Maximum allowable velocity through a plug valve

[Lan123]

What is the maximum permissible velocity through a plug valve. The size is 30". The application is raw sewage that could contain grit and sand.

Or is the velocity governed by the maximum head loss through the valve that we are planning to control?

Thanks in advance.

 

[bimr]

If you have an on/off valve function, the valve size is generally the same size as the line size.

A control valve is used to modulate flow. When a modulating control valve is sized, a small pressure drop (2-5 psig) is designed to be taken across the control valve. The pressure drop helps to eliminate erratic control and improves control stability and accuracy.

If you are talking about a modulating control valve, note that a 30-Inch valve is quite large. The pressure drop across a large control valve will consume significant energy. For energy savings, it would probably make sense to evaluate the use of a VFD on the pump drive instead of a control valve.

 

[stanier]

Your question leaves a lot to be desired as we are unaware of what you are trying to achieve with this valve. Are you throttling the flow to control velocity in the pipeline or simply asking what is the recommended maximum velocity for a fully open 30" valve? Ask a dumb question and you will get a lot of dumb answers!

Wear is proportional to velocity to power 2 to 4.5m/s. BHRA has some useful papers on this aspect.

Generally Dezurik eccentric plug valves are used in sewage service for throttling. I would consult them as they have a wealth of experience. Anything above 3m/s for long periods would be a concern. When modulating over shorter periods you will get some wear and expect the valve to need maintenance.

If the valve is oversized then it will be throttled to control flow and expect some high velocities across the trim.

If using an inverted plug valve or conventional plug valve then the maximum velocity could be lower but wear depends upon material of construction that you have not shared with us.

Cavitation can be as damaging as solids if this exists in the valve.

"Sharing knowledge is the way to immortality"
His Holiness the Dalai Lama.

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