Mycom W series | High oil consumption

[passandscore]

Hi guys,

Equipment: W series, Mycom Compressors
Refrigerant: NH3
Application: Ice Arenas
Pressures: Discharge 150psi. Suction 25psi

I have recently been dealing with the same problem at separate facilities. The customers have been reporting high oil consumption. These systems all have horizontal oil separators with armstrong liquid drainers that connect back to the crankcase. The common problems I have come across are:

1) Clogged liquid strainer
2) High crankcase heater setpoint. This leads to to oil with low viscosity. This oil is more likely to pass by the oil seperator. The heater is only energized when the compressor is offline but when it starts up it takes that over heated oil and pushes a good portion through the separator element.

Of course a faulty separator is always suspect but I have found that to be a rare occurrence.

One question I have is: Would you expect high oil consumption if a bank of pistons were left in a manually unloaded state?

Thanks in advance

[RANGER1]

Hi guys,

Equipment: W series, Mycom Compressors
Refrigerant: NH3
Application: Ice Arenas
Pressures: Discharge 150psi. Suction 25psi

I have recently been dealing with the same problem at separate facilities. The customers have been reporting high oil consumption. These systems all have horizontal oil separators with armstrong liquid drainers that connect back to the crankcase. The common problems I have come across are:

1) Clogged liquid strainer
2) High crankcase heater setpoint. This leads to to oil with low viscosity. This oil is more likely to pass by the oil seperator. The heater is only energized when the compressor is offline but when it starts up it takes that over heated oil and pushes a good portion through the separator element.

Of course a faulty separator is always suspect but I have found that to be a rare occurrence.

One question I have is: Would you expect high oil consumption if a bank of pistons were left in a manually unloaded state?

Thanks in advance

Passandscore,
With bank of cylinders unloaded for extended period, that head may fill with some oil as no gas flow in that area.

If a 4WB could have possibility of high discharge temperature, what is your discharge, oil & suction superheat temperatures with conditions you give?
I estimate 112 deg C discharge with 10 deg C superheat, maximum oil temperature 50 deg C

Over time we have found in WB compressors, pressurisation of crankcase can lead to excessive oil carryover.
That can occur from original hard chrome type of top piston ring not sealing so well, gas passing into crankcase.
They changed top piston ring, now has a groove machined in it. still hard chrome (some years ago now).
During that time Mycom suggested install a baffle in gas equalisation hole between crankcase webbing cast in internal casing entering around cylinder liners (suction gas stream.
This prevented oil easily entering suction gas stream from sump area.
Another issue can be pressure equalisation valve between discharge & sump.
It is open when compressor off to equalise allowing easier start.
When running oil pressure forces piston to close in equalisation valve.
Sometimes this wears or fails to seat, so discharge gas is entering sump, forcing it through equalisation hole into suction gas stream.
If this line is hot when running, it is leaking, should be ambient temperature.

A broken valve, scored cylinder liner, damaged unload piston, leaking oil return float are some other possibilities. see manual trouble shooting 6.1

https://refrigerationcompressorparts.net/wp-content/uploads/2018/12/MYCOM-WA-WB-SPARE-PARTS1.pdf

[passandscore]

RANGER1,

Thanks for the detailed reply.

a) Discharge Temp = 103°C . Oil Temp = 51°C (Superheat was not measured)

b) Mycom has changes there rings many times over the years and I know that technicians have their preferences. I am certain that the compression rings are not the chrome typed.

c) If oil where to get from the crankcase to the suction stream, how does that lead to high oil consumption?

d) Another issue can be pressure equalisation valve between discharge & sump ~~ I must be missing something here. I have rebuilt numerous mycoms and have never heard of such a valve. I searched the manual that you attached a found no reference of this valve. Do you have additional information on this? Perhaps a photo?

f) I did not mention valves, liners or pistons as I was looking to identify all external causing before determining whether or not is was internal.

[RANGER1]

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQ9ccwmLnNeUVo9T4xPluXc2160h518WrczJxuTmd30f8D2rd0kVFpVSCjy8Q&s=10http://www.refrigeration-engineer.com/forums/blob:http://www.refrigeration-engineer.com/02557cbf-781c-4e8c-b49d-8770f5e8448c

See valve directly below unload solenoid.
Maybe not everyone gets it, but standard when we order.
It’s just tiny piston inside that closes with oil pressure on it.
When no oil pressure 1/4” line from discharge to sump opens.
Can’t find in any manual.

[passandscore]

Okay, I understand what you mean.

Thank you