The main reason for noise generated by pressure relief valve can be divided into three parts: mechanical vibration noise of pressure relief valve, hydrodynamic noise, aerodynamic noise.
Noise generated by Mechanical vibration
When the fluid flows, the component of pressure relief valve, pneumatic control valve will produce mechanical vibration. The vibration can divided into two parts:
1. Low frequency vibration
This vibration is caused by jet and pulsation of medium, the main reason is that the flow rate of the valve outlet is too fast, unreasonable pipeline layout and rigid deficiency of the moving components of valve.
2. High frequency vibration
This vibration in the natural frequency of the valve and the media flow caused by the same excitation frequency, the hydraulic control valve will cause resonance. It is generated by pressure release valve in a certain range of pressure. Once the conditions are slightly changed, there will be a huge noise change. The mechanical vibration noise has nothing to do with the velocity of medium flow, mainly due to the unreasonable design of the valve. The measure to reduce mechanical vibration noise is reasonably design the clearance between the pressure reducing valve bush and the valve stem, improve machining accuracy and natural frequency of valve and rigidity of active parts and correctly use materials.
Hydrodynamic noise
Hydrodynamic noise is generated by the turbulence and vortex generated by the fluid passing through the pressure release valve, the process can be divided into two periods:
1. Turbulence noise of electric actuator, namely, noise generated by the interaction between the turbulent fluid and the pressure release valve or the inner surface of the pipe line. Its frequency and noise level are relatively low.
2. Cavitation noise, namely the pressure release valve in the process of decompression, fluid (liquid) begins to vaporize. When the pressure of the air bubbles in the liquid reaches a certain value, it will explode. When the bubble explodes, it will generate a high pressure and shock wave. Self regulating valve the impact of instantaneous pressure is up to 196MPa. However, away from the explosion center, the pressure is sharply reduced. This shock wave is one of the main factors that cause cavitation and noise of pressure release valves. The measure to reduce the vibration noise of the machine is in the design of pressure release valve, the valve must be controlled at the value of the pressure below the critical value. And, it is best to control in the following initial delta P(Below the value of initial Δp is the best). Because the actual decompression valve reaches a p initial value, the liquid begins to generate cavitation, and the noise is gradually increase. In addition to self operated control valve, also pay attention to the flow direction of the fluid medium relative to the valve flap.
Aerodynamic noise
When the steam and other compressible fluid through the valve in the vacuum position, the fluid mechanical energy generates into sound energy. Above all, basically the pressure release valve noise is related to its own design and manufacturing process.
