Help: Stroke of the stop valve spool
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Which expert knows what the stroke of the valve plug for a DN20 globe valve is?
First, open the valve and then close it, and measure the distance between the upper and lower points of the valve stem. And that led to a result.
Mine is an electric control valve; the specified stroke is 10 mm, but there is still internal leakage when it is fully closed (manually). I suspect that the stroke of the valve stem might be greater than that of the electric control mechanism
When considering the flow coefficient of control valves, their stroke is generally slightly larger than that of ordinary globe valves; for typical globe valves, a theoretical stroke of more than 25% of the pipe diameter is sufficient. This is determined by comparing the area of the overcurrent curtain with the inner diameter of the valve seat
So, the stroke of a DN20 stop valve is generally greater than 5 mm, and it shouldn’t exceed 10 mm either, right?
What’s the point of looking at globe valves? Forged steel valves are pretty much sufficient; for cast steel valves, one needs to consider the casting process involved. In some cases, the cost can reach 15 or 20 times more. A larger stroke definitely helps increase flow rate without increasing costs – so why not go for it?