Refriend ice flaker

[setrad7791]

I've been having some problems with a 3 tonne ice flaker machine and was hoping someone had some advice... The flaker has a 4h 15.2 bitzer compressor and seems to have a problem removing the ice from the drum after 20-30mins of run time. It's running on r404a with a danfoss tes12 ext equalized tx valve, orifice no 2 which has a nominal capactiy of 15.4kw at -30c. it is fitted with and oil sep and suction accumulator with subcooler. On startup the systems seems to floodback for aprox 10mins then settle's down to correct operating, i.e -35c sst and 7k superheat (-28c) but after a period of time the ice on the drum seems to lose temp and begins to slide on the barrel instead of flake off drum! the water flow is correct and the scraper blade is adjusted correctly (the system is brand new). Has anyone had any experience with this? My thoughts were the drum has been poorly manufactured and isnt transfering correctly..... it is a cheap chinese import after all!... Also the water cooled condensor seems oversized and i can only reach 1300kpa h/p with the pump restricted! would this affect the effiency at all?

[NH3LVR]

I have never worked on this machine, although it seems similar to a Howe or Northstar, which I do service.
The first question I have is does this machine use salt in the water?
Second does the superheat and suction pressure stay stable when the machine starts to make poor ice?

[Peter_1]

MAy I ask what brand? It's because I'm planning to import also a flake ice generator machine from China.
Is it a Geneglace look-a-like?

An oversized condensor will only increase capacity and lower suction temperature.

Can you see frost forming all over the surface after 15 ' running?

Where have you measured the -35°C evaporating temperature?

There's not too much oil in the drum? It's anyhow a DX system, so this should normally be OK.Where's the refrigerant injected: lower or upper part of the drum?

Is the temperature of the ice good and at least 7K subcooled?

If I understand you correctly: the ice isn't sticking on the surface of the cilinder, is this assumption right?

[setrad7791]

Its called a Refriend. The machine is running on salt water but can also run on fresh water (with no problem) the liquid appears to enter the bottom of the drum with the suction at the top, The tx valve seems to operate correctly even though the ice begins to melt off, I have a suction pressure of 10 psi which should give me around -35 and i have measured the suction temp at the outlet of the evap/drum.. Note the machine works fine on fresh water. Their appears to be frost all over the barrel during running but after freezing on drum it begins to melt away and slide instead of cracking off and falling down the chute.

[NH3LVR]

I am going to go out on a limb here.
I have lots of freshwater experience with North Star, but none with saltwater.
So here goes.
Is it possible for the salt to be concentrating in the pump reservoir as you run. causing the ice to get softer and softer as time goes on?

[Peter_1]

Exactly the same brand I was planning to buy. I needed to contact in fact yesterday our Chinese RE member LcShi to help me because communication with them goes so difficult.
And my Chinese isn't that good.

Besides the problem you have now, what's your general opinion abouth this machine? I'm planning only to buy the generator (1 ton) Is it well made/engineered?

Now your problem, if it runs fine on fresh water, then I have only the same thoughts as NH3LVR, your salt concentration is too high and you don't go low enough to solidfie the salt water. Don't forget that your DT with the ambient increases also seriously when adding salt.
So it will melt again much faster.

[Peter_1]

Just another thought, going that low with your compressor means also that the capacity of the machine decreased perhaps in such a big way that there's not enough capacity left to freeze this mass any longer.

Evaporating at -35°C (-31°F)makes that the refrigeration capacity of the machine has decreased to 1/3 of the caapcity at -15°C to -17°C (5°F/1.5°F) which is the normal or design evaporating temparature for flake ice.

So you have 2 problems: saltwater freezes much slower and much more difficult and to achieve this, you have to run your compressor also on a lower evaporating temperature which makes it even more difficult for the compressor itself.

I think that your problem has to be searched here.

[setrad7791]

in my opinion i would not recommend this machine as it is obviously poorly manufactured! their is rust underneath the new paint job and all the welds are rough! Nothing is correctly sized i.e to large condensor, incorrectly sized overloads on contacters and the tx valve's are incorrectly sized! If you want a fool proof system then go with a maja! german enginered and flawless in design... apart from the shaft seals on the barrel which tend to leak from time to time if not oil consistenly! hope this helps....