Evacuating Ammonia piping after repair

[Phil2]

I will be valving off the high side of a large ammonia plant for the purpose of replacing some isolation valves at the evap condensers. I will recover everything from the discharge service valves to the inlet to the receiver, including the thermosyphon. If I recharge the ammonia as liquid, once above saturation, is purging at the top of the system an adequate way of ridding the system of most of the non condensables or is evacuation necessary. The pump would have to be substantial, based on the time frame available.

[lowtempman]

Yes, evacuation pump is the best procedure. If time is of essence, after reharging the section you have isolated, before startin ghte compressors, run the evap condenser fans and water pumps for about 15 minutes to condense as much of the ammonia gas to liquid as possible, then purge from the highest point you can in each condenser. You will get air, water vapor and ammonia gas in your purge gas but the per cent ammonia will be lessened by making the condensers as cold as possible. If ambient is below 32 F, [like where I live], just run the fans.

[Magoo]

Hi Phil2.
definitly evacuate if at all possible, if time restricts, evac and purge.
Does system have an auto-purger to clean up non-condensibles, I have found auto-purgers the best thing since sliced bread for keeping systems clean and tidy

[Phil2]

Thanks. Running the fans is a great idea. The outdoor temp will likely be in the 30s

[Phil2]

Yes, I do have a multipoint auto purger.