MD type mining wear-resistant multi-stage centrifugal pumps are widely used in mining, petroleum, chemical and other industries and play a very important role. A slight failure may cause a major electromechanical personal accident. This article takes MD type mining multi-stage pump in the central water pump room of coal mine as the object, and analyzes the faults and treatment measures of the water pump during installation and operation. The pump is produced by Changsha Zhonglian Pump Industry Co., Ltd., the model is MD155-30*10, the displacement is 155m3/h, and the head is 300 meters.
Impeller and mouth ring:
The blades of wear-resistant multi-stage centrifugal pump impellers for mining are mostly damaged by cavitation or inhalation of solids and metal impurities. The wear of the mouth ring (also known as the seal ring is generally caused by improper wear during the installation process, and may also be caused by the loosening of the back cap of the impeller. If the mouth ring is severely worn, the impeller should be replaced. If the mouth ring is lightly worn, It can be repaired.
Balance device:
When the balance plate and the balance ring are worn too much (generally more than 2mm) or uneven, first repair welding or grinding the groove on the pump casing and add a 3mm thick PTFE pad at the joint surface of the balance ring and the pump casing. piece. In this way, the unevenness of the flat plate caused by manual grinding after repair welding is eliminated, and the gasket material is moderately soft and hard. When there is too much wear, a new balance ring and balance plate should be replaced.
Machinery Seal:
The mechanical seal has a pair of end faces perpendicular to the axis of rotation. The end faces rely on the cooperation of the auxiliary seal under the action of fluid pressure and compensating the mechanical external elastic force to keep close to the other end and slide relatively to prevent fluid leakage. The proportion of mechanical seal leakage accounts for more than 50% of the leakage of all repaired pumps. The performance of mechanical seals directly affects the normal operation of the pump. The leakage of the mechanical seal will cause a large amount of axial movement of the pump rotor, and the interference between the auxiliary seal and the shaft will increase, and the moving ring cannot move flexibly on the shaft. The displacement cannot be compensated after the pump is turned over and the static ring is worn out. When assembling the mechanical seal, the axial movement of the shaft should be less than 0.1mm, and the interference between the auxiliary seal and the shaft should be moderate. While ensuring the radial seal, it must also ensure that the moving ring can move flexibly on the shaft after assembly (handle The ring presses against the spring to spring back freely).
Pump shaft:
MD type wear-resistant multi-stage centrifugal pump shaft for mining is the core part of the rotor. It is equipped with an impeller and a shaft sleeve that rotates at high speed in the pump body. The bending of the pump shaft and the deviation of the coaxiality between the bearing seat and the pump shaft will cause the wear of the impeller, the guide vane, the pump casing, the sealing ring and the shaft sleeve, which will increase the vibration of the pump body and increase the axial thrust, and the balance disc and the balance seat will occur. friction. As long as the pump shaft does not produce cracks and serious surface wear or bending, it can be repaired and used. The bending amount of the shaft should not exceed 0.06mm. When it is greater than this value, it should be straightened. It is best to straighten it with a screw press without heating.
Bearing temperature:
The factors that cause the bearing temperature rise to be too high and eventually burn the bearing are: ①The balance drum is not effective in balancing the axial force, and the residual axial force is too large, which causes the bearing to be overloaded. ②The amount of unqualified lubricating oil is insufficient or there are impurities such as iron filings in the oil cavity entering the bearing. ③The angle error of the pump bearing is too large, which increases the bearing load. ④ Insufficient bearing clearance or cross positioning of the inner and outer rings of the bearing will cause the inner and outer rings to be misaligned and increase the load.
Axial movement of rotor:
After the pump is assembled, the overall displacement of the rotor should be measured. Before installing the balance plate, install a shaft sleeve at the place where the balance plate is installed and use a lock nut to lock it together with each level of the rotor into a rigid body. The depth gauge measures the distance a from the shaft shoulder to a certain plane of the pump body. Then pull the rotor to the discharge side so that the back cover of the impeller is close to the guide vane. The distance measured at this time is b, and a-b is the total displacement of the pump. After measuring the total channeling volume, compare it with the channeling volume value given in the pump manual. If the measured value is greater than the given value 1mm, the worn impeller should be replaced. If the amount of axial movement is large, it is allowed to add an adjustment pad with a smooth surface and uniform thickness between the balance plate and the balance ring.
Coupling clearance:
During the operation of MD-type wear-resistant multi-stage centrifugal pump for mining, the rotor will continue to move to the suction side as the balance plate wears out. Therefore, the clearance of the coupling should be adjusted appropriately during maintenance. Taking into account the influence of the thermal expansion of the pump shaft, according to the relevant maintenance standards, the clearance of the coupling should be 2-3mm larger than its specified value.
