When the coating process is normally done by jacketing, the PTFE tube is slightly reduced in diameter and, under pressure, is introduced into the part. Then the coating is normalized, stress relief and perfect molding on the inner surface of the tube is achieved.
By this process, even if the inner wall of the tube has irregularities, the coating will be perfect, avoiding the so-called “false wall”.
In the case of the PTFE ferrule, all work is done hot and with suitable pipe expansion devices.
The temperature is controlled throughout the process ensuring that PTFE ferrule does not rupture, which would compromise the entire coating.
In both cold reduction and hot expansion, PTFE should be well sintered or compacted. Otherwise the material will rupture.
PTFE coated carbon steel tubes are used for conducting corrosive chemicals.
Advantages: Lower coefficient of friction, Working temperature -70ºC + 250ºC, Chemical inertia for almost all products (except alkali metals, fluorine, F), trifluorinated chlorine (CLF).