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Why Chemical Centrifugal Pump Oil Leak?

Published on 2019/08/07

chemical centrifual pumps

In the chemical production plant, all kinds of the medium are poured into the column by the pump for spraying circulation. At the same time, all kinds of finished products such as tar import into the storage area. Use the centrifugal pump is very common, also the oil leak phenomenon. Why chemical centrifugal pump oil leak? What is the influence of the oil spill?

The chemical centrifugal pumps oil leak will cause oil waste, environmental pollution, waste the maintenance resources, and also affect the company image. This paper will analyze the seal between bearing gland and shaft of this pump type.


Principle analysis

The bearing gland that at both ends of the bearing box of the chemical centrifugal pump as shown in figure 1. Bearing gland inner circle has two slots which form a labyrinth seal. While the bearing side of the groove on both sides of the hole that call back the oil hole. When the pump operation, the splash oil into the tank, the oil will flow through the return hole back to the bearing box. Then continue to recycle to cause the oil leak.

figure 1: centrifual pump principle

In addition, the gap between the bearing gland and shaft can not be too large. If the gap is too large, the lubricating oil is easy to directly splash out. The unilateral gap between bearing gland and shaft should be 0.25 mm. Every time the pump maintenance, not only check the unilateral clearance, but also clean out the bearing gland inner ring groove and oil return hole. It can avoid sludge blocked oil channel and the seal without the effect of lubricating oil.


Oil Leak Analysis

Through the long-term practical maintenance of the centrifugal pump, it concluds that the main reasons cause the seal oil leak between the bearing cap and shaft.

(1) Refuel over capacity when filling or replenishing the oil from the upper oil hole of bearing box. Usually after the overhaul pump refueling, or add oil when lack. It aways refuels at the bearing box upper oil hole. Because the lubricating oil needed in the bearing boxes is less, it is difficult to control the oil level. Then resulting the oil level exceeding the correct oil level.

When the lubricating oil level is too high, and above the lower edge of the bearing gland bore. The oil will leak out from the clearance between the bearing gland and the shaft before the pump is started. When the oil level is lower than the lower edge of the bearing gland inner hole, and higher than the central position of the rolling body at the bottom of the bearing gland inner hole. As the oil level is close to the lower edge of the bearing gland inner hole. When the pump is running, the lubricant splash easily causes leakage. The normal oil level should be slightly lower than the center of the bottom roller of the bearing. From the point of view of the oil level mirror, it is only necessary to control the oil level not less than one-third of the mirror.

(2) The oil return hole of the bearing gland oil return groove is blocked. As the environment contains more dust that result in the back oil tank and back oil hole plug. At the same time, lubricating oil in the back oil process, heavier sludge will be deposited into the back oil tank, which also can cause plugging.

(3) The air-permeable cap at the top of the bearing box is blocked. High-speed rotation of the bearing oil splash which causes a certain amount of oil gas. If the chemical centrifugal pump bearing box on the breathable cap plugging, the oil gas can not be out which causes the internal and external pressure of bearing box imbalance. Further, lead to the gap between the bearing gland and shaft leak. Because of the dirty air in the field, the mixture of oil gas and dust from the oil mud that easy to block the air permeability cap. The air permeability cap discharges the oil gas not free. Resulting in the imbalance of the internal and external pressure of the bearing box and oil leakage.

(4) The oil level controlled by the Constant Position Oil Cup is too high. The Constant Position Oil Cup keeps the lubricating oil in the bearing box at the designed position. As shown in Fig. 2, the oil level in the bearing box depends on the high point of the II plane inclined plane. Some oil cups are not made in a standard way, resulting in the high point of the II plane inclined plane. Thus cause a high oil level in the bearing box. When the pump is running, the lubricating oil easy to leakage from the labyrinth seal between bearing gland and shaft.

Fig. 2: the oil level in the bearing box


According to the above analysis of the reasons, the establishment of related maintenance operation norms and improvement measures.

1. Regulate the maintenance process.
Refueling after repaired, it needs to take off the Oil Cup, screw down the gas cap. Refueling from the upper bearing box at the gas cap refueling hole. When the bottom of the cup oil that should stop. At this time, the oil tank is close to the appropriate position. Fill the oil cup through it auto-fill to the required oil level. If the Oil Cup less than one-third of the oil level add to more than half. When the pump oilless in the normal operation, top up the oil cup. Absolutely not fill from the oil hole. It needs to top up the oil cup, automatic filling of bearing box oil to the desired position through oil cup.

2. Disassembly overhaul it once a year
In the normal operation process, once a year disassembly overhaul. After each disassembly, thoroughly check and clean the bearing gland oil tank and oil return hole in the oil mud. clean up to avoid the return of oil caused by poor oil leakage.

3. Periodic cleaning of the upper air-permeable cap of bearing box.

After the equipment is normally used, the dirt in the air permeability cap should be cleaned up in time. The air permeability cap can discharge the oil gas smoothly when the pump is in normal operation.

4. If the oil level on the bearing case is too much higher than one-third of the oil level. You can choose to lower the oil level in the bearing case by lowering the high point of the Oil Cup II slope. In addition, under the premise of ensuring the full lubrication of the bearing, it can cut off some cup holder. The oil level controlled by the constant position oil cup can be reduced to achieve the goal of controlling the proper oil level. Besides, Purchase the standard processing specification of the oil cup. It can avoid oil leakage or lack of oil failure after repair.


Improve The Forecast Effect

Through the above-improved norms and measures, it can greatly reduce the chemical centrifugal pump oil leakage. And reduce the lubricating oil waste, environmental pollution, maintenance resources waste, maintain the company’s image. And also greatly ensure smooth and stable production.