PIN-YM 2826548 - Caterpillar

Makeup Valve
Illustration 1 g00815980
Makeup Valve (1) Passage to Cylinder Head End (2) Drain Passage (3) SpringMakeup valves are located in the control valve sections for bulldozer lift and ripper lift. The makeup valves are in the passages to the head end of the bulldozer lift and ripper cylinders.When there is pressure in the head end of the bulldozer lift and ripper cylinders, the makeup valve is held closed. However, when the blade or the ripper is lowered rapidly, the pressure in drain passage (2) is greater than the pressure in head end passage (1). Pressure from the drain passage is felt in the cavity of the makeup valve. The pressure moves the valve to the left. Spring (3) is compressed. Drain oil can now flow into the head end of the cylinders.Combination Line Relief and Makeup Valve
Illustration 2 g00783886
Valve Cross Section (1) Passage to Spring Chamber (2) Valve (3) Spring (4) Passage to Tank (5) Pilot Valve (6) Spring (7) Screw (8) LocknutCombination line relief and makeup valves are located in the control valve section for the bulldozer angle. The valves are in the passages to the head end and the rod end of the angle cylinders. Also, a combination line relief and makeup valve is located in the control valve section for bulldozer lift on machines that are equipped with a ripper. The valve is in the passage to the rod end of the bulldozer lift cylinders.Work port oil flows through passage (1) into the spring chamber. This pressure and spring (3) hold valve (2) closed. The pressure of the oil is also against pilot valve (5), which is held closed by spring (6) .When the oil in the chamber of spring (3) has more pressure than the force of spring (6), valve (5) will open. The oil in the chamber of spring (3) now goes past open pilot valve (5). This oil goes through passage (4) to the tank. The pressure of the work port oil against valve (2) opens the valve and the work port oil goes to the tank. The open relief valve keeps the pressure of the work port oil from going higher than the setting of the relief valve.The relief valve is also a makeup valve. The makeup valve is used when the pressure of the pump oil is less than the pressure of the return oil. Therefore, the pressure in the chamber of spring (3) is also less than the return oil. When the pressure of the return oil has more force on valve (2) than spring (3), the valve opens. The return oil now goes past valve (2) into pump oil. The pressure of the pump oil and the return oil becomes equal.If the relief valve setting needs adjustment, screw (7) is turned in order to adjust the pressure setting. Locknut (8) is used to keep screw (7) from turning after the adjustment is made.