The Clarke Pressure Limiting Driver (PLD)-equipped engine is a UL/FM certified diesel engine fire pump driver that reduces pump speed to limit the maximum pump discharge pressure to prevent over-pressurization of the sprinkler system. The PLD senses sprinkler system water pressure via a sensing line connected at the pump discharge pipe (between the pump flange and the discharge check valve) and physically moves the engine throttle to manage engine speed.Clarke Fire Protection Products.