KIT-BEVEL GEAR 1072227 - Caterpillar

Illustration 1 g03202022
Main Return Valve for hydraulic tankThe main return valve for the hydraulic tank is equipped with a bypass valve. The bypass valve is closed until the return line pressure exceeds 241 kPa (35 psi). The IQAN system monitors the bypass valve and alerts the operator when the valve is open via a message displayed on the operator monitor.When the temperature of the hydraulic oil is low, the viscosity of the hydraulic oil is high. This results in higher than normal oil pressure in the return system. Bypass check valve regulates the flow of return oil in the return system in order to regulate the hydraulic oil temperature and return oil pressure.Return oil from the main control valve flows into the port and combines with return oil from the swing control valve in the passage. When the temperature of the hydraulic oil is low, the viscosity of the hydraulic oil is high. The resistance to oil flow through the hydraulic oil cooler is high. This resistance will cause the return oil pressure in the passage to be greater than the oil pressure at normal operating temperature. The increased return oil pressure in the passage overcomes the force of the spring on the spool in the valve. The spool in the valve moves toward the open position. This valve opening allows a portion of the return oil to flow through the return line and neutral flow control valve to the hydraulic tank. This results in increased return oil flow to the hydraulic tank and decreased return oil flow to the hydraulic oil cooler. Since the amount of return oil flow to the hydraulic oil cooler is decreased, the temperature of the return hydraulic oil now raises to the normal operating range at a faster rate. The pressure of the oil in the return system is reduced.As the temperature of the return oil increases, the return oil pressure in the passage decreases. The decrease in return oil pressure in the passage allows the force of the spring to move the spool in the valve toward the closed position. As the opening in the valve decreases, return oil flow to the hydraulic tank decreases and return oil flow to the hydraulic oil cooler increases. As a result, the hydraulic oil temperature is maintained at a moderate level.