Plate heat exch glycol air purging

[RONB]

I've just started to commission chiller cases with PHE condensers. We are on a tight handover schedule. What is the quickest method of purging the air out of the glycol system,we have various purge valves in the system. Two are on the high point of the flow and return,one is on the top of the dry air cooler and one is on the pump station. The pump station and the DAC are both on roughly the same level (wall mounted),would it be worthwhile valving off the pump station/ pressurisation vessel and vaccing out the glycol lines to the PHE and DAC to get rid of the air or is this a bad idea.

[install monkey]

dont vac out, if its been installed as per consu,tants spec then just stop the pumps and vent at all points- also vent at pump - usually a manual bleed, run pumps for 10 mins the re vent ,run pumps and again revent

[Grizzly]

And just to Add!
If there is an expansion tank fitted?
Don't forget to pressurise the bladder before charging.
You would be amazed how many glycol systems have pressurisation units fitted which short cycle or create all sorts of issue.
Because their expansion tanks have not been primed / Pressurised.
grizzly

[MikeHolm]

This is the fastest and best way to get it all out. Run a pressure pump and keep adding the glycol to the bucket till no more air comes out, just clean glycol. Stop the system for 20 min and start again for a while.

10022

[RONB]

Thanks for all the info it is much appreciated. Mike, your drawing is the main method we are using at the moment but once the air stops bubbling out into the glycol and the drain line is pure glycol we are still having air problems. Once the drain line is pure glycol dose that mean the system is totaly vented,if so we are still having air problems and we start venting at the purge valves. It looks ok but then the next day we still have to vent again. We know the system is leak free as it is pressure tested to just below the blowoff valve setting and it holds ok.

[MikeHolm]

Then, either the pump you use cannot generate enough velocity to push the air out all the way or there are nice pockets for it to hide. Sometimes I have to tun the pump on and off for a couple of hours on a 200L system and then I have an auto air vent with a ball valve under it on an air scoop just to get it all out. It may take some time.

At what static pressure does the system run? It is also possible that on the suction side of the circ pump, the pressure is low enough at some conditions that air will come IN the auto vent if it is placed there.

[RONB]

We are using two variable speed pumps,one run and one on run hours change over. We are trying to maintain at least a 2 bar pressure but just when we think its ok the pressure starts bouncing up and down and you can hear the air coming through the pipe work. I know eventually the air will go but because we have such a short period of time on each job I am just looking for a quick fix,but maybe I am being a bit impatient. Would it be better if I ran the pumps at max speed to possibly move the air around the system a bit quicker then shut the pumps off and then purge from the high point.

[MikeHolm]

We are using two variable speed pumps,one run and one on run hours change over. We are trying to maintain at least a 2 bar pressure but just when we think its ok the pressure starts bouncing up and down and you can hear the air coming through the pipe work. I know eventually the air will go but because we have such a short period of time on each job I am just looking for a quick fix,but maybe I am being a bit impatient. Would it be better if I ran the pumps at max speed to possibly move the air around the system a bit quicker then shut the pumps off and then purge from the high point.

To some extent, a higher speed might work BUT a higher speed entrains the air more so a "spirovent" would help which has a wire brush like element in it which will take out the micro-bubbles. If there is time and budget, I would look at it. A bit of extra time means no call back (I hope)

[RONB]

Mike you mentioned an airscoop. What position in the system would it go?We are using 3 inch stainless steel pipe,would we be able to get an airscoop to fit stainless steel and would they be available here in the UK from a pipe supply company?

[MikeHolm]

They are available from BSS industrial, but I am sure there are others. this type of unit can go just about anywhere but i like them before hitting a coil or any other known trap. Some are inline and some would go on an elbow from a riser to a horizontal pipe and it could weld in any standard threaded fitting. A quick google brought me the BSS link.

www.bssindustrial.co.uk

[PaulZ]

Hi RONB
As Mike has said there could be pockets of air, switch the lines so you use the gear pump to pump in on the other side of the pump. Sometimes this can clear out any air pockets.
Paul