Orifice plate sizing 1

[hosec]

Are you able to advise the size of an orifice plate that will be fitted into a fire hydrant main to give a pressure drop, (when 1 hydrant is running at full bore) from 180 psi to 55psi.

The main is Thin Wall Stainless Steel line with an internal diameter of 150mm, and a fire hydrant connection is nominally 50mm dia.

 

[mech52]

hosec
I agree with this opinion that orifice plate not use on hydrant pipes.
but "ISO-5167 standard" and "shell flometer eng. handbook" are good reference to designing orifice plate for water and gas.

 

[boonng]

May I know where can I get a flow coefficient,Cf versus beta (orifice outer diameter/orifice inner diameter) graph? How do I obtain flow coefficient without doing experiment? Thanks for answering.

 

[m777182]

In the EN ISO 5167-1995/A1 you will find in TAB A1...TAB A11 (pages 4..14)values for coeff. C as a function of beta(for beta=0.1 to 0.5 by step 0.2 and 0.5 to 0.75 by step 0.1), Re-number (for Re=5E3 to 1E8) and type of deltaP joint ( 3 types of deltaP joint).
m777182

 

[m777182]

Hello mech52
I wrote a Vba code for orifice sizing according to EN ISO 5167-1995 too; at the moment it works for air flow only because that was what I needed.
m777182

 

[25362]

The Chem. Eng. Plant Notebook of August 17, 1987 brings an article by Herman E. Waisvisz titled Quick sizing of restrictive orifices that may serve as a tutorial, with a worked out example.

 

[aatara]

I agree with TD2K. The result is a 0.7 inch hole in the center of the plate. However you must chek that the plate is cavitation free. With 125 psi delta P and 55 psi downstream pressure the cavitation coefficient is less
than the plate cavitation index, so you will have cavitation and noise in the plate. To avoid this I suggest to use a multiple orifice plate. I have tested different plates of this type (3 to 30 inches size) and the first
results were piblished in POWER, September 1991.I n this paper you can find how to calculate multiple perforated plates.
Regards

 

[abcmex]

I am amazed, How many answers focus how to size a orifice plate (probably well intended) but

does a properly sized orifice plate solve the problem described originally?

Hosec, focus on your problem you will see that an orifice plate will only work at full flow as soon as you reduce the flow or use the nozzle at the tip of the fire fighting hose the parameters are different.

Kind regards

 

[bulkhandling]

If NFPA allows, I don't see the orifice a problem. The pipe is for one hydrant only. If the discharge valve is an on-off valve, you always get full flowrate; if the valve is a throttling one, when the flowrate is smaller, the orifice does give a smaller pressure drop, but the throttling valve will do the rest.
But I have the same concern with aatara, cavitation can be a problem. Multiple orifices can be a good choice.
Regards

 

[wkleppe]

Hallo,

I have searched the net for the article about quick sizing of restrictive orifices ( chem. eng. plant handbook, augustus 17 1987 ) as mentioned by member 25362. I did not find it. How can i obtain a copy of the article.

Kind regards

W. Kleppe