Polyethylene (PE) is the most commonly applied liner material and one of the most widely produced plastics in the world (tens of millions of tons are produced worldwide each year). PE liners should not be exposed to operating temperatures above 60 °C in water service. In hydrocarbon service (combined liquid and gas phases), the recommended maximum operating temperature is lower and depends on the fluid composition but should not exceed 50 °C.
Polyethylene is a lightweight, durable thermoplastic with variable crystalline structure. Polyethylene is used in applications ranging for films, tubes, plastic parts, laminates, etc. in many markets (chemical, oil & gas, packaging, automotive, electrical, etc.).
Polyethylene is made from the polymerization of ethylene (or ethene) monomer. Polyethylene chemical formula is (C2H4)n.
For lining applications in the energy industry, three types of PE are used; in increasing order of strength and chemical resistance, they are:
- Medium-density polyethylene (MDPE), used in low-pressure water and gas distribution applications;
- High-density polyethylene (HDPE), used in all types of service;
- Ultra High Molecular Weight (UHMW-HDPE) used in demanding applications.