Mechanical seal of the seal failure is why?

Mechanical seal of the seal failure is why? 2019 - 8 - 12 mechanical seal is the seal failure would happen, so what is the reason of this occurring? What pay attention to the operating process? The following analysis analysis together. 1, overheat because of the sealing surface will generate heat, so the rubber ring used temperature should be lower than the design specification. The use of fluorine rubber and teflon temperature is 216 ℃, the use of nitrile butadiene rubber temperature is 162 ℃, although they are able to withstand higher temperatures, but because of the sealing surface heat is higher, so the rubber ring is in danger of continue to sulfide, eventually lose elasticity and leakage. （ Cold area consider cold short) Also caused by thermal medium crystal surface, such as carbon, caused by sticking and sealing surface by condensation sliding parts. And some of the polymer in overheating and coking, some fluid lost even lubrication and flash fire due to overheating. Overheating except can change the condition of the medium, but also increases its corrosion rate. Cause deformation of the metal parts, alloy surface cracking, and some coating cracks, the design should choose the balance type mechanical seal, in order to reduce the pressure to prevent overheating. 2, the sealing surface is opening in the repair of mechanical seal, 85% of the seal failure is not caused by wear and tear, but had been leaked before wear. When the sealing surface is opened, the medium under the action of solid particles in the liquid pressure into the sealing face, sealing surface after closure, the solid particles embedded soft ring ( Usually the right ink loop) Surface, it has become a 'wheel' will damage the hard surface of the ring. Because of a ring or rubber ring fastened on axis ( Collar) , when axial string move, ring is not fit in time, and make the seal face open, and the lagging of the sealing surface closed, makes the solid particles into the sealing face. At the same time axis ( Collar) And there exists between sliding parts of solid particles, rubber band, or ring sliding ( Relative dynamic seal, common failures) 。 In addition, the media will be in the rubber ring and shaft ( Collar) Friction produce crystal, in the spring will have solid matter, will open the sealing surface. 3, super bad correct assembly tolerance, it is necessary for the installation of mechanical seal, shaft ( Collar) Must have the appropriate surface roughness and the correct size, but makers seldom provide tolerance data, the data is essential for installation. （ Rely on the experience and common sense) Mechanical seal of the dimensional accuracy and shape tolerance must conform to the requirements of the drawings, ultra difference will lead to seal failure in advance. Looked at the above content, believe everybody already knows the seal failure of mechanical seal.