Major blockage in discharge line blew head gasket. Why put a check valve on a recip discharge line?

TLDR; wrong discharge pipe sizing with a check valve caused multiple compressor failures, and consequences of poor brazing practices show its ugly face. Swapped out a 2D compressor on a parallel rack, due to a mechanical failure. This compressor shares a discharge header but has its own suction. The previous company installed a 5/8” discharge line with a check valve b/w service valve and discharge header. I guess this setup worked well enough until it didn’t. So, I pulled the guts out of the check valve and the diaphragm was missing its hard plastic ring and the spring. So I put the new compressor in. I double-triple checked my work; high and low pressure controls seemed to check out; I opened up suction, oil, and discharge lines. So I gave it power and the head pressure shot up crazy fast and blew the head gasket, refrigerant was pissing out from b/w the head plate and cylinder head. After replacing the head gasket, had to pump down the rack, abandon the 5/8” line and drill into the discharge header to put the correct 7/8” discharge line on. Everything works well now. I cut into the the 5/8” discharge line and found the spring and that the wall at the tip of the copper tubing folded into itself. Must’ve been a poor braze job, not enough heat to permit proper capillary attraction + wetting. Also, replaced the pressure switches since the high pressure and low pressures wouldn’t trip. But I’m curious why put a check valve on a recip discharge line? Any of you gotta see that before? submitted by /u/Special-Unique [link] [comments]