Slurry pump introduction

20 May.,2022

Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge and obtains energy, leaving the outer edge of the impeller at a high speed and entering the volute pump casing.


Working principle

Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge and obtains energy, leaving the outer edge of the impeller at a high speed and entering the volute pump casing. In the volute pump casing, the liquid is decelerated due to the gradual expansion of the flow channel, and part of the kinetic energy is converted into static pressure energy, and finally flows into the discharge pipeline at a higher pressure and sent to the required place. When the liquid flows from the center of the impeller to the outer edge, a certain vacuum is formed in the center of the impeller. Since the pressure above the liquid level of the storage tank is greater than the pressure at the inlet of the pump, the liquid is continuously pressed into the impeller.



The slurry pump conveys a mixture of solid particles containing dregs and water. But in principle, the slurry pump belongs to a kind of centrifugal pump.
The commonly used slurry pump structure is as follows.

(1) Pump head structure. The pump body adopts a double-layer pump shell (internal and external double-layer metal structure), and the double-pump shell shell structure is a vertical middle-opening type. In order to effectively prevent the leakage of the shaft seal, a combination of dynamic seal, packing seal or mechanical seal is used. There is a labyrinth gap seal between the impeller and the rear guard plate, which greatly reduces the leakage of the slurry to the stuffing box and effectively ensures the reliability of the seal. The impeller is equipped with a back blade, which discharges the backflow slurry in time, thereby increasing the volume ratio, reducing backflow and erosion, and improving the life of overcurrent components. In order to facilitate maintenance and disassembly, a disassembly ring is provided to avoid the phenomenon of shaft cutting due to inability to disassemble.

(2) Bracket structure. The bracket structure is a horizontal open type, which is optimized in terms of hydraulic design and structural design in order to prolong the service life of the bearing. The radial force and axial force are reasonably distributed, and the bearing type, model, cooling and lubrication method are correctly selected, so as to meet the requirements of low heat generation and long service life of the bearing.

(3) Shaft seal form. The shaft sealing device acts as a seal between the pump body and the pump shaft. It can prevent air intrusion into the pump and a large amount of water leaking out of the pump. The sealing form of centrifugal slurry pump usually adopts auxiliary impeller and packing seal. The auxiliary impeller and packing seal are hydrodynamic seals. The pressure head generated by the auxiliary impeller resists the leakage of the liquid at the outlet of the impeller. At the same time, the impeller cover is used to set the back vane. Water seal rings and packings are added to prevent air from entering, and back blades and water seal rings are used to reduce the pressure at the packing, which has the effect of preventing impurities from entering the seal.



The following checks should be carried out when the slurry pump is installed:

(1) The size, position and elevation of the foundation should meet the design requirements, the anchor bolts must be properly and correctly fixed in the concrete foundation, and the machine should not be missing, damaged or corroded;

(2) According to the characteristics of the medium conveyed by the slurry pump, the materials of main parts, shaft seals and gaskets should be checked if necessary;

(3) The leveling and alignment of the slurry pump should comply with the requirements of equipment technology. If there is no regulation, it shall comply with the regulations of the current national standard "General Specification for Construction and Acceptance of Mechanical Equipment Installation Engineering";

(4) The installation of all pipes and fittings connected to the slurry pump and the cleaning requirements of the lubricating oil pipes shall comply with the relevant national standards.


Start Condition

The conditions for starting the slurry pump are as follows:

(1) Check the slurry pump according to the routine inspection requirements of the pump before starting.

(2) Confirm that the slurry pump pipeline has been connected, the thickening bin has been selected, the water inlet door has been opened, the selected thickener has been operated, the thickener slag discharge door and flushing door have been closed, and the slag discharge pump has been chained.

(3) Check that there is no debris in the slag pool, and the water level is greater than 1.2m.

(4) Check that the disturber corresponding to the slurry pump has been started and is normal.

(5) Adjust the frequency converter of the slurry pump to less than 10%.

(6) Start the slurry pump on the DCS, and slowly adjust the frequency of the inverter after the outlet valve is fully opened, so that it can meet the water volume of the reuse pool.

