D
Deleted member 3303
Dear CSA I shall update you regarding current questions tonight , now end of night shift and preparing for going home ,
You right CSA .Irfan ahmed qureshi,
First, the language/translation issue is making it difficult (for me, at least) to understand most of the technical information you are trying to convey.
Second, you seem to have this idea that we know or should know all the differences of the six machines at your site because you know the differences and you're trying to explain them to us. We're not there alongside you and you have to understand that we're not there alongside you and when we're dealing with multiple units from half way around the world and the details are changing--and are unclear (because of the language issue, also) we can't be of much help. Unless you are willing to put the information in a form we can easily refer to.
I'm going to offer up this one final observation and then I'm going to follow Curious_One's lead and not get any further involved in this thread. It's a rabbit whole of unknown depth and it's not going to lead to a good conclusion in this thread.
Most industrial control systems that use T/C's employ a concept called cold junction temperature compensation. You can use your preferred World Wide Web search engine to learn why it's necessary. The Mark* uses it also; it's mentioned in manual GEH-6721 in the section on T/C I/O Packs and terminal boards. I'm offering this information because it's a possible explanation which should be investigated if for no other reason than to eliminate it as a possible cause of the issue which is being discussed in this thread.
I once worked at a site with two Mark* control panels (actually located in the same room just a couple of metres apart). One of the panels was exhibiting some very odd--and intermittent--behaviours which were preventing reliable operation (at unusual times), AND the power output of this particular unit would ”drift” throughout the day slowly going up and down, seemingly randomly. The air conditioning outlets for the room were in the ceiling, and one of them was directly above the panel which was having the problems. It was found that when cold air from the vent directly above the panel with the issues was blowing into the vents of the panel it was altering the cold junction compensation temperatures of two of the three control processors in the Mark*--which was causing the T/C temperature readings to fluctuate (as the air conditioner started and stopped) by as much as 6-12 deg F. This was causing the Mark* to think the exhaust temperature and the compressor inlet temperature and the compressor discharge temperature were all going up and down, which was causing the Mark* to change fuel flow-rate and fail to transition combustion modes at times and just behave erratically.
A piece of cardboard was taped in place to cover the louvers at the top of the Mark* to block the direct flow of cold air from the air conditioner vent into the Mark*. Immediately the unit output started to settle into a more constant range and over the next few days as the unit was started and stopped the problems with combustion mode transfers stopped.
I AM NOT saying this is exactly what is happening at your site. What I AM saying is that it's entirely possible that something is causing the cold junction compensation in the Mark* control panels to be causing the temperature difference you are seeing and trying to report and trying to associate with the power output deviation you are trying to describe.
I can tell you further that GE does not not follow its own engineering recommendations for mounting Mark VIe I/O Packs to prevent heat from adjacent I/O Packs from affecting nearby I/O Packs. (Anyone reading this who doubts how much heat Mark VIe I/O Packs can generate just needs to put their hand above a PDIO I/O Pack at the bottom of a vertical column of PDIO I/O Packs and then move their hand slowly up that column to the top to see how much warmer it is near the top than the bottom. Do the same with the combined analog I/O Packs/terminal board combinations (I believe they are called TCATs).)
That's one possible explanation for the temperature differences you are trying to describe--presuming there are no other physical differences between the unit's we can't be aware of.
ToolboxST can be used to check the cold junction compensation temperatures of each I/O Pack, in each Mark VIe panel.
Also, T/C wiring is ”finicky.” If the wiring between the actual T/C and the Mark* is not correct all along the circuit, then there can be small errors introduced such as you are trying to describe. (Some I&C Tech's will argue that T/C's are simple two-wire devices and the individual terminations are NOT important--but you want to avoid those I&C tech's because they don't know what they are doing.) It's a simple matter to make these checks in a couple of junction boxes and in the Mark* to eliminate this as a possible cause.
Troubleshooting is often a process of elimination--especially for unusual and/or intermittent problems.
Best of luck. I wish I could help, but to do so I would have to be there on site, and that's not going to happen.
[As an aside, I have been in several similar situations before, where a ”problem” was assigned to a new or junior employee by a supervisor or manager who just didn't want to deal with the ”problem” or wanted the new/junior employee to just go away. In every case, the problem turned out to be more significant than first believed. In every case but one, the supervisor/manager jumped in and took complete credit for the troubleshooting and resolution, completely ignoring the efforts of the new/junior employee. That's life, eh? In this case, it sounds like you have a lot of procedures and possibly some biases to overcome, and you need to get multiple groups to work together to gather data, and be involved in a process of elimination--which some people object to. They don't offer any help or input but they're sure what you're suggesting is not the answer.]