The distinctive valve body construction made of solid plastic is enhanced by a sophisticated actuator design. The actuator housing is made of fibre-glass reinforced polyester resin for high mechanical durability. The construction of both corrosion-resistant housing covers is reversible to allow the operating mode to be reversed. The housing holds the colour-coded
sets of springs which are necessary for the two safety settings - “Normaly OPEN (NO)“ or “Normaly CLOSED (NC)“. The EXNER actuator model K 22O is used for small nominal diameters up to size DN 50, while model K 330 is used for larger nominal diameters DN 65 up to size DN 100. Should the control medium fail, both guarantee actuation of the control valve to the safety
position. The fabric-backed seal diaphragm has certainly proved its worth. A contoured rim on the rubber diaphragm behaves like an O-ring, preventing the control air from being released via the seal surfaces of the actuator diaphragm.