Is this real?
Is this real?
(OP)
We are being told that we need "weep holes" on teflon lined piping in order to vent corrosive gasses away from the steel portion of the pipe because we are insulating. These weep holes are not cheap. Has anyone seen this before?





RE: Is this real?
RE: Is this real?
There are two main styles of TFE-lined pipe: "swaged" (Dow-style) pipe and "loose" or "flared" liner pipe. The swaged pipe has internal rifling and permeation is vented via a special washer between the liner flange face and the metal flange face. The "loose" lined pipe has a liner which is not tight in the pipe. The pipe needs weep holes at intervals. If you're insulating, you need half-couplings welded over these weep holes, and "sacrificial" threaded nipples to carry the vented material outside of your insulation cladding- sacrificial because they often corrode away when the permeated stuff hits the moist atmosphere. If you don't use this method, the permeate can be trapped by the cladding and accumulate, eventually eating your pipe from the outside inward...
Crane Resistoflex offers very good info on this stuff in their catalog.
RE: Is this real?
So, a gaseous bubble could collapse a piping liner, as moltenmetal warned. I think this would generally only be a problem if the pipe was used first in high pressure service and then low. Or, if an acid permeated the liner, its reaction with the steel would release hydrogen.