Introduction and principle of IS series single-stage single-suction centrifugal pump

 

The lubrication of the centrifugal pump rolling bearing is mainly to reduce the friction power consumption, reduce the wear rate, and also play the role of cooling, dustproof, rustproof and vibration absorption. Doing a good job of equipment lubrication is to ensure the normal operation of the equipment. Effective measures to reduce equipment wear, prevent equipment accidents, reduce power consumption, and extend repair cycle and service life.
The centrifugal pump used in the circulating water system of our roaster is a single-stage single-suction pump. The various technical parameters are as follows:
The model is IS150-125-250, the flow rate is 200m3/h, the head is 20m, the shaft power is 18.5kw, and the speed is 1450r/min.
This type of pump rolling bearing lubrication is lubricated by 30# (winter) or 40# (summer) mechanical lubricants. Due to design reasons, the leakage of the dynamic seal is very serious, which not only causes a large amount of oil to be wasted, the bearing burns out, but also pollutes the environment, which is not conducive to the safe operation of the equipment and civilized production. In the work of several years, in order to solve this problem, many small reforms were carried out.
Schematic diagram of equipment structure and bearing lubrication, as shown in Figure 1.
1. The process of lubrication mode transformation
1.1 Felt seal changed to single layer skeleton oil seal
The original bearing housing seal is sealed with felt, as shown in Figure 2. The leakage is very serious. The fuel consumption of each pump is about 300kg/a, which causes a lot of oil to be wasted, and the oil on the ground is thick.
In order to change this oil leakage condition, change the felt seal to the skeleton seal as follows:
1 The inner and outer end caps of the bearing housing are machined, and a round hole of Φ65mm and depth of 12mm is arranged for the frame to fit a frame oil seal of 45mm×60mm×12mm.
2 Remove the felt and gently insert the skeleton oil seal with a hammer and install it properly. Specifically shown in Figure 3.
After the transformation, the equipment is operating normally, the vibration displacement is about 0.04mm, and the external temperature of the bearing is about 50°C. The annual consumption of oil per pump is only about 50kg. The pump room is kept clean and hygienic, and the bearing and shaft damage accidents caused by lack of oil are prevented, and the equipment is running well.
1.2 Single-layer skeleton oil seal changed to double-layer skeleton oil seal
In order to reduce the leakage amount, according to the structure of the bearing box end cover, a modification scheme is proposed, and the inner hole of the bearing box end cover is processed into a Φ65mm through hole. Change the single-layer skeleton oil seal to double-layer skeleton oil seal, as shown in Figure 4:
The trial run shows that this method is very effective in preventing oil leakage in the short term. However, after 6 months of continuous operation, the leakage of the skeleton oil seal will increase.
2. Defects of the skeleton oil seal
The felt oil seal was changed to the skeleton oil seal, and 4a was used. Although the effect was good, there were also obvious defects.
In actual work, because the skeleton oil seal has a short life and needs to be replaced frequently, when the skeleton oil seal is replaced, the equipment needs to be completely disassembled, on the one hand, the labor intensity of the worker is increased, and on the other hand, in the process of dismantling and repairing the equipment, the impeller is sometimes caused. Damage to parts such as bearings does not meet the economic management requirements of the equipment, but if the oil seal is not changed, it will cause leakage, which is not conducive to sealing, and also directly affects bearing life. In short, practice has proved that the skeleton oil seal does not completely solve the oil leakage problem of the bearing housing of this structure.
3, grease instead of lubricating oil
At present, there are no cheap and leak-free sealing devices, and some have good sealing effects, but they are expensive and economically unfeasible. After investigation and research, it was decided to test the boldness - lubricating with grease instead of lubricating oil.
3.1 Transformation method
Considering that the pump shaft power is only 18.5kw, the flow rate is only 200m3/h; the pump speed is 1450r/min, and the line speed is 3.4m/s. From the above two points, lubrication with grease is feasible.
3.2 The specific method is as follows
1 Discharge the oil in the fuel tank and clean the bearing housing.
2 Open the end cover and the oil drain hole at both ends of the bearing housing to remove the air inside the box.
3 Use a grease gun to fill the lithium grease from the oil filler hole to the bearing housing, add the grease from the two end caps and the oil drain hole, and consider it to be full, and tighten the bearing end cover and the oil drain hole plug. . Use the hand-cranked car to distribute the grease evenly inside the box.
After starting the pump, open the outlet valve to operate the pump under normal conditions, and monitor the bearing temperature and oil quality at both ends of the pump. The temperature was monitored with an infrared thermometer as shown in Table 1:
Table 1 Bearing temperature changes with operating time

After the transformation, the vibration displacement is about 0.04mm.
The grease oil quality is good, no change, the pump is running normally. It can be seen from the temperature monitoring data and the vibration monitoring data that it is feasible to replace the lubricating oil with grease, which can be promoted and used on the same type of pump.
3.3 Grease lubrication effect
Grease is not easy to leak, which is beneficial to the lubrication of the pump bearings, ensuring safe and stable operation of the pump, greatly reducing the amount of fuel and the number of refueling. Not only save fuel, but also reduce the labor intensity of workers. Specifically:
1 save oil costs. The consumption of lubricating grease is 9kg/a per pump and the cost is 63 yuan/a. The oil consumption is 4kg/month under the condition of the skeleton oil seal, and the cost is 200 yuan/a. Each pump can save 137 yuan / a, greatly reducing the cost of lubrication.
2 reduce maintenance costs. The average life of the skeleton oil seal is 4 months. In order to replace the skeleton oil seal, it needs to be dismantled and repaired about 3 times a year, and it is changed to lithium grease lubrication to reduce labor costs. Material and mechanical costs, and avoid damage to equipment parts during maintenance.
3 extended the equipment operating cycle. From vibration. Temperature and other aspects of monitoring, the use of grease sealing performance, bearing good operation, extending the life of the bearing.
4 improved the job environment.
4, the conclusion
In short, the use of grease instead of mechanical lubricants is practical for such low-speed, low-flow pumps, and has obvious economic and environmental benefits. It is an effective measure to make the equipment economically and reasonably operate.