Orifice Design (noise, cavitation, number of holes)
Orifice Design (noise, cavitation, number of holes)
(OP)
I am doing research regarding an orifice plate that was originally designed with a single hole but was changed to about 150 small openings. About 5 inches in diameter, It looks like a honey comb and often gets confused with a strainer. The holes in the orifice clog up quite often (even though there are strainers in the system upstream of the orifice) and a larger or single hole would be more appropriate for this reason.
I don't have a lot of history about the change and why it was made (its been years, and nobody remembers... etc etc) but the drawing is labeled "Quiet Orifice Plate" so we believe that it was a noise issue. This seems flawed since the environment is already very very loud, but its possible that the testers wanted quieter operation and made the change.
If noise is the only issue then it makes sense for us to go back to the single hole and end the clogging issues.
Some system specs, 1200 gpm, 3 to 4 inch orifice, though the current design is 150 holes with a 0.221 diameter spread over an area of closer to 6 inches.
What I am looking for information on is:
-How to determine noise across orifices with different hole sizes and shapes
-Cavitation calculations dealing with orifices
-Other possible reasons this design might have been changed that I should look into?
Thanks! :)
I don't have a lot of history about the change and why it was made (its been years, and nobody remembers... etc etc) but the drawing is labeled "Quiet Orifice Plate" so we believe that it was a noise issue. This seems flawed since the environment is already very very loud, but its possible that the testers wanted quieter operation and made the change.
If noise is the only issue then it makes sense for us to go back to the single hole and end the clogging issues.
Some system specs, 1200 gpm, 3 to 4 inch orifice, though the current design is 150 holes with a 0.221 diameter spread over an area of closer to 6 inches.
What I am looking for information on is:
-How to determine noise across orifices with different hole sizes and shapes
-Cavitation calculations dealing with orifices
-Other possible reasons this design might have been changed that I should look into?
Thanks! :)





RE: Orifice Design (noise, cavitation, number of holes)
http://www.optimal-systems.demon.co.uk/flow-orifice.htm
http://cav2001.library.caltech.edu/documents/disk0/00/00/02/22/00000222-00/Pan-Xiang-Wu.pdf
http://cav2001.library.caltech.edu/documents/disk0/00/00/02/21/00000221-00/Zhang-Liu-Jin.pdf
http://www.accutech2000.com.au/index.html
RE: Orifice Design (noise, cavitation, number of holes)
you are gealing with a restriction plate (also called a Lo-db plate).
multiple holes are for control of noise.
what pressure drop are you dealing with and what sort of solids build-up?
RE: Orifice Design (noise, cavitation, number of holes)
The pressure drop is approx 70 psi over such an orifice. The clogging is gradual deposits from the salt water (I'm waiting for my co-worker to confirm that for me).
Sara
RE: Orifice Design (noise, cavitation, number of holes)
RE: Orifice Design (noise, cavitation, number of holes)
For the single hole L/d is under 0.2
And I found your post in another thread about the tea-pots.
http://www.eng-tips.com/viewthread.cfm?spid=384&newpid=384&sqid=36566
Very useful. Thanks!
RE: Orifice Design (noise, cavitation, number of holes)
Such a plate should only be used in clean, non-plugging services. Sea water applications have too much solids and biological activity for such a plate.
Suggest that use valve possibly with a pressure controller.
RE: Orifice Design (noise, cavitation, number of holes)
RE: Orifice Design (noise, cavitation, number of holes)
The modern solution is to use a multi stage anti-cavitation valve. The cadillac version is a Fisher turbo cascade , Cav IV, or equivalent from other vendors. Be sure the seat area is suitable for the salt water environment, though.
If there is only a mild turndown, maybe a better solution is a few "capillary tubes" in parrellel. Zero noise and zero erosion if the alloy is selected properly. If 3/4" tubing is used, each tube 10 ft long in a coil, fL/d of 160, you can quickly estimate how many are required for the 70 psi DP. Cleaning them may be an issue, though.
RE: Orifice Design (noise, cavitation, number of holes)
Wilbert
RE: Orifice Design (noise, cavitation, number of holes)