Basic Structure and Daily Maintenance of Slurry Pumps

In terms of working principle, slurry pumps belong to the category of centrifugal pumps. Conceptually, they refer to equipment that converts electrical energy into the kinetic and potential energy of solid-liquid mixed media by means of centrifugal force (generated by the rotation of the pump impeller). Slurry pumps are commonly used in industries such as mining, power, metallurgy, coal, and environmental protection to transport slurries containing abrasive solid particles. Examples include ore slurry transportation in metallurgical beneficiation plants, hydraulic ash removal in thermal power plants, coal slurry and heavy medium transportation in coal washing plants, dredging operations, and river desilting.

Basic Structure of Slurry Pumps

I. Pump Casing of Slurry Pumps

1. Slurry pumps mostly adopt a double-casing structure (inner and outer metal layers). The outer casing consists of the pump body and the pump cover, while the inner casing comprises the impeller, liner, front wear plate, and rear wear plate. The materials used for the outer casing include gray iron, ductile iron, and cast steel. The double-casing structure features a vertically split design, and the discharge outlet can be installed in eight different positions at 45-degree intervals.

2. The inner casing structure, also known as the wet parts of the pump, is made from three materials: KMTBCr26, Cr15Mo3, and rubber. These components represent the core quality of the slurry pump and account for a significant portion of the manufacturing cost of spare parts. Therefore, they are a critical factor to consider when selecting a slurry pump.

3. To effectively prevent shaft seal leakage, expeller seals, packing seals, or mechanical seal combinations are employed.

4. A labyrinth gap seal is installed between the impeller and the rear wear plate, significantly reducing slurry leakage into the stuffing box and ensuring sealing reliability.

5. The impeller is equipped with back vanes to promptly discharge slurry, thereby improving volumetric efficiency, reducing and erosion, and extending the service life of the wet parts.

6. A dismantling ring is provided to facilitate maintenance and disassembly, avoiding the need for shaft cutting due to inability to disassemble.

II. Shaft Seals of Slurry Pumps

Shaft seals for slurry pumps are divided into three types: packing seals, expeller seals, and mechanical seals.

1. Packing Seals
   Packing seals rely on the between the packing and the shaft sleeve to achieve sealing. This type of seal requires the addition of seal water, with a pressure must exceed the pump’s discharge pressure by 1.5 bar. This sealing method is widely used in beneficiation plants and coal washing plants.

2. Expeller Seals
   Expeller seals utilize the pressure generated by an auxiliary impeller to achieve sealing. The allowable back pressure must not exceed 15% of the pump’s discharge pressure. This method is adopted when water resources are limited.

3. Mechanical Seals
   Mechanical seals rely on the close contact between dynamic and static rings for sealing. They are further divided into three types:

   • Non-injected mechanical seals: Do not require seal water; service life is approximately 4,000 hours.

   • External flush injected mechanical seals: Require seal water with a pressure of 1.5 bar; service life is approximately 6,000 hours.

   • Internal flush injected mechanical seals: Require seal water with a pressure exceeding the pump’s discharge pressure by 1.5 bar; service life is approximately 8,000 hours.

III. Drive Section of Slurry Pumps

The drive section consists of the pump shaft, bearings, and bearing housing. Bearing lubrication can be achieved through grease lubrication or oil lubrication. For pumps handling high-temperature media or large-scale slurry pumps, oil lubrication with forced cooling water is generally required.

Daily Maintenance of Slurry Pumps

1. Ensure the water pressure and flow rate for the bearings meet specified requirements. Adjust (or replace) the packing tightness in a timely manner to prevent shaft seal leakage. Replace shaft sleeves as needed.

2. When replacing bearings, ensure the bearing assembly is free of dust and the lubricating oil is clean. During operation, the bearing temperature should generally not exceed 60–65°C, with a maximum allowable temperature of 75°C.

3. Maintain alignment between the motor and the pump. Ensure the elasticity coupler’s cushion is intact and correctly installed; replace it immediately if damaged.

4. Ensure all pump components and pipeline systems are installed correctly and securely.

5. Some components of slurry pumps are wear-prone parts. Regularly monitor their condition and perform maintenance or replacement as needed. During assembly, ensure proper installation and adjust gaps appropriately to avoid friction and binding.

6. The suction pipeline system must be airtight. During operation, monitor the suction inlet for blockages. Since the media handled by slurry pumps often contain solid particles, the screen placed in the pump sump should comply with the particle size requirements of the pump to prevent blockages caused by oversized particles or long-fiber materials.