Loose Polyethylene sleeving was first developed by CIPRA (since 1979, DIPRA) in the US in 1951 for use in highly corrosive soil. It was employed more widely in the US in the late 1950s and first employed in the UK in 1965 and Australia in the mid-1960s. Loose Polyethylene Sleeving (LPS) remains as one of the most cost effective corrosion protection methods available today with a proven track record for reliability and effectiveness.
LPS comprises a loose sleeve of polyethylene that completely wraps the pipe, including the bells of any joints. The sleeving inhibits corrosion by a number of mechanisms. It physically separates the pipe from soil particles, preventing direct galvanic corrosion. By providing an impermeable barrier to ground water, the sleeve also inhibits the diffusion of oxygen to the ductile iron surface and limits the availability of electrolytes that would accelerate corrosion. It provides a homogeneous environment along the pipe surface so that corrosion occurs evenly over the pipe. The sleeve also restricts the availability of nutrients which could support sulfate-reducing bacteria, inhibiting microbially induced corrosion. LPS is not designed to be completely water-tight but rather to greatly restrict the movement of water to and from the pipe surface. Water present beneath the sleeve and in contact with the pipe surface is rapidly deoxygenated and depleted of nutrients and forms a stable environment in which limited further corrosion occurs. An improperly installed sleeve that continues to allow the free flow of ground water is not effective in inhibiting corrosion.
Polyethylene sleeves are available in a number of materials. The most common contemporary compositions are linear low-density polyethylene film which requires an 8 mil or 200 μm thickness and high-density cross-laminated polyethylene film which requires only a 4 mil or 100 μm thickness. The latter may or may not be reinforced with a scrim layer.
Polyethylene sleeving does have limitations. In European practice, its use in the absence of additional zinc and epoxy protective coatings is discouraged where natural soil resistivity is below 750 ohm/cm. Where resistivity is below 1500 ohm/cm and where the pipe is installed at or below the water table, where there are additional artificial soil contaminants and particularly stray currents again it is recommended for use in addition to zinc and epoxy coating. Because of the vulnerability of polyethylene to UV degradation, sleeving, or sleeved pipe should not be stored in sunlight, although carbon pigments included in the sleeving can provide some limited protection.
Polyethylene sleeving is standardised according to ISO 8180 internationally, AWWA C105 in the US, BS 6076 in the UK, and AS 3680 and AS 3681 in Australia.