Removing entrained air in water process lines
Removing entrained air in water process lines
(OP)
Hello,
I'm searching for a easy way of removing entrained air from seawater piping (2" up to 30"). More than 2000 m3/h is not uncommon.
In all simpleness one can say that seawater is pressurized with air upstream pump(s). There will be pressure drops on the way, giving entrained air on pump(s) suction side. Worst case might get around 7-10 vol% air.
I have read elsewhere that one can fit a high point auto vent, ball and float arrangement, but can someone direct me to a more detailed way of design?
Other ways of design?
Many thanks
I'm searching for a easy way of removing entrained air from seawater piping (2" up to 30"). More than 2000 m3/h is not uncommon.
In all simpleness one can say that seawater is pressurized with air upstream pump(s). There will be pressure drops on the way, giving entrained air on pump(s) suction side. Worst case might get around 7-10 vol% air.
I have read elsewhere that one can fit a high point auto vent, ball and float arrangement, but can someone direct me to a more detailed way of design?
Other ways of design?
Many thanks





RE: Removing entrained air in water process lines
Most of the steam-trap companies offer products in this categoty, and their application handbooks will give you guidelines for how big, how many, and where to install them in your system.
Here is one: http://www.spiraxsarco.com/pdfs/TI/p017_02.pdf
For seawater you might want to use bronze/monel, or you might search a bit more for a plastic-bodied valve. Google is a good thing.
RE: Removing entrained air in water process lines
Check out perhaps Wessels Company's "Severe Service SS air separators" or ITT Bell & Gossett "Rolairtrol". Both offer up to 24" flanged connection sizes for their separators.
RE: Removing entrained air in water process lines
Been in contact with Spirax Sarco, but unfortunately they were not unable to meet the volumes of seawater (and nitrogen) we can have.
I was hoping to solve this without going down the road of a separator vessel as this would increase complexity somewhat. (This application is both off- and onshore in Oil&Gas Business, and complexity adds costs at greater pace by adding equipment).
Any new ideas?
Many thanks,
RE: Removing entrained air in water process lines
Excuse me if I get a bit off track, but how/why do you expect to get so much entrained air into seawater? Is this really seawater or produced water? Might you be coming from a deoiling unit where you've entrained air to aid in floating dispersed oil droplets? Though I've worked with those situations, I haven't seen the concerns you are raising. Ultimately however, it is garvity (buoyancy) and time that will separate entrained air from a liquid. Temperature will help with more favorable equilibrium conditions AND lower viscosity.
Doug
RE: Removing entrained air in water process lines
First;
I wrote air, but really it's nitrogen. Just simplified.
Anyway:
This is seawater injection for on- or offshore application. Seawater is lifted topside, treated and pumped/injected into oil reservoirs. In our case we treat the seawater by mechanically stripping the seawater with nitrogen, to removed dissolved oxygen (preventing corrosion and bacterial growth downstream). The seawater is normally pressurized to 2-6 barg in the stripping process. The seawater would then be saturated with nitrogen at this pressure, but as there would be pressure drops before suction side of injection pumps downstream, nitrogen would "vaporize" on the way.
Only done some rough calculations, but came up with a possible worst case of ~7-10% entrained nitrogen if seawater pressure was brought down from ~6 barg to ~1 barg at pumps suction. (Only assumed that the difference between nitrogen saturation at 6 barg and 1 barg, would be volume entrained at pump suction side)
Looked at http://www.spirotherm.com/ as well, but was hoping for something "simpler".
I have attached a paper that goes even deeper into the details if anyone is interested.
many thanks,
RE: Removing entrained air in water process lines