using 2 vacuum pumps

Hi Guys..
Just wondering.
I'm evacuating a large air cooled condenser which had a lot of moisture in it.
I have 1 connection, teeing off to 2 vacuum pumps. Alternating one to the other as their oil turns milky thereby maintaining 1 vacuum pump operating at all times. The vac pump oil colour has now stabalized.

Now.. As I am running out of time, I'm thinking of running both pumps together to speed things up, but I'm a bit concerned that, since I only have one connection at the condenser, and if one pump has better efficiency than the other, could they begin to counter act each other and therefore slow the evacuation process all together,??...

Your thoughts would be greatly appreciated.

Peter

try fiting nonreturn valves to pumps tryed this without valves and sucked the oil out of one pump
but vacuuming can not be rushed it takes as long as it takes have you used ofn tripple vac

G'day mate..
Whats "ofn".?. Are we talking about, pull down, break with N2, Pull down again, etc.?... Yea... I've done that a few times now.
Thanks for your feed back. I was thinking something like that would happen so I maintained 1 pump at a time...
Its all looking good now.. I have the water in my vac tester freezing now. I'd say, roughly guessing, around -2 C (as my thermometer went "Ali Baba". You gota watch your tool's around here in Indonesia. Tools have a tendency of walking......) So the condenser is looking pretty dry and now I can finish this off and get home...

Thanks again Martin.
Cheers

Peter

ofn - oxygen free nitrogen- u need a torr gauge fitted onto the condenser- preferably not at the vac pump connection- to moniter vaccing to ensure u get less than 2 torr , then shut the vac pump off and see if the gauge rises within an hour- anything more than 2 torr rise then keep vaccing- also change ur vac pump oil too

happy vaccing

Break the Vac and add an additional service connection as far as possible from the original .Connect your vac gauge here.Apply heat to the coil to speed things up ,you want to avoid pulling to deep a vac to soon as any trapped moisture will freeze and this is what slow's everything down.
Cheers
Stu

if it's warm there keep the condenser fan running to help prevent freezing of moisture and help evaparate any droplets and CCH if fitted

Open your gas ballast on the pumps if they don't have any then fit a vapour trap this will stop moisture. Freezing

.

Do not run two vac pumps together when in a deep
vacuum. No mater how good the machines are one will
always overpower the other and then you could lose your
vac.

Regards

coolrunnings.

.

Well.. Thank you All, Very much.... That is great feedback from all of you. I really appreciate it...
After several pull downs and breaks with nitrogen, along with high ambient temps here in Indonesia, and having the availability of running one pump continuously, my condenser now is finaly dry.

Now I can finish this commissioning and finally get home... not that I mind working here.. Indonesia is a good place and their people are great

Thank you all again...

As long as you are above the vac capabilities of both the vacuum pumps, two will work better than one. If you got all the way down to where one was slightly more powerful than the other, then you might end up with one sucking the oil out of the other.

Besides, if you think that there is high qty of water ............you might have to change the vac pump oil

Do NOT NOT use any one way valve as the pressure to open them will kill your vacuum.

One pump running is good
if possible create a flow with dry air or nitrogen evaporation is difficult but in air is working very good when humidity is low.

Never use 2 pump's in one system if you can't fully separate efficiensi of pumps , they will kill each other!

As long as both pumps are running, you shouldn't be able to suck oil out of either one if they are on separate connections and you valve them off when changing oil.