Effective Area of Diaphragm Actuator

For a diaphragm actuator, the effective area is that part of the diaphragm area that is effective in producing a stem force. Usually the effective area will change as the valve is stroked - being at a maximum at the start and at a minimum at the end of the travel range.

Flat sheet diaphragms are most effected by this, while moulded diaphragms will improve the actuator performance and a rolling diaphragm will provide a constant stem force throughout the entire stroke of the valve.