Dear sir
Nice to connect with you
Fristly I would like to explain our gas turbine frame 7ea fail to ignite we change Flow dividor and restrat the unit it working but when the unit is shutdown for few days we try to start unit again it fail to ignite we try to rotate the Flow dividor it not rotate freely to but unit ignite. This repeated more Time. Now we change 4 Flow dividor and problem is still found "fail to ignite"
Is There any investigation?

 

@Ahmed Saad,

Does the exhaust temperature increase at all during firing--probably not all the exhaust T/Cs, but at least a few of them?

Do you see any white smoke coming from the exhaust after the failure to ignite? (This would be an indication that one or more of the combustors was lit, if only for a few seconds.)

Have you checked the false start drains to see if there is any liquid fuel flowing out of them during or after the firing--including the exhaust plenum false start drain?

What liquid fuel(s) do(es) the machine burn? Diesel (sometimes called HSD (High Speed Diesel) or light fuel oil (LFO)? Does the machine switch to heavy fuel oil (HFO) once it reaches FSNL, or shortly after synchronization?

What made you believe the flow divider was the problem and that it needed to be replaced?

I presume the original flow divider wasn't giving the same problem--at least not as often. Please confirm.

Have you tested the ignitors (spark plugs) to ensure they are both working properly? (That would mean the ignitors (spark plugs) would need to be pulled from the combustors they are mounted on, grounded and excited (have voltage applied to them) for a visible spark/sparking. Usually, the gasket between the ignitor (spark plug) body and the ignitor flange on the combustor will not be damaged, but, even if it is it is easily replaced. (There are two spark plugs, for redundancy--only one has to work for the machine to ignite fuel.)

Are you 100% certain that the replacement flow dividers have exactly the same number of teeth on the flow divider wheels that rotate under the speed sensors?

Are you 100% certain that the gap between the face of the speed sensors and the toothed wheel(s) of the flow divider are as per specification?

Does the turbine control system have a way of trending (graphing) the machine speed and flow-divider speed input to the control system and the liquid fuel flow-rate during firing?

Does the liquid fuel control valve have LVDT(s)? Can you trend those signals as well?

Can you trend FQR during firing (usually the control signal name for the liquid fuel flow reference?

Can you trend FQL (or FQL1) the calculated liquid fuel flow-rate during firing?

After you change the flow divider(s), do you ensure there is no air in the liquid fuel lines? (This is usually accomplished by performing what's often called a "false fire"--which involves disabling the ignitors (spark plugs) and initiating a START in FIRE or AUTO mode and let the machine go through a firing sequence where liquid fuel will be flowing BUT since the ignitors (spark plugs) are disabled they machine won't actually fire/establish flame. This is done, again, to push any air in the liquid fuel system--before and after the liquid fuel control valve and the liquid fuel flow divider into the combustors. during the "false firing" it is customary to have some monitoring the false start drain valves to see if liquid fuel actually flowed into the machine and drains out of the false start drains. It's also a good idea after the "false fire" to CRANK the machine for 10 or 15 minutes to push any combustible vapors out of the machine before enabling the ignitors (spark plugs) and attempting a normal START.)

And, while it's the last question is IS one the MOST IMPORTANT questions: Specifically--what other alarms are annunciated during the unsuccessful firing attempts? Process Alarms AND Diagnostic Alarms--in chronological order. Even if you don't think they're relevant.

The purpose of all of the questions is try to cover as many of the possible problems that can lead to a failure to ignite when STARTing on liquid fuel. What is necessary for any internal combustion engine to start? Fuel. Spark. Air. It's pretty safe to say that there is sufficient air. We don't know if you've checked the ignitors (spark plugs) and if you did what the results were. And, fuel. If the flow feedback from the speed pickups on the liquid fuel flow divider is incorrect because the number of teeth on the speed wheels is not the same as the original flow divider then that can cause problems. AND, the problem can be EITHER too much fuel (which can "drown" the ignitors (spark plugs)--another reason to pull the ignitors (spark plugs) shortly after a failure to ignite to ensure the tips are not excessively wet from the fuel) OR too little fuel.

I would also suggest that any liquid fuel filter upstream of the liquid fuel flow divider should be pressurized with fuel and vented to ensure there is no air in the filter canisters.

