What are the forming methods of PTFE bellows of mechanical seals

The bellows are generally made of pure polytetrafluoroethylene. In case of just for the aims of wear resistance and media resistance, different formulas of filled tetrafluoride materias are adopted in the head and tail parts, and pure polytetrafluoroethylene is still used the bellows section. 

According to the forming method, the PTFE bellows can be divided into two types: (1) PTFE bellows made of vehicle: made of PTFE circular billet, and the billet can be divided with different components of PTFE according to the requirements. When turning, attention should be paid to that PTFE has the characteristics of low thermal conductivity and large line expansion coefficient, the cutting speed should not be too fast, and the cutting capacity should not be too large to ensure the processing accuracy. The general speed is 500~600r / min, and the cutting capacity is about 0.08mm.

(2)pressed forming PTFE bellows: From the pressure die directly pressed into the required bellows, the current domestic has made the friction ring and bellows two different components of the material pressure into a single structure.

At present, China has made two different component materials like the friction sealing ring and bellows into a single structure.

As mentioned above, the end faces section of bellows mechanical seal shall be resistant to wear, corrosion resistance and good self-lubrication and thermal conductivity; the bellows section requires sufficient elasticity and bending performance; the rear section shall be stable in size for transmission or fixation. For this purpose, as for bellows mechanical seals made of PTFE, the end face section is filled with PTFE, and if the grinding material is alumina ceramic after test, 20% glass fiber filled PTFE can be adopted ; When paired with silicon nitride, it is more ideal to adopt PTFE filled with 15% graphite and 5% glass fiber. Pure PTFE can be used in the middle bellows part. In order to reduce the influence of cold flow in the latter section, PTFE filled with 20% glass powder can be selected.

Domestically produced pump use corrosion resistant mechanical seals 151,152,153 are Teflon bellows type mechanical seals.