The Differences Between Hydraulic Valves and Pneumatic Valves

Hydraulic valves utilize pressurized fluid in order to generate force, and hydraulic devices typically feature mineral oil, water or a combination of synthetic oils. In contrast, pneumatic valves require pressurized air, which allows the components to control flow rates in many types of pipes, hoses, smaller pipelines and tubes. Hydraulic valves can handle significantly higher levels of pressure than pneumatic valves; however, devices that use compressed air are generally less expensive than hydraulic valves. Moreover, pneumatic components can be substantially smaller than hydraulic devices because hydraulic valves require reservoirs that store the fluid.

The Designs

In general, the designs of pneumatic valves are less complex than the layouts of hydraulic valves, and the components of pneumatic control valves have lower prices than the parts of hydraulic devices. A pneumatic component may feature a spring that can control the spool and may modify the device's position. Additionally, many pneumatic valves are equipped with needles, which allow customers to precisely manage the flow of air.

Certain hydraulic equipment may feature check valves, and these devices can allow fluid to move in one direction while stopping liquid from flowing in the opposite direction. Most hydraulic devices also have filters that are designed to block small pieces of metal and particles of dirt from entering the hydraulic fluid.

Utilizing the Valves and Performing Routine Maintenance

The costs of maintaining pneumatic valves are substantially lower than the expenses that are associated with servicing hydraulic components, and pneumatic valves are less likely to require maintenance because of their relatively basic designs. Furthermore, valves that utilize compressed air are typically made of especially durable materials, such as zinc, aluminum and thick plastic.

Pneumatic components will commonly generate extra heat when the air is being compressed. As a result, the valve can lose some necessary air and will commonly require more energy than hydraulic valves.

Pneumatic Valves vs. Hydraulic Valves - Evaluating Each Device's Abilities

In general, certain hydraulic valves can handle 4,000 pounds per square inch of pressure. Conversely, most valves that use compressed air may regularly withstand 200 pounds per square inch of force. However, a pneumatic valve's actuator can move more rapidly than a hydraulic device's controller due to the rapidity of the air that flows through the valve.

The Cylinders

Many analyses have indicated that the components of hydraulic valves are substantially stiffer than the parts of valves that require air. Unlike hydraulic fluid, compressed air can allow pockets to form and may generate uneven pressure. Additionally, hydraulic parts produce more friction than pneumatic devices.

Operating Rapidly

If a hydraulic valve closes swiftly, the fluid must be transferred to the valve's main reservoir, yet a pneumatic device can rapidly expel air into the surrounding area when the valve is swiftly activated. Consequently, most pneumatic valves can close more rapidly than hydraulic devices.

Preventing Leaks

Every valve in the market will leak in time. Pneumatic valves will leak air and hydraulic valves will leak the fluid inside the cylinders. When designing machines that must prevent contamination, most manufacturers will add pneumatic valves because hydraulic devices can periodically leak if components become corroded. Pressurized hydraulic fluid can eventually create apertures in pipelines or cause seals to become misaligned.

Ball Valves

These devices feature a circular device that can rapidly move, and the spherical components are commonly made of titanium, brass, nickel or stainless steel. Multiple reports have indicated that ball valves can generally handle more pressure than other valves that have a similar size. Furthermore, ball valves that utilize compressed air may withstand extreme conditions that involve very high temperatures, excessive levels of moisture and swift drops in pressure.

Controlling the Flow of Fluid

Many hydraulic machines are equipped with control valves, which can be linked to sensors and may modulate the flow of liquid. Unlike pressure relief valves, devices that precisely manage pressure are almost always open, and they can partially close in order to rapidly increase flow rate.

Producing Pressure

Unlike the air in pneumatic devices, hydraulic fluid may not be entirely compressed, and consequently, hydraulic valves can ensure that a line's level of pressure remains consistent. In contrast, a pneumatic valve may sometimes allow variations in a line's flow rate because of the uneven distribution of air within the valve's components.

Applications for Pneumatic Valves

Most internal combustion engines are equipped with pneumatic valve springs, which are able to retract rapidly and to create clearance for each piston. Many vehicles also contain poppet valves that can manage the flow of gasoline into the engine, and these pneumatic valves may also modulate the amount of vapor that reaches a car's motor.

Pneumatic valves are found in air brakes, which feature a piston that can be moved by compressed air. The system usually has a parking brake that is linked to springs, and the parking brake's pneumatic valve can be operated manually by the driver. Moreover, air brakes typically have pressure relief valves, which can extend the lifespans of the system's components.

Numerous analyses have shown that pneumatic valves are able to lower the risk of contamination, and devices that require compressed air are commonly added to machines that are used by companies that manufacture food, pharmaceuticals, automotive components and medical equipment. In addition, manufacturers regularly add pneumatic valves to most systems that transport drinking water.

Devices That Typically Feature Hydraulic Valves

Hydraulic devices are commonly found in forklifts, which can sometimes transport objects that weigh more than 20,000 pounds. Moreover, hydraulic valves are regularly added to jacks that lift cars, machines that are involved in mining, axial piston pumps, tractors, ships that can raise sunken vessels and gear pumps.

The Effects of Moisture and Dirt

When developing machines that will operate in environments with high levels of moisture, most manufacturers install hydraulic valves because condensation can precipitate an unbalanced distribution of pressure in pneumatic components. If an excessive amount of moisture mixes with hydraulic oil, the fluid will become cloudy, and when the concentration of water exceeds 200 parts per million, the user should replace the hydraulic fluid.

Extreme Temperatures

Pneumatic valves can be used in locations that feature high temperatures, but hydraulic valves are rarely able to withstand extreme heat because high temperatures can reduce the viscosity of hydraulic fluid. Frequent drops in pressure may also raise a hydraulic valve's temperature, and sometimes, a business can install a heat exchanger, which typically features a piston and many smaller hoses. Additionally, a cold environment may substantially augment the fluid's thickness and decrease the rapidity of a hydraulic valve's moving components.


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