Splash oil lubrication is used in the crankcase of Nachi plunger pump. The skeleton oil seal is installed at the connecting rod of crankshaft and cross head and the outer part of the box to prevent oil leakage. The skeleton oil seal consists of an oil seal body, a reinforcing skeleton and a self-tightening coil spring.
The inner diameter of rubber lip of oil seal body is smaller than that of journal and connecting rod, and interference fit is adopted in installation. During the operation of Nachi plunger pump, oil leakage often occurs. Sometimes oil leakage occurs in a short time after replacement. This not only results in the increase of oil consumption when Nachi plunger pump is running, but also causes worse lubrication of crankshaft bush and cross head cylinder barrel after the oil level drops, which is prone to crankshaft lapping or cross head cylinder pulling accidents.
1. Oil leakage caused by deflection of oil seal installation
When the oil seal is installed, the lip and the journal should be fully fitted. The deflection of the oil seal installation will cause the lip of the oil seal body to be not vertical to the journal or connecting rod. Under the traction of the reinforced skeleton, the lip will change from circular to elliptical. The asymmetry of the lip contact surface will cause the eccentric abrasion of the lip seal, and the increase of the clearance will cause the oil leakage of the Nachi plunger pump seal.
2. Oil leakage caused by too large or too small lip of oil seal
(1) The quality of the oil seal is not up to standard. If the lip of the oil seal is too large, there is a gap between the lip and the journal after installation. Although the lip rubber can be fixed on the journal by self-tightening coil spring, the lip rubber will be stretched and deformed. The contact surface between the lip and the Journal will change from a ring groove to a single ring, and the contact surface will become smaller, so it can not be in the lip. The lubricating oil film is formed between the mouth and the journal, so the sealing effect of Nachi plunger pump becomes worse, resulting in the leakage of the oil seal.
(2) If the lip of the oil seal is too small, the radial pressure between the journal or connecting rod and the lip of the oil seal will be too large. Although this can enhance the sealing performance of the oil seal of Nachi plunger pump, it is difficult to form oil film on the groove contact surface between the oil seal and the Journal ring. The lip rubber and the journal or connecting rod will be dry-grinded and oil leakage will occur in a short time.
(3) Oil leakage caused by falling off of self-tightening coil spring
The self-tightening coil spring is installed outside the lip of the oil seal, which plays the role of aligning the lip and adjusting the radial pressure. After Nachi plunger pump runs, the temperature in the crankcase rises. Because of the different material of lip rubber and journal, the deformation after heat rise is different, and the gap between lip and Journal of oil seal increases. At this time, the gap between lip and Journal of oil seal needs to be restrained by spring elasticity. If the spring falls off, the radial pressure of lip of oil seal on Journal cannot be maintained. Force increases the clearance between oil seal and journal, resulting in oil leakage in a short time after starting Nachi plunger pump.
(4) Oil leakage caused by overtightening of self-tightening coil spring
If the self-tightening coil spring is too tight, the radial pressure of the lip of Nachi plunger pump is too large, so that the lubricant can not enter the contact surface between the lip and the journal to form a continuous oil film, it will produce dry grinding, serious lip wear in a short time, resulting in oil leakage.
3. Oil leakage due to low surface finish of journal or connecting rod
(1) Because there are scratches or corrosion holes on the surface of the journal or connecting rod, the wear of the lip of the oil seal will be aggravated during operation, and the gap between the corrosion holes and the lip of the oil seal will be formed, resulting in oil leakage.
(2) Oil leakage due to excessive radial jump of journal or connecting rod
If the radial jump of crankshaft is too large, the deformation of oil seal lip can not synchronize with the jump of journal in the process of high-speed rotation, which will cause the gap between lip and journal, and aggravate the eccentric wear of lip and cause leakage. The connecting rod of Nachi plunger pump runs in reciprocating mode and wears oil seals in reciprocating mode. The wear degree of the connecting rod exceeds that of the journal, and the leakage degree will be more serious.
4. Oil leakage caused by impurities in lubricating oil
There is a bearing bush between the crankshaft and connecting rod of Nachi plunger pump. The wear debris of the bearing bush will enter the gap between the lip and the Journal of the oil seal with the lubricating oil. With the rotation of the journal, the scraping of the lip contact surface will occur, which will not only wear the rubber of the lip seal, but also the journal, and make the oil seal seal invalid.
5. Oil leakage of oil seal of connecting rod caused by wear of copper sleeve of crosshead pin
Crosshead is the main component of crankshaft connecting rod mechanism, connecting crankshaft and plunger rod. The cross pin sleeve is copper material, which can avoid the wear of the cross pin and connecting rod. If the cross pin sleeve is worn, it will cause the connecting rod to deviate from the axis in the reciprocating process, which will form a gap between the lip of the oil seal and the connecting rod. At the same time, it will aggravate the wear of the oil seal of Nachi plunger pump and cause oil leakage of the oil seal.