MDC Butterfly valves require only one-quarter turn rotation of the handle to go from fully open to the fully closed position. In the 1–1/3" Mini Del-Seal™ CF flange series, a spring loaded ball bearing becomes seated in an indent providing a positive mechanical stop. All other size valves employ a roll pin stop method. These quick-acting Butterfly Valves feature an improved sealing action. The opening in the body of the valve has been machined at a slight angle to the plane of the flapper. The flapper is set to rotate slightly off-center. On closure, this causes the sealing pressure to be applied more uniformly all around the O-ring. A reliable, positive seal is made and the tendency of previous designs to roughen the surface of the O-ring and eject it from its groove is eliminated. 

MDC Butterfly Valves are low outgassing. All internal surfaces are machined from solid stainless steel bar stock. The handle is made of aluminum. A small O-ring on the stem prevents shaft leakage. The valves are offered with a choice of Del-Seal™ CF ultrahigh vacuum metal-seal flanges or ISO Kwik-Flange™ O-ring seal flanges.