Consultation flooded plate freezer not working correctly

[dkarlberg]

We need some help getting our plate freezing system working correctly. We bought a slightly used plate freezing system that needed some work. We hired a firm to complete the work, but the machines does not perform as it should.

Now we have the machine in a remote Alaskan location, and have to figure out the correct engineering before this next salmon processing season (June 2013)

This system is extremely hard to start when beginning freezing, and when it gets really cold and freezing is complete it also is hard starting. The machine is causing power interruptions in the community where it is located.

To even get the machine running, one has to close the King valve manually and continue to "bump" the electric motor until the crankcase pressure falls below 110psi, and then finally open the king valve fully. Sometimes this process takes hours.

The unit is powered by a Carlyle 5H120 with a 75hp electric motor. This machine has a 120 gallon high pressure tank, and a 120 gallon low pressure tank. It has 15 36" x 72" Jackstone plates and is a flooded system running on R404a. (aprox 1200 lbs of R404a)

The condenser is a Keeprite air condenser model KHC 1A12 027-A-TAC-1697. I believe it is rated at approx. 33 tons at a 30 degree temp differential. Take this with a grain of salt, though as I am a fisherman, and not a refrigeration engineer.

The system is unstable and the hot gas does not work. The compressor has air cooled heads.

We just need some good engineering to make this unit perform efficiently, and would eternally grateful for any good advice to solve our problems.

We suspect that this system was not engineered correctly to begin with and have run out of money for head-scratching.

You can contact me offline at douglaskarlberg at yahoo dot com

[NH3LVR]

This is one I can get into. I cannot go into length at the moment, but some more information would be helpful. What is the suction and discharge pressure when you try to start? It sounds as if the unloaders may not be working. These open of the suction valves when the machine stops. Also you may need to pump out the plates before shutdown. There are tricks to start a compressor that is stubborn. Spending hours trying to bring the suction down is not one of them.
Where is your location in AK?

[Tycho]

first off, I gather it's only one plate freezer on the system? if so, that is why the hot gas does not work, because when you want to defrost, the low pressure side is cold, and you need to get the heat from somewhere to convert into hotgas, so ideally you should have had 2 plate freezers, so you can alternate between them.
When you want to defrost one, start freezing the second one, and the heat from that will provide hotgas for the one you want to defrost.

On the compressor, I am not familiar with this type of compressor, but ideally you should start it with the suction valve almost closed and keep the suction pressure below 2 bar (30 psi) and slowly take the pressure in the LP drum down (for first time start).
if it starts rough when the LP side is down, I'd agree NH3LVR that it might be starting with all the cylinders loaded.

If i'm thinking correct the LP drum is above the freezer and there is a level controller on it to keep the freezer flooded, or is it a pump circulating the ***** on the freezer?


if you had a schematic over the pipe system and the electrical it would be easier to see for us, and also easier to explain