Air in ammonia system

Hi all

System runs in a vacuum due to blast freezer setups. Just wondering how does one locate the leak? Thanks

Stop the system/increase suction pressure to observe ammonia leak, or shut one circuit off to determine if the circuit still is sucking in air.
Normal places of leakage might be compressor shaft seal, valve flanges etc..

I assume your issue is rising head pressure.
How long does it take under vacuum to cause problems?
As HwT mentioned the first step is to raise the head pressure and look for a leak. Sulfur sticks are my preferred method.
You can have a leak which does not show up under positive pressure. That make it more difficult.
As an example I had a operator leave a hand oil pump connect to a Mycom piston compressor, which was not unusual. Unfortunately he forgot to close the crankcase valve. It did not show up until the next morning. The night shift operator restarted to drop the product temp before the product was cased. At the deeper vacuum level it overcame the head of the oil and drew it all into the machine, followed by a lot of air. As I was going around looking for the issue I noticed that the crankcase was overfilled. Shut off the valve and started purging!

By my experience in vacuum system if you have more than one unit and one of this its not in operation I found that air come in the system through shaft seal on compressor.
I find that many times.

Ok thanks guys. Good information right here. Will look more into it