When the excavator diesel tank is filled with diesel after assembly, a large amount of diesel oil stain is found on the ground. This indicates that the diesel tank is leaking. After careful inspection, it was found that the leakage part was at the right angle transition pipe joint from the bottom of the diesel tank to the diesel engine oil pipe. The transition pipe joint is a right angle joint with adjustable end nut sealing, and the thread specification is M18 × 1.5。 Through analysis, it is believed that there are three reasons for the oil leakage of the oil pipe transition pipe joint. First, the internal thread at the bottom of the diesel tank or the thread of the transition pipe joint is unqualified. Second, the fastening torque of the transition pipe joint is too large or too small. Third, the sealing method is unreasonable. The following will be checked according to these three aspects for reference only.
1. Check the thread quality
The inspector used a special thread inspection tool to check the size and accuracy of the internal thread at the bottom of the diesel tank and the thread of the transition pipe joint. Confirm that the thread size and fit meet the international seal standard.
2. Check the tightening torque
The torque value recommended by the supporting manufacturer of the transition pipe joint is 70N.m. Check the threads of the diesel tank and transition pipe joints, and no obvious damage is found. Therefore, it can be ruled out that the torque value is too large. Check that the production operators use special torque wrenches to tighten the transition pipe joints according to the process requirements when installing them. Moreover, the force measurement mark of torque wrench is obvious, and there is no problem that the torque value is too small. The diesel tanks of several excavators of this model in the same batch were inspected for leakage, which indicates that the sealing form of the transition pipe joint may be defective.
3. Check the sealing form
When installing the transition pipe joint, the original O-ring and retaining ring were removed. After sealing with combined gasket, the transition pipe joint has oil leakage fault. It is concluded that there is a problem with the sealing method.
