Steel Lined Equipment Product & Service

Material selection depends primarily on temperature, media aggressiveness, and geometry. PTFE (Polytetrafluoroethylene) serves general corrosive chemicals up to 180°C–200°C with universal chemical inertness. PFA (Perfluoroalkoxy) is chosen when complex melt-process molding is required for intricate valve bodies and offers superior permeation resistance. PO (Polyolefin) and PP (Polypropylene) offer cost-effective resistance for non-oxidizing acids, brine, and slurry abrasion up to 80°C–90°C, making them standard for large storage tanks and non-critical transfer runs.

Polymer linings possess inherent molecular porosity; trace corrosive gases can permeate the liner over time. Vent holes in the carbon steel outer shell release permeated vapors into atmospheric escape paths. Without proper venting, pressure builds between the liner and shell, causing liner collapse during system depressurization or catastrophic unobserved external corrosion of the steel casing.

Under vacuum conditions, ordinary loose linings can collapse inward. To withstand negative pressure (up to full vacuum, -0.1 MPa), Ruitu utilizes bonded lining methods: tack-welding expanded metal mesh (dovetail lock structures) onto the inner carbon steel wall before rotational transfer molding (ETFE/PFA), or applying mechanical grooving and chemical bonding adhesives. This ensures the liner remains permanently secured to the vessel wall across continuous thermal cycles.

Every lined component undergoes rigorous NDT testing according to ASTM F1545 and HG/T 21562. This includes: 1) High-voltage electrostatic spark testing (15,000V–25,000V) to detect pinholes or micro-fissures; 2) Hydrostatic pressure testing to 1.5 times the rated design pressure; 3) Dimensional flange face parallelism and liner thickness verification using magnetic induction gauges; and 4) Full vacuum hold testing where specified.

Fluoropolymers are susceptible to creep (cold flow) under uneven bolt loading. We provide calibrated torque tables engineered specifically for lined raised faces and recommend cross-pattern torque wrench tightening in 25% increments. We also supply Belleville spring washers to maintain constant sealing pressure throughout cyclic temperature expansions and contractions.