Checking the gap of the liquid fuel flow dividers speed sensors is important--too close and the flow divider may not rotate easily. Too far and the speed feedback may be erratic or not there at all--even if the flow divider is turning.

Some liquid fuel flow dividers have a small motor to help them get started turning--this is more common on machines that also burn heavy fuel oil. We don't know if the machine at your installation has this "helper" motor on the liquid fuel flow divider or not, and if so is it working correctly? (If the machine trips while buring heavy fuel oil it can remain in the liquid fuel flow divider and make starting on light fuel oil/HSD difficult--which is why the "helper" motor is there.

So, there's a lot of reasons why the machine may not be starting. Simply changing the liquid fuel flow divider and clicking on START without purging the liquid fuel system and fuel lines to the individual combustors and expecting the machine to fire is not sound practice. The more information you can provide (we aren't there beside you to know what was happening, and what was done to try to resolve the problem--other than changing liquid fuel flow dividers) the better and more concise the answers you will get. It would be VERY helpful to know what fuel(s) the machine burns, what kind of combustion system it has (conventional or DLN). And, WHAT ALARMS ARE PRESENT DURING THE FIRING SEQUENCE--PROCESS- AND DIAGNOSTIC??? (I'm presuming the machine uses a GE Mark* turbine control system, but even if it doesn't it would still be VERY HELPFUL to know the alarms being annunciated during an unsuccessful firing attempt.)

You want help. We need information. We have given you a lot of hints about what the problem could be (which is what you essentially asked) not knowing very much about the machine and the circumstances, other than the liquid fuel flow divider has been changed multiple times (and we don't know why it was felt necessary to change the liquid fuel flow divider...).

If you resolve the issue before you answer the questions above please write back to let us know how you resolved the problem.

Thank you!

 

@Ahmed Saad,

Does the exhaust temperature increase at all--probably not all the exhaust T/Cs, but at least a few of them?

Do you see any white smoke coming from the exhaust after the failure to ignite? (This would be an indication that one or more of the combustors was lit, if only for a few seconds.)

Have you checked the false start drains to see if there is any liquid fuel flowing out of them during or after the firing--including the exhaust plenum false start drain?

What liquid fuel(s) do(es) the machine burn? Diesel (sometimes called HSD (High Speed Diesel) or light fuel oil (LFO)? Does the machine switch to heavy fuel oil (HFO) once it reaches FSNL, or shortly after synchronization?

What made you believe the flow divider was the problem and that it needed to be replaced?

I presume the original flow divider wasn't giving the same problem--at least not as often. Please confirm.

Have you tested the ignitors (spark plugs) to ensure they are both working properly? (That would mean the ignitors (spark plugs) would need to be pulled from the combustors they are mounted on, grounded and excited (have voltage applied to them) for a visible spark/sparking. Usually, the gasket between the ignitor (spark plug) body and the ignitor flange on the combustor will not be damaged, but, even if it is it is easily replaced. (There are two spark plugs, for redundancy--only one has to work for the machine to ignite fuel.)

Are you 100% certain that the replacement flow dividers have exactly the same number of teeth on the flow divider wheels that rotate under the speed sensors?

Are you 100% certain that the gap between the face of the speed sensors and the toothed wheel(s) of the flow divider are as per specification?

Does the turbine control system have a way of trending (graphing) the machine speed and flow-divider speed input to the control system and the liquid fuel flow-rate during firing?

Does the liquid fuel control valve have LVDT(s)? Can you trend those signals as well?

Can you trend FQR during firing (usually the control signal name for the liquid fuel flow reference?

Can you trend FQL (or FQL1) the calculated liquid fuel flow-rate during firing?

After you change the flow divider(s), do you ensure there is no air in the liquid fuel lines? (This is usually accomplished by performing what's often called a "false fire"--which involves disabling the ignitors (spark plugs) and initiating a START in FIRE or AUTO mode and let the machine go through a firing sequence where liquid fuel will be flowing BUT since the ignitors (spark plugs) are disabled they machine won't actually fire/establish flame. This is done, again, to push any air in the liquid fuel system--before and after the liquid fuel control valve and the liquid fuel flow divider into the combustors. during the "false firing" it is customary to have some monitoring the false start drain valves to see if liquid fuel actually flowed into the machine and drains out of the false start drains. It's also a good idea after the "false fire" to CRANK the machine for 10 or 15 minutes to push any combustible vapors out of the machine before enabling the ignitors (spark plugs) and attempting a normal START.)

