justification for class 300 valves
justification for class 300 valves
(OP)
Would appreciate a few comments.
Here's our situation:
We will be using seawater for our fire protection. Valves will be nickel aluminum bronze.
I believe class 150 NAB valves are rated at 19bar/276psi which is still higher than 245. Pump pressure at zero discharge is 215psi.
The water is polluted and rubbish are normally floating on the water. I'm worried if rubbish gets into the system, the pressure will shoot up above 215psi. Being a fire protection system, It seems "safer/smarter" to specify class 300. I'm also worried the EPC is just trying to save a few bucks by using class 150.
Q: How do we justify using class 300 valves instead of class 150?
Here's our situation:
We will be using seawater for our fire protection. Valves will be nickel aluminum bronze.
I believe class 150 NAB valves are rated at 19bar/276psi which is still higher than 245. Pump pressure at zero discharge is 215psi.
The water is polluted and rubbish are normally floating on the water. I'm worried if rubbish gets into the system, the pressure will shoot up above 215psi. Being a fire protection system, It seems "safer/smarter" to specify class 300. I'm also worried the EPC is just trying to save a few bucks by using class 150.
Q: How do we justify using class 300 valves instead of class 150?





RE: justification for class 300 valves
Why not be as safe as you can be. Make the thing nuclear bomb proof.
Your valves as specified meet or exceed the service requirements. What is your beef. If you have the money, go for it, but don't expect the EPC to gold plate the job just to put suspenders on a belt (unless, of course, they are working for cost plus).
rmw
RE: justification for class 300 valves
one would think that the rubbish+water is screened and filtered before entering the pump.
please rethink and revise your question if needed.
good luck!
-pmover
RE: justification for class 300 valves
Steady state pressure is one thing but pressures can be very much greater without mitigation measures.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: justification for class 300 valves
Our consultant is also claiming he won't guarantee the system if the EPC doesn't upgrade to class 300.
Rmw-I remembered when sizing motors for pumps, you normally move 1 step higher. So for valves, 1 pressure class higher. But I like the reasoning for nuclear proofing :)
pmmover - I would expect rubbish may clog the pipes. So similar to putting a thumb over a garden hose, the pressure will go up.
We do have basket strainers for our other pumps but rubbish (styrofoam, disposable utensils, plastic bags,even parts of flip flops) still gets in.
stanier - No waterhammer analysis was done. What are the effects of waterhammer? How high will the pressure kick? Will it exceed 275psi? We do have a PRV though.
RE: justification for class 300 valves
If there is column separation due to pump stop and the columns recombine you could end up with a 10 fold increase in pressure. Goodbye fire protection system just when you need it.
All standards and codes require a surge analysis to determine the design pressure rating. Without it you are just guessing.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: justification for class 300 valves
Get a new EPC.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: justification for class 300 valves
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: justification for class 300 valves
Is the design to NFPA standards? I am not familiar with these standards as I am in Australia. Others may be more familiar and be able to help if this is relevant here.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: justification for class 300 valves
Pump pressure at zero discharge is 215psi. If I assume 50% overpressure (to be conservative), that's 322psi, which is above the rated 276psi. Wouldn't the PRV handle the kick? How long will this overpressure be? Is this enough to justify class 300?
RE: justification for class 300 valves
Lord Kelvin [PLA, 1883-05-03]
Unless you do the analysis you DONT know what you have on your hands.
If the EPC is owned by a major shareholder then there is a conflict of interest. If the facility burns down then the insurance company will either not pay out or will chase the EPC company responsible and its directors. Insurance companies dont like giving money away. If someone dies in the fire you may go to jail.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: justification for class 300 valves
If you buy into the reasoning that a 300# system will function for transient pressures, that could turn into your personal problem in that you may be severely critized for spending unwarranted money without proper justification. Your decision.
Many codes give an allowable, short term, transient pressure which is higher than design pressure, 10% or so, check YOUR code. Any pressure above that high transient allowable must be relieved, or the design pressure will need to be increased.
I would think that a reasonably sized system would justify the cost of the transient study, even if it was considered an extra payment although it is usually not in my world. It would be IMO a good idea to determine if you could use 150# or if you actually did need the 300#ers, or for that matter, 600#, but if it's only 100 feet of pipe and a couple of flanges, maybe it's not worth the argument. That's for you to decide.
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: justification for class 300 valves
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/
RE: justification for class 300 valves
pmmover - I would expect rubbish may clog the pipes. So similar to putting a thumb over a garden hose, the pressure will go up."
I am calling this myth BUSTED. Putting your thumb over a garden hose does not increase pressure. It increases velocity due to the restricted opening. If the thumb trick did work, then why do we need pumps??? Why not just install a whole bunch of restrictions (valves) and create pressure out of nothing?
RE: justification for class 300 valves
If it ain't broke, don't fix it. If it's not safe ... make it that way.
RE: justification for class 300 valves
Sea water carries organisms such as the Zebra mussel. These will grow quite happily in stagnant sea water to the point where they will choke the system. Many desalination plant intakes have super chlorination and acid dosing facilities to remove the molluscs and dissolve their shells.
The build up of molluscs on the pipe walls will also create a very high surface roughness and affect the performance of the pumps. Any loose particles can indeed clog a system and take the pressure to the stalled head of the pump. The challenge isn't the increase in pressure but the reduction in flow when you are fighting a fire.
“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King
http://waterhammer.hopout.com.au/