What to do if a slurry pump seal fails or cavitation occurs?

Slurry pumps in concentrators are mainly used to transport abrasive particles and viscous, high-concentration slurries. After long-term operation, most concentrators encounter various slurry pump problems, affecting not only the normal operation of the entire concentrator but also its economic benefits. Common problems in daily operation include seal failure and cavitation. If these are not detected and controlled in time, they will affect the normal operation of the pump.

I. Slurry Pump Seal Failure

Currently, the most common shaft seal methods for slurry pumps are packing seals and mechanical seals. Slurry pump packing seals continuously inject pressurized water into the packing to prevent slurry leakage from the pump body. During routine maintenance or repair, the screws at the pump packing gland need to be adjusted frequently to prevent over-tightening, thus ensuring the temperature and quality of the packing. If the screws are not tightened properly, they will loosen over time, leading to seal failure and slurry leakage. Alternatively, improper control of the sealing water volume can easily lead to excessive or insufficient pressure, causing slurry pump seal failure and resulting in internal or external leakage. Note: This type of seal inherently has significant drawbacks; therefore, during routine maintenance and repair, the maintenance procedure should be strictly followed, and training should be strengthened to ensure mastery of the tightening standards for each pre-tightening component. The shaft seal water injection should also be performed according to standards.

A slurry pump mechanical seal consists of at least one pair of end faces perpendicular to the axis of rotation. Under the action of fluid pressure, the elastic force of the compensation mechanism, and the cooperation of auxiliary seals, they maintain contact and slide relative to each other, forming a device to prevent fluid leakage.

1) During the maintenance, replacement, and installation of mechanical seals, excessive or insufficient compression, or unclean sealing surfaces, can cause premature seal failure.

2) Improper installation, such as using tools to strike the seal or improper installation of the auxiliary ring, can also lead to premature mechanical seal failure.

3) During daily operation of the slurry pump, phenomena such as cavitation, pressure buildup, etc., can cause significant axial forces, leading to separation of the dynamic and static ring contact surfaces and ultimately seal damage. Note: Strict control should be exercised during the daily maintenance and replacement of mechanical seals in slurry pumps. The installation skills of maintenance workers should be improved, and violations of regulations should be strictly prohibited. At the same time, supervision and management of daily operations should be strengthened to ensure correct operation and accurate inspection.

II. Slurry Pump Cavitation

When the internal water surface pressure of a slurry pump is lower than the vaporization pressure of water, the water will gradually turn into gas. Under the influence of the internal water pressure exceeding the vaporization pressure, it will eventually become liquid. This phenomenon is called cavitation. When a slurry pump is running, the impeller rotates continuously, causing the liquid's energy to increase rapidly, exhibiting a trend of rapid rise in pressure and kinetic energy. When the liquid pressure is equal to or lower than the liquid's vaporization pressure at that temperature, a large amount of steam or gas will overflow, gradually forming many bubbles. These bubbles, driven by the liquid flow, enter the high-pressure area, where the pressure difference causes the bursting bubbles to recombine. Simultaneously, liquid particles rapidly approach the bubbles, colliding with each other and generating significant forces that impact the impeller, ultimately accelerating the damage and aging of the impeller inside the slurry pump. Cavitation in a slurry pump causes internal vibration and noise, and reduces the pump's flow rate, head, and power, thus affecting the overall performance of the pump, shortening its service life, and even disrupting its normal operation. Note: Operators must pay close attention to cavitation phenomena in slurry pumps and strengthen pump testing, management, and maintenance. In addition, operators need to master and rationally apply the cavitation specific speed C method and the Thomas cavitation coefficient method to calculate the pump's net positive suction head (NPSH) to ensure the stable operation of the slurry pump.

The above are common problems encountered during the operation of slurry pumps. Slurry pumps operate under harsh conditions. To ensure their long-term stable operation, in addition to thorough daily maintenance, operators need a comprehensive understanding of the slurry pump and a thorough grasp of the slurry's characteristic parameters. They must be able to match and adjust the pump according to operational requirements to ensure its normal operation.