Improvement of Bearing Lubrication Method for Single Stage Single Suction Centrifugal Pump

Keywords: Centrifugal pump; Lubrication; Sealing; Vibration

Centrifugal pump lubrication is mainly to reduce friction friction, reduce wear rate, but also play a cooling, dust, rust and vibration absorption and so on. Do a good job of equipment lubrication is to ensure the normal operation of equipment. Reduce equipment wear and tear, prevent equipment accidents, reduce power consumption, extend the repair cycle and service life of effective measures.

Centrifugal pumps used in our roaster circulating water system are single-stage single-suction pumps with various technical parameters as follows:

Model IS150-125-250, flow rate of 200m 3 / h, head 20m, shaft power 18.5kw, speed of 1450r / min.

This type of pump roller bearing lubrication is 30 # (winter) or 40 # (summer) mechanical lubrication. Due to the design reasons, the dynamic seal leakage is very serious, which not only causes a great deal of wasted oil, burns out the bearings, but also pollutes the environment, which is not conducive to the safe operation of equipment and civilized production. In the course of several years of work, in order to solve this problem, many minor changes have been made.

Equipment structure and bearing lubrication diagram, shown in Figure 1.

1, the lubrication process of transformation

1.1 felt seal instead of single-layer skeleton oil seal

The original bearing box seal is sealed with felt, shown in Figure 2. Leakage is very serious, each pump fuel consumption of about 300kg / a, resulting in a large number of oil waste, a thick layer of oil on the ground.

In order to change this situation of oil leakage, change the felt seal to a skeleton seal as follows:

① The inner and outer end of the bearing housing for processing, the car out of a Φ65mm, 12mm deep hole, suitable for a size of 45mm × 60mm × 12mm skeleton oil seal.

â‘¡ remove the felt, the skeleton seal gently hit into with a hammer, and the correct installation. Concrete schematic shown in Figure 3.

After transformation, the equipment is operating normally, the vibration displacement is about 0.04mm, and the temperature outside the bearing is about 50 ℃. The annual oil consumption of each pump is only about 50kg. Maintains the cleanliness of the pump room, put an end to the bearings, shaft damage due to lack of oil, the operation of the equipment intact.

1.2 single-layer skeleton oil seal into double-layer skeleton oil seal

In order to reduce the leakage more, according to the structure of the bearing housing cover, and put forward the transformation program, the bearing housing cover hole processing Φ65mm through-hole. The single-layer skeleton oil seal into a double-layer skeleton oil seal, the schematic diagram in Figure 4:

Test run shows that this method is very effective in preventing oil spills in the short term. However, continuous operation for 6 months, due to the skeleton oil seal wear will increase the amount of leakage.

2, skeleton seal defects

The felt seal to skeleton oil seal, the use of 4a, although the effect is better, but there are obvious shortcomings.

In actual work, because the skeleton oil seal has a short service life, it needs to be replaced frequently. When the skeleton oil seal is replaced, all the equipment needs to be disassembled to increase the labor intensity of workers. On the other hand, during the process of equipment disassembly and maintenance, impellers, Bearings and other parts of the damage, does not meet the requirements of economic management equipment, but if you do not change the oil seal, resulting in leakage, is not conducive to sealing, but also directly affect the bearing life. In short, the practice proved: skeleton oil seal did not completely solve the problem of oil leakage bearing housing.

3, grease instead of lubricating oil

At present, there is not yet a cheap and leak-free sealing device, and some sealing effect is good, but expensive, economically unfeasible. After investigation, decided to boldly test - with grease instead of lubricating oil to lubricate.

3.1 transformation methods

Considering the shaft power is only 18.5kw, only flow 200m 3 / h; pump speed of 1450r / min, a linear velocity of 3.4m / s. From the above two point of view, with grease lubrication is feasible.

3.2 specific methods are as follows

â‘  the oil tank let go of the bearing box for cleaning.

â‘¡ the bearing housing at both ends of the end Cap and oil drain plug open, to exclude the air inside the box.

â‘¢ with a grease gun lithium grease from the filling hole to the bearing box filled, added to the grease from both ends of the cover and put the oil hole extrusion, as full, and tighten the bearing cover and oil drain plug . Hand crank, the grease evenly distributed in the box.

After starting the pump, open the outlet valve , so that the pump is running under normal conditions, monitoring the bearing temperature and oil conditions at both ends of the pump. Infrared thermometer temperature monitoring, the data shown in Table 1:

Table 1 bearing temperature changes with the running time