Ball valves,Gate valves,Cv

joe_6

A few questions about valves: 1.What does 250# SWP on ball valve mean.I have seen ball valves with 250# SWP on them and 150# SWP on them.2.What type of ball valve can be used on a 250# steam drip leg,this is commercial building with main steam coming in at 250# and being reduced downto 10# pressure.All the driplegs use gate valves on the blow down for strainers and get corrode and lock up and i would like to use ball valves for quick opening and closing.3.Please explain Cv rating for valves,is this ratingpressure drop using water gpm and how does this correspond to avalve used on steam.Sorry to run on,thought i would ask the experts.Thanks alot.

DanHolohan

SWP

stands for Steam Working Pressure.

Cv always reads as a number and that number represents the amount of water (in Gallons Per Minute) that will cause the flow to take a 1 psi drop from one side of the valve to the other. If you know the Cv of a valve, you can tell the flow rate or the pressure drop under any conditions, as long as you know one or the other of those two things.

Good questions. Thanks for asking them.

RBT

WOG ?

What does WOG stand for? I just looked at a ball valve and it was marked 400 WOG.

DanHolohan

That's

Water, Oil, Gas

[Deleted User]

and if it says CWP

thats cold working pressure..so if it says 600 cwp and you put the valve on hot water, you may not get 600 psi capability..this link should help. its a handy chart
http://www.edwardvalves.com/pdf/catalogs/vogt/V134.pdf

Tony Conner

It Always...

...is a good idea to actually see the literature on stuff like this for yourself. There's always a chart or graph that shows the pressure and temperature ratings. As the temperature goes up, the pressure rating drops like a stone. There are lots of valves with big BIG pressure ratings for things like hydraulic systems, that aren't rated for steam service at all.

And when you see "WSP" or "SWP", that's where the system safety valves have to lift, so the operating pressure will be lower. There are loads of "125 WSP" valves and components in steam systems that RUN at 125 PSIG or lower, but the system safety valves usually lift at 150 PSIG. The lure is that 125 and 150 flanged stuff have the exact same dimensions, and 125 cast iron is quite a bit cheaper than 150 cast steel. But where the system safety valves are set at over 125, they don't meet ASME code requirements.

joe_6

Thanks one and all