PUMP GP-GEAR 7T4764 - Caterpillar

Electric Protective System
Introduction
The electric protective system is designed to activate an alarm or shut the engine off if there is a problem or a failure in any of five different engine systems. The engine systems monitored are: engine overspeed, starter motor crank terminate, engine reversal, engine oil pressure and engine coolant temperature.The electric protective system consists of the basic components that follow: tachometer speed sensor, electronic speed switch, water temperature contractor switch, two time delay relays and two slave relays. This system monitors the engine from starting through rated speed.Component Description
Tachometer Speed Sensor (TSS) - The sensor generates a signal that measures engine speed, but also has a special characteristic that sends the signal in a certain sequence. If the direction of rotation is changed, the signal sequence is changed. Electronic Speed Switch (ESS) - The speed switch has controls (in a single unit) to monitor four of the basic functions. These four functions are: Engine Overspeed - An adjustable engine speed setting (normally 118% of rated speed) that gives protection to the engine from damage if the engine runs too fast. This condition will cause a switch to close that shuts off both the inlet air and the fuel to the engine. Crank Terminate (Starter Motors) - An adjustable engine speed setting that gives protection to the starter motor from damage by overspeed. This condition will cause a switch to open that stops current flow to starter motor circuit, and the starter motor pinion gear will then disengage from engine flywheel ring gear. Engine Reversal - A condition where the engine starts to run backwards. This will cause a change in the signal from the TSS, which will close a switch to cause the fuel to be shut off to the engine. Engine Step Oil Pressure - An adjustable engine speed setting that gives protection to the engine from a failure caused by not enough oil pressure. To maintain desired protection through the complete speed range of engine operation, two different oil pressure switches are used [280 kPa (40 psi), 140 kPa (20 psi)]. Once the step oil pressure speed setting is made, an engine that runs above this speed setting must maintain an oil pressure that is more than 280 kPa (40 psi). An engine that runs at a speed below this speed setting must maintain an oil pressure that is more than 140 kPa (20 psi). If either condition is not correct, a switch will close and cause the fuel to be shut off to the engine. Water Temperature Contactor Switch - This contactor switch is a separate unit (mounted in the regulator housing) that is wired into the shutdown circuit. It has an element that feels the temperature of the coolant (it must be in contact with the coolant). When the engine coolant temperature becomes too high, the switch closes to cause the fuel to be shut off to the engine. Time Delay Relays - These relays are special ON/OFF switches with two controls