And, while it's the last question is IS one the MOST IMPORTANT questions: Specifically--what other alarms are annunciated during the unsuccessful firing attempts? Process Alarms AND Diagnostic Alarms--in chronological order. Even if you don't think they're relevant.

The purpose of all of the questions is try to cover as many of the possible problems that can lead to a failure to ignite when STARTing on liquid fuel. What is necessary for any internal combustion engine to start? Fuel. Spark. Air. It's pretty safe to say that there is sufficient air. We don't know if you've checked the ignitors (spark plugs) and if you did what the results were. And, fuel. If the flow feedback from the speed pickups on the liquid fuel flow divider is incorrect because the number of teeth on the speed wheels is not the same as the original flow divider then that can cause problems. AND, the problem can be EITHER too much fuel (which can "drown" the ignitors (spark plugs)--another reason to pull the ignitors (spark plugs) shortly after a failure to ignite to ensure the tips are not excessively wet from the fuel) OR too little fuel.

I would also suggest that any liquid fuel filter upstream of the liquid fuel flow divider should be pressurized with fuel and vented to ensure there is no air in the filter canisters.

Checking the gap of the liquid fuel flow dividers speed sensors is important--too close and the flow divider may not rotate easily. Too far and the speed feedback may be erratic or not there at all--even if the flow divider is turning.

Some liquid fuel flow dividers have a small motor to help them get started turning--this is more common on machines that also burn heavy fuel oil. We don't know if the machine at your installation has this "helper" motor on the liquid fuel flow divider or not, and if so is it working correctly? (If the machine trips while buring heavy fuel oil it can remain in the liquid fuel flow divider and make starting on light fuel oil/HSD difficult--which is why the "helper" motor is there.

So, there's a lot of reasons why the machine may not be starting. Simply changing the liquid fuel flow divider and clicking on START without purging the liquid fuel system and fuel lines to the individual combustors and expecting the machine to fire is not sound practice. The more information you can provide (we aren't there beside you to know what was happening, and what was done to try to resolve the problem--other than changing liquid fuel flow dividers) the better and more concise the answers you will get. It would be VERY helpful to know what fuel(s) the machine burns, what kind of combustion system it has (conventional or DLN). And, WHAT ALARMS ARE PRESENT DURING THE FIRING SEQUENCE--PROCESS- AND DIAGNOSTIC??? (I'm presuming the machine uses a GE Mark* turbine control system, but even if it doesn't it would still be VERY HELPFUL to know the alarms being annunciated during an unsuccessful firing attempt.)

You want help. We need information. We have given you a lot of hints about what the problem could be (which is what you essentially asked) not knowing very much about the machine and the circumstances, other than the liquid fuel flow divider has been changed multiple times (and we don't know why it was felt necessary to change the liquid fuel flow divider...).

If you resolve the issue before you answer the questions above please write back to let us know how you resolved the problem.

Thank you!

 

Thanks for Your support
. In our gas turbine frame 7ea we used Dual fuel distillate /Crude
. I will try to follow your recommendation
But finaly I want to asking about the Flow dividor magintic pick up proble
If the gap is not correct will do fail to ignite and how Can I know?

 

@Ahmed Saad,

I might be able to answer that question if you would provide some data from the turbine control system (graph; recorded data) as requested. It would be necessary to know what the speed feedback from the liquid fuel flow divider was doing during the firing sequence. Checking the speed pickup gap is a relatively simple procedure, loosen the locking nut of each speed pickup and turn it clockwise until it stops turning; it should turn easily by hand—do not force it with a wrench. Use a machinist’s caliper to measure the distance between a flat surface of the speed pickup and the body of the flow divider. Turn the speed pickup anti-clockwise and after a couple of rotations measure the distance between the SAME TWO points. Compare the difference in the two distances to the value of the liquid fuel flow divider speed pickup gap specified in the Control Specification, Section 05.01.nn, provided with the machine. Adjust the speed pickup until the difference in the original reading and the actual reading is within the acceptable range of the gap as listed in the Control Specification paragraph. The using one wrench to hold the speed pickup stationary use a second wrench to set the locking nut to hold the speed pickup in the proper position.

