Valve Port Terminology Clarification
Valve Port Terminology Clarification
(OP)
I have a customer that has a piping specification that refers to ball valves as "regular port" and "full port". Now, I'm very clear, when referring to "full port", as to what I'm referring to. On the other hand, when someone refers to a ball valve as "regular port", what specifically are we refering to? I'm fairly sure I know, but I want to see what the general concensus is. This may sound picky or silly, but it's important to me at the moment.
Thanks,
CW
Thanks,
CW





RE: Valve Port Terminology Clarification
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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RE: Valve Port Terminology Clarification
RE: Valve Port Terminology Clarification
Here is the specs for a Durco ball valve. It shows the size and Cv of full and regular ports.
h
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Valve Port Terminology Clarification
I'm curious. Are you getting any training? Isn't there anybody at your company from who you can get important information like this from? What's the rest of the story?
http://virtualpipeline.spaces.msn.com
RE: Valve Port Terminology Clarification
RE: Valve Port Terminology Clarification
Although this shows up as a reduced Cv, in actuality the "regular Port" Cv is so large you'd be hard pressed to measure a pressure drop at flowrates that won't be so high as to erode the pipe. Full Port Cv values are also published but I have always contended the Full Port Cv should be infinite, as a full-port valve has the same restriction as an equivalent length of straight pipe. Sometimes, due to the better surface finish inside the ball than inside the pipe, the valve actually has LESS pressure drop than an equivalent length of pipe.
Unless you need to pig the line or pass some sort of probe through the valve, a regular port valve will serve well, and it is more economical: lower purchase price, and lower torque required to turn the smaller ball probably saves you a pile of money on the actuator.
RE: Valve Port Terminology Clarification
http://virtualpipeline.spaces.msn.com
RE: Valve Port Terminology Clarification
Just a note, flow through a piece of pipe is not infinite Cv, there is still a number as there is still pressure drop. Granted, it is a very large number.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: Valve Port Terminology Clarification
http://virtualpipeline.spaces.msn.com
RE: Valve Port Terminology Clarification
The valve contributes no loss to the system. THe system loss is the same whether the valve is open or if there is a spoolpiece there instead of the valve. Therefore the DP atributable to the valve is Zero, which implies infinite Cv. Cv= Q*Sqrt (sg/DP), so you're dividing by zero. In third-decimal-place context is the little disruption you have at the seat ring and the radiused edge of the ball. Does it really matter since it lives in the boundary layer? Not a lot. It's gonna be a helluva lot less (theoretical)disruption than a full-port Gate valve. Practically, the pressure loss may be 0.0002 for the ball valve and 0.002 [units intentionally omitted]for the gate. Somebody might freak out that the gate has 10x the lost pressure but in reality both pressure drops are so low as to be meaningless in other than academic considerations.
Full-bore valves also are not properly used for throttling, so Cv curves for a full-bore valve are pretty-well meaningless. Size a full-port ball valve for system velocity just like you do the pipe, and use it for on-off service only.
RE: Valve Port Terminology Clarification
http://virtualpipeline.spaces.msn.com
RE: Valve Port Terminology Clarification
"The valve contributes no loss to the system. THe system loss is the same whether the valve is open or if there is a spoolpiece there instead of the valve. Therefore the DP atributable to the valve is Zero, which implies infinite Cv. Cv= Q*Sqrt (sg/DP), so you're dividing by zero."
I must disagree with this statement, the proper conclusion is as follows:
The valve contributes loss to the system the same as a spoolpiece. THe system loss is the same whether the valve is open or if there is a spoolpiece there instead of the valve. Therefore the DP atributable to the valve is the same as a spoolpiece, and the spoolpiece has friction, generally equal to f * L / D. Therefore the DP atributable to the valve is non-Zero, which implies a finite Cv.
RE: Valve Port Terminology Clarification
Would you agree with Jim Casey if the statement was amended to read:
"The valve contributes no additional loss to the system beyond that attributable to a spool piece..."
jt
RE: Valve Port Terminology Clarification
Regular Port, or Standard Port is one pipe size down.
Reduced Port is (2) pipe sizes down.
MARKFLOW
RE: Valve Port Terminology Clarification
Regular port- when ball valves came out, this was the standard port size which was, as said in other strings, 1 port size smaller than the line size.
Full port- as logic has it, a full line size according to sch 40 pipe. Note, a full port valve is not full line size if you are talking sch 10 pipe- can cause pigging problems.
Reduced port- this was a way to drive costs down further in valves and is actually a port size smaller than regular port valves. Not seen very often now, but was more prevalent in the 70's!