What types of damage are common in PTFE-lined tower sections during operation?

Common damage forms in PTFE-lined tower sections during operation mainly fall into four categories: lining peeling, substrate corrosion, thermal stress cracking, and mechanical damage. Lining peeling is a typical failure mode, usually occurring under conditions where media penetration leads to interfacial corrosion or temperature changes cause differences in thermal expansion. When the bond strength between the lining and the substrate is insufficient, the media may penetrate along the interface and corrode the substrate, forming an expansive rust layer that forces the lining to bulge and detach. Thermal stress cracking is more common in situations with frequent temperature fluctuations. The linear expansion coefficients of PTFE and steel differ by more than 10 times; rapid heating and cooling can cause interfacial shear stress to exceed the bond strength. Mechanical damage includes localized thinning caused by solid material erosion, cracks formed by installation collisions, and edge warping caused by vibration fatigue.

Substrate corrosion is particularly prominent after localized damage to the lining. Acidic media erode the carbon steel substrate through the defects, forming ulcer-like pitting corrosion and accelerating the spread of lining peeling. Under high temperature and pressure conditions, PTFE linings may experience creep deformation leading to seal failure. Long-term use and material aging can also decrease impermeability. Specific forms of damage include fluoride ion stress corrosion (against stainless steel substrates) and breakdown/perforation caused by electrostatic accumulation. These types of damage often have a mutually reinforcing effect; for example, mechanical damage can induce media penetration, thereby accelerating substrate corrosion and lining peeling. Preventative maintenance should focus on stress concentration areas such as flange edges and weld transition zones, as well as scouring areas where media flow direction changes.