York OM Turbomasters

[imer]

We recently converted two York 2500 ton units to R134A. The machines are turbine driven.
Ever since than we have been having all kinds of problems:We'v had to replace thrust bearings twice, there are problems with load control etc.
I am curious if anyone out there has had similar problems with this kind of machines.

[shogun8]

This sounds to me lke you are having surge problems due to poor load control. Assume that the compressor is operating at Point A on the 100% speed curve (mass flowrate) and the external load resistance gradually increases (higher head pressure) while the speed remains constant, the flow decreases and the operating point will move to the left along the 100% speed characteristics curve. When it reaches Point B, the mass flow has decreased and the pressure has increased from the maximum pressure the compressor can produce at this speed. Pont B lies on the surge limit line (the area to the left of this line is the surge zone). At this point the characteristic curve is practically flat and the operation of the compressor becomes unstable. This condition, called surging, appears as rapid pulsation in the flow and discharge pressure, producing high-frequency reversal in the axial thrust on the compressor shaft. The amplitude of the flow reversal and the frequency of surge cycles varies. In some machines surging can become severe enough to cause mechanical damage such as damage to thrust bearings.. you need to get better stablization of the speed control on the turbines in my estimation.

[no8no3]

I've had a similar problem on this type machine, the software was corrupt and the changes in setpoints were not complete. Have you been through the program?

[imer]

Thanks for the replay. Both of you are correct. There are major surging problems. On low load days especially, the machine does not respond well to load changes.
As it pertains to the software, we have the Millenium panel and it has all kinds of software problems. I am trying to bring someone from York to reprogram the panel but so far no response. York has lost the maintenance contract for this building so thy are not qick to respond.

[RichardL]

My money is on the Shaft spacing being off.
I'm also assuming that the Rotor Impeller assembly was Re-cut for the 134 refrigerant.
I have converted a few to 134 w/no problems at all, short of a slight loss in tonnage with the 134.

The York OM Installation-Alignment procedures must be followed to the last period on Turbine alignment & spacing. Two years ago I watched as another service company went thru 3 sets of thrust bearings before they ever reached full speed. The spacer between the "York-Flex" coupling must be cut to the .001" or thrust failure is most likely.
Assuming this is a 238 compressor and the balance piston clearances and pressures are in order there is no reason for this brute to die such an early death..

I would advise you to monitor....."Closely" the "Balance- Piston-Pressure" and assure yourself that it is as close to half-way between Suction & Discharge pressure as possible. Should the Balance Piston Pressure start moving upwards towards the Discharge pressure the thrust bearing "Will" be knocked out.
But as I stated, I am betting that the Shaft Spacer is incorrect in its thickness.....And the turbine is imparting a severe Thrust load on the compressor.

Also;
Should someone have messed with the Booster control Valves(Also called Injector Valves) on the Outside of the Turbine Casting, The Turbine can....and will put a failing thrust load on the York compressor.
Please let us know whatcha' find on this Beast...