Vacuuming.

[TheDogFather]

Ive got a container I want to put some gas in, that used to have Helium in it.

Ive got a good vacuum pump. Roughly how long should I vacuum it for ?

TDF.

[TheDogFather]

Someone must have some idea.

Whats it got to do, remove the air ?

5 min, a hour, 5 hours ???

TDF.

[Omega1]

At a guess I'd say atleast a couple of hours if you can heat the bottle to 60c then even less but i don't think it would do any damage to go 5/10 hours.

[chilly1]

You should pull it down to a 500 micron vacume at least, it the helium was let out and the cylinder remained sealed there should be little else in it.. I would like to see a 250 micron vacume.

[TheDogFather]

Thanks guys.

I let air in when I tested to see if it had a one way valve.

TDF.

[Marci]

And whack it in the freezer first. Get the bottle really cold... as well as vaccing it down... refrigerant always moves to the coldest point so it makes recovering easier and is the way folks used to do it years ago before proper recovery machines became mainstream (apparently!)

[TheDogFather]

lol

My freezers full of food, so I'll have to go round asking friends if they have room to put this container in their freezer.

I can imagine the responses.

Nice tip though. :)

TDF.

[chilly1]

Use ice and salt .. or dry ice ....

[TheDogFather]

Something I saw while searching Google for a dry ice supplier jogged my memory. I can get access to a giant walk in freezer.

Thanks for the help and ideas guys.

TDF.

[chilly1]

A zero micron vacume would also be at absolute zero and would contain no molecules that were moving. Impossiable. So if we consider 0 psi to be atmosphere, at 14.7psi +- baraometric pressure at sea leval, then a zero micron vacume to be Atmosphere minus 14.7 psi, so to convert Bara to their english values we must consider that 1 bara is 14.7 psi., therefore a 500 micron vacume is actually .5 bara. which is actually a lower pressure than atmosphere. Which means that 1/2 of the pressure absolute remains in the system after an acceptable vacume. So how much contamination is acceptable. 1/2 or 50%. Of volume absolute/atmosphere.

[Gary Lloyd]

Why would we stick the tank in a freezer to pull a vacuum on it? If anything we would stick in the oven.

[TheDogFather]

I think Marci meant stick it in the freezer after it had been vacuumed, the colder the tank the easier the gas will move to it.

Is that not right ?

Chilly fired that last salvo about 3 foot over the top of my head. :(

TDF.

[Gary Lloyd]

Actually 500 microns is something like .001 bara, but I think the point Chilly1 was making is that no matter how deep the vacuum, there is always some tiny amount left in the container.

[kayl]

when vacuuming, to reduce the time need to acquire a good vacuum its best to heat which part of the system.
the condenser, the evaporator or the compressor.
im guessing the condenser
is 500 micron vacuum 29inch , 100PSI

[Omega1]

kayl you would need to heat the entire system to 60 degrees
which is not something most people can do,that is why it is best to do a triple evac with dry nitrogen on the first 2 and use the gas that it will be filled with on the third.

[kayl]

Originally posted by Omega1
kayl you would need to heat the entire system to 60 degrees
which is not something most people can do,that is why it is best to do a triple evac with dry nitrogen on the first 2 and use the gas that it will be filled with on the third.


ive heard of the term triple evac, but i dont know how to do it?
how do i do a triple evac with dry nitrogen on the first two, and use the gas it will be used with on the third?
what does the process involve?:confused:

[saratoga]

microns has the wrong units for pressure, so whats the proper term? micro pascals? microbars? Something else? Sorry I have little experience with HVAC stuff.

[Redwolf]

micron of mercury.

I'm sure I can speek for all of the Service Techs here. When I say this.........
Vacuuming and clean work habbits to me are almost the most important aspects of the job.
One can calculate, design, ponder, wonder, experiment, etc all they want to. But when it comes to it. If you've got enough of the following: carbon deposits from brazing, copper shavings, dirt, water, non-condensables, wax, etc. Whats the point. You're just going to end up cleaning that crap out one way or another. Those of us non lazy techs in the field have to do it all the time.

The first step in a system lasting for a long time is having the proper tools and knowledge on how to use them.

[Omega1]

Originally posted by kayl
ive heard of the term triple evac, but i dont know how to do it?
how do i do a triple evac with dry nitrogen on the first two, and use the gas it will be used with on the third?
what does the process involve?:confused:

You would find the answer if you did a search :),but

With your gauges connected, one to lowside one to high side
of your system you pull a vacuum through the lowside for a while
(the longer the better)then shut your lowside valve off,disconnect from vac pump and connect to your dry nitro then you open your high side valve to let in enough to bring the low side gauge up to about 0hg then you shut the high side valve off,connect to your vac open the low side valve and pull a vacuum again.
Do this twice and on the third you use the gas you will fill the system with:job done. :)

Just remember when you add nitro/refrigerant to the system
to loosen the centre hose from the manifold and let a bit through to bleed out any air that would be inside it.

[Epsilon]

I do not have any nitro here, can i do the triple evac with refrigerant (ofcourse r290 ;), wouldn't even ask this question when using r404a) ?

PS :I will be using a old compressor as vacuumpump

[chilly1]

Yes the purpose of a triple evac it to "rinse" the system out of the noncondensibles.