Parallel oil system problem

[Tom C]

Feeling like a bit of a leech at the moment. The only times I have been here is for help. Promise this will change.

Last year (June 09) I posted a problem with the oil system on a parallel rack in NY that we manufactured. The oil system blew the lines off at the levelers.

This is a repeat of another rack in Lake Tahoe.
This is a medium temp, 3 compressor equal scroll wc (5hp) rack. A cv valve was not installed, with a vent to the suction line (same setup as last time).

The system has been in operation for 9 months without any major problems. Last night, an oil line at one of the levelers blew, dumping the oil, ref charge, etc. As the pressure in this line is equal to the suction pressure (very low), I'm thinking that the only possibility is hydraulic action. Oil flooding back so quickly that it blocks the vent line and blows at the weakest point (flare nut at the leveler).

Has anyone seen something like this happen?

When it happened last year, I thought it was a fluke. Evidently not. We have not used a P/R valve at the reservoir, nor have I seen them on other systems. I'm thinking that this may be a relatively inexpensive means to prevent this type of a catastrophic event from happening in the future.

Anyone have a take on this?

[Magoo]

Sounds like metal fatigue, with temp changes and vibration, flares are not good in that situation. Perhaps try retro fitting connects with flexibles.

[jose-carvalheir]

Do you have liquid gas formation on the oil line, seen it happen because of liquid formation apoun standstill of compressores , reason no checkvalves on the main discarghe line,and if you don´t have c7v valve maybe also the reason. use only flexible conections.

[oldesky]

My company manufactures systems with oil return lines and we have used flexible lines for about 6 years with no brakages or blow outs. Before this we would suffer an occasional blow out due to fractures in the tube or on the flare itself. We now make up our own flexible lines for convenience. We also do the same for pressure control lines to the compressor.