Pneumatic valve actuator VSF

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Pneumatic actuators come in many design types, but all share the same need for basic understanding of how their torque operates a valve. Whether you size a valve yourself, or you get someone else to do it, accuracy is critical. Incorrectly sizing an actuator can lead to a multitude of problems. Sometimes an actuator will have enough torque to open a valve but not enough to close it. Sometimes a valve may get stuck in mid-stroke. Other times, an actuator may provide so much torque that it damages the stem of the valve which it is operating. When sizing an actuator, first consider the valve’s torque requirements. You need to consider Break Torque Running Torque Closing Torque Maximum Shaft Torque Different valve types have completely different torque signatures. For example, a metal seated butterfly valve requires a large amount of torque to break or close and very little torque while traveling between the two positions. A metal seated ball valve requires a large amount of torque to open or close but also has an elevated torque requirement while traveling. Some basic valve definitions you need to know are: Break Torque Also known as Opening Torque. This is the amount of torque required to start the movement of a valve from the closed position. Running Torque Also known as Mid-Stroke Torque. This is the amount of torque required to maintain movement of the valve between open and closed positions. Seating Torque Also known as Closing Torque. This is the amount of torque required to seat a valve into its closed position. Maximum Allowable Stem Torque (MAST) The torque required to permanently deform or break the valve stem. Safety Factor