ckeck valve sticking

[CONROD]

Got a reocurring problem with a 4 compressor pack,discharge check valves keep jamming/sticking. The dicharge (1,1/8) comes off the body down about 300mm into a swept 90 elbow, straight into a check valve, out and away to the header pipe.I've changed the complete valve but it only lasts about 10 weeks before sticking again. Design fault? Any thouhgts?

[taz24]

Any thouhgts?

Is it sticking open or closed?
What is the make of the valve?
How long has the system run?
Have any of the others failed?

Cheers taz.

[TSK]

4 compressors, what type & capacity, is the sticking valve one of four, one for each comp?

[joe magee]

Is this valve a defrost dif valve like an A8 valve? If so I know what the problem is.

[CONROD]

The pack has 2 15HP comps and 2 25HP comps, all have individual henry NRV's.The smaller bodies are 1 1/8, the larger 1 3/8.Comps are new generation Artic Circle( aluminium bodies).The problems are only with the smaller compressor NRV's, sticking open.It has been suggested that the NRV's are too close to the discharge service valve and are also soldered directly into a 90 elbow.Max temp rating of the valve is about 120 degrees C.During normal operation the valve is running about 100 degrees,(R404a 12 bar HP).System is 18 months old.

[Andy]

The pack has 2 15HP comps and 2 25HP comps, all have individual henry NRV's.The smaller bodies are 1 1/8, the larger 1 3/8.Comps are new generation Artic Circle( aluminium bodies).The problems are only with the smaller compressor NRV's, sticking open.It has been suggested that the NRV's are too close to the discharge service valve and are also soldered directly into a 90 elbow.Max temp rating of the valve is about 120 degrees C.During normal operation the valve is running about 100 degrees,(R404a 12 bar HP).System is 18 months old.

A tad on the high side I would say should be in the 70's

I would talk to Artic Circle and get their opinion

Kind Regards Andy

[taz24]

It has been suggested that the NRV's are too close to the discharge service valve and are also soldered directly into a 90 elbow..

How long have they been in?

From experience I have known this type of valve to dry out and then jam with the extreme temp. Check the discharge temps of all four comps when running and note them down. Then stage off the larger comps and measure the temps, do this with all the possible combinations.
You may find the larger comps are overpowering the smaller ones and causeing the problem.

taz.

[chillin out]

The pack has 2 15HP comps and 2 25HP comps, all have individual henry NRV's.The smaller bodies are 1 1/8, the larger 1 3/8.Comps are new generation Artic Circle( aluminium bodies).The problems are only with the smaller compressor NRV's, sticking open.It has been suggested that the NRV's are too close to the discharge service valve and are also soldered directly into a 90 elbow.Max temp rating of the valve is about 120 degrees C.During normal operation the valve is running about 100 degrees,(R404a 12 bar HP).System is 18 months old.

How are you finding this out? I mean, how did you come to the conclusion that they were sticking open?
It's not that I am doubting your work, it's just that surely the head valves would hold the gas back anyway?

Chillin

[CONROD]

SORRY, NRV's sticking and jamming shut not open, comps tripping HP. Larger 25 Hp bodies running about 80degrees C at the NRV, smaller comps running same temp when running 50% but nearer 100 degrees C fully loaded.Will be back on site Monday to investegate further, keep you posted.

[chillin out]

And when you get to site you have to change the NRVs every time to get the pack running again?

Are you sure the stop valve after the oil seporator is fully open?

I have never seen one of these valves sticking open, on anything. I mean, in your case, you have 300psi behind it. It would be hard for anything to seal closed in this application. Not that I am saying it can't happen but it is very hard to believe.

Have you tried to open and inspect the old NRVs?

What did Arctic circle say about it?

Chillin

[Andy]

SORRY, NRV's sticking and jamming shut not open, comps tripping HP. Larger 25 Hp bodies running about 80degrees C at the NRV, smaller comps running same temp when running 50% but nearer 100 degrees C fully loaded.Will be back on site Monday to investegate further, keep you posted.

Hi CONROD

most compressor designs or the ones that use discharge blocking will overheat if run for lenghtly periods at the unloaded position.

You check valve problem is down to the timings of the pack controller which is keep the compressors running too long at part load. The check valve is seeing very warm discharge gas and the piston is expanding quicker than the material in the valve body causing it to stick.


Change you pack controller settings and keep the pack from running for long periods unloaded

You could change the check valves to NRVA's but you still have the compressor overheating, this is also partly down to the compressor body material BUT it could be down to the pack selection at minimum load, basically not enough load turn down unless you unload and then it over heats

Pack will probably have even compressor sizes, which is not the best way to match any load profile.

A pack is better designed as three compressors such as 6hp 12hp and 18hp, instead of three 12hp compressors.

Hope this helps.

Kind Regards Andy

[750 Valve]

Sorry not familiar with arctic circle and I may be missing something here but are these recips? If so, why the checker? Not sure with rack design - piping may dictate but don't often see 1 checker per comp on a recip rack.
Any discharge valves worth their weight will hold, if not they should be changed or is this a screw or scroll rack?
100C is WAY high on 404 at 12 bar discharge unless it has about 100K superheat! Is this a low temp rack? Maybe air or nitro in system? Bad evacuation? These temps are high

[kingice]

Normally the check valve (1) is in the main discharge header after the oil seperator,I would remove the individual checks.