Turbine starting with electrical start motor when reach 25% speed trip with excessive liquid fuel.knowing that the turbine was running and stops for PMP.does the burner nozzels cuase problem or air in fuel sys ?

 

Hello sir,

is your turbine already fire when trip occurs?

do you think excessive fuel flow is real or safety controller is fool by faulty measurement ?

 

Presuming PMP means something like "Preventive Maintenance Program" (a maintenance-oriented outage), we don't know what was done during the outage so it's difficult for us to say if the fuel nozzles ("burners") might be at fault.

We also don't know how often the machine starts and runs on liquid fuel, or if it is a dual fuel (natural gas/distilllate or distillate/naphtha or ???) machine. We don't know if the liquid fuel filters (low-pressure and/or high-pressure) were changed, or the liquid fuel tubing from the discharge of the liquid fuel flow divider was removed and re-installed and then purged of air. We also don't know the age of the machine or the version of the control system.

But the Number One cause of excessive fuel flow trips during starting is air in the liquid fuel supply piping--inc;uding the fuel canisters, followed by oscillating liquid fuel supply pressure from the liquid fuel strage tank(s). Far and away. As air is moved through the liquid fuel supply piping and through the liquid fuel flow divider the internal wheels of the flow divider will alternately slow down and speed up. When they slow down due to lack of fuel the liquid fuel control valve will move to immediately increase the flow of liquid fuel and when a "slug" of liquid fuel then passes through the flow divider it will likely be well in excess of the required flow-rate--resulting in the control system interpreting that as excessive liquid fuel flow during starting. It usually happens during firing (after purging is complete during STARTing) but can also happen after flame is established and liquid fuel flow-rate increases to help with acceleration; the increase in liquid fuel flow-rate can move pockets of air in the liquid fuel supply piping along and ultimately to and through the liquid fuel flow divider causing the excessvie flow detection. (The main purpose of the excessive liquid fuel flow-rate during starting detection is to protect the hot gas path parts from abnormally high thermal stresses caused by high fuel flows and resultant high internal temperatures. Yes; this will most likely lead to exhaust overtemperature alarms and trips but damage to hot gas path parts can occur in the interim. And, if unburned liquid fuel pools in the lower parts of the turbine and exhaust it can be ignited and lead to BIG booms and mechanical damage to the turbine and the exhaust area/stack and waste heat recovery boiler if one is present. These are just a couple of the protective functions the excessive liquid fuel flow-rate detection serves.)

We don't know if the liquid fuel flow divider was inspected, refurbished or replaced during the PMP. We don't know if the liquid fuel flow divider speed pick-up gaps have been checked or set properly. If the present turbine control system is an upgrade to a previous turbine control system and new interconnecting wiring was installed between the turbine and auxiliaries and the control system if the proper wire was used and if accepted wiring practices were used (proper earthing of twisted, shielded pair wiring drain wires), and even the use of twisted, shielded pairs for low-level signal wiring (such as the liquid fuel flow-divider speed pick-ups).

But, unless you are 110% sure the liquid fuel supply piping from the liquid fuel storage tanks all the way through the liquid fuel stop valve and all the way to the liquid fuel check valves at the liquid fuel nozzle inlets (all 10 of them!) are free of air, then the site personnel should be checking and venting all the sections of liquid fuel piping and tubing, all the way to the fuel nozzle liquid fuel check valves.

If the fuel nozzles ("burners") were disassembled and reinstalled during the PMP, it's possible they might not have all be reassembled or re-installed correctly--not likely, but possible. And, even if the majority of them were not properly atomizing liquid fuel (mechanical atomization) that probably wouldn't lead to tripping due to excessive liquid fuel flow-rate.

If the unit is a dual fuel (natural gas/distillate) machine AND the liquid fuel purge check valves were not properly installed or the purge control valve was not working properly that MIGHT cause excessive liquid fuel flow-rate--but it probably wouldn't allow flame to be established (depending on the severity of the problem(s) with the liquid fuel purge system).

Please write back to let us know what is determined to be the cause of the problem. A LOT of people read and learn from these threads, and it's the feedback that makes them so useful and informative.

 

Presuming PMP means something like "Preventive Maintenance Program" (a maintenance-oriented outage), we don't know what was done during the outage so it's difficult for us to say if the fuel nozzles ("burners") might be at fault.

We also don't know how often the machine starts and runs on liquid fuel, or if it is a dual fuel (natural gas/distilllate or distillate/naphtha or ???) machine. We don't know if the liquid fuel filters (low-pressure and/or high-pressure) were changed, or the liquid fuel tubing from the discharge of the liquid fuel flow divider was removed and re-installed and then purged of air. We also don't know the age of the machine or the version of the control system.

