Normally closed and normally open valves with pneumatic actuators

摘要

Butterfly valves have become one of the most popular types of pipe valves in the world over the past few decades. Simple design, relatively low cost and decent consumer properties have made this type of valve popular at pressures up to 2.5 MPa. This article will focus on the application aspects of the above type with pneumatic actuators with a safety position function. Butterfly valves are popular for applications in technical processes, where a certain position of valve shut-off device is required for actuation of the safety and accident prevention function in case of absence of a control action. In a typical design of the body and seat of noneccentric butterfly valves (hereinafter referred to as "BV"), the disk rotates around its axis and the valve has no mechanical stops limiting its rotation. Actually, the disk can make a full 360 degrees revolution around its axis. The quarter-turn actuator (manual pneumatic, electric) that is used for the BV, has mechanical stops that limit the rotation angle of the BV disk to 90 degrees.