Hydraulic Valves, which are used to control hydraulic power by regulating the flow of fluid, are as complex as they are vital to a hydraulic system.
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As control managers of the system’s flow, valves are capable of redirecting pressurized fluid, controlling flow to specific areas, or completely closing a line.
Valves have the ability to manipulate flow, the direction of flow, and perhaps most importantly, the amount of pressure coursing through a hydraulic system.
Hydraulic pressure relief valves not only limit the maximum pressure within a hydraulic circuit; they also create a new path for flow when that pressure exceeds a limit.
Let’s examine further how pressure relief valves operate to dispense built-up pressure, what can happen when they fail, and how to problem-solve any common issues.
Pressure Relief Valves limit maximum pressure in a hydraulic circuit by opening an alternate path that relieves pressure that exceeds a preset level.
All fixed-volume circuits require a pressure relief valve to avoid excess pressure that can cause system failure. They can be direct-acting or pilot-operated to perform this function.
Pressure relief valves are the most widely used type of pressure control valve in nearly every hydraulic system.
How they work is pretty simple:
For more understanding, let’s examine how pressure relief valves appear on a schematic and in a simple circuit.
In this example, a poppet is held inside the valve by a heavy spring. The poppet is forced off its seat when the pressure exceeds a set value, and flow is released through an outlet into a tank.
A pressure relief valve has the critical task of protecting a system from any overloads of actuators that can compromise the system.
When a pump unloads or actuators are in motion, fluid movement is not a problem. A relief valve is essential when the actuators stall or to balance hydraulic force with spring force, opening in response to pressure and releasing heat.
Without a pressure relief valve, when pump flow is stalled or stopped, the system would sustain damage, power wastage, overheating, or even failure due to excess pressure.
Relief valves can last up to 30 years when maintained properly. However, problems can arise that may need some troubleshooting.
In the meantime, look for signs of common pressure issues, such as sticking or leakage, that can lead to pressure relief valve failure.
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If the system is not reaching the designed pressure or is exceeding the maximum pressure, it can be a sign of valve issues. Checking the relief valve for common problems can determine the problem.
Here are some reasons these common issues may occur:
Wear and corrosion, excess debris, and leakage may lead to pressure relief valve replacement.
However, to avoid these issues, calibrate and install pressure relief valves properly and plan on performing routine checks and adjustments.
Here are 6 steps to use while setting, checking, and adjusting a hydraulic relief valve:
Hydraulic systems are the lifeblood of countless industrial and mobile applications — from construction equipment and agricultural machinery to manufacturing lines and aerospace components. At the heart of these systems lies a crucial safety and performance component: the hydraulic relief valve. One often overlooked but essential aspect of these valves is pressure override.
In this blog, we’ll break down what pressure override is, why it matters, and how managing it properly can lead to improved system efficiency, component longevity, and overall safety.
Pressure override refers to the amount of pressure increase above a hydraulic relief valve’s set point required to achieve full flow through the valve. In simpler terms, even after a relief valve is set to open at a certain pressure (e.g., 2,000 psi), it may need to reach 2,200 psi or more before it opens fully. This additional pressure is the “override.”
High pressure override leads to more energy being used than necessary. Every extra psi above the desired relief pressure consumes additional power, often resulting in increased fuel or electricity usage. In large-scale systems, this inefficiency translates into substantial operational costs over time.
Relief valves are designed to protect components like pumps, hoses, and actuators from excessive pressure. A valve with too much override might delay pressure relief, exposing sensitive components to damaging spikes. Over time, this can lead to premature wear or catastrophic failure.
Excess pressure in a hydraulic system usually results in heat buildup. This heat not only reduces the efficiency of the system but also degrades hydraulic fluid and seals faster, leading to more frequent maintenance and potential breakdowns.
By minimizing unnecessary pressure peaks, you extend the life of all hydraulic components. Proper control over pressure override reduces strain on the system and prevents issues like seal blowouts or metal fatigue.
In applications requiring fine control — such as CNC machinery or agricultural sprayers — lower pressure override contributes to more accurate and consistent performance, enhancing product quality and system reliability.
While pressure override in hydraulic relief valves might seem like a small detail, its impact on system performance, safety, and operational cost is anything but minor. By understanding and managing pressure override effectively, engineers and maintenance teams can significantly enhance the efficiency, durability, and precision of hydraulic systems.