I am currently on an MI Outage for a FR6b unit where there are 6 of the same unit type. A long standing issue has been high Wheelspace temperatures in the Summer when on the rare occasion a unit is required to run at full load. The issue is not insertion depth nor alarm constant setting problem.
My question is basically a clarification. The Compressor discharge casing has 5 bore plugs on both the top and lower halves of the casing and I wanted to know if anyone had any information or has heard of a percentage of these plugs being removed for additional cooling. I have a fleeting memory that I have been to a site were this was the case but I can find no reference to a GE NIC/TIL that may discuss this. I have a small document that possibly alludes to this plug removal and it refers to a "BOM group". Again it would really help if someone knew this GE term "BOM Group". This is not an urgent request but as we have this one unit opened for outage it maybe a chance to suggest this change if it is an actual real modification that I can find some information on.

 

topcat123,

I can only answer the BOM Group question. In the Parts List section of the Operation & Maintenance Manuals there is usually a set of parts lists (8-1/2”x11” or A4 size sheets with only letters and numbers) which lists the part number, brief description and quantity of each item identified on the associated drawing (such as a Piping Arrangement or a Conduit Arrangement, etc. At the top of each Parts List you will find a drawing number that matches the drawing number on the main drawing (the Piping- or Conduit Arrangement itself)—and that number will be followed by a Group Number, also sometimes referred to as a BOM (Bill of Materials) Group Number. It will usually be some designation such as G01, or G03, or G11. The Group Number has the parts numbers for the specific parts used for a particular machine—most machines use the same drawing number for a particular system or component, but the individual parts used on a particular machine may have different dimensions or characteristics (such as bore hole plugs or pins or nozzles or switches) and the Group Number lists those part numbers for a particular machine (the one covered by the Operations & Maintenance Manuals for the machine(s) at a site).

I hope that’s not too bad an explanation of Group Numbers. But that’s all I can add to this thread, as it’s not really related to a controls issue. Well, sort of. Maybe. But the mechanical field service people take care of things like bore plugs and such, not the controls field service people.

Hope this helps answer the Group (or BOM Group) Number question at least.

 

Thanks CSA.

Long time no speak. The Controls part comes with the relation to high Wheelspace temp which usually get put in our department. As I am working alongside the mechanical guy who ventured the possible mod, I guess I just ran home to this part of the forum to ask the question. The info on the BOM Group might just do the trick if the drawings here relate to BOM Group 002-005 which calls for less plugs. Will let you know how we get on. Of course we might get that answer but would never go ahead with anything without first passing it by our engineering.

Topcat

 

Yes; I understand so well how high wheelspace temperatures become the controls guy’s (non)responsibility—as if the Mark* controls air flow to the wheelspaces.

The Mark* does not—for anyone reading this and thinking it does. Just because the high wheelspace temperature alarms come up on the Mark* displays DOES NOT mean or imply that the Mark* controls the air flow to the wheelspaces. But since most operators and their supervisors and Plant Managers don’t understand how the unit works and just generally have a deep-rooted and unjustified distrust and hatred of the Mark*, well since the Mark* annunciates the alarm well the problem gets thrown over to the controls guy. Makes sense, right! NOT!!!

Anyway, good luck! Be safe—and stay healthy!!!

 

Probably been looking at the drawings for years and never noticed the BOM Group as it was never relevant to what I required from the drawing at the time, but on looking closer there it was. BOM Group 001. I also noted that on this units data plate on the Inlet plenum was also marked with Group 1. Not sure if its the same relation but sometimes you see things that have been in front of your nose all along.

On the subject of enquiry we kept investigating thru other channels and it does come up that GE may have removed one or two of these plugs during commissioning on certain sites with differing results but nothing has ever been documented officially or turned into any kind of field recommendation. So therefore I would say this subject remains in the air as an "Urban Myth" and the unit we were working on has now been re-built with all its plugs still installed.

So I would like to close any further discussion for this thread for this time

 

topcat123,

MANY thanks for the feedback! My first commissioning job turned into a four month-long "resident engineer" assignment, and it was for a Frame 5 peaking unit which didn't run very much that summer. I had a LOT of time--and I wisely used it to go through the Operation & Maintenance Manuals and the Parts List very closely. I also had THE BEST Product Service man anyone could ever ask for, and he helped me understand a lot of what I was looking at. Some things I glommed on to on my own; others, he gave a push in the right direction. And, the things he didn't know--he had a Rolodex and knew exactly who to call in Schenectady to answer my question. I wrote down my questions and called him a couple of times a week (this was way before the Internet and email, almost before fax machines--they were very expensive!), and he was extremely patient and helpful. I got spoiled. A couple of years later, I was on an installation and had a different Product Service guy, and learnt how good I had had it!

Anyway, yeah--as you say, sometimes you look at things and it just doesn't seem important at the time and it doesn't prompt any further action or investigation. I had--and took--the time to STUDY every piping arangement and conduit arrangement and conduit tree and tubing tree and even went out to the unit to actually find everything I could (that wasn't in the L.O. reservoir). Honestly, I was BORED stiff, but in hindsight it was the PERFECT experience for a newbie like me.

Add to that the fact the Customer had hired a fellow with 25 years' experience with Frame 5's and that he was a fountain of information and knowledge. I knew a LITTLE about the Mark IV, and almost nothing about Frame 5's, and he answered all my questions patiently and gave me most of his tips, hints and tricks. The ONLY Process Alarm we had during first fire was High Atomizing Air Temp--and we were both so happy we literally jumped and high-fived each other, several times. (And that start was on Liquid Fuel, too!). He took me immediately out to the AA Temp Regulating Valve--and the L.O. Temp Regulating Valve--and instructed me in THE PROPER--and PATIENT--way to adjust those valves. Not intuitive, but I've never forgotten that lesson. We were both so happy and proud of that start.

Ahhh, ..., the good old days! Thanks for sparking my little trip down memory lane.

I'll bet if my "mentor" was still alive, he would know about bore plugs and cooling.... He worked on Frame 5 units in the desert of the very Southwest corner of the USA. But, alas, he passed; a great loss for me. He's the reason I try so hard to share information with others--he gave so freely and willingly, I feel an obligation to pay it back and hopefully pay it forward at the same time.