Are the liquid fuel flow dividers being used to replace the original flow divider new or refurbished? If they are refurbished, are they refurbished by the manufacturer or a company certified by the manufacturer?

Also, the amount of liquid fuel flowing out of the false start drains should be a good indication of the amount of liquid fuel flowing into the machine. If there’s any increase in individual exhaust T/C values and the average exhaust temperature (signal name TTXM) AND there is any white smoke visible from the exhaust stack during it after firing that is an indication that there is liquid fuel flowing into—but the amount is either too low or too high to permit ignition. A check of the ignitors (spark plugs) immediately after a failure to ignite will show if the flow is excessive if the plug tips are very wet.

 

@Ahmed Saad,

Does the exhaust temperature increase at all during firing--probably not all the exhaust T/Cs, but at least a few of them?

Do you see any white smoke coming from the exhaust after the failure to ignite? (This would be an indication that one or more of the combustors was lit, if only for a few seconds.)

Have you checked the false start drains to see if there is any liquid fuel flowing out of them during or after the firing--including the exhaust plenum false start drain?

What liquid fuel(s) do(es) the machine burn? Diesel (sometimes called HSD (High Speed Diesel) or light fuel oil (LFO)? Does the machine switch to heavy fuel oil (HFO) once it reaches FSNL, or shortly after synchronization?

What made you believe the flow divider was the problem and that it needed to be replaced?

I presume the original flow divider wasn't giving the same problem--at least not as often. Please confirm.

Have you tested the ignitors (spark plugs) to ensure they are both working properly? (That would mean the ignitors (spark plugs) would need to be pulled from the combustors they are mounted on, grounded and excited (have voltage applied to them) for a visible spark/sparking. Usually, the gasket between the ignitor (spark plug) body and the ignitor flange on the combustor will not be damaged, but, even if it is it is easily replaced. (There are two spark plugs, for redundancy--only one has to work for the machine to ignite fuel.)

Are you 100% certain that the replacement flow dividers have exactly the same number of teeth on the flow divider wheels that rotate under the speed sensors?

Are you 100% certain that the gap between the face of the speed sensors and the toothed wheel(s) of the flow divider are as per specification?

Does the turbine control system have a way of trending (graphing) the machine speed and flow-divider speed input to the control system and the liquid fuel flow-rate during firing?

Does the liquid fuel control valve have LVDT(s)? Can you trend those signals as well?

Can you trend FQR during firing (usually the control signal name for the liquid fuel flow reference?

Can you trend FQL (or FQL1) the calculated liquid fuel flow-rate during firing?

After you change the flow divider(s), do you ensure there is no air in the liquid fuel lines? (This is usually accomplished by performing what's often called a "false fire"--which involves disabling the ignitors (spark plugs) and initiating a START in FIRE or AUTO mode and let the machine go through a firing sequence where liquid fuel will be flowing BUT since the ignitors (spark plugs) are disabled they machine won't actually fire/establish flame. This is done, again, to push any air in the liquid fuel system--before and after the liquid fuel control valve and the liquid fuel flow divider into the combustors. during the "false firing" it is customary to have some monitoring the false start drain valves to see if liquid fuel actually flowed into the machine and drains out of the false start drains. It's also a good idea after the "false fire" to CRANK the machine for 10 or 15 minutes to push any combustible vapors out of the machine before enabling the ignitors (spark plugs) and attempting a normal START.)

And, while it's the last question is IS one the MOST IMPORTANT questions: Specifically--what other alarms are annunciated during the unsuccessful firing attempts? Process Alarms AND Diagnostic Alarms--in chronological order. Even if you don't think they're relevant.

