DESCRIPTION

The majority of valves shown in this catalog are furnished as standard with direct-acting topworks; that is, air or gas pressure is applied below the diaphragm to open the valve and the spring pushes down to close the valve as pressure is removed.

Most valves can be fitted with a reverse acting topworks as an option. In this configuration the spring pulls up to hold the valve open until sufficient air or gas pressure is applied above the diaphragm to push down and close the valve.

The type of topworks contained within the diaphragm case can be determined in two ways. One is by the model number of the valve: D = Direct, DX = Reverse. The other method is to observe the shape of the adjusting screw at the top of the diaphragm case (Direct = Hex Head or Square Head Screw, Reverse = Round with Flats on Two Sides.