Help!! I dont understand ?

[chungming]

1-why all the manual valve shall be of external shaft and can be closed turning the wheel clockwise when in front of the wheel

2-why all the butterfly valves may be set in both, closed or open position, evan with the actuator & mechanism disassembled ?

 

[gerhardl]

You are probably referring to a general description for a project or a valve standard for a major company.

Both have with standardization to do.

1. Anti-clockwise constructions exists, but generally clockwise operation is dominating today to avoid doubt or misoperation.

2. Has to do with application in the process or pipeline. Similar to automated valves that will be described either as 'normally closed', eg closed in 'neutral' (starting or no current/air to actuator or spring return etc.) or the opposite: normally open.