Didn't catch the pumping down to 1 bar when shutting down.

But I'm still leaning more towards a plug of oil in the bottom of the evaporator coil, preventing self circulation to start until there is Higher level on the feed side than on the boil of side.

Consider... if the plant was pumped down and liquid was moved to the HPR.

When they started the plant up again, the "pilot valve" would be full open, dumping HP liquid into the LPR at a rapid rate, and the the amount of liquid that is fed in, should expand into a much larger volume than the compressors can take, until the system is in balance.

So instead of the compressor pumping down, they should have to throttle the suction valves on the compressor to keep the gas flow at a manageable flow.


What I see is that they only pump down every now and then, and they only drain oil once a year or so.

Normally, draining oil on an ammonia plant is a weekly part of maintenance.


@aakbar, says they are draining water and ammonia, but this is a positive pressure system, so unless they have received contaminated ammonia in the first place, what they are draining is Oil.

The video Aakbar posted that showed oil drain, that is what oil mixed with ammonia looks like, gray and comes out like toothpaste

Then the video that shows the amount of oil that is drained from the coils... that is a huge amount.

and, as Ranger1 said, I would add an oil collector, not on the LPR, but on the liquid side on the coils.


I mean in HPR recievers that we design today, the pipes stick 10-15CM up into the receiver, and the Oil collection points are flush, to collect the oil.

Not so on older designs, on those, most connections are flush, so oil has to be collected "from the lowest point on the system" and in this case that is the evaporators.


But also, don't pump down... just hit stop on the compressor and let the liquid in the plant settle in whatever receiver