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. Both for electrical and pneumatic actuators on centric soft sealing butterfly 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.

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