NeilForster:
I've operated a lot of recips in the Americas and in Europe, but I'm not familiar with Bellis or Morcom. No matter, I'm confident that I could disassemble both without any instructions and put them back in original state. The reciprocating compressor is probably one of the only mechanical devices that has never changed much from country to country or culture to culture. By "condition based maintenance" I assume you mean: "Don't do any maintenance until something starts going wrong or fails".
I've had to operate recips 330 days/year, 24 hrs/day and I've also had to do the following regarding maintenance:
1) Under an austere operating budget and a penny-smart, dollar foolish General Manager I've had to wait until something went wrong with the machine and a shut down was inevitable;
2) When I had control of the operations budget I always planned a strict and rigidly timed interval when each recip underwent a complete inspection and overhaul (if needed); I kept rigourous logs on the mechanical condition of each of the critical components that I know of by experience - depending on the type, stages, fluids, and other characteristics of each machine. This program was in line with what I learned through the years working with such machines as Ingersoll-Rand, Clark Bros., Cooper-Bessemers, Chicago Pneumatics, Norwalks, Worthington, and many more. I think my program was more strict than the manufacturers - mainly because I had more to lose than the manufacturer in the event of an unscheduled shutdown due to mechanical failure.
I always monitored my recips whenever and whereever I could. The monitoring I did involved those critical components that are unique to each machine depending - as I stated above - on the type, stages, fluids, and other characteristics of each machine. Some of the critical monitoring critical to any recip are the following:
1) The discharge temperature (taken at the immediate valve discharge valve outlet within the discharge chamber) on each discharge valve. This is probably the most important item for a recip and my favorite diagnostic indicator as to the running condition of a recip. This item indicates not only the condition of a discharge valve, but also is an excellent indicator of how the piston rings on a double-acting cylinder are sealing. When ring wear starts to become a factor, the discharge temperature starts to climb due to internal by-passing of the rings and subsequent re-compression of hot gas withing the cylinder. I always painted my compressors with paint on the discharge valve covers that would char or burn at temperatures exceeding 300 oF. Since I have religiously always specified maximum discharge temperatures of 275 oF for all recip stages, I could spot a faulty, over-heated valve from across the room.
2) The suction valve temperature; this indicates the leakage of the seats on the valve. Sometimes I would opt for not monitoring this (because of expense) but, instead, depended on the operators to place their hand palms on the valve covers on a routine basis each time they made their rounds. This method would immediately alert an operator of a leaking suction valve. Today, this is almost impossible with DCS, everything centralized and operations being so down-sized in personnel. With all these managerial "economies", the trade-off is more thermocouples placed on the compressor valves. Sorry, but nothing comes free when monitoring your expensive investment.
3) Compressor frame vibration; this is an attempt to spot any bearing wear and knocking. Depending on your design, you still may have to contend with babbitted bearings and crosshead tolerances that are subject to normal mechanical wear and tear. One test I always did on my running recips was to balance an "Indian Head" Nickel coin on edge on the top of the leading cylinder on the compressor. If the Nickel would remain on edge and not move, the machine was balanced and the bearing were running well. This test has never failed me.
The above items - valves, rings, bearings - have always been the main items of concern for me in any recip design or application. There are other items that must be considered, of course, such as oil lubrication but those are the main ones for me. Strangely enough, in more than 15 years of exposure to recips in the field I never suffered more than 2 shut down events due to mechanical failure - one was a shattered discharge valve and the other was an electric motor drive burn-out. Love, care, and attention (as in any marriage) are items that a reciprocating compressor thrives under. I could continue to write about reciprocating compressors -complete with photos of all the compressors I operated, but a forum is certainly not the place conducive for such a novel.
I hope the above experience is of some guidance for you.
Art Montemayor
Spring, TX
