HAWE relief valve PSVFA2/280-5 in stock

Brand

HAWE/Germany

Application Areas

Chemical, Petroleum, Mining, Road/Rail/Marine, Comprehensive

Main Functions of HAWE Relief Valves (Germany):

**Constant Pressure Relief:** In a fixed-displacement pump throttling system, the pump provides a constant flow rate. When system pressure increases, the flow demand decreases. The relief valve opens, allowing excess flow to return to the oil tank, ensuring a constant inlet pressure (i.e., pump outlet pressure) (the valve opening fluctuates with pressure).

**Pressure Stabilization:** Connected in series in the return oil line, the relief valve generates back pressure, increasing the smoothness of moving parts.

**System Unloading:** A small-flow solenoid valve is connected in series to the remote control port of the relief valve. When the solenoid is energized, the remote control port of the relief valve connects to the oil tank, unloading the hydraulic pump. The relief valve then functions as an unloading valve.

**Safety Protection:** The valve is closed during normal system operation. The relief valve opens only when the load exceeds the specified limit (system pressure exceeds the set pressure) to provide overload protection and prevent further pressure increase (typically, the set pressure of the relief valve is 10%~20% higher than the system's maximum working pressure).

In practical applications, it is generally used as a unloading valve, a remote pressure regulating valve, a high/low pressure multi-stage control valve, a sequence valve, and to generate back pressure (connected in series in the return oil line).

Relief valves generally have two structures: 1. Direct-acting relief valve. 2. Pilot-operated relief valve.

The main requirements for relief valves are: large pressure regulation range, small pressure regulation deviation, small pressure fluctuation, sensitive operation, large overload capacity, and low noise.

Precautions for German HAWE relief valves:

Noise and vibration

In German HAWE hydraulic systems, pumps and valves are generally considered to be the most prone to noise generation, with relief valves and solenoid directional valves being the main contributors. Many factors contribute to noise generation.

The noise from German HAWE relief valves includes two types: flow velocity noise and mechanical noise. Noise generated by flow velocity is mainly due to oil vibration, cavitation, and hydraulic shock. Noise generated by mechanical means is mainly due to the impact and friction of valve components.

(1) Noise caused by uneven pressure

The pilot valve section of the German HAWE relief valve is a vibration-prone part, as shown in Figure 3. During high-pressure overflow, the axial opening of the pilot valve is very small, only 0.003~0.006 cm. The flow area is very small, and the flow velocity is very high, reaching 200 m/s, which easily causes uneven pressure distribution, resulting in an imbalance of radial force in the cone valve and vibration. In addition, the ellipticity generated during the machining of the cone valve and cone valve seat, dirt adhering to the pilot valve port, and deformation of the pressure regulating spring can also cause cone valve vibration. Therefore, the pilot valve is generally considered the source of noise. The presence of elastic elements (springs) and moving mass (cone valves) creates conditions for oscillation. The pilot valve's front chamber also acts as a resonant cavity. Therefore, vibration of the cone valve easily causes resonance throughout the valve, generating noise. This noise is usually accompanied by severe pressure fluctuations.

(2) Noise from cavitation

When air is drawn into the oil for various reasons, or when the oil pressure is lower than atmospheric pressure, some of the dissolved air in the oil will precipitate, forming bubbles. These bubbles are larger in low-pressure areas, but when they flow with the oil to high-pressure areas, they are compressed, causing their volume to suddenly decrease or the bubbles to disappear. Conversely, if the volume is initially smaller in high-pressure areas, it suddenly increases when flowing to low-pressure areas. This rapid change in bubble volume generates noise, and because this process occurs instantaneously, it causes localized hydraulic shocks, resulting in vibration. The pilot valve port and main valve port of a pilot-operated relief valve experience significant changes in oil flow rate and pressure, making them prone to cavitation, which in turn generates noise and vibration. (3) Noise from Hydraulic Shock

When unloading, the German HAWE relief valve generates pressure shock noise due to the rapid drop in hydraulic circuit pressure. The higher the pressure and capacity of the operating conditions, the greater this shock noise. This is because the unloading time of the relief valve is very short, resulting in hydraulic shock. During unloading, the rapid change in oil flow velocity causes a sudden pressure change, creating a pressure wave impact. The pressure wave is a small shock wave, generating very little noise itself. However, as it travels through the system with the oil, if it resonates with any mechanical part, it can amplify vibration and increase noise. Therefore, hydraulic shock noise is usually accompanied by system vibration.

(4) Mechanical Noise

The mechanical noise emitted by the German HAWE relief valve generally comes from the impact of parts and friction caused by machining errors.

Sometimes, the noise emitted by the German HAWE relief valve includes high-frequency mechanical vibration, generally referred to as self-excited vibration. This is the sound generated by the high-frequency vibration of the main valve and pilot valve. Its occurrence rate is related to factors such as the configuration of the return oil pipeline, flow rate, pressure, and oil temperature (viscosity). Generally, smaller pipe diameters, lower flow rates, higher pressures, and lower oil viscosity lead to a higher rate of self-excited vibration.

Daily preventative measures for HAWE relief valves (Germany):

Measures to reduce or eliminate noise and vibration in pilot-operated relief valves:

Generally, vibration damping elements are added to the pilot valve section.

The damping sleeve is usually fixed in the front cavity of the pilot valve, i.e., the resonant cavity, and cannot move freely.

Various damping holes are provided on the damping sleeve to increase damping and eliminate vibration. Additionally, because the resonant cavity contains additional components, its volume is reduced, and the stiffness of the oil increases under negative pressure. Based on the principle that stiffer components are less prone to resonance, the possibility of resonance is reduced.

The damping pad generally moves freely within the resonant cavity. The damping pad has a throttling groove on both sides, which dampens the oil flow, altering the original flow pattern. The addition of the damping pad introduces a vibration element, disrupting the original resonant frequency. The resonant cavity incorporates damping pads, which also reduces its volume and increases the stiffness of the oil under pressure, thereby reducing the likelihood of resonance.

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SG2W-NUH The company mainly deals with European and American brands and can source brands from any European country. For example, our key German brands include: BURKERT, DEMAG, HAWE, REXROTH, HYDAC, PILZ relays, FESTO, IFM sensors, E+H, HEIDENHAIN, P+F sensors, SICK, TURCK, and HIRSCHMANN industrial switches. German brands: Hengstler, Murr, Schmersal, Samson, EPRO (Emerson Group)

American brands: MOOG, ASCO, MAC, NUMATICS, PARKER, VICKERS, ROSS

British brands: Norgren

Italian brands: OMAL, ATOS, CAMOZZI, UNIVER, Camozzi