But the Number One cause of excessive fuel flow trips during starting is air in the liquid fuel supply piping--inc;uding the fuel canisters, followed by oscillating liquid fuel supply pressure from the liquid fuel strage tank(s). Far and away. As air is moved through the liquid fuel supply piping and through the liquid fuel flow divider the internal wheels of the flow divider will alternately slow down and speed up. When they slow down due to lack of fuel the liquid fuel control valve will move to immediately increase the flow of liquid fuel and when a "slug" of liquid fuel then passes through the flow divider it will likely be well in excess of the required flow-rate--resulting in the control system interpreting that as excessive liquid fuel flow during starting. It usually happens during firing (after purging is complete during STARTing) but can also happen after flame is established and liquid fuel flow-rate increases to help with acceleration; the increase in liquid fuel flow-rate can move pockets of air in the liquid fuel supply piping along and ultimately to and through the liquid fuel flow divider causing the excessvie flow detection. (The main purpose of the excessive liquid fuel flow-rate during starting detection is to protect the hot gas path parts from abnormally high thermal stresses caused by high fuel flows and resultant high internal temperatures. Yes; this will most likely lead to exhaust overtemperature alarms and trips but damage to hot gas path parts can occur in the interim. And, if unburned liquid fuel pools in the lower parts of the turbine and exhaust it can be ignited and lead to BIG booms and mechanical damage to the turbine and the exhaust area/stack and waste heat recovery boiler if one is present. These are just a couple of the protective functions the excessive liquid fuel flow-rate detection serves.)

We don't know if the liquid fuel flow divider was inspected, refurbished or replaced during the PMP. We don't know if the liquid fuel flow divider speed pick-up gaps have been checked or set properly. If the present turbine control system is an upgrade to a previous turbine control system and new interconnecting wiring was installed between the turbine and auxiliaries and the control system if the proper wire was used and if accepted wiring practices were used (proper earthing of twisted, shielded pair wiring drain wires), and even the use of twisted, shielded pairs for low-level signal wiring (such as the liquid fuel flow-divider speed pick-ups).

But, unless you are 110% sure the liquid fuel supply piping from the liquid fuel storage tanks all the way through the liquid fuel stop valve and all the way to the liquid fuel check valves at the liquid fuel nozzle inlets (all 10 of them!) are free of air, then the site personnel should be checking and venting all the sections of liquid fuel piping and tubing, all the way to the fuel nozzle liquid fuel check valves.

If the fuel nozzles ("burners") were disassembled and reinstalled during the PMP, it's possible they might not have all be reassembled or re-installed correctly--not likely, but possible. And, even if the majority of them were not properly atomizing liquid fuel (mechanical atomization) that probably wouldn't lead to tripping due to excessive liquid fuel flow-rate.

If the unit is a dual fuel (natural gas/distillate) machine AND the liquid fuel purge check valves were not properly installed or the purge control valve was not working properly that MIGHT cause excessive liquid fuel flow-rate--but it probably wouldn't allow flame to be established (depending on the severity of the problem(s) with the liquid fuel purge system).

Please write back to let us know what is determined to be the cause of the problem. A LOT of people read and learn from these threads, and it's the feedback that makes them so useful and informative.

Sorry it is frame3 dual gas ans liquid turbine.
It was general PMP and it was running with gas we just started up with liquid, during we just check liquid fuel pressure transmitter and low press switch,remove and clean 12 check valves(setting was between 65-110 psi) and ckeck clean 6 fuel nozzels.these what checked in liquid fuel system durin PMP .
This trip alarm appear before ignition immeditly after stop liquid fuel valve open at 25% hp speed.
Note:One trend picture attached for starting up
Green line for HP speed
Red line for liquid flow
Blue line for servo valve current
Light blue line for liquid stop valve


Gree

 

Hello sir,

is your turbine already fire when trip occurs?

do you think excessive fuel flow is real or safety controller is fool by faulty measurement ?

1-Trip occured befor fire at 25% hp speed
Its real measurd with two flow sensor

 

You don’t know the frame size of the machine that’s experiencing the problem?

Ummm, …, I don’t see no stinking trend picture.

A GE-design dual fuel (gas/distillate) Frame 3 is going to have six fuel nozzles, six liquid fuel check valves and six liquid fuel purge check valves. You checked all of these?

How are you venting air from the liquid fuel supply system? (Piping; fuel filters; fuel lines downstream of the high-pressure liquid fuel pump all the way to the liquid fuel check valves just before the fuel nozzles? Did you check the tell-tale leakoff of the liquid fuel purge line to be sure none of the liquid fuel purge check valves are leaking during firing?

Finally (and I do mean FINALLY) tripping on excessive liquid fuel flow BEFORE flame is established is CLASSIC air in the liquid fuel lines. It’s been written MANY TIMES on Control.com—do the best possible job of making sure there is no air in the liquid fuel piping all the way up the the high-pressure liquid fuel pump. START the turbine on gas fuel, at FSNL initiate a transfer to liquid fuel. This is the best way to force liquid fuel into the fuel lines up to the fuel nozzles. Have someone watching the tell-tale leakoff for any sign of leaking liquid fuel purge check valves (so if there are leaks you will immediately know it and can resolve them—if fuel goes to drain instead of to the fuel nozzle(s) that’s a big problem, too). The transfer should help push air out of the tubing downstream of the flow divider. STOP the machine (if it doesn’t trip during the transfer), and then re-START it again on liquid fuel. It should work much better—presuming the air has been vented/purged from the liquid fuel piping and tubing and the liquid fuel purge check valve(s) aren’t leaking.

Best of luck.