The push/pull method moves liquid and vapor anhydrous ammonia out of a system without venting it to atmosphere. Here is what happens on site, from survey to final draw-down.
Why systems get pumped out
Anhydrous ammonia is an outstanding refrigerant, but any time a system is being retired, relocated, opened for major repair, or modified with hot work, the charge has to come out first. Venting is not an option: it is dangerous, it is a reportable release, and it wastes a valuable product that can often be reused.
A professional pump out recovers the ammonia into DOT-compliant tankers so it can be hauled away, stored, or moved to another facility.
The push/pull method
Push/pull uses a pressure differential to move liquid ammonia from the system into a receiving tanker. Vapor from the tanker is compressed and pushed back into the system, raising pressure on the sending side while lowering it on the receiving side. Liquid follows the differential and flows across on its own.
This is a closed loop. Nothing is released to atmosphere, and the transfer rate can be controlled precisely, which matters when you are drawing from vessels with unknown internal condition.
What happens on site
The crew walks the system first and reviews drawings to identify every vessel that holds liquid: receivers, accumulators, intercoolers, surge drums and low-side piping. Isolation points are confirmed with your team, and lock-out/tag-out is verified before a single fitting is touched.
Liquid comes out first. Once the liquid phase is recovered, remaining vapor is drawn down to a target pressure so the system can be safely opened. Gas detection runs continuously throughout, and full PPE is worn by everyone in the hot zone.
How long it takes
A small packaged system might be finished in a single shift. A large multi-vessel plant with several thousand pounds of charge can take multiple days, especially if piping is long or oil-fouled. The honest answer always comes from the site survey, not from a phone call.