Full And Reduced Port 1

[Berenger]

When do you use reduced port valves and when do use full port ones? I'm working with a client that has same size of both types of valves, but there is nothing in their specification that explains when to use a reduced or full port. I asked for their preference, but they said it's up to me.

I understand that reduced port is usually used for gas streams and places additional restrictions on the stream (such as pressure or temperature). That's the extent of my knowledge.

Thanks for your anticipated assistance.

 

[DRWeig]

Calculate the valve Cv needed to insure stable control over the widest range of flows. Choose the valve with the Cv that is closest to but larger than calculated. It might be the reduced-port, it might be the full-port. Some of the small valves (1/2") used in HVAC applications have a choice of two or even three sizes of reduced port so you can match the Cv closely.

Gas or liquid doesn't matter. Calculate the need.

Best to you,

Goober Dave

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[Latexman]

Is this for control or just open/closed? If open/closed, pick the cheapest of the two. If in a line with relief device or it needs to drain (no pockets or sloped), use full port.

Good luck,
Latexman

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[BigInch]

Be sure to use a full port, if it is to be installed on a pipeline that will require pigging.

Independent events are seldomly independent.

 

[bimr]

If the fluid contains solids that may clog a reduced port valve, then you should specify full port valves.

 

[DRWeig]

Great answers all,

I don't know why I just assumed the OP's valves were for control...

Perhaps the OP could tell us.

Best to you,

Goober Dave

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[zdas04]

I must say that "great answers" is not the phrase I would use. There were some really good ones, and some not so good.

DRWeig,
The full port/reduced port discussion never applies to a control valve. Full port and reduced port have very similar control characteristics (i.e., terrible, and quite non-linear), and neither should ever be installed in a throttling application.

bimr,
I have never seen the solids in a flow that would collect in the dam created by a reduced port installed on the horizontal, and plugging really isn't an issue. If you look at flow visualizations, the acceleration happens some distance upstream of the restriction and solids just don't seem to collect there. I have seen evidence of liquids accumulating upstream of a reduced port valve where the line was running vertically down to a 90 and then the valve when the gas flow was really small, but that is the only time and it wasn't much liquid. For lines running liquids, the damning just doesn't happen.

I have to go with BigInch (it really sucks to try to cram a big pig through a reduced port valve) and Latexman (I've seen many instances where supply and demand have had full port valves less expensive than reduced port valves).

I tend to always specify full port trunnion ball valves for any line big enough to pig (i.e., 3-inch and bigger). I've just had too many instances of "non piggable" lines that someone wanted to go back and install pigging facilities. It is painful to remove pigging bars and replace reduced port valves.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[pmover]

perhaps this posting will further aid you . . .

When is a reduced port ball valve a better choice?
thread408-20283

good luck!
-pmover

 

[bimr]

The only reason to select a reduced port valve seems to be to save a little money. Perhaps a false economy because a better quality reduced port valve is needed because of the higher velocity that the reduced port valve will experience. Most engineers will just use line size valves instead of saving pennies.

Here are some valve references:

http://www.pdhengineer.com/courses/m/M-4001.pdf

http://www.piping-designer.com/Ball_Valve

 

[katmar]

I believe that the first answer given by DRWeig is the correct (and very well stated) answer and it is absolutely reasonable to assume that this is a control application that is being discussed. The OP has used the term "reduced port" and in my experience this is used almost exclusively for control valves. If we are talking of ball valves, and piggable valves, then we would normally use the terms "full bore" and "reduced bore".

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[zdas04]

Katmar,
That convention is far from universal. Your terminology makes sense, but I've seen more people use the "port" terminology for ball valves than I've seen using the "bore" terminology. The words seem to be used interchangeably by the masses. I've never heard the reduced (or standard) vs. full discussion used for anything except on/off valves.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[katmar]

I suppose that the terminology does vary - especially from country to country. With regard to ball valves the terminology I am used to is to use "port" when we talk of multi-port valves (same for plug valves), but we use "bore" when we talk of the diameter of the hole through the ball.

With globe type control valves, where a smaller plug and seat have been used than the normal full sized ones, we would talk of reduced port or restricted trim. Different suppliers use different descriptions - but I can't lay my hands on them right now to see if they are geographically distinct.

The only real answer is to wait for Berenger to come back and tell us what he was actually asking. Like so many times in these forums we find ourselves answering a question that the OP never asked. My signature byline was chosen out of exactly this frustration.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[BigInch]

Does it matter to the fluid or the pig.... or the valve for that matter.

Independent events are seldomly independent.

 

[zdas04]

Katmar,
Gotcha. I say that as "you can draw any line you want through a single point".

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Latexman]

Agreed. I did not catch the different words until katmar noticed. They were interchangable to me up to that point.

I do use a ball valve for control in one application quite frequently. That's for batching liquids into a weigh tank. The ball valve stays 100% open until it gets close to target weight, then it closes to 5-10% open to slow things down until it gets to the "pre-act" weight, where it closes. It works quite well and gives good, tight shut-off (no leakage).

Good luck,
Latexman

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[bimr]

He did not say "ball" valves but a conventional ball valves will have relatively poor throttling characteristics and is not usually used as a control valve. In a throttling position, the partially exposed seat rapidly erodes because of the impingement of high velocity flow.

Bores of Ball Valves:
•Full Port - A full port or more commonly known full bore ball valve has an over-sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted but the valve is larger and more expensive so this is only used where free flow is required, for example in pipelines which require pigging.
•Reduced Port - In reduced port or more commonly known reduced bore ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in flow area being smaller than pipe.

http://www.petrovalve.com/valves/types/ball.html

 

[BigInch]

right bimr, I too would favor a plug valve, maybe diamond pattern, for throttling that app.

Independent events are seldomly independent.

 

[Latexman]

It's in "dribble mode" for 1-3 minutes/batch about 3 times/day. They seem to last forever.

Good luck,
Latexman

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[zdas04]

Latexman, I always figure that Engineering Judgement should trump any "rule". My rule is that I "never" design a system where operators are required to throttle a ball valve or rely on a globe valve to seal. I've broken that rule many times over they years for very specific cases like yours. Once I've determined that breaking the rule doesn't create unnecessary safety or environmental risks then I don't hesitate to break it. I'll explain the circumstances to a client, but I won't apologize for the deviation.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Krausen]

Another advantage of full-bore/port: If the valve is an auxiliary tap to a process line, it can be isolated and removed from the process without a shutdown via specialized equipment. This is basis for many full-bore/port valve purchase orders in various processes, and well worth the extra cost.