commissioning of propylene refrigerant cycle

[kika]

Hello to everybody!
I've just found this site and I hope that you can help me to solve the following problem.
I'm studing how to perform a commisioning of a propylene refrigerant circuit. I have a lot of references where is written that after blowing with nitrogen I have to put the system under vacuum to evaporate residual water and dry all the lines. Don't you think that blowing with nitrogen is enough?Do you know if water can react with propilene and cause some problem to the system?
A part from freezing, what is the problem of having water inside the line?

I hope that you can help me

KIKA

[The Viking]

Vacuum and why to do it???

Firstly, your nitrogen is a "non condensable" gas, this means that any nitrogen left in the system will reduce the performance (and most likely stop the system working all together).

Depending on what oil your system uses, even small amounts of moisture will turn the oil in to accid (not desireable).

Also, even small amounts of moisture will be able to block expansion devices and other small orifices in your system.


There really aren't any excuses NOT to give the system a good, deep, standing vacc before you commission it.

[US Iceman]

Water can affect the oil used.

Residual nitrogen can increase the discharge pressure and operating costs if not evacuated from the system.

Water can freeze into ice at the expansion devices causing operation problems.

It is important to ensure the oil has sufficient viscosity to allow for dilution, which can and will occur.

Pull a vacuum, like any other refrigeration system!

[NH3LVR]

Welcome to the forum Kika

I saw this post this morning and was confused as to your question.
Were you asking about water in the Propylene Side of the system?

[kika]

Thank you for your suggestions. I wasn't thinking of the problem of the dilution of the oil. For what concerning nitrogen I think that it can be easily evacuated from the uncondensable line of the propilen condenser. Is this a desirable solution?
Moreover I was thinking to install in the system a filter for the absorption of residual water and flow the gassous propilen from time to time.
....Our team is trying to reduce the time of commissioning because in the past we had a lot trouble and vacuuming lasted more than 2 weeks!!! I know that this time may seem short, but the system is very small.
I have another question about the circuit. What about the connections? Once again I see that flanged connection aren't desirable on the line. Do you suggest to weld all the valves? What about the connections between main equipment and the pipes?
Waiting for your precious answer
KIKA

[US Iceman]

My recommendation is to minimize the use of flanges. Use welded valves and fittings as much as possible.
When using threaded joints; seal weld the joint.

Purge with nitrogen, and then vacuum. Manual purging of nitrogen off of the condenser does not remove all of the nitrogen.

If it is taking too long to vacuum a system then the vacuum pump is too small, or you have too much water in a system.

[pendlesteve]

Italy is part of the EU & should comply with EN:378 which states a vacuum of 200 microns should be acheived on the refrigerant side of the system.