PDA

View Full Version : Thermosyphon Relief valve leaking







Winchester
29-06-2012, 04:15 PM
I have three Ammonia compressors that have weeping reliefs and three that do not leak. We are using Crosby valves. Head never above 190# and relief at 250#. Has anyone seen or heard of this valve leaking or what my have caused this? We are having them tested and disassembled mybe vibration we think. Thanks

RANGER1
29-06-2012, 10:53 PM
Winchester,
It would be interesting if relief valve company can give you some kind of report on leakage & set pressure before dis-assembly. Maybe springs are faulty?

Have also heard of an issue with Henry relief valves in USA.

Vibration could upset them, as the correct way to store & transport relief valves is vertically with lots of packing.

When you mention vibration, is it excessive or abnormal.
VSD drives cause some strange frequencies & vibration.

Your relief valves obviously must vent to atmosphere, I think relieving thermosyphon reliefs back into system is safer if yo can do it. There is relief valves suited for this purpose, but harder to maintain.

cricri
30-06-2012, 07:51 AM
Winchester,
relief valves are designed to relief gaz, as written by ranger. you can use A2CK from US Reco
you must relief back into the system at a lower pressure than the pressure vessel to protect.
if you are using hot gaz to defrost your system there is probably a check valve between the gaz return from the thermosyphon and the hot gaz line for defrost. Then you must make sure that the pressure switch or pressure sensor for the pump and fan of the condenseur is connected after the check valve.

Magoo
01-07-2012, 06:48 AM
Hello Winchester,
are the compressors screws, and are the leaking ones on the oil side of thermosyphon. Ditto what Ranger suggested, vent relief side back to system. The composition of the seat /seal could also be affected by higher temps, in conjunction with ammonia and type of oil used.

Boomer333
16-08-2012, 03:38 AM
The problem with a relief valve is that it is in a dead leg on the piping , ie there is no flow thru the relief. This can lead to any dirt or foreign particles collecting under the valve , & they can over time get forced under the seat & disc. Remember this is not a service valve , the components of it are not of the same quality as a regular service valve would be , they are prone to leakage over time , springs wear , lose tension , if it has blown once chances are it might not seat properly again , as the disc might not find the proper position on the seat.
I work in Canada , Alberta , & here we have to tag all relief valves with the month and year of installation & are required by law to change them every 5 tears on a refrigerant system , on a boiler they must be tested & rebuilt re-certified every 2 years.
Don't think I would be venting the relief side back into the system , this might give you a massive flood of refrigerant if the valve ever opened , & if it did open & was passing how would you know that this was the cause of the system problems you might find associated with this condition. By venting it back into the system on a thermosyphon , if the valve did open you might be interfering with the syphon action.
Think your problem with the valves mounted on the compressors is one of dirt being forced under the seat of the valve over time , as I said , it is a dead leg , & any minute bits of FOD will collect under the valve & eventually over time work their way under the seat