Yearly LPR Woes

[gproud]

Hi There:

My LPR is hammering when it starts to fill. I had a post last year around this time and I closed up the Hand expansion valve as directed.

We have made a lot of changes over the last couple of weeks getiing the system set back to it's design settings. Since then I am in the same situation as last year. Whenthe LPR fills, Head pressure goes up 15 pounds, suction pressure rises 6", tunnel temperature rises 4 degrees C. I have been slowly closing the expansion valve at the LPR and it seems to be worse. Is it possible this could happen?

Also, when the LPR starts feeding it is around 30% and immediately drops to about 16-18%. When it stops filling it is about 32% and immediately jumps to high 60's to low 70's %. Is this unusual and does it indicate an issue somewhere that we have missed?

Thanks and have a great day chillin'

Gordie

[RANGER1]

Are you short of liquid in reciever ?
This will upset balance of plant if liquid seal in reciever is broken.

[CHIEF DELPAC]

gproud I have a vertical L.P.R. with an electronic level controll. I found that running a liquid level 30 to 35% would sometimes cause wild fluctions of level sometimes enough to shut the engine room down on high level. I now run the level at 23% and havent had any level problems. The rise in head and suction pressures could be caused by the flash gas.Is the LPR large enough for the system? No new evaporators added to system.DO you need more compressor or condenser capacity for the load? The LPRs in my plant have the high pressure liq. go through a liquid sub cooler. I also have a horizontel LPR with a gauge o matic level cotroll. sometimes the float chamber gets dirty and sticky from the oil. This causes the float to not work properly causing erratic lpr levels.

[gproud]

Thanks for replying Ranger1 and Chief. This is the first chance I have had to sit down at the computer since I posted.

First in reply to Ranger1: We have plenty of liquid in the reciever, although overall I think we are down a bit in the system.

Reply to Chief: Our level control is a selenoid type with a level reading control panel that opens the selenoid when liquid is needed. We did have it set to 20% and this is where we went to a dangerously low level in the reciever when it started feeding.
The LPR is plenty big and we have not added anything since the plant has been in operation. We only run the full horsepower (1100) of the plant for about 8 weeks a yaer. The rest of the time we run only one small compressor (100HP) for the cold storage or maybe up to 400 HP if we run cranberries through our tunnel.
We have economizers running on three of our 5 compressors. This is the first year we have used them. The other two will be started after repairs. I will have our mechanic check out the float system for the reciever to see if oil or sticking could be an issue.

The design specs said that we should run our hand expansion valve at the LPR at 1 1/4 turns. We have closed the valve to 3/4 of a turn and this seems to be working much better for us. We still have some hammering when the valve opens, but we are not losing tunnel temperature or suction temperature and our head pressure is staying constant at this setting. The level still fluctuates quite a bit but does not go as low or as high at this setting.

What could cause the hammering we get? It does not hammer every time, just on occasion.

I do appreciate your replies and the time you take to do this. Thanks again.

Gordie

[RANGER1]

The liquid makeup solonoid should be on approx 70% of the time under full load. This avoids constant steady flow into LPR.
If you are now using economizer there will be less flash gas so regulating valve may have to closed in more once everything settles down.
Liquid reciever should always be min 20 - 30% level as dip pipe does not always go to bottom and is cut on 45 deg angle.

[gproud]

Thanks Ranger1.

Appreciate the advice. I have been closing the valve bit by bit and I think I have it so that we are not losing as far as pressure and temperature. I believe my biggest issue now is air in the system which will be purged off tomorrow. Weather is cool here and I am still running 160-165 head pressure and my auto purger is down.

Will post tomorrow night to let you know how things are working if they get the purge done tomorrow.

Thanks again
Gordie