Answer: The operation and life of a mechanical seal largely depend on the conditions of the equipment itself. Therefore, before installing a mechanical seal, carefully inspecting the equipment will reduce the possibility of seal failure and the cost of repair. The equipment must be inspected from the following aspects:
(1) The diameter and depth of the seal cavity should be consistent with the dimensions on the seal assembly drawing, with a general deviation of ±0.13mm; the dimension deviation of the shaft or sleeve is ±0.03mm. Check the axial displacement of the shaft. The total axial displacement should not exceed 0.25mm; Check the radial runout of the shaft. The radial runout of the shaft is generally less than 0.05mm. Excessive radial runout may cause: wear of the shaft or sleeve, increased leakage between the sealing surfaces, and increased vibration of the equipment, thereby reducing the life of the seal.
(2) Check the curvature of the shaft. The maximum curvature of the shaft should be less than 0.07mm. Check the runout of the seal cavity surface. The runout of the seal cavity surface should not exceed 0.13mm. If the surface of the sealing cavity is not perpendicular to the shaft, it may cause a series of mechanical seal failures. Because the sealing gland is fixed to the sealing gland by bolts, the seal cavity jumps too much, causing the gland to be installed tilted, which in turn causes the sealing static ring to tilt, resulting in abnormal shaking of the entire seal, which is the main reason for micro-vibration wear. In addition, the wear of the auxiliary seal between the mechanical seal and the shaft or sleeve will also increase. In addition, the abnormal shaking of the seal will also cause wear and fatigue of the metal bellows or transmission pins, leading to premature failure of the seal.
(3) Check the alignment of the sealing cavity hole and the shaft. The misalignment should be less than 0.13mm. The misalignment of the sealing cavity hole and the shaft will affect the dynamic load between the sealing surfaces, thereby shortening the operating life of the seal.
