HIMAYA is a new external coating to protect ductile iron pipes laid in highly corrosive soils. The coating consists of 2 layers: the front layer which is a continuous thick layer of crack resistant HDPE, with density superior to 910 kg/m3, blue color and a back layer which is a layer of 85/15 zinc-aluminum alloy, with a minimum surface density of 400g/m2, applied onto the surface of the ductile iron.
The HIMAYA technology, combining the properties of a zinc-aluminum alloy layer with the qualities of a thick continuous crack resistant polyethylene layer, enables a long lifetime of the pipelines in highly aggressive environments.
Field of use
Pipes with Himaya coating is suitable for laying in highly corrosive environment, including:
·Areas with soil resistivity <500 Ω.cm beneath marine water table
·Acidic peaty soils
·Soil containing refuse, cinders, slags or polluted by wastes or industrial effluents.
·Occurrence of stray currents in soil. Stray currents generated by the tramway’s electric power supply system can corrode metal unless appropriate protective measures are taken. The dielectric properties of HIMAYA dependably insulate ductile iron pipes against the effects of stