I have been having an odd problem, maybe something you guys have seen before.

I am building a dual circuit glycol chiller with 2 2DA3075E Discus compressors.

I moved the sight glasses around so they would be at the front so they are easier to see. An hour or two I was bending over to pick up a tool, and I noticed that the sight glass on the #2 compressor was cracked. It had circular, curved cracks. They didn't seem to go all the way through, but I don't want to sell that to my customer so I went to United and bought another one. The sight glass on the other compressor was okey dokey.

Before putting on the new sight glass, I inspected that face area on the compressor body, the sight glass, made sure the gasket/o-ring/washer was in straight. Installed the new one, made sure to tighten the screws evenly. About 1/8 turn each one, in a circle.

This one cracked too! But not near as bad. As I tightened you could see the circular cracks beginning to form on the outside of the glass, as if you were bending the thing in half.

Since the cracks were only noticeable when you looked at an angle and the light was right, I replaced the oil, and started to put the unit on vacuum. Don't remember the number exactly, but I couldn't drop below 3k microns. I looked at the sight glass, and saw little bubbles. I mean they were tiny (tiny bubbles, in the wine). For shits and giggles I put 100 psi of nitrogen, and soaped the glass and the outside edge of the glass frame. Nothing.

Tightened the crap out of the glass, cracks seemed worse, but not as bad as the first one. Pumped it down again, bubbles were gone, 1000 microns and dropping slowly and I went home.

I have built a lot of chillers, but as lame as it sounds this is my first time with semis. Luckily my customer has run into permit delays on their new brewery, so I can take my time to make it right.

Is this something weird? Am I jsut a dunce and doing something wrong? At this point I am planning on putting a new sight glass on the side like it was shipped. You can still see it, just not as easily.

Thanks for any input.