Featuring double-distance piece design with 3 sets of packing, Models HD943 and HDL943 maintain product purity and prevent oil migration for applications that require maximum leakage control. External ports are located at top and bottom of distance piece chambers for purging, pressurizing, or venting. Other features include ductile-iron valves with PEEK valve plates, ductile-iron head and cylinders, self-lubricating PTFE piston rings, precision-ground crankshaft, and pressure-lubricated crankcase.