Direct mounting butterfly valves

[bao2ye]

The butterfly valve disc always has an angle when it is seating on the seat. It is impossible to make valve disc zeron degree alignment on the seat.
It seems like if we mount the actuator directly on the valve, the valve can not be fully closed.

In this case, do we need the actuator has angle adjustment founction?

Regards

 

[dcasto]

The stem should be zero degrees. The seat may be damaged of you do not have enough torque to fully close the valve.

 

[gerhardl]

The answer is my opinion both yes and no.

Both for electrical and pneumatic actuators on centric soft sealing bfl. valves, it could be necessary (and often is required) for the valve stroke to be somewhat adjusted for optimum sealing and to limit closing /opening torque, and adjust for mechanical slack.

An electrical actuator with both limit and torque switches will properly adjusted be set to close against adjusted limit (travel) switch. The torque switch will be adjusted to a higher than the end stop torque, to give further protection.

For centric bfl valves supplied equipped from supplier or producer complete with double acting pneumatic actuators the valves are normally already tested and are often and commonly supplied without adjustment possibillities, or adjusting screws is extra equipment.

Summary:

Further adjustment could be required for difficult or problem cases.

A good electrical actuator will always have integrated travel limit switches and travel can be adjusted.

Pneumatic actuators are commonly supplied without adjustment screws /devices but should be specified with or with the possibillity of adding adjustment devices.

Difficult and problem cases can occur where you wouldn't expect it.

 

[JimCasey]

When we mount Butterfly valves here to actuators that do not have a travel stop, we offset the coupling by 1.5 degrees to correct for twist in the valve shaft.

We are changing our actuator design to provide travel stops.

You must also watch that the coupling between the valve shaft and the actuator is tight. It is very easy for a loose connection to have has much as 2 degrees of lost motion.

 

[gerhardl]

.....and from a recent case:

ensure that opening and closing direction of actuator when mounted is correct, so that the actuator do not force the disc from the opposite side over the midpoint of the soft seat sealing when opening.