Model 745ASC Rubber Flapper Swing Check valve with adjustable spring closure (ASC) has epoxy-coated ductile iron body with encapsulated valve disc that is custom-molded Buna-N and comes in 3–14 in. sizes. Spring-assisted closure offers accelerated response with short stroke of 45°, and use of field-adjustable spring avoids slamming while simultaneously allowing valve disc to be stabilized under normal flow conditions. ASC device is field adjustable and can be replaced without removing valve.