Time:2024-01-04 15:58:21 Browse: 120
Troubleshooting and Solutions for Common Faults in the Speed Control Valve of a 315 Ton Hydraulic Press: Insights from Hydraulic Press Manufacturers
I. Flow Rate Adjustment Malfunction
Adjusting the speed control valve without a change in the oil outlet flow is mainly due to radial jamming of the spool and faults in the throttle adjustment section. Radial jamming in the fully closed position leads to zero flow in the oil outlet, while in the fully open position (or with the throttle adjusted properly), it results in no change in the flow in the adjusting throttle section.
Solution: When spool jamming or faults in the throttle adjustment section occur, cleaning and repair should be carried out. In cases of severe damage, replacement with a new speed control valve is necessary.
II. Inaction of the Pressure Compensation Mechanism, Rendering the Speed Control Valve Inoperative
1. The pressure relief valve spool is jammed due to dirt, causing it to be inoperative. Disassembling and cleaning can resolve this issue.
2. Inlet and outlet ports are blocked by debris. Disassembling and cleaning can address this problem.
3. Insufficient pressure difference between the inlet and outlet; PL and P3 for medium- and low-pressure speed control valves should be at least 0.6MPa, while for medium- and high-pressure, it is generally 1MPa.
III. Anomalies in Small Steady Flow
To achieve stability in low-speed feeding of actuators such as hydraulic cylinders, the flow valve specifies a limit for small steady flow. However, within this limit, low-speed feeding of the actuator is often unstable. The analysis attributes this to variations in small steady flow, caused by excessive internal leakage, primarily in the throttle spool and pressure relief valve spool. The concentricity of the spools, due to their large and small heads being coaxial, requires sufficient clearance during assembly to compensate for machining deviations (0.025mm for the large head, 0.008-0.015mm for the small head), resulting in increased internal leakage and unstable small steady flow.
Solution: Replacing the two concentric spools of the speed control valve with two separate valve bodies helps overcome the drawbacks of excessive assembly clearance due to coaxiality errors between the inner and outer rings of the valve sleeve and the coaxiality errors between the large and small ends of the pressure relief valve spool. This significantly reduces internal leakage, effectively minimizing the impact of leakage variations on small steady flow.
IV. Unstable Flow Rate
After locking the throttle adjustment of the speed control valve, unstable flow rates may occur, especially at small steady flow rates. Causes include loosening of the locking device, blockage in the throttle section, elevated oil temperature, too low pressure difference in the inlet and outlet oil chambers, and reverse connection of the inlet and outlet oil chambers. When hydraulic oil flows backward through the speed control valve, the pressure relief valve fails to provide pressure compensation for the throttle valve, turning the speed control valve into a throttle valve. Any changes in oil chamber hydraulic pressure during the course will alter the flow, leading to flow instability.
Solution:
1. Clear blockages in the throttle section to ensure smooth hydraulic oil circulation.
2. Adjust the connection of the inlet and outlet ports of the speed control valve to prevent reverse connections.
3. Check for faults in the cooling system to avoid excessively high hydraulic oil temperatures.
V. Increased Internal Leakage
When the pressure relief throttle-type speed control valve's throttle is closed, it relies on clearance sealing, inevitably resulting in some internal leakage. Excessive wear on the sealing surfaces (pressure relief valve spool, throttle valve spool, and one-way valve spool sealing surfaces) increases internal leakage, causing flow instability, especially affecting steady flow.
Solution: Check whether the seals of the speed control valve are aging or damaged, and replace them to resolve the issue.
VI. Difficulty Operating the Adjustment Handle
1. The adjustment rod is jammed due to dirt, or the adjustment handle thread is poorly matched. Cleaning blockages or adjusting the handle thread can resolve the issue.
2. When used for inlet oil throttle adjustment, if the outlet pressure (generally load pressure) of the speed control valve is too high, release the pressure first before adjusting the handle.
