Facebook
Google
GitHub
Linkedin
GE Gasturbine Start Check L3STCK_LS
- Thread starter hohoim2
- Start date
@hohoim2,
It’s presumed you are looking at the descriptions of the Start Check permissives status. If so the display should indicate which L3STCKn rung this signal is in (where “n” is a whole number starting with 0). You can then use Rung Display (if the turbine control uses a Mark* V HMI or <I>) or Toolbox or ToolboxST to find L3STCK rung and find L3STCK_LS and see if you can determine where the isolation valve limit switch is located.
My personal guess is the limit switch is mounted on a fuel isolation valve that was closed for a maintenance outage and didn’t get fully opened prior to the start—or wasn’t connected properly and loop-checked prior to the start after the valve was removed during the outage. But that’s just a personal guess.
Usually a limit switch has the device number 33 in its name—for example, L33CB1O indicates the open status of the #1 compressor bleed valve). But, sometimes signal names aren’t chosen correctly.
But the isolation valve is something that should normally be either fully open or fully closed prior to a start and for some reason the limit switch is not giving the proper indication to the Mark*. Either the isolation valve is not in the right position, or there’s something wrong with the limit switch or its mounting bracket, or there is a wiring problem.
Please write back to let us know what you find and how you resolve the problem!
It’s presumed you are looking at the descriptions of the Start Check permissives status. If so the display should indicate which L3STCKn rung this signal is in (where “n” is a whole number starting with 0). You can then use Rung Display (if the turbine control uses a Mark* V HMI or <I>) or Toolbox or ToolboxST to find L3STCK rung and find L3STCK_LS and see if you can determine where the isolation valve limit switch is located.
My personal guess is the limit switch is mounted on a fuel isolation valve that was closed for a maintenance outage and didn’t get fully opened prior to the start—or wasn’t connected properly and loop-checked prior to the start after the valve was removed during the outage. But that’s just a personal guess.
Usually a limit switch has the device number 33 in its name—for example, L33CB1O indicates the open status of the #1 compressor bleed valve). But, sometimes signal names aren’t chosen correctly.
But the isolation valve is something that should normally be either fully open or fully closed prior to a start and for some reason the limit switch is not giving the proper indication to the Mark*. Either the isolation valve is not in the right position, or there’s something wrong with the limit switch or its mounting bracket, or there is a wiring problem.
Please write back to let us know what you find and how you resolve the problem!
By the way, @hohoim2, it would help if you let us know what turbine control system is used on the machine you are working on.
And a little about the machine--like Frame size, fuel(s) the machine burn(s), etc.--could be really useful.
This site doesn't use avatars, in which members could tell us a little about the machine(s) they work on so we didn't have to ask. (We can look up past posts to learn a few things, but that can take time.)
And a little about the machine--like Frame size, fuel(s) the machine burn(s), etc.--could be really useful.
This site doesn't use avatars, in which members could tell us a little about the machine(s) they work on so we didn't have to ask. (We can look up past posts to learn a few things, but that can take time.)
I am working with a 7FA turbine, Mark VIe control system, and LNG as fuel. Currently, I don't know how to use the Rung Display function. When I check the logic, it shows a MOVE Block, but I can't fully understand the information from there. The MOVE Block's "block enable" and "source variable" are labeled as 'Heat_vent.Exhstfmblowr.'
Additionally, I don't think the issue is with the fuel isolation valve. The reason is that the valve is currently open as the turbine is in startup, and the signal is showing "True."
Additionally, I don't think the issue is with the fuel isolation valve. The reason is that the valve is currently open as the turbine is in startup, and the signal is showing "True."
@hohoim2,
Thank you for the additional information. The Mark* VIe doesn’t have a Rung Display function (the Mark* IV and Mark* V did); you need to use ToolboxST to look at the application code (logic; programming; sequencing) as you seem to be doing.
You may be looking at the “guts” of a macro, one of which is a MOVE block. These can be very difficult to decipher—at least for me. Without being able to see what you’re looking at and reading it is hard to tell what is being described. You can paste a clear photo of the code you’re looking at to a post.
I tend to be very leery of reading things written in GE manuals about a specific machine; people change things in the Mark* very often without changing the documentation…. If you hover the mouse cursor over a signal or left-click on a signal ToolboxST will usually show the “long name” of the signal (if the creator gave it a long name; it’s not required, but it should be). Sometimes you can right-click on a signal and get a drop-down menu of choices, one of which will take you to the location where the signal is “written to” (the coil name or the input of the logic signal). Or you can use the Search function of ToolboxST to find the origin of the signal (not the pin, but the place where the value of the signal is determined).
It’s possible the “start-check” signal you’re looking at is not for the turbine START—but for an exhaust frame cooling system start/run bit of code. Have you checked the Cooling & Sealing Air P&ID to see if there are any check valves/isolation valves with limit switches on the turbine-exhaust frame?
Is there a Process Alarm associated with this L3STCK_LS signal? If so what is the alarm text?
Thank you for the additional information. The Mark* VIe doesn’t have a Rung Display function (the Mark* IV and Mark* V did); you need to use ToolboxST to look at the application code (logic; programming; sequencing) as you seem to be doing.
You may be looking at the “guts” of a macro, one of which is a MOVE block. These can be very difficult to decipher—at least for me. Without being able to see what you’re looking at and reading it is hard to tell what is being described. You can paste a clear photo of the code you’re looking at to a post.
I tend to be very leery of reading things written in GE manuals about a specific machine; people change things in the Mark* very often without changing the documentation…. If you hover the mouse cursor over a signal or left-click on a signal ToolboxST will usually show the “long name” of the signal (if the creator gave it a long name; it’s not required, but it should be). Sometimes you can right-click on a signal and get a drop-down menu of choices, one of which will take you to the location where the signal is “written to” (the coil name or the input of the logic signal). Or you can use the Search function of ToolboxST to find the origin of the signal (not the pin, but the place where the value of the signal is determined).
It’s possible the “start-check” signal you’re looking at is not for the turbine START—but for an exhaust frame cooling system start/run bit of code. Have you checked the Cooling & Sealing Air P&ID to see if there are any check valves/isolation valves with limit switches on the turbine-exhaust frame?
Is there a Process Alarm associated with this L3STCK_LS signal? If so what is the alarm text?
@EBUWAODUWA,
What a mess. I am replying to this paragraph:
“@WTF? thanks for your swift reply, the issue was resolved yesterday, it was observed that the 20TV-1 stem was stuck, so it was replaced immediately. presently the main lube oil is not able to drive the machine to full speed no load. What could be the cause.”
Typically, a GE-design Frame 7FA heavy duty gas turbine does not really have a “main” lube oil pump, per se. it has two, redundant AC (Alternating Current) motor-driven lube oil pumps. Typically, one of these redundant pumps is selected to be the lead pump and the second becomes the “lag” or standby pump in the event the lead pump or pump motor fails.
You might be trying to say the machine can’t get to FSNL or load on the lead lube oil pump, and the Mark* starts the lag (standby) pump.?.?.? If that’s the case, there should have been an alarm to say the standby (lag) lube oil pump is running—and that will happen if the lead lube oil pump or its motor is not capable of maintaining sufficient pressure to safely operate the machine. So, either the pump has failed or is failing for some reason, or the pump motor has failed or is failing (such as an excessive current draw—which would likely cause an alarm to indicate the motor is overloaded).
You can look at the Lube Oil P&ID to see the foot valves and check valves and such in the lube oil system. One of them may be stuck. It could also be that the in-service Lube Oil filter is excessively dirty if both Lube Oil pumps are having a problem maintaining sufficient pressure to safely operate the machine.
This is most likely NOT a controls-related problem. If the machine sat for a year (approximately) and the Lube Oil system was never operated it’s entirely possible the lube oil quality is very low. But, that’s not likely a control’s-related problem, either.
Best of luck with your issues. Please write back to let us know what you find and how you resolve this new issue.
What a mess. I am replying to this paragraph:
“@WTF? thanks for your swift reply, the issue was resolved yesterday, it was observed that the 20TV-1 stem was stuck, so it was replaced immediately. presently the main lube oil is not able to drive the machine to full speed no load. What could be the cause.”
Typically, a GE-design Frame 7FA heavy duty gas turbine does not really have a “main” lube oil pump, per se. it has two, redundant AC (Alternating Current) motor-driven lube oil pumps. Typically, one of these redundant pumps is selected to be the lead pump and the second becomes the “lag” or standby pump in the event the lead pump or pump motor fails.
You might be trying to say the machine can’t get to FSNL or load on the lead lube oil pump, and the Mark* starts the lag (standby) pump.?.?.? If that’s the case, there should have been an alarm to say the standby (lag) lube oil pump is running—and that will happen if the lead lube oil pump or its motor is not capable of maintaining sufficient pressure to safely operate the machine. So, either the pump has failed or is failing for some reason, or the pump motor has failed or is failing (such as an excessive current draw—which would likely cause an alarm to indicate the motor is overloaded).
You can look at the Lube Oil P&ID to see the foot valves and check valves and such in the lube oil system. One of them may be stuck. It could also be that the in-service Lube Oil filter is excessively dirty if both Lube Oil pumps are having a problem maintaining sufficient pressure to safely operate the machine.
This is most likely NOT a controls-related problem. If the machine sat for a year (approximately) and the Lube Oil system was never operated it’s entirely possible the lube oil quality is very low. But, that’s not likely a control’s-related problem, either.
Best of luck with your issues. Please write back to let us know what you find and how you resolve this new issue.
@wtf yes the machine was idol for one Year and six months. we are operating GE Frame 9E. WE have Main lube oil and Auxiliary lube oil. the main lube oil is not able to maintain the machine to FSNL, so the the Auxiliary lube oi came up and the machine could not attain FSNL. presently we are topping oil.
Any one please explain L4T= TRIP , L86= protection lockout relay, L30= drive electrically enersized or fault please how to get all this type of tag first letter explain i am new member here
@Dharmrajsinh,
These are GENERAL rules/statements regarding naming of Mark* signals.
The L means--ALMOST always--the signal is a logic signal, meaning it's only ever a "1" or a "0."
The numerals used in Mark* signal names correspond to GE's interpretation of the ANSI device numbering system. For example, a device with a "4", such as L4T, is a 'master control device.' In this example, L4T means the logic will be a "1" when the turbine is to be tripped (the T in L4T means TRIP) for some emergency condition, such as low-low Lube Oil pressure, or high-high exhaust temperature, or high-high vibration. When L4T becomes a logic "1" when the turbine is running (starting or during loaded operation or during a normal shutdown) then the Master Control Logic signal, L4, will be switched to logic "0" which will immediately close the fuel shut-off valves which will extinguish the flame in the machine. So, there is an L4 logic signal, which must be a logic "1" for the machine to run and continue to run, and there is an L4T logic signal which must be a logic "0" for the machine to run. When L4T switches to logic "1" then L4 will be switched to logic "0" which will trip the machine (shut off the flow of fuel to the machine).
A device number of "86" refers to a lock-out relay--almost always a device which must be manually in the latched (or 'reset') position for the machine to start and/or run. When a lock-out relay trips or is tripped from the latched ('reset') position that almost always causes the L4T logic signal to switch from logic "0" to logic "1" which causes L4 to switch from logic "1" to logic "0"--which immediately shuts off the flow of fuel to the machine. (If a machine is at rest and L4 is a logic "1" that means it's can't be started unless all of the conditions which must be met for the control and protection of the machine are satisfied.
A device number of "30" usually means the logic signal is associated with an alarm condition, such as low- or low-low Lube Oil pressure, or high- or high-high exhaust temperature. What I'm trying to say is that the logic signal that causes an alarm text message to be displayed, such as when something trips the machine, for example, usually has a signal name that has L30xxxxx (where 'x' may be alpha characters or numerals). Typically when a signal with a name that begins with L30 goes to a logic "1" then a text message will be displayed to alert a conscious operator to some condition that requires attention and resolution. (This often includes an audible alarm signal of some sort, but the audible alarm generator usually gets disable or muffled on many GE turbine installations.)
There have been many threads about GE signal naming conventions--but the thing to remember is that these signal naming conventions ARE NOT PUBLISHED, either inside GE or outside GE. They are mildly enforced, and only generally known. And, it's my understanding that GE is changing their signal naming conventions after many decades. Why? Because some people think it's "old school" like dot matrix alarm printers are "old school" in the days of laser printers. (And who needs an alarm printout, anyway? It's just a big waste of paper, right?)
There was one thread many years ago that went on and on and on and on. It had multiple parts, but it was very good at helping to explain and understand GE signal names. (At least I thought it was a good write-up on how to "read" GE signal names.) Unfortunately, I can't find the original thread that started the chain of threads, and, unfortunately, the chain ended abruptly--which happens on these World Wide Web forums. Here's what I found with a quick search:\
Getting a better understanding of GT control PART 2 | Automation & Control Engineering Forum
Reading GE signal names is really like reading a different language--which is explained in the thread above and its "sister" threads. In general, all logic signal names were intended to be chosen such that when the logic associated with the signal was a "1" the signal name would describe the situation. So, for example, when L4 was a logic "1" that would mean that the Master Control Signal would permit fuel to flow to the turbine. And when L4T was a logic "1" that fuel flow to the turbine would be immediately shut off (and by extension when L4T switched to a logic "1 " then L4 would switch o a logic "0" to shut off the fuel flow).
If you're really interested in how to understand ("read") GE signal names you would do well to start with the thread above and find the other related threads in Control.com, and then learn how to use the GE operator interface (HMI or <I>) to look at the sequencing or application code to find the Longname descriptions of the signal names--ALL THE WHILE REMEMBERING that Longnames are another of those conventions that was never enforced and Longnames, while usually correct, are NOT always correct. And, in fact, some signals were never assigned a Longname (which is a real shame).
These are GENERAL rules/statements regarding naming of Mark* signals.
The L means--ALMOST always--the signal is a logic signal, meaning it's only ever a "1" or a "0."
The numerals used in Mark* signal names correspond to GE's interpretation of the ANSI device numbering system. For example, a device with a "4", such as L4T, is a 'master control device.' In this example, L4T means the logic will be a "1" when the turbine is to be tripped (the T in L4T means TRIP) for some emergency condition, such as low-low Lube Oil pressure, or high-high exhaust temperature, or high-high vibration. When L4T becomes a logic "1" when the turbine is running (starting or during loaded operation or during a normal shutdown) then the Master Control Logic signal, L4, will be switched to logic "0" which will immediately close the fuel shut-off valves which will extinguish the flame in the machine. So, there is an L4 logic signal, which must be a logic "1" for the machine to run and continue to run, and there is an L4T logic signal which must be a logic "0" for the machine to run. When L4T switches to logic "1" then L4 will be switched to logic "0" which will trip the machine (shut off the flow of fuel to the machine).
A device number of "86" refers to a lock-out relay--almost always a device which must be manually in the latched (or 'reset') position for the machine to start and/or run. When a lock-out relay trips or is tripped from the latched ('reset') position that almost always causes the L4T logic signal to switch from logic "0" to logic "1" which causes L4 to switch from logic "1" to logic "0"--which immediately shuts off the flow of fuel to the machine. (If a machine is at rest and L4 is a logic "1" that means it's can't be started unless all of the conditions which must be met for the control and protection of the machine are satisfied.
A device number of "30" usually means the logic signal is associated with an alarm condition, such as low- or low-low Lube Oil pressure, or high- or high-high exhaust temperature. What I'm trying to say is that the logic signal that causes an alarm text message to be displayed, such as when something trips the machine, for example, usually has a signal name that has L30xxxxx (where 'x' may be alpha characters or numerals). Typically when a signal with a name that begins with L30 goes to a logic "1" then a text message will be displayed to alert a conscious operator to some condition that requires attention and resolution. (This often includes an audible alarm signal of some sort, but the audible alarm generator usually gets disable or muffled on many GE turbine installations.)
There have been many threads about GE signal naming conventions--but the thing to remember is that these signal naming conventions ARE NOT PUBLISHED, either inside GE or outside GE. They are mildly enforced, and only generally known. And, it's my understanding that GE is changing their signal naming conventions after many decades. Why? Because some people think it's "old school" like dot matrix alarm printers are "old school" in the days of laser printers. (And who needs an alarm printout, anyway? It's just a big waste of paper, right?)
There was one thread many years ago that went on and on and on and on. It had multiple parts, but it was very good at helping to explain and understand GE signal names. (At least I thought it was a good write-up on how to "read" GE signal names.) Unfortunately, I can't find the original thread that started the chain of threads, and, unfortunately, the chain ended abruptly--which happens on these World Wide Web forums. Here's what I found with a quick search:\
Getting a better understanding of GT control PART 2 | Automation & Control Engineering Forum
Reading GE signal names is really like reading a different language--which is explained in the thread above and its "sister" threads. In general, all logic signal names were intended to be chosen such that when the logic associated with the signal was a "1" the signal name would describe the situation. So, for example, when L4 was a logic "1" that would mean that the Master Control Signal would permit fuel to flow to the turbine. And when L4T was a logic "1" that fuel flow to the turbine would be immediately shut off (and by extension when L4T switched to a logic "1 " then L4 would switch o a logic "0" to shut off the fuel flow).
If you're really interested in how to understand ("read") GE signal names you would do well to start with the thread above and find the other related threads in Control.com, and then learn how to use the GE operator interface (HMI or <I>) to look at the sequencing or application code to find the Longname descriptions of the signal names--ALL THE WHILE REMEMBERING that Longnames are another of those conventions that was never enforced and Longnames, while usually correct, are NOT always correct. And, in fact, some signals were never assigned a Longname (which is a real shame).
@Dharmrajsinh,
As with all "rules" ("standards") related to Mark* turbine controls, there are exceptions to the one about signal names beginning with the letter "L". (Isn't this fun?)
If a signal name has the letter "K" in the second or third position of the signal name, such as LK90PSEL or TNK14HR1 for example, that means the signal is most likely what's known as a Control Constant, a parameter used to define operating limits or bounds or similar.
Learning to understand (I liken it to learning to read a new language) Mark* turbine control signal naming is critical to becoming a good technician, or even a good operator. It's not easy, but it's also far from impossible. Since I was basically "raised" reading Mark* control literature and sequencing (relay ladder diagrams and algorithms) and application code it has become second nature to me over the decades. It was a struggle in the beginning but I recognized patterns and I could see very early in my career that learning this "code" was going to make my life easier and make me a better technician. It would have been MUCH easier if there was a manual or book that GE published for how control signal names should be chosen by anyone writing or modifying sequencing or application code--but that simply never existed and probably never will. But, as with life there are few certainties beyond death and taxes.
MANY people believe relay ladder diagrams are outdated, but I can assure you there are thousands of GE-design heavy duty gas turbines, aero-derivative gas turbines in power generation and pumping applications, and steam turbines running perfectly fine using relay ladder diagrams and the signal naming you are probably struggling with right now. Don't give up. It's a valuable skill to have, now and in the future.
Those numbers in many GE signal names are also EXTREMELY important to learn and commit to memory. There are many techniques for doing so, but flash cards are about the simplest. Use your preferred World Wide Web search engine to look up "flash cards in studying" for some interesting, and entertaining videos and descriptions of a very important learning tool used for centuries, probably, in some form or another.
As with all "rules" ("standards") related to Mark* turbine controls, there are exceptions to the one about signal names beginning with the letter "L". (Isn't this fun?)
If a signal name has the letter "K" in the second or third position of the signal name, such as LK90PSEL or TNK14HR1 for example, that means the signal is most likely what's known as a Control Constant, a parameter used to define operating limits or bounds or similar.
Learning to understand (I liken it to learning to read a new language) Mark* turbine control signal naming is critical to becoming a good technician, or even a good operator. It's not easy, but it's also far from impossible. Since I was basically "raised" reading Mark* control literature and sequencing (relay ladder diagrams and algorithms) and application code it has become second nature to me over the decades. It was a struggle in the beginning but I recognized patterns and I could see very early in my career that learning this "code" was going to make my life easier and make me a better technician. It would have been MUCH easier if there was a manual or book that GE published for how control signal names should be chosen by anyone writing or modifying sequencing or application code--but that simply never existed and probably never will. But, as with life there are few certainties beyond death and taxes.
MANY people believe relay ladder diagrams are outdated, but I can assure you there are thousands of GE-design heavy duty gas turbines, aero-derivative gas turbines in power generation and pumping applications, and steam turbines running perfectly fine using relay ladder diagrams and the signal naming you are probably struggling with right now. Don't give up. It's a valuable skill to have, now and in the future.
Those numbers in many GE signal names are also EXTREMELY important to learn and commit to memory. There are many techniques for doing so, but flash cards are about the simplest. Use your preferred World Wide Web search engine to look up "flash cards in studying" for some interesting, and entertaining videos and descriptions of a very important learning tool used for centuries, probably, in some form or another.