The purpose of all of the questions is try to cover as many of the possible problems that can lead to a failure to ignite when STARTing on liquid fuel. What is necessary for any internal combustion engine to start? Fuel. Spark. Air. It's pretty safe to say that there is sufficient air. We don't know if you've checked the ignitors (spark plugs) and if you did what the results were. And, fuel. If the flow feedback from the speed pickups on the liquid fuel flow divider is incorrect because the number of teeth on the speed wheels is not the same as the original flow divider then that can cause problems. AND, the problem can be EITHER too much fuel (which can "drown" the ignitors (spark plugs)--another reason to pull the ignitors (spark plugs) shortly after a failure to ignite to ensure the tips are not excessively wet from the fuel) OR too little fuel.

I would also suggest that any liquid fuel filter upstream of the liquid fuel flow divider should be pressurized with fuel and vented to ensure there is no air in the filter canisters.

Checking the gap of the liquid fuel flow dividers speed sensors is important--too close and the flow divider may not rotate easily. Too far and the speed feedback may be erratic or not there at all--even if the flow divider is turning.

Some liquid fuel flow dividers have a small motor to help them get started turning--this is more common on machines that also burn heavy fuel oil. We don't know if the machine at your installation has this "helper" motor on the liquid fuel flow divider or not, and if so is it working correctly? (If the machine trips while buring heavy fuel oil it can remain in the liquid fuel flow divider and make starting on light fuel oil/HSD difficult--which is why the "helper" motor is there.

So, there's a lot of reasons why the machine may not be starting. Simply changing the liquid fuel flow divider and clicking on START without purging the liquid fuel system and fuel lines to the individual combustors and expecting the machine to fire is not sound practice. The more information you can provide (we aren't there beside you to know what was happening, and what was done to try to resolve the problem--other than changing liquid fuel flow dividers) the better and more concise the answers you will get. It would be VERY helpful to know what fuel(s) the machine burns, what kind of combustion system it has (conventional or DLN). And, WHAT ALARMS ARE PRESENT DURING THE FIRING SEQUENCE--PROCESS- AND DIAGNOSTIC??? (I'm presuming the machine uses a GE Mark* turbine control system, but even if it doesn't it would still be VERY HELPFUL to know the alarms being annunciated during an unsuccessful firing attempt.)

You want help. We need information. We have given you a lot of hints about what the problem could be (which is what you essentially asked) not knowing very much about the machine and the circumstances, other than the liquid fuel flow divider has been changed multiple times (and we don't know why it was felt necessary to change the liquid fuel flow divider...).

If you resolve the issue before you answer the questions above please write back to let us know how you resolved the problem.

Thank you!

Good evening
After more trial we change check valves and Flow dividor
Every thing is normal but after unit shutdown for few days and need to start unit again we should rotate Flow dividor, flow dividor not new it repaired by company, we absorve that in winter more problems of Flow dividor than summer, anthor unit we change Flow dividor in 5 October today when we try to restrat the unit
Flow dividor stuck it's repair also

 

Good evening
After more trial we change check valves and Flow dividor
Every thing is normal but after unit shutdown for few days and need to start unit again we should rotate Flow dividor, flow dividor not new it repaired by company, we absorve that in winter more problems of Flow dividor than summer, anthor unit we change Flow dividor in 5 October today when we try to restrat the unit
Flow dividor stuck it's repair also

And I want explnation for the effect of magintic pick up gap

 

@Ahmed Saad,

If the magnetic speed pickup is somehow in very close proximity to the toothed wheel it may interfere with the rotation of the toothed wheel. This can happen when a backing wrench (a second wrench) isn’t used when tightening the lock nut of the magnetic speed pickup. If the fuel passing through the flow divider is heated that can also cause differential expansion in the various parts of the flow divider and could also lead to problems.

But it seems you have discovered one or two problems. Cold weather could also cause clearance issues and so could poor workmanship, poor assembly procedures and/or poor parts used in the reassembly of the flow divider after overhaul.

So, it’s likely there is more than one cause for the issue you are experiencing—as is common in some problem resolutions. We all suspect and look for THE (as in single) cause and solve the issue. But sometimes it’s just not that simple.

Best of luck. We don’t know what the circumstances are for choosing the company that is performing the maintenance or refurbishment of the flow dividers but if electric power generation is and the revenue derived from the power generation are of high importance then cost-cutting consequences can occur, unfortunately.

 

@Ahmed Saad,

By the way--thanks for writing back to let us know what you are finding.