L.O. reservoir--they usually go to the gas turbine drains tank, which is underground. It is difficult to imagine a way for anything in the gas turbine drains tank to get up into the L.O. reservoir.

Things like compartment drains and the false start drains and the Tell-Tale Leakoff, drain, by gravity, to the gas turbine drains tank (sometimes called the oily waste tank).

Was the gas turbine drains tank level checked and recorded before and after the holiday period?

Again, several unusual things would have to happen at the same time for fuel to get past the 90-100 psig check valves at the inlet to each of the 10 fuel nozzles, and then for the diesel to find its way to the L.O reservoir.

Obviously, my curiosity is piqued! My money's on someone mistakenly putting diesel meant for the diesel starting means fuel tank into the L.O. reservoir because the fill lines usually look very similar and are on the same side of the Accessory Compartment (though, often the diesel starting motor fuel tank fill line is inside the compartment and the L.O. reservoir fill line is outside the compartment).

It would be interesting to hear about the L.O. tank level alarm and the gas turbine drains tank level before and after the 10-day period.
 
Bobby,

Thank you for getting back to us with some answers.

The P&IDs really hold the information you need, but I'll try to summarize here.

But, first, I have a question: Did the Mark VI annunciate an alarm "L.O. LEVEL HIGH"? (or something to that effect)

Most sites have some diesel storage tanks where the liquid fuel for the turbine is stored. There is usually a small skid with two pumps which draw fuel from the storage tanks, through a strainer, and pump it to the turbine Accessory Compartment. On the fuel forwarding skid there is usually a solenoid-operated stop valve, 20FD-1, and a pressure regulator to limit the pressure downstream of the skid and upstream of the turbine Accessory Compartment. That pressure regulator is usually set for approximately 55-60 psig. (Some AEs (Architect-Engineers) or EPCs (Engineering Procurement Companies) provide their own skid for forwarding fuel from the storage tanks to the turbine, and sometimes there is a pressure regulator and sometimes there is not.

The fuel, on its way to the turbine Accessory Compartment, usually passes through one low pressure liquid fuel filter. Sometimes, on newer units there is a second low-pressure liquid fuel filter in the Accessory Compartment. The fuel, at a pressure of around 55-60 psig then goes to the Liquid Fuel Stop Valve, I think the device number is VS1-1, which is controlled by a solenoid-operated valve, 20FL-1. This liquid fuel stop valves requires hydraulic oil pressure to open the stop valve, and there is a limit switch to indicate when the valve is closed (it has to be closed in order to be able to START the turbine initially). And, usually there are alarms to say if the valve is open when it should NOT be open, too, but not always.

After the liquid fuel leaves the stop valve is then passes through the high pressure liquid fuel pump, which is driven by an output shaft of the Accessory Gear through and electric clutch. So, in order for the high-pressure liquid fuel pump to rotate the turbine shaft has to be turning AND the electric fuel pump clutch has to be energized.

Depending on the age of the turbine there is usually a liquid fuel bypass valve around the high pressure liquid fuel pump, and by controlling the opening and closing of this bypass valve the fuel flow-rate to the turbine is controlled. The bypass valve is usually OPEN when the unit is at rest, so there is a path for fuel to flow AROUND the high pressure liquid fuel pump and towards the fuel nozzles/combustors.

After the fuel flows through the high pressure liquid fuel pump it then passes through the liquid fuel flow divider, whose function is to equally divide the fuel flowing out of the high pressure liquid fuel pump into ten equal flows to each of the 10 fuel nozzles/combustors. There is a gauge and a manual selector valve which can be used to check the liquid fuel pressures to each of the 10 fuel nozzles/combustors, as well as the output pressure of the high pressure liquid fuel pump and the inlet pressure to the high pressure liquid fuel pump.

After the fuel leaves the flow divider in 10 individual tubes it then has to flow through a check valve which requires 100 psig oc pressure (sometimes it's only 90 psig)--but the check valve cracking pressure is supposed to be at least 50% or so higher than the liquid fuel pressure from the forwarding pumps at the fuel storage tanks. This should prevent flow which might get through the liquid fuel stop valve and around the high pressure liquid fuel pump (through the open liquid fuel bypass valve) from getting into the fuel nozzles and combustors.

I was at one site in the late 1980s where the AE used 300 psig pumps to send the fuel from the storage tanks to the turbine Accessory Compartment--without any pressure regulator. When the turbine tripped due to high exhaust temperature the 300 psig fuel pressure would not let the liquid fuel stop valve close--and fuel flow to the turbine fuel nozzles and combustors did NOT stop. We had to close the manual isolation valve at the edge of the turbine Accessory Compartment to shut off the flow of fuel to the turbine and prevent an overspeed and worse....

There is another check valve which the liquid fuel has to get past on it's way to the fuel nozzle, and that's the liquid fuel purge check valve. These have been known to leak and allow liquid fuel to flow in the reverse direction (back towards the Atomizing Air Compressor), but there is a three-way valve which should direct any leakage to the gas turbine drains tank through what's identified on the Liquid Fuel Purge P&ID as the 'Tell-Tale Leakoff'--so named because any flow out of this drain would be an indication that at least one of the 10 atomizing air check valves was leaking in the reverse direction.

So, under typical conditions and a typical design, even if the liquid fuel forwarding pumps were started by the Mark* AND the liquid fuel forwarding stop valve, 20FD-1 was energized to open the valve, liquid fuel would flow towards the turbine Accessory Compartment up to the liquid fuel stop valve (VS1-1). To open the liquid fuel stop valve, there would have to be L.O. pressure and hydraulic pressure--from either the Aux. Hyd. Pump (if present) OR the unit would have to be spinning (from the diesel starting means). IF the liquid fuel stop valve was open liquid fuel could flow around the high-pressure liquid fuel pump to the flow divider and to the 10 liquid fuel check valves at each of the fuel nozzles/combustors. BUT, the liquid fuel pressure would have to be greater than 90-100 psig in order to open the liquid fuel check valves and allow the liquid fuel to flow into the fuel nozzles and combustors. With no flame or no air flow (I'm presuming the unit was NOT spinning), the fuel would puddle in the bottom of the combustion wrapper, and the lower combustors and would flow out of the normally open false start drain valves and into the gas turbine drains tank.

The Frame 5 is a two-bearing machine, so I don't know how liquid fuel would get from the combustion wrapper and into the L.O. reservoir--there's no path I'm aware of for that to occur. The bearings are basically "sealed" (covered) so the turbine would have to "fill up" with liquid fuel to even get into the bearing enclosures past the labyrinth seals to get into the bearing drains and make its way back into the L.O. reservoir.

On all of the GE-design heavy duty gas turbines I've seen all of the liquid fuel piping is OUTSIDE of the L.O. reservoir, to prevent any leaks from getting into the L.O. reservoir.

What I have also heard of (I wasn't at the site where this occurred) was that the diesel fuel supplier who provides the diesel fuel for the diesel fuel starting motor was new and no one was around when he arrived to fill the diesel starting motor fuel tank in the turbine Accessory Compartment. He mistook the L.O. reservoir fill line for the diesel starting motor fuel tank fill line and pumped a whole bunch of liquid fuel into the L.O. reservoir before someone realized the L.O. LEVEL HIGH alarm had been annunciated and went out to investigate. A little bit of paint would have saved a LOT of oil and work (two different colors for the two different fill lines, which are sometimes located close to each other and look an awful lot alike).

I simply can't imagine any other way for fuel to get into the L.O. reservoir--with the exception of the diesel starting motor fuel tank (which, again, is usually under the diesel motor and above the L.O. reservoir) having a leak. Again, if enough fuel leaked into the L.O. reservoir there should have been a L.O. LEVEL HIGH alarm. And, the level in the diesel starting motor fuel tank would be very low. The diesel starting motor has it's own "forwarding" pump from its own fuel storage tank, and it has its own high-pressure fuel pump for the injector--all outside of the L.O. reservoir, though directly above it.

If the fuel did in fact get all the way to the fuel nozzles/combustors and then through the false start drain valves and into the gas turbine drains tank, there's usually an alarm to warn of a high gas turbine drains tank level (either on the gas turbine control system, or the plant DCS or balance-of-plant control system). But, it's not clear to me how liquid fuel would get from the combustion wrapper and lower combustion cans into the L.O. reservoir.

So, it would be VERY MUCH APPRECIATED if you would keep us posted on what you find!!! Because this is pretty strange. And a LOT people read these threads, and will for many years, so you would be helping a lot of people avoid a similar problem.
Hi
Thank you for all you’re help . It could be a while before we get to the bottom of the problem due to Covid 19 and manning levels being reduced . I will let you know what we find.
 
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