VALVE CLOSURE TIME FOR ESD

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The 'ideal closure time' for a 24" butterfly valve depends upon the application.

In a water supply situation, the closure time must not be too short, as the phenomenon known as 'water hammer' can occur, which has the potential to damage equipment and shorten valve life. 10-30 seconds would be a reasonable closure time, maybe more.

In a gas supply situation, maybe an emergency shut-off arrangement feeding a package boiler burner assembly or a bank of them perhaps, 5 seconds might be too long.

Pneumatic actuators vent according to the pressure of air and the volume of it within the actuator chest, and the restriction placed upon the vent line. They may be slowed down by placing a restrictor valve, either in the incoming air line(s) or in the vent line(s) as appropriate, and to speed them up a quick-release valve can be attached to the vent port, arranged so that loss of air signal causes a diaphragm to open the vent port to atmosphere locally to the valve rather than running the air back through the impule line to the solenoid many metres away.

There is no formula, as such. "Suck it and see" seems to be the approach, based upon experience.

1sec for 1' round about

I remember the argument about closure time on pipeline ESD's. All the engineers argured and the control people were spouting how fast electronics were than pnuematics.

I piped up and said, how much energy is already in the system and how much energy will be added to that system between the 5 seconds you are arguing about. They all shut up after that.