Even the best-lined valve can fail prematurely if installation guidelines are ignored. Fluoropolymer linings such as PTFE, PFA, FEP, and PVDF provide exceptional chemical resistance, but they are softer and more sensitive than metal surfaces. For this reason, lined valves demand disciplined handling from the moment the box is opened until the system is commissioned. A small oversight during installation can reduce years from the expected service life.
The first and most critical rule is never expose lined valves to welding heat. Fluoropolymers have defined temperature limits, and direct or indirect heat from welding can distort, shrink, or melt the lining. The damage is often invisible from outside yet becomes evident later as leakage or blistering. All hot work, stress relieving, and pipe fabrication must therefore be completed before the lined valve is brought to site. If welding near an installed valve is unavoidable, the valve should be removed temporarily to protect the lining.
Flange alignment plays an equally important role. Misaligned pipes introduce bending and torsional stress on the valve body. Unlike metal valves, lined valves cannot tolerate such mechanical strain; the internal lining may crack or separate from the body. Proper pipe supports, expansion joints, and accurate face-to-face alignment are essential. Gasket selection should match the process media, and bolts must be tightened gradually in a cross pattern using manufacturer-recommended torque values to avoid uneven compression.
Handling during lifting and transportation is another frequent cause of failure. Lined valves must always be supported from the body or designated lifting lugs. Using the actuator, hand lever, or stem for lifting can disturb internal alignment and damage the seats. Even a minor drop on the shop floor can create micro-cracks in the lining that later develop into full-scale leaks when exposed to chemicals and temperature cycling.
For actuated valves, correct torque setting and calibration are vital. Excessive actuator torque compresses soft PTFE seats, leading to high operating friction and early wear. Insufficient torque, on the other hand, results in passing and poor shut-off. After installation, actuators should be calibrated with the actual process pressure in mind, and limit switches must be set to prevent over-travel.
Prior to commissioning, the pipeline should undergo thorough flushing and cleaning. Welding slag, metal chips, or construction debris can cut the lining like a knife edge. Installing temporary strainers upstream of lined valves in new pipelines is strongly recommended until the system is completely clean.
Routine post-installation checks further enhance reliability. Inspect fastener torque after the first thermal cycle, verify actuator performance, and ensure that the valve is not subjected to external loads from piping or platforms. Maintaining spare seats and gaskets from the original manufacturer also helps preserve performance.
These disciplined practices may appear simple, yet they dramatically increase the service life and safety of lined valves. Proper installation protects the substantial investment made in fluoropolymer technology and ensures leak-free operation in even the most aggressive industrial environments.
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