blast freezer

[mikesref]

I am working on a fish processing plant with a bitzer condensing unit with two 75 hp. screw compressors in parallel, I am having a problem with the discharge pipe off the #1 compressor with cracking(leaks)and joint stress ( you can see the pipe fittings warped from stress) The discharge line on the # 1 compressor is
2 1\8 in. is piped into a 3 1\8 in. manifold the #1 discharge line comes off the discharge valve approximately 8in. and go's in a long sweep 90 degree elbow were it 90's down into a 2 1\8 in ball valve then it bullheads (branch) into a 3 1\8 in tee. I have not had any problem with the #2 compressor, its discharge line comes off 2 1\8 in and 90's into the
3 1\8 manifold.
I have replaced the whole section of pipe and valve once, on the # 1 compressor and with in a year I have had numerous leaks. also when I examined the replaced valve you could see were the section of pipe inside the valve was seperated away from the valve. kind of like taking channel locks and squeezing the end of the pipe. I have checked for pressure drop between the valve and the oil seperator and there is none.
I am going to repipe this again and need to know the bes way. any ideas on whats happining?
Help
Mike

[Mark Selby]

Just had the same kinda issues on same comp. On the 3rd time I went back in with sch 40 black pipe and no more broken lines or valves

[US Iceman]

...then it bullheads

If the discharge lines from each compressor are really bullheaded, that's your problem. Any time you have compressor discharge lines flowing together into the run side of a tee and running out of the branch side the piping can leak.

If you take on discharge line and run it into a header and then further down install the other discharge line, and then continue with the discharge header the gas flow is continuous. In other words, the gas goes in the direction of flow, not against it.

[mikesref]

The system I am on is copper pipe, I have switched to the #2 compressor to be lead, now it has developed a leak on the ball valve joint, can harmonics cause this to happen, seems as though it is when the the product is getting down to temperture and only the lead compressor is running. This # 2 compressor elbows straight into the suction manifold.

[chemi-cool]

One of the common way to stop harmony or vibrations, is to change the direction of rotation to one of the compressors.
In your case you can not do it , but... you can try something else, you can change the phases and keep the same direction of rotation by doing it like this:

R > S
S > T
T > R

This way you change the angel between the three phases but keep the same direction.