EXPLANATION OF PILOT VALVEFigure8-PilotValve(Ref.No.17,page7)NOTE: Pilot valve (Z-180) pressurerange is 140 to 170 psi.Optional Pilot ValvesPart No.Pressure RangeZ-180A120-140 psiZ-180B80-100 psiZ-180C35- 40 psiThe Pilot Valve is designed to act as an automatic "on"and "off" air switch. When in the "on'” position, it allowsair to flow from the tank thru the tube to some devicesuch as a compressor head unloader mechanism, thusactuating it. In the "off" position, this valve stops the flowof air thru the valve and releases the pressure in the lineto the device.The pilot Valve works as follows: Tank air pressure actson the bottom of the valve. When pressure is greatenough to overcome spring force holding valve down onlower seat, it lifts off seat and allows air to flow aroundvalve and out through side opening in Pilot Valve. Whenvalve lifts off lower seat it moves up and seats on upperseat where it is held by tank air pressure. Whenpressure in tank and on valve drops, spring forces valveback down on lower seat. Air in line to device beingactuated can then escape through upper seat and outvent hole. The pressure at which the Pilot Valve is "on"or "off" is controlled by the spring, which has beeninstalled at the factory. A small adjustment can be madein the field by changing the spring force by compressingthe spring more or less with the adjusting screw providedon the Pilot Valve.ADJUSTING PRESSUREThe unload pressure is adjusted by turning the pressureadjusting nut #1 clockwise to increase, and counter-clockwise to decrease, pressure.Changing the differential (difference there is betweenload and unload pressure) is accomplished by holdingthe lock nut closest to the body of the valve #2 so it doesnot move, then turning the large nut #3 next to it veryslightly clockwise to increase the differential, andcounter-clockwise to decrease it.IMPORTANT: REFER TO OPERATING MANUAL & SERVICE GUIDE, FORM 5S1408, FOR COMPREHENSIVE AIRCOMPRESSOR INSTRUCTIONS.
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