Hydraulic Directional Control Valves: Failures, Causes and Troubleshooting
The directional control valve is the centerpiece of any hydraulic circuit, controlling the start, speed and stop of a given component. Directional control valves are available in a variety of configurations, from manual to electro-pneumatic and electro-hydraulic. While some valves are integrated into complete systems, such as an injection molding machine or press, others may function as standalone units. There are several common failures associated with hydraulic directional control valves, some of which may be due to improper installation or an undetected system fault. This article will discuss the most common types of failures and their corresponding causes, with a focus on troubleshooting.
Common types of failures
The most common types of failures related to hydraulic directional control valves involve: Overpressure, Leaks, Jamming, and Sticking.
Overpressure
When pressure levels exceed the limits of the valve, overpressure can occur, potentially leading to damage of the valve and other elements of the circuit. Overpressure may be caused by congested or clogged filter elements, improper flow control, poor system design, delivery failure due to unexpected surges in pressure, and even incorrect mounting of the valve.
Leaks
In addition to overpressure, leaks can also occur. This is usually due to inadequate seals, improper assembly, incorrect dimensions or tolerances for the parts, or an undetected system fault. O-rings are particularly prone to cracking and wear, meaning that they should be regularly checked for damage and replaced when necessary.
Jamming
Jamming involves a blockage in the valve, preventing it from functioning as intended. Jamming can be caused by debris in the hydraulic fluid, incorrect installation of the valve, poor system design, or a misaligned actuator. To avoid jamming, manual valves should always be fully examined before being installed, and any debris should be removed from the hydraulic fluid.
Sticking
When a valve sticks, or does not open or close as desired, it is usually because of a worn or damaged seal, or inadequate lubrication. If sticking occurs, the source of the problem should be identified and repaired before the valve is used again.
Troubleshooting
When troubleshooting the source of the failure, it is important to be aware of the system’s design and operating parameters. Any changes in pressure or flow should be noted, and any noise generated by the valve should be documented. Once the problem has been identified, corrective measures can be taken to address the issue.
In the case of overpressure, it may be necessary to clean and calibrate the filter element, install a larger orifice in the valve, or reduce the flow rate. If the valve is leaking, the seals should be checked for wear and damage and replaced as necessary. To avoid jamming, the actuator should be regularly examined and maintained, and any debris should be removed from the hydraulic fluid. Finally, if the valve is sticking, lubrication should be applied and worn seals should be replaced.
Conclusion
Understanding the most common types of failures related to hydraulic directional control valves is essential for identifying and correcting any issues that may arise. The source of the failure should be identified as soon as possible to minimize downtime and prevent further damage. Once the condition of the valve is determined and any repairs are performed, the system should be checked for correct operation and pressure levels.
