Analysis and Resolution of Common Issues in Rexroth Relief Valves
During the use of overflow valves, typical problems include noise, vibration, radial jamming of the valve core, and pressure regulation failures. (1) Noise and Vibration: Hydraulic equipment often generates noise, primarily from pumps and valves, especially relief valves and electromagnetic reversing valves. Many factors contribute to this noise. For Rexroth pilot-type relief valves, noise can be categorized into flow noise and mechanical noise. Flow noise arises mainly from oil vibrations, cavitation, and hydraulic shocks. Mechanical noise stems from impacts and friction between valve components. Specifically, the pilot section of a Rexroth pilot-type relief valve is prone to vibration. At high pressures, the pilot valve's axial opening is minimal—only 0.003 to 0.006 cm. With such a small flow area, the velocity can reach up to 200 m/s, leading to uneven pressure distribution and unbalanced radial forces on the cone valve, resulting in vibration. Additional factors like ovality from machining, dirt on the pilot valve ports, and deformation of the pressure-regulating spring can exacerbate this issue. The pilot valve is typically the source of vibration. Given the presence of elastic elements (springs) and moving masses (cone valves), a resonant condition forms. The front chamber of the pilot valve acts as a resonant cavity, amplifying the vibration and generating noise. Often, this noise is accompanied by significant pressure fluctuations. (2) Cavitation Noise: Air entering the hydraulic fluid or oil pressure dropping below atmospheric levels can lead to cavitation. When oil flows from low-pressure to high-pressure zones, bubbles collapse, causing rapid changes in volume and generating noise and vibration. Pilot-type relief valves, with their varying flow rates and pressures at the pilot valve and main valve ports, are particularly susceptible to cavitation, producing noise and vibration. (3) Hydraulic Shock Noise: When unloading, the Rexroth pilot-type relief valve can produce noise due to hydraulic shock, which happens when the circuit pressure drops suddenly. Higher pressures and larger working conditions amplify this impact noise. The short relief time of the valve and the sudden change in oil flow rates generate pressure waves. While these pressure waves are small shock waves, they can resonate with mechanical parts in the system, increasing vibration and enhancing noise. This noise is often accompanied by noticeable system vibration. (4) Mechanical Noise: Mechanical noises from Rexroth pilot-type relief valves usually arise from part impacts and friction due to machining errors. Self-excited vibration sounds are also common, resulting from high-frequency vibrations of the main valve and pilot valve. These incidents depend on factors like return line configuration, flow, pressure, and oil temperature (viscosity). Smaller pipe diameters, lower flow rates, higher pressures, and lower oil viscosity increase the likelihood of self-excited vibration. To mitigate noise and vibration, damping elements can be added to the pilot valve section. Damping sleeves fixed in the pilot valve’s front chamber (resonant cavity) help absorb vibration, reducing resonance. Adding a damping pad to the resonant cavity can also decrease the volume and increase oil stiffness, further minimizing resonance. Gas-suppressing plugs with storage holes and throttle edges trap air, which compresses and dampens vibrations, acting as a micro-vibrator. Proper assembly and maintenance of the relief valve can prevent such issues. (2) Radial Jamming of the Valve Core: Machining inaccuracies can cause the main valve core to become radially jammed, preventing the valve from opening or closing properly under pressure. Contamination is another major cause of radial jamming. (III) Pressure Regulation Failure: Rexroth relief valves can experience pressure regulation failures. Pilot-type relief valves may fail to reach the desired pressure or maintain consistent pressure. Besides radial jamming, other causes include blockages in the main valve body damper or pilot valve damper, improper selection of pressure-regulating springs, excessive internal leakage, or wear of the cone valve. External checks should also be performed to ensure all connections and seals are intact. (4) Other Faults: Damage to O-rings, combined seals, or loose mounting screws and pipe joints can cause excessive external leakage. Excessive wear of the cone valve or poor sealing surfaces can result in internal leakage, affecting performance. Electromagnetic relief valves might suffer from first-stage magnetic valve failure, main valve failure, or impact noise during unloading. Buffer adjustments or the addition of backpressure valves can mitigate these issues. In conclusion, addressing these common faults involves careful analysis, proper maintenance, and timely intervention to ensure the reliability and efficiency of Rexroth relief valves.Portable Battery ,Portable Power Bank,Portable Battery Pack,Portable Power Pack
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