control valve size 1

[3500sunday]

most company valve specifications limit the size of control valves to 6" even when it is to be installed on a bigger line.Can someone help explain the reason for this.

 

[pennpiper]

Here is a website with Control Valves to size 10"

http://www.haitima.com.tw/valve/control-valve/control-valve-h800p18.htm

Sometimes its possible to do all the right things and still get bad results

 

[aliansari]

No, it may be correct partially. Valve size can be different from the size of the pipe, it is installed in. According to the best practices, minimum size of a valve can be half of the pipe size, it means, a 6" valve can be installed in a line of size upto 12 inches, if the sizing parameters permit. However, a 6" valve should not be installed in a pipe size exceeding 12".

There are many vendors produce and supply control valves of sizes more than 6", and you can surf their websites

 

[georgeverghese]

Not aware of such limitations, but turndown on control valves should always be checked.

 

[srini66]

Hello Sunday,

It is not correct to say that control valve suppliers limit the size to 6 " on a 12 " line. Control valve manufacturers size the valve based on the process data and select the size based on the Cv and other parameters. It is a general rule and recommendation that valve size should not be less than half the line size to avoid pipe stresses.

 

[aliansari]

Hello Srini66

It is one of the recommendations generally used in sizing and selection of control valves that selected valve should not be less than half of the line size. It is not a sizing fundamental however. Control valve sizing of a control valve is a different matter altogether.

Here is the link where it is said, "some people believe that it is poor piping practice to install a control valve smaller than half of the line size"

http://www.valin.com/resources/articles/size-matters-control-valve-sizing-101

 

[EmmanuelTop]

It doesn't really make sense to install 2" valve on a 10" line. If that's the case in a real system, the line was so greatly oversized that the system hydraulics should be matched with process flow requirements in a different way - e.g. install a smaller pump and a smaller line, rather than wasting pumping energy and generating noise with high pressure drop across a small valve.

Dejan IVANOVIC
Process Engineer, MSChE

 

[Bohlool]

Hi,
the statement about maximum control valve size of 6" is not sounding general, assume a 24" line which needs control valve to be specified, it will most probably be a 20" control valve.
it is common to specify control valve size 1 or 2 sizes smaller than the main line, but if it come up with too small control valve, the line sizing calculations should be checked again, its possible the line is over sized.

 

[davefitz]

Now I am beginning to understand why we can no longer build nuclear plants on time and within budget.

"Nobody expects the Spanish Inquisition!"