ammonia pump problem

[Sukhvinder]

can anyone help me about ammonia recirculation pump?

we are using ammonia over feed system in our cold storage, when we run the compressor the pump get down! without compressor the ammonia runs at 7 kgs without any problem but when we run the compressor the pump get down.

please help me out!

[Tycho]

can anyone help me about ammonia recirculation pump?

we are using ammonia over feed system in our cold storage, when we run the compressor the pump get down! without compressor the ammonia runs at 7 kgs without any problem but when we run the compressor the pump get down.

please help me out!

What kind of pump are you using, and how is it piped?


it is possible that when you start the compressor, you get boiling in the ammonia and the pump cavitate because it's not pumping pure liquid.

[Sandro Baptista]

I agree with Tycho. Start the compressor at low capacity and increase the capacity slower. The problem maybe occurs after the liquid be very hot (high saturated temperature) and with the high decrease rate of the suction there is much formation of vapour on the middle of the liquid.

[US Iceman]

One item to consider: start the compressors first to reduce the suction pressure and liquid temperature with the pump off. This will cool down the pump. Then let the compressor unload to maintain the lower temperature. after the pump begins to cool for about 30 minutes you can try to start the pump then. Do not let the compressor capacity increase too much. if it does, the pump may cavitate again.

[aawood1]

Hi, just for info on our new LT surge drum we had fitted last year with Hermetic liquid Ammonia pumps. One of them will start at -0.4 Bar and pump well but the other one will only start around zero Bar. They came from the same producting line and the serial numbers follow each other and are rated at the same duty. The makers can not say why we have this problem with them.

[mbc]

All of advice for running compressor is right , you have to run first compressor and after you system be come to your design temperature then start your pump also on - off of compressor should not have a too much difference.
But to install NH3 pump you have to be careful.

Size of inlet and out let and slope of inlet pipe is very important and also to chose right type pump with right head.

[ref717]

I agree Iceman, start the compressor first manually at reduced load and wait for the surge drum pressure to stabilize before starting your ammonia pumps. But remember not to put too much load on your pumps during its start-up. Load your evaporators one by one until your system stabilizes.

[Tycho]

if the pumps are piped correctly you shouldnt need to run the system by hand.


on all our pumps we have a t-connector on the pump suction the same size as the suction pipe, on top we put a reducer to 2" and a pipe up to the liquid separator again to allow most of the flash gas to escape.

I have never had a pump with delivery pressure problems because the compressor loads to fast, sure I've seen it oscillate from 2.5- 3 bar, but never loosing the pressure completely.

but we are missing some info, cause he says he has 7 bar pump pressure with only the pumps, but not by how much it drops.

and in any regard, 7 bar is pretty high for a liquid pump

[Jahangir]

Dear friends,
I think that it migt be cause of the lack of ammonia in system. by the way if this is not true tell me.
thanks

[Sridhar1312]

For using refrigerant pumps it is always best practice to have a low pressure receiver from where the suction gas is taken to the compressor suction and pump suction is connected to the low pressure receiver.The liquid from condenser/receiver is fed to the low pressure receiver.

If the above is followed pump may cavitate only when the total refrigerant charge is less due to some leak.

[michaelm]

Tycho,
If I understood you correctly, that you place a tee near the suction port of the pump going directly to the pump. The “up” portion of the tee is reduced to 2” connected to the top part of the liquid separator. Is it correct? Would not be the same to pipe from the receiver down to the pump with a bigger dia. pipe to allow bubbles to escaped up to the receiver and then to reduce it the size of the suction port without the tee.