pressure drop in seawater lines HDPE
pressure drop in seawater lines HDPE
(OP)
HDPE pipe manufacturers sustain that HDPE pipes maintain a very low rugosity even for seawater intakes and pipings (< 0.015 mm)
That sounds non-realistic to me. I was wondering if you have a better figure of the effective rugosity of HDPE pipes after some months/years of use.
The case I am involved - a intake pumping station for 1300 m3/h plus a 2000 m long seawater line up to a power plant (seawater is for make up of cooling towers) - includes for each pump a suction filter (Johnson, 2 mm gap)and means for chlorination (constant and shock). Even then I think some sort of deposits / incrustation will occur either bioufouling or mineral or both. I think pressure drop calculation should take a rugosity of 0.5 mm at least. Do you agree? Any other hint?
Thanks
That sounds non-realistic to me. I was wondering if you have a better figure of the effective rugosity of HDPE pipes after some months/years of use.
The case I am involved - a intake pumping station for 1300 m3/h plus a 2000 m long seawater line up to a power plant (seawater is for make up of cooling towers) - includes for each pump a suction filter (Johnson, 2 mm gap)and means for chlorination (constant and shock). Even then I think some sort of deposits / incrustation will occur either bioufouling or mineral or both. I think pressure drop calculation should take a rugosity of 0.5 mm at least. Do you agree? Any other hint?
Thanks
fabio vincent
www.figener.com.br





RE: pressure drop in seawater lines HDPE
Let your acquaintances be many, but your advisors one in a thousand' ... Book of Ecclesiasticus
RE: pressure drop in seawater lines HDPE
Now, whether the pipe will collect scale and slime from sea water, of course it will. A 2-inch accumulation of slime on the inside of the pipe will both reduce the ID and increase the effective surface roughness. Both actions rais the dP.
If I know the dP and the flow rate, then I can adjust efficiency (not surface roughness) to get a measure of the amount that the pipe is fouled. When I've been responsible for seawater piping I did this on a regular basis and I had a minimum acceptable value. When the effeciency reached that point I cleaned up (or replaced) the pipe or I cleaned out the heat exchanger and accepted the slimed pipe.
David
RE: pressure drop in seawater lines HDPE
zdas04, do you think a 2 inch accumulation is a reasonable value to consider for such pipe (diameter is 600 mm) or that value is only a "might be"? Have you ever experienced such accumulation in HDPE piping operating with seawater? Can you give me any figures on the rate of accumulation (inch/year) of a well designed pipe and well chlorinated system?
As to the roughness I agree, of course, it will be dictated by accumulation properties and not by the bare clean pipe properties.
regards
fabio vincent
www.figener.com.br
RE: pressure drop in seawater lines HDPE
David
RE: pressure drop in seawater lines HDPE
Let your acquaintances be many, but your advisors one in a thousand' ... Book of Ecclesiasticus
RE: pressure drop in seawater lines HDPE
RE: pressure drop in seawater lines HDPE
If you want some accurate information check with operators of desalination plants. Veolia Water or Acciona Agua are two of the largest.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: pressure drop in seawater lines HDPE
While it was not a seawater intake application, I am some sensitive to such issues as I am aware of a specific major water pipeline (60" or ~1500mm diameter) several years ago where a plastic pipe material was chosen (in that case fiberglass/GRP) over other more traditional pipes, it appeared assuming build-ups would not occur and same would thus maintain (as it turned our unrealistic) high flow coefficients as promoted. While I don't know that build-up was the only problem with the line, it was reported there was a significant slime or scale build-up inside that plastic pipe that later caused flow and/or other problems (more details in prior thread at h
An equally or maybe even more important question in some applications may be can the chosen pipe handle aggressive e.g. mechanical cleaning means to restore flow capacity and/or re-lining etc., if/when whatever kind of build-ups eventually occur?
RE: pressure drop in seawater lines HDPE
Sea life does not read standards and will adhere to anything unless it contains copper. In Malaysia I came across an organism that burrowed into the PE material used for pile covers in marina.
If you want evidence of PE with barnacles just visit your local harbour and check out the piles for oysters.
Pe and GRP are used for marine systems but are chemically treated in a regular dosing regime with chlorinated water and sulphuric acid.
"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.
http://waterhammer.hopout.com.au/
RE: pressure drop in seawater lines HDPE
While I guess I understand how something like hypochlorite etc. might be injected (with some bother, expense, and maintenance etc. e.g. at the entrance to an intake to be sucked up?), was just curious how are "regular dosings" applied or helpful to the exterior of submerged piping, as I am not familiar with this application?