Analysis of common faults of Manifold Block electromagnetic relief valve
In front of the introduction of the “direct acting relief valve working principle and structural characteristics” and “leading relief valve typical fault diagnosis and troubleshooting methods”, the following introduction of electromagnetic relief valve common faults and cause analysis.
In the use of electromagnetic relief valve, the common faults are noise, vibration, valve core radial clamping and pressure regulation failure.
The components that are easy to produce noise in the hydraulic device are generally considered to be pumps and valves, and the relief valve and electromagnetic reversing valve are the main components. There are many factors that produce noise. The noise of electromagnetic relief valve has two kinds of velocity sound and mechanical sound. The flow velocity noise is mainly caused by oil vibration, cavitation and hydraulic impact. Mechanical sound is mainly caused by the impact and friction of parts in the valve.
1. Noise caused by uneven pressure
The e pilot valve part of the electromagnetic relief valve is a vibration part. In the case of 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, the flow rate is very high, up to 200 m/s, easy to cause uneven pressure distribution, so that the popper valve radial force imbalance and vibration. In addition, the ellipticity of the poppet valve and the cone seat produced when processing, the dirt of the pilot valve port and the deformation of the pressure regulating spring, etc., will also cause the vibration of the poppet valve. Therefore, it is generally considered that the pilot valve is the source of noise.
Because of the existence of elastic elements and motion mass, constitutes a condition for producing oscillations, and the front cavity of the pilot valve plays the role of a resonance cavity, so the vibration of the poppit valve is easy to cause the resonance of the whole valve and emit noise, and the noise is generally accompanied by severe pressure beating.
2. Noise generated by holes
When for various reasons, the air is inhaled into the oil, or in the oil pressure is lower than atmospheric pressure, dissolved in the oil part of the air will precipitate to form bubbles, these bubbles in the low pressure area of the larger volume, when with the oil flow to the high pressure area, by compression, volume suddenly smaller or bubbles disappear; Conversely, such as in the high pressure area, the volume was originally small, and when the flow to the low pressure area, the volume suddenly increased, the rapid change in the volume of bubbles in the oil phenomenon. The sudden change of bubble volume will produce noise, and because this process occurs in an instant, it will cause local hydraulic shock and vibration. The pilot valve port and the main valve port of the electromagnetic relief valve, the oil flow rate and pressure change is very large, it is easy to appear cavitation phenomenon, resulting in noise and vibration.
3. Noise generated by hydraulic impact
When the electromagnetic relief valve is unloaded, the pressure shock noise will occur because of the sudden drop of the pressure in the hydraulic circuit. The higher the working condition of high pressure and large capacity, the greater the impact noise, which is caused by the hydraulic impact caused by the relief valve’s short unloading time. During unloading, the rapid change of oil velocity causes the sudden change of pressure and the impact of pressure wave. Pressure wave is a small shock wave, its own noise is very small, but with the oil into the system, if resonance with any mechanical parts, it may increase the vibration and enhance the noise. Therefore, when the hydraulic impact noise occurs, it is usually accompanied by system vibration.