A large amount of diesel oil stain was found on the ground when the diesel tank of a certain excavator was filled with diesel after assembly. 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. According to the analysis, there are three reasons for the oil leakage of the oil pipe transition pipe joint. Firstly, the internal thread at the bottom of the diesel tank or the thread of the transition pipe connector is unqualified. Secondly, the tightening torque of the transition pipe connector is too large or too small. Thirdly, the sealing method is unreasonable.
Standard requirements for adjustable end nut sealing right angle joints. If an O-ring groove is machined at the end of the thread in the diesel tank, an O-ring can be added at the end of the external thread, and the transition pipe joint and nut can be directly screwed on the internal thread. If there is no O-ring groove at the end of the internal thread, a retaining ring shall be equipped on the outside of the O-ring. The O-ring groove is not machined at the external threaded hole at the bottom of the diesel tank. After the removal of the combined sealing gasket, the O-ring and retaining ring shall be used for sealing, and the diesel tank shall be free of oil leakage after adding diesel. For this batch of diesel tank oil leakage prototype, replace the O-ring and retainer ring. After installation, the right angle transition pipe joint at the bottom of the diesel tank has no oil leakage problem.
It can be seen that the adjustable end nut sealing right angle joint must be equipped with O-ring. Whether it is necessary to use a retaining ring depends on whether the internal thread of the diesel tank oil pipe interface is equipped with an O-ring groove. The reason for the oil leakage fault of the right angle joint was that the designers did not fully understand the sealing principle of the adjustable end nut sealed right angle transition pipe joint. When applying the new structure in the future, it is necessary to fully understand its principle and track and confirm its trial assembly effect.
