Model and specification

Size

Double acting actuator
The suggested safety factor for double acting actuators under normal working conditions is 20%-30%.
Example:
The torque needed by valve=100Nm
The torque considered safety factor (1+30%)=130Nm
Air supply=5Bar
According to the above table, we can choose the minimum model is C-105DA.

Spring return actuator
The suggested safety factor for spring return actuator under normal working conditions is 30-50%.
Example:
The torque needed by valve=80Nm
The torque consider safety factor (1+30%) = 104Nm
Air supply=5Bar
According to the table of spring return actuators output, we find output torque of C-140SR k7 is:
Air stroke 0º=318.5Nm
Air stroke 90º=257.5Nm
Spring stroke 90º=181Nm
Spring stroke 0º=120Nm
All the output torque is large than we needed.
Attention:
During the restoration, the spring return actuators output torque will not be affected by the input air from the port B. On the contrary, it will help the restoration of springs.

Economical sizing
During selecting the spring return actuators, we can choose the more reasonable and more economical actuators, if we know the different torque needed by the valve working at opening, operating and closing.
Example:
The max torque needed by the butterfly valve=104Nm
The torque after opened (operating) 104x30%=32Nm
Air supply=5Bar
We can select the C-125SR K11
Output torque is:
-Air stroke 0º=141.4Nm>104Nm
-Air stroke 90º=83.4Nm>32Nm
-Spring stroke 90º=173Nm>32Nm
-Spring stroke 0º=115Nm>104Nm
The above data show the actuators torque can satisfy the requirement of the butterfly valve.