Plastic-lined Piping

Metallic pipe is strong, easy to work with and inexpensive, but even mildly corrosive fluids can rapidly eat away at it, from the inside out, severely limiting it’s lifespan. Nonmetallic piping, fiberglass and thermoplastics, does not have the physical strength of metallic piping, but has excellent chemical resistance. Plastic lined piping combines the best of both common piping systems into one.

Plastic lined piping systems provide the chemical resistance of plastics and the inherent strength of steel, or alloy metallic piping systems. This is excellent for handling acids, corrosives and hazardous materials. Plastic lined pipe can be fabricated with either a loose or locked in liner, however, a locked in liner reduces the effect of the difference in expansion coefficient between the metal and the liner.

There is a lot of misinformation in the market place concerning PTFE lined pipe. The way some plastic lined pipe manufacturers act you are led to believe that it is the solution to all your plastic lined pipe requirements and will handle all service conditions from mild to hazardous. That is simply not true. PTFE lined piping systems are prone to several very important problems:

1. PTFE lined pipe and PTFE lined fittings must be vented according to the ASTM specification for plastic lined pipe and plastic lined fittings, F-1545.  PTFE is the most permeable fluoropolymer we line with and because it is vented, everything that permeates the liner is released into the atmosphere. 

2. PTFE has the poorest mechanical properties of any fluoropolymer we line with. The joints in a PTFE lined piping system are constantly being affected by joint creep and cold flow as described in the piping hot news link below. Tight joints are crucial to the integrity of a plastic lined piping system. The only thing worse than releasing your product into the atmosphere is dumping it on personnel, the ground, or equipment through a leaky joint.

3. PTFE is the least expensive fluoropolymer resin used in plastic lined pipe and plastic lined fittings. It is 15 to 20% of the cost of other fluoropolymer resins. The trade off is that you give up excellent permeation resistance and mechanical properties to save money. Plastic lined piping systems are most often used to carry chemicals that are dangerous and hazardous to health.