Refrigerant Purity

[tarik]

I am an engineer working in a factory producing household reffrigerators, we use R134a as a refrigerant, recently we received cylinders with an air percentage up to 10%.

I would like to know:
- the acceptable percentage of air.
- the effect of air on the system.
- if there is any way to remove this air before charging the refrigerators.

Thanks

[CrankNMelville]

Do you mean air as in the atmosphere we breathe or refrigerant in a vapor?

This is very odd.

[tarik]

Yes it is the air of the atmosphere, we analyzed the refrigerant using an identifier.

[Tesla]

Hi tarik and welcome to our forum.
No air is acceptable in a refrigeration system.
The effect is detrimental on a refrigeration system by increasing the head pressure, mixing with refrigerant air and the moisture with it produces acid and sludge.
Several ways to remove air are - fractional distillation, manually with several refrigerant cylinders by purging from one to the other to gain a more pure quality each time.

If you search non condensables on this forum you will find much more detail on this topic.

[tarik]

Many thanks Tesla.
I have another question related to the subject. We used another type of refrigerant containing 75% of R22, on our R134a domestic refrigerators by mistake. The compressor was damaged severly, and there is alot of oil residue in the system.
We would like to know the best method to clean the system specially the evaporators if possible.

[Tesla]

Hi tarik
It really depends on how many fridges you need to clean and keep in mind I only work on commercial refrig and ac. In the old days we used R11 but now use more friendly solvents like SP141.
First set the system up for a "back flush" then a flush. Use a cylinder that you can pour the solvent into with a fitting to pressureise with dry nitrogen. When the nitro pressureises the system it will force the solvent through. The dirty solvent should be collected.
If you had more than say ten to clean up in a row, I would set up an open drive compressor from a car ac and pump a small amount of solvent around the system then reverse the direction with a reversing valve with large capacity suction and liquid burnout filter driers - you could use a recovery (large) compressor for this.
After the flushing/cleaning process replace compressor, add burnout suction line filter and drier and (after vacing, leaktesting and charging the refrigeration system needs to run for at least 48 hours = about one week. Then remove the suction line filter and replace liquid line drier for a standard one.