Vacuum pump to drain sprinkler line

[BronYrAur]

I posted this thread on the "piping and fluid mechanics" forum, but then it occurred to me that I should consult you refrigeration pros. You routinely pull vacuums on lines before charging. Has anyone ever pulled a deep enough vacuum to vaporize and remove water from lines?

I have a fire protection sprinkler line above a finished space that needs significant modification. The mains are no problem to drain; however, each drop down to the heads is about 6' long. Those drops will not drain until the heads are removed, thereby making a mess all over my office space. We will of course put down tarps, buckets, etc. but I would like to get all of the water out before breaking the line.

There is a rotary piston vacuum pump on site. Can it be used to pull a deep enough vacuum to vaporize/suck out the water? in theory, the pump claims to be able to pull 29" Hg. Anyone ever done this?

 

[MintJulep]

It would take a long time and would leave all of the disolved minerals and suspended crud that is in each drop at the bottom of each drop.

 

[Yorkman]

We use deep vacuume to dehydrate refrigeration system all the time, but generally we are not talking about gallons of water. The process is quite slow as MintJulep said. You would need to reduce the absolute pressure to about
.4 PSIA before you would start to boil the water. We usually get the vacuumes down to < 1000 microns. I don't think this would be a good application.

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int.

 

[MikeHalloran]

Instead of trying to remove the head intact, and having the water and crud dump out as the last thread is disengaged, how about surrounding each head with a big bucket and cutting the fusible link with wire cutters?



Mike Halloran
Pembroke Pines, FL, USA

 

[Yorkman]

BronYrAur,
You could you use the vacuum pump to suspend the water while you remove several head and then break the vacuum to allow the drops to drain. We've suspended the whole charge in an absorbtion chiller while we pulled a pump seal we're talking 300 gallons of solution that wieghted about
13lbs/gal. Pretty cool but a bit tense at times. Better stick with the bucket method!!

I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int.

 

[TedLinsle]

Maybe it'd be cleaner to remove the drop-to-branch connection and draining from that end? You mention that the modification is significant, so they'll probably have to be removed anyway.

 

[eric2718]

You probably have already solved this problem, but here is my answer anyway. We have found it quite easy to remove moisture from our system using a vacuum pump. However, our problem is the excess moisture that gets into the vacuum pump oil.