Venting and Insulation
Plastic-lined pipe is often insulated to prevent freezing, save energy or maintain a certain process temperature. Some operating experience has shown that heat tracing and insulating can also reduce permeation rates by lowering the temperature differential across the pipe wall. If installed improperly, however, insulation may block the paths for venting permeants on most PTFE-lined components. Under conditions which favor high permeation rates, blockage of the vent path can lead to high exterior steel shell corrosion rates, liner collapse and ultimately to premature failure of the lined components. Swaged PTFE-lined pipe spools are designed to vent at the flange. Spiral grooves on the interior of the steel shell transport permeated vapors to the flange area, whereby they exit the annulus along a patented vent collar. When insulating swaged PTFE-lined pipe spools and flange connections, care must be taken to extend the vent path through the insulation. One simple way is to drill a hole through the bottom of the insulation and insert a piece of 1/4" flexible tubing into a position between the flanges. This is shown in Illustration A. THERMALOK PTFE-lined pipe and PTFE-lined fittings are vented via vent holes in the pipe, casting or fabricated steel shell. Welded half couplings and vent extenders can be used to extend the vent path through insulation on pipe or around fittings, as shown in Illustration B & C. Couplings are available as 3000lb. 1/8" or 1/4" sizes.
Venting Resistoflex plastic-lined pipe
A. Vent extender at insulated pipe joint with Swaged pipe		B. Vent holes and couplings on THERMALOK pipe
C. Vent extender for fittings