LS selection valve

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I.Overview

This valve is installed on the path of the hydraulic output of the rotary PLS. In the middle of the two LS shuttle valves, it can prevent the higher PLS oil pressure generated by the rotary movement from entering the IS circuit of the system when the mouth rotation and the boom lift move simultaneously, resulting in slow boom lifting, ensuring the coordination of turning and boom lifting compound movements.

II.Location

III.Structure

IV(IIII).Working principle
1 Boom lift PPG oil pressure BP off
1) Zhu Han (3) is pushed to the lower end by the spring (2).
2) If the rotary operation is performed at this time, the pressure of the rotary PLS is passed through the rotary spool (5) Open the valve body downwards (1)
3) The turning PLS force P1 enters the LS shuttle valve circuit (9)

Boom lift PPG oil pressure BP is turned on (pictured)
1) BP pressure pushes the piston (3) up.
2) Overcoming the spring (2) force
3) The piston (3) is pressed against the valve body (1), and the oil circuit of A and B is cut off.
4) If the rotation is operated at this time, the PLS pressure generated by the rotation cannot enter the LS shuttle valve circuit (9).
5) Ensure the coordination of movements when turning and boom lifting work at the same time

V. Fault diagnosis

Symptom: When the boom and swing are operated at the same time, the boom is lifted slowly and the swing is fast.

Test result: boom pressure PPG signal pressure BP = 0

Failure analysis: From the BP pressure of 0 in the figure above, the system is always subject to rotary PLS

Pressure control, this LS pressure oil will flow to the boom pressure compensation valve, reducing the flow of the deactivation such as the oil cylinder, as a result, the moving pipe lifting speed is reduced

Troubleshooting: Replace the oil pipe of the LS selection valve to the boom PPG valve, etc.