Hydraulics rams, also known as hydraulic cylinders, are steel tubes with a chrome shaft inside that extends or contracts under pressure. Found on backhoe arms, car lifts, tow trucks and more, these control valves divert high pressure hydraulic fluid to hydraulic cylinders and motors. The control valve explained here has three valve positions. Push a control valve and the cylinder expands with great force. Release the valve and it springs back to the centre position. The centre, neutral position allows the fluid to flow through the system. Pull that same valve and that same cylinder contracts with great force.
- Skill level:
Things you need
- Wrench set
- 4 Hydraulic hoses
- Hydraulic ram
- Control valve
- Plastic Tie straps
Route one hydraulic hose, from the hydraulic pump "out flow" mounted on the truck engine, under the truck frame to the hydraulic lift gate's control valve. The control valve is mounted near the lift gate. Plumb the other end of the hose to the "in flow" side of the control valve. Use an open end wrench to tighten the hose at the control valve and at the hydraulic pump.
Route one hose from the "out flow" side of the control valve, back under the truck frame, toward the front of the truck, to the hydraulic reservoir mounted in the engine compartment. Use an open end wrench to tighten the hydraulic hose at the control valve and at the reservoir.
Connect one hose from the "push side" of the control valve to a fitting in the lift gate's hydraulic ram. Use a wrench to tighten the line fittings on the ram and the control valve, after making the connection.
Connect one hose from the "pull side" of the control valve to the remaining open fitting in the lift gate's hydraulic ram. Use a wrench to tighten the line fittings on the ram and the control valve, after making the connection.
Start the truck, engage the hydraulic pump. Proceed to the lift gate, push the control valve lever and the lift gate goes down to the ground for loading. Pull the control valve lever and the lift gate goes back up, level with the truck bed for packing.
Tips and warnings
- The push side of the control valve refers to the fitting on the valve bank when the lever is pushed. The pull side of the control valve refers to the fitting on the valve bank when the lever is pulled. Use plastic tie straps to join lines together every couple of feet.
- Wear eye protection when working on hydraulic systems. Hydraulic oil is a known irritant, avoid contact with skin. Hydraulic fluid under pressure can be dangerous, never work on a hydraulic system while the equipment is running.
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