Weir installation on sea water network 1

[MT47]

Hi
Is there any one to has experience of weir installation citeria on sea water net work,my means when weir should be installed in ney work? and is it possible to consider vacuume breaker instead of weir? I will be thanks to reply me as soon as possible.

Best regards

 

[joerd]

A weir can be installed to make sure that the topmost exchangers in the system are always filled with water. This however means that your weir should be as high as the elevation of the highest exchanger in the system. Another way to ensure positive pressure at the highest exchanger is a backpressure valve. You will need some protection like a vacuum breaker for the case that the valve gets stuck or opens inadvertently, and you lose backpressure in the system.
The alternative is to make the return line self-venting, with the vent point at the highest exchanger. You'll need to size the return line for that (it usually becomes bigger). All this can be fairly easily computed using Bernoulli's law.
So if the highest exchanger is 20 m above the return point, and you want 1 bar overpressure after the exchanger, you will need a backpressure valve that drops 3 bar. Note that seawater usually contains dissolved air, which will come out of solution when the pressure is dropped. The valve and support design should take this into account (vibrations).

Cheers,
Joerd

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MikeHalloran]

A vacuum breaker will not last long in a seawater system, given the susceptibility of its moving parts to corrosion, silt, and barnacles, among other things. I'd use at least three, if someone held a gun to my head and made me use any at all.

Use a weir or a standpipe. It has the ideal number of moving parts; none. And it will still require replacement, eventually.





Mike Halloran
Pembroke Pines, FL, USA

 

[MT47]

Joerd,thanks for replying to me.

There is one point for me.where the return line should be connected ,inlet or outlet of heat exchanger,I think to outlet line of heat exchanger.In this case it seams pressure drop of back pressure valve should be considered 1 bar.Please clarify.What is difference between self-venting line and vacumm breaker valve operation in this case.

Thanks again