(7) After the slurry pump is started normally, pay attention to the coordination of the effluent of the slurry pump, the effluent of the reuse pump and the water temperature of the slag removal machine.


Debug and run operations

The trial operation of the slurry pump should meet the following requirements:

(1) The steering of the drive motor should be the same as that of the pump;

(2) There should be no looseness in each fixed connection part, and the specification and quantity of lubricant added to each lubricating part should meet the requirements of the equipment technical file;

(3) The parts requiring pre-lubrication should be pre-lubricated according to regulations;

(4) All indicating instruments and safety protection devices should be sensitive, accurate and reliable;

(5) The cranking should be flexible and no abnormal phenomenon;

(6) The high temperature pump should be preheated before the trial operation, the temperature should rise evenly, and the temperature rise per hour should not be greater than 500%; the temperature difference between the surface of the pump body and the process pipeline with the working medium inlet should not be greater than 400 °C;

(7) A connection device to eliminate the influence of temperature rise is provided, and a bypass connection device is provided to provide a cooling water source.


The following points should be paid attention to when operating the slurry pump:

(1) It is forbidden to run without water, do not adjust the suction port to reduce the displacement, and it is forbidden to run under too low flow;

(2) Monitor the operation process, completely prevent the leakage of the stuffing box, and use new stuffing when replacing the stuffing box;

(3) Ensure that the mechanical seal has sufficient water flow for flushing, and excessive water flow is prohibited for water-cooled bearings;

(4) Do not use too much lubricant;

(5) Check according to the recommended cycle; establish operating records, including operating hours, adjustment and replacement of packing, adding lubricant and other maintenance measures and time; centrifugal pump suction and discharge pressure, flow, input power, cleaning Fluid and bearing temperatures and vibrations should be recorded regularly.


Wear Factor

The factors of slurry pump wear are as follows:

1) Media properties.

2) Material properties.

3) The interaction of abrasive and material.

The main ways to improve the life of pump overcurrent components are reasonable selection of materials, reasonable selection, and improvement of hydraulic design.

When the slurry pump pumps the solid-liquid mixture, the most worn parts are the impeller, followed by the pump body or the overcurrent parts such as the sheath and the guard plate. The wear of the pump depends on the internal relationship between the following parameters:

1) Rheological properties of solid-liquid mixtures.

2) Solid particle size, shape, hardness and density, etc.

3) The structure type and parameters of the pump.

4) The rotational speed of the pump or the peripheral speed of the impeller.

5) The properties of pump materials, such as hardness, strength (elongation, acid and alkali resistance, heat resistance), etc.
Among the factors affecting the life of the slurry pump, the first is the performance of the material, the second is the characteristics of the medium, the third is the structure and hydraulic parameters of the pump, and the operating conditions are the last.



The following points should be paid attention to when maintaining the slurry pump:

(1) The bearing water pressure and water volume must meet the regulations, adjust (or replace) the tightness of the packing at any time, and do not cause the shaft seal to leak. And replace the shaft sleeve in time.

(2) When replacing the bearing, it is necessary to ensure that there is no dust in the bearing assembly and that the lubricating oil is clean. The bearing temperature is generally not more than 60-65 °C when the pump is running, and the maximum temperature is not more than 75 °C.

(3) To ensure the coaxiality of the motor and the pump, to ensure that the elastic pad in the coupling is complete and correct, and should be replaced in time after damage.

(4) Ensure that the pump components and piping system are installed correctly, firmly and reliably.

(5) Some parts of the slurry pump are wearing parts. In daily use, attention should be paid to the wear and tear of the wearing parts, and they should be repaired or replaced in time. During the maintenance or replacement of the wearing parts of the slurry pump, it is necessary to ensure that the assembly is correct, the clearance adjustment is reasonable, and the occurrence of tight friction is avoided.

(6) The suction pipeline system of the slurry pump must be free of air leakage, and attention should be paid to whether the suction port is blocked during operation. The medium that the slurry pump needs to handle mostly contains solid particles, so the grille placed in the pump tank should meet the requirements of the particles that the slurry pump can pass through, so as to reduce the possibility of blockage caused by excessive particles or long-fiber materials entering the pump body. sex. [3]