Scrubber heaters sit in a gas stream loaded with acid mist, droplets and entrained slurry. The gas condenses on the cooler sections of the tube, forming a concentrated acid film that attacks bare 316 within weeks. The pitting starts where droplets impinge and evaporate, leaving acid salts behind. A filled-PTFE cladding seals the 316 from this mist, because the smooth fluoropolymer surface does not wet and the dense film does not let the acid through.
The glass-fiber filler, loaded near twenty percent, gives the film abrasion resistance against entrained slurry. The pre-treated fiber is twin-screw dispersed, and the composite is sintered to a low-porosity film. Material-selection service specifies the scrubber-grade cladding, with extra film weight on the droplet-impingement zone. At each outage, the holiday wand checks the impingement zone, and the surface is inspected for wear.
The controller also directs the gas away from impinging directly on a bare spot. The smooth surface sheds droplets, and the dense film beads the condensate. Procurement buys the scrubber-grade coated heater and writes the impingement-zone thickness on the drawing. The film covers the flanges and supports. The result is a heater that survives the acid mist and slurry.
The cladding also resists the scrubber chemistry, because the PTFE matrix is inert to the acid. The glass filler is stable. At each maintenance, the coated surface is rinsed rather than brushed, because mechanical brushing wears the film. Plants that had rapid pitting on bare 316 scrubber heaters switched to the cladded version and extended life from weeks to years.
The scrubber environment is deliberately hostile: droplets carry concentrated acid, the gas stream carries entrained solids, and the wall temperature cycles as the load changes. A bare 316 tube in this service develops impingement pits within weeks, because each droplet leaves an acid salt that never fully washes away. The material-selection service treats the droplet-impingement zone as the critical length and builds the film thicker there. The glass-fiber filler, at roughly twenty percent loading, gives the composite abrasion resistance that pure PTFE cannot match, so the entrained slurry wears the film slowly rather than cutting through it. The pre-treated fiber is twin-screw dispersed, and the sintering step fuses the film to a low-porosity barrier that the acid mist cannot penetrate. At each turnaround, the inspector runs the holiday wand along the impingement zone and inspects the surface for wear, and the smooth, non-wetting surface means the acid droplets bead and run off instead of concentrating. Procurement writes the impingement-zone thickness directly on the drawing, and the cladding extends over the flanges and supports. Plants that watched bare 316 scrubber heaters pit out in weeks switched to the filled-PTFE cladded version and extended the life to years, because the dense, inert, abrasion-resistant film takes the mist and the slurry that the metal cannot.
The controller also directs the gas away from direct impingement, because even the best film wears where a jet hits. At each maintenance, the surface is rinsed rather than brushed, since brushing wears the composite. The material-selection service logs the cure cycle. The result is a scrubber heater whose film takes the mist and slurry for years, because the impingement zone is built thicker and inspected on every turnaround.
