Avoiding a vacuum when draining a pipe with no High point vent
Avoiding a vacuum when draining a pipe with no High point vent
(OP)
Hi all,
I have a problem I cannot get a simple answer to.
I need to drain a pipe (diameter 450mm) that has been brought over a structure and back to working level where it will be drained. This structure is creating a head of around 35m from the top to the draining level. Due to design there is no way to drain it in any other configuration.
The end of the pipe has a pullhead which has 2 ports (1x 2", 1x 1/2") both of which can be changed to add valves prior to the head difference being created.
with a rough pressure of 4 bar at draining level due to the weight of water from the head difference there will be an initial force pushing the water out however as I understand this will create a "gluging" release of the fluid inside. something I am trying to avoid as much as possible.
Is there any other way to remove this?
Cheers,
I have a problem I cannot get a simple answer to.
I need to drain a pipe (diameter 450mm) that has been brought over a structure and back to working level where it will be drained. This structure is creating a head of around 35m from the top to the draining level. Due to design there is no way to drain it in any other configuration.
The end of the pipe has a pullhead which has 2 ports (1x 2", 1x 1/2") both of which can be changed to add valves prior to the head difference being created.
with a rough pressure of 4 bar at draining level due to the weight of water from the head difference there will be an initial force pushing the water out however as I understand this will create a "gluging" release of the fluid inside. something I am trying to avoid as much as possible.
Is there any other way to remove this?
Cheers,





RE: Avoiding a vacuum when draining a pipe with no High point vent
Dejan IVANOVIC
Process Engineer, MSChE
RE: Avoiding a vacuum when draining a pipe with no High point vent
Ted
RE: Avoiding a vacuum when draining a pipe with no High point vent
I do not need to purge the entire line. Only as much as will flow out if the pullhead is removed.
There is no other inlet higher up in the line. The only 2 ports available are on the end fitting.
RE: Avoiding a vacuum when draining a pipe with no High point vent
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: Avoiding a vacuum when draining a pipe with no High point vent
RE: Avoiding a vacuum when draining a pipe with no High point vent
Then turn the water flow off then blow air into the pipe - you'll need in excess of 3.5 bar. Monitor pressure on the 2" valve port - when it reaches sat 4-4.5 barg, open it up again and then either match water out with air in - in a pipe of this size the flow velocity shouldn't be so high that the air bubbles are blown down, basically anything less than about 1m/second in your big pipe will allow the air bubbles to migrate upwards - work out what your flow rate from the 2" pipe is but at that pressure I can't see your velocity being in the 20-30m/second range coming out out the 2" pipe
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Avoiding a vacuum when draining a pipe with no High point vent
RE: Avoiding a vacuum when draining a pipe with no High point vent
I have to ask, How did the pipe get full of water in the first place if there is no vent to let the air out?
Sometimes its possible to do all the right things and still get bad results