Printable View
Out of 3 reciproating compressors, two have oil freezing issue. Oil temperature goes to 7C. Are we facing liquid carry over?
Secondly one compressor motor takes full load 230 amp at start up even at no load against 150amp in normsl operation? What is the possible reason? Its oil is not freezing. It is third compressor.
Rize1159,
Yes you are getting liquid refrigerant back into compressor.
You will probably notice discharge of compressor very low.
Can you explain what is on suction of compressor, like suction accumulator or suction trap.
You need to rectify or damage will occur.
High amps, check all 3 phases are drawing current.
Also try to turn compressor by hand if difficult to turn over.
Does this one have cold oil or any other problems?
Suction of the compressor is from knockout drum. System gravity feed as HP receiver--->Xpansion valve--->knockout drum--->evaporator PHE---->return to knockout drum ----> compressor suction. I have checked history of alarm. There are high level alarms at accumulator.
compressor with high amp problem dont have cold oil problem. Rather its outfeed valve is giving continuous noise when it is turned off. I feel its disc has opened and noise is due to other two compressors discharge pressure due to common header.
We are checking amp and hand turning. I will update.
Visually check level in PHE vessel, also frost on float switch, if you have one.
Sometimes oil can slow reaction in level control column.
Drain oil from all points. Make sure solenoid on liquid makeup is not leaking., close isolation valve to lower level while working things out.
PHE is just a plate heat exchanger and welded, so no way to check level in PHE and there is no float as well.
In accumulator we have level control column and option for oil drain, I will check in level control column here for oil drainage.
Solenoid, I am not sure it is leaking, How to check it, if we close hand valve before it?
We have checked this compressor by rotating with hand, it is rotating freely.Quote:
Originally Posted by RANGER1
All three phases are drawing currents.
Current is not changing with load, motor starts with full load current. Can their be some problem with capacity control mechanism of compressor? I am suspecting that capacity control solenoids are not closing and its coil is giving false alarm.
Here on this compressor we don't have oil cooling problem.
Hand valve before solenoid and expansion valve was 100% open. To reduce feed to accumulator, we have closed it and now it is open only 33%. This was done as in HP receiver, liquid level was fluctuation at very fast rate, building level and then emptying at very fast rate. My colleague was of opinion that it is abnormal. So we closed hand valve and then open it 33%. Now level HP receiver is going low at slow rate. But another thing started, HP receiver has started to fill up to 100%. This we are checking from gauge glass. Also when feed to accumulator starts on system loading, gauge glass gets empty as well. So HP receiver is fluctuating between 0% to 100%. This may lead to operation of safety valve on top of HP receiver, we suspect. If we restore previous settings, accumulator is giving high level alarm. HMI has history of accumulator high level alarm.Quote:
Originally Posted by rize1159
How to control liquid level between HP receiver & accumulator? We don't have any automatic valve between condenser and HP receiver, there are manual valves only. Between HP receiver and accumulator, there is manual valve, solenoid and manual expansion valve.
Is our system in balance, I think it is out of balance. Do we need to adjust expansion valve? if so what is procedure.
Rize,
Normally only adjust hand expansion valve, not stop valves.
Hand expansion valve should be adjusted so solenoid is on 60-70% of the time under high load, with liquid level at all times in liquid receiver.
If you can tell me what size & brand of hand expansion valve, hopefully Danfoss.
I think you mentioned it is 1000kw plant.
As far as unloaders you have to test manually if they function first, then go from there as to determine problem.
It is Danfoss ICS3- 50 with SVA, ICF, ICS+EVM, REG 50. Plant is 3000KW capacity.
You mean liquid should remain in HP receiver but solenoid should remain partly open 60-70% of time giving liquid to suction drum?Quote:
Hand expansion valve should be adjusted so solenoid is on 60-70% of the time under high load, with liquid level at all times in liquid receiver.
Can't understand this. What do you mean by un-loaders?Quote:
As far as unloaders you have to test manually if they function first, then go from there as to determine problem.
[QUOTE=rize1159;328431]It is Danfoss ICS3- 50 with SVA, ICF, ICS+EVM, REG 50. Plant is 3000KW capacity.
50 Reg Valve should be set at 4 turns open for 3000kw capacity as a good starting point.
You mean liquid should remain in HP receiver but solenoid should remain partly open 60-70% of time giving liquid to suction drum?
Solenoid is open or closed, nothing in between.
Ideally a modulating valve is best for this type of plant so everything is very smooth.
A Danfoss ICM & level probe are ideal for this & controls under varying loads.
Can't understand this. What do you mean by un-loaders?
Compressor capacity control solenoids.
Now following are the settings and results:
1- SVA 5 turns open
2- Solenoid remain open for 40-50 minutes and closes for 10-20 minutes in an hour
3- Reg is 2.5 turn open.
Liquid level is stable in HP receiver. Also Accumulator seems stable and high level alarm is not observed.
We have not tested un-loaders.
Rize,
Sounds a bit more stable.
With capacity control it should be in steps with time between each step.
Example compressor starts, say 15 seconds second capacity control increase etc,
Reduce capacity control steps usually much quicker, example 5 seconds between each step.
Each system different depending on size & characteristics.
Once settled down it should be reasonably smooth.
Can you describe control system
Maybe you have this already.
Have compressor sumps oil warmed up?
10 out of 10 for your Continued Help with this post ranger.
Rep points Added.
Has anyone discussed the crankcase heaters?
If fitted that is?
Historically i have seen this when a hot gas bypass (used to maintain load when control system requires a running comp) is passing.
Which caused condenced liquid build up in the comp sump and high standing suct pressures.
I will leave you in Rangers capavle hands. But I am troubled by this passing valve scenario.
Cheers Grizzly
Good point Grizzly, sometimes easy to forget basics, as you do them on site without thinking.