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





RE: Orifice plate sizing
More data is needed, You need to know the required flowrate. If you do not have the requreid flowrate, then you need to specify the additional restriction caused by the firehpse and spray nozzle.
RE: Orifice plate sizing
RE: Orifice plate sizing
If there is a suggestion to buy one , please tell me! I really need it!
RE: Orifice plate sizing
RE: Orifice plate sizing
Just curious, why would you want to restrict the flow to a fire hydrant?
RE: Orifice plate sizing
1 TD2K - How did you calculate that? what is the correct formula to use?
2 EGT01 - This is a client request. I'll try and find out, but I can suggest that the main pressure of 180 psi (12.4 bar) results in a too high a reaction force on the fire fighting hoses.
RE: Orifice plate sizing
RE: Orifice plate sizing
with the crane paper, the flow to regulate and the drop pressure, you can get the inside diameter of the orifice plat for these variables
RE: Orifice plate sizing
please consult the NFPA on this. I recall something about orifice plates not being allowed at all in firewater distribution pipelines in some applications. I don't know in what NFPA standard I saw it because I was going through the standards looking for something else.
charrid,
I can send you a exel spread sheet I drawn up that calculate orifice sizing I made for gasses if your interested. Else you can get the info from the ISO spec on the matter of flow restricting massflow meters from which I made. Can't remember the number though. To buy one such software is not necessary, the calculation is straight forward.
Martindup
RE: Orifice plate sizing
There are several good programs available on the market. Before spending a lot of really good doe, I would suggest a book by Miller, Measurement Handbook. This book is an industry reference. a benchmark as so to speak, to orifice plate measurement computations for pipeline, hydrocarbon and related industries. My suspicion is that it will lend itself well to water applications.
In general, you are running an ANSI Class 150 application which suggests that a beta ratio of 0.65 would give you near a 100 inch of water differential pressure across the orifice plate. This would suggest 0.705 inches is erroneous under the American Gas Association Report Number 4, which is equivalent to API 14.3, as a throat diameter for the orifice plate. On the other hand, buddy wants a dP equal to 180 psi to 55 psi when the fire hydrant is full bore. This is yet a bigger issue.
I would suggest using a Venture Nozzle and not and Orifice Plate due to structural mechanical issues associated with energy transfer to the equipment. In conventional Bernoulli Obstruction Theory, why would you want to restrict flow to dP= 180 psi in a throat design anyways? Number one, you're going to bend the orifice plate, number two, coefficient losses exceed expected dP losses, number three you need bolts bigger than Anna Nicole Smith's legs to keep the flanging together!
And from where I sit, that's getting rather ulgy!
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Orifice plate sizing
Cockroach,
With all due respect, dropping 125 psi across an orifice is not that big a deal; less than 3800 lbf across the entire flat plate
In fact, the actual drop across the orifice will be somewhat larger than 125 psi because downstream pressure recovery should also be accounted for.
When applying (or misapplying, as the case may be) an orifice as a restriction - as a throttling device - using a venturi or flow nozzle would be exactly NOT the point.
Keeping Beta ("Beta" is a ratio, "Beta Ratio" is redundant.) within certain ranges is important when using an orifice as a flow metering device.
RE: Orifice plate sizing
I agree with COCKROACH, your client is trying to get something it may not work. The pressure drop that has been calculated probably is not relevant to your application. The problem is (my understanding) that you have a high pressure on the FF-pipeline, if you put an orifice you will drop the pressure only with full flow .
The way a fire hose works may be different; it has a variable nozzle (orifice) itself and this will reduce the flow, less flow, less pressure drop on the orifice, less pressure drop, higher reaction force
MARTINDUP is right you should review the applicable code too. In China they sell hydrants with a pressure reducer intergrated because they accept only 4 bar in hydrant located inside buildings.
RE: Orifice plate sizing
martindup - I would be interested in seeing the spread sheet - I can be mailed at andrew_1_3@hotmail.com
RE: Orifice plate sizing
John
RE: Orifice plate sizing
m777182
RE: Orifice plate sizing
Can't comment on whether it is allowed to have orifices in fire mains, leave that to a NFPA guy.
Orifices can be made thicker, but that isn't the question posted.
RE: Orifice plate sizing
RE: Orifice plate sizing
Please refer British Standard BS 1042, you can design on your own orifice plate.
regards,
KMP
RE: Orifice plate sizing
http://www.efunda.com/formulae/fluids/calc_orifice_flow...
RE: Orifice plate sizing
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.
RE: Orifice plate sizing
RE: Orifice plate sizing
m777182
RE: Orifice plate sizing
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
RE: Orifice plate sizing
RE: Orifice plate sizing
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
RE: Orifice plate sizing
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
RE: Orifice plate sizing
But I have the same concern with aatara, cavitation can be a problem. Multiple orifices can be a good choice.
Regards
RE: Orifice plate sizing
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