Briefly describe the methods for reducing noise during the operation of high-viscosity pumps

High-viscosity pumps are positive displacement pumps that utilize specialized working principles in conjunction with high-quality drive systems. These rotor pumps are capable of delivering strong driving torque at low speeds, ensuring continuous, pulse-free material transfer without compromising the physical properties of the conveyed materials. Additionally, they can be equipped with a mechanically sealed structure featuring water flushing capabilities. This prevents the high-viscosity material from solidifying on the mechanical seal faces during operation, thereby ensuring the normal functioning of the equipment and extending the service life of the mechanical seals in harsh environments.

Before starting a high-viscosity pump, the pump chamber must be completely filled with the liquid to be transferred to ensure a stable startup. If the material temperature is too low, hot steam should be introduced into the pump for preheating before operation. The motor's direction of rotation must match the pump's inlet and outlet ports. If the pump is being operated for the first time or after a long period of idleness, it is recommended to run it under no-load or light-load conditions for a while to warm it up. If any issues arise during operation, the pump should be shut down immediately for inspection to prevent damage. The inner diameter of the suction pipeline must be sufficiently large, and narrow passages or sharp bends should be avoided. Reduce the number of bends at the inlet and outlet, and remove unnecessary valves and accessories to minimize resistance at the pump's inlet and outlet. Furthermore, lower the installation height of the pump as much as possible and shorten the suction pipeline to reduce suction resistance.

Poor surface roughness, significant tooth profile errors, and tooth deformation on the gears of a high-viscosity pump can lead to uneven gear meshing, resulting in noise. If the gear pump is being operated for the first time or after a long period of idleness, it is best to run it under no-load or light-load conditions for about an hour for a break-in period. If abnormal temperature rises, leakage, vibrations, or noise are detected during this break-in phase, the pump should be shut down for inspection. It is advisable to install a check valve on the discharge pipeline of the gear pump to prevent backflow of the system fluid during pump or pipeline maintenance.

When shutting down a high-viscosity pump under load, measures should be taken to prevent the pump from reversing and creating a partial vacuum in the discharge pipeline. Care must be taken to ensure that the check valves at the inlet and outlet are not installed backward or jammed. Control valves and other protective devices should also be installed on the discharge pipeline so that the pressure can be relieved if the flow passage becomes blocked. Gear pumps used for transferring high-viscosity liquids are a primary source of system noise. Selecting the correct operating speed based on the medium's viscosity helps avoid resonance frequencies between the gears and the shaft, thereby preventing amplified noise. The rotation direction of the gear pump must also align with the inlet and outlet ports.

Methods for reducing noise during the operation of high-viscosity pumps:

Noise increases when the fundamental frequency and resonance frequency of the pump coincide with the natural mechanical or hydraulic frequencies. Improper oil selection, such as excessive viscosity, increases suction resistance and generates noise. Additionally, sudden expansions or contractions in the internal flow passages and sharp bends can also cause noise.

For small- and medium-displacement gear pumps, if gear grinding technology is not used, noise can be reduced by improving the precision of the gear cutting tools and processing equipment to minimize tooth profile errors without altering the tooth shape. Alternatively, modifying the tooth profile while maintaining precision can also achieve a "low-noise" effect.

For high-displacement gear pumps operating under heavy loads, gear grinding technology is typically employed to improve tooth profile precision. This process not only corrects tooth profile errors caused by heat treatment deformation but also improves the surface roughness of the tooth faces to meet meshing precision requirements, thereby reducing noise.

A common measure to reduce gear pump vibration is to install accumulators and silencers at the pump's discharge port to dampen the noise. Excessive rotational speeds in high-viscosity pumps can also cause resonance.

Undersized flow passages can cause turbulent flow, vortices, and jetting of the hydraulic fluid, all of which increase noise. Furthermore, improper bearing installation or excessive coaxiality deviations between the pump shaft and the connected equipment can also amplify noise. These issues should be inspected promptly, and components should be replaced when necessary.