One reason: hollow shaft and equipped with rotating concentricity is not enough. Countermeasures: checking the size and precision of the adjustment and rotation of a fixed connection.
Second reason: equipped with precision machines low (end verticality, radial, axial clearance), greater vibration. Countermeasures: find the reasons to repair fitted equipment.
Three reasons: sludge, dirt and other foreign matter into the friction surface. Countermeasures: add filter or strainer, transform the swivel joint type.
Four reasons: speed beyond the matching rotary joint using pressure and temperature range. Countermeasures: a study on the operating conditions, to ask the research units or factories, equipped with swivel joint type modified.