Powerfist 11G-2-30H, User Manual

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3.1.2 CONTROLS
1. Unloader/Check Valve
The unloader (see Figure 2 below) maintains pressure between the “cut-in” and “cut-out” pressure
levels. At low-pressure levels, all the compressor discharge air passes through the unloader into the
tank. When the tank air pressure reaches the desired cut-out pressure, the vent port in the unloader
opens allowing all compressor discharge air to be vented to atmosphere. At the same time, a check
valve internal to the unloader closes, preventing any air from leaving the tank through the vent port.
As air is used from the tank, the air pressure drops until the desired cut-in pressure is reached. Then
the check valve changes back to its original configuration where all the compressor discharge air is
flowing through the valve into the tank. This cycle continues, maintaining tank pressures between the
cut-in and cut-out levels. The unloader is pre-set at the factory and should not be tampered with.
2. Pressure Relief Valves
The pressure relief valve (item G in Figure 1, page 3) aids in preventing system failures by relieving
pressure when compressed air reaches a determined level. They are available in various pressure
settings. Pressure relief valves are pre-set by the manufacturer and under no circumstances should
the setting be changed by anyone other than the manufacturer. All pressure relief valves must be
tested on a regular basis and kept clean by pulling the ring connector on the end of the valve.
3. Throttle Control Cable
The throttle control cable (see Figure 2 below) is used to slow down the driving engine. It is a small,
single-acting, spring return air cylinder that moves the throttle lever on the engine to the idle position
when the cylinder cable is extended in the cut-out (venting) mode.
ENGINE THROTTLE
CONTROL
TOGGLE-UNLOADING
LEVER
OUT-PORT TO TANK
IN-PORT DISCHARGE
FROM COMPRESSOR
VENT PORT
Figure 2: Unloader/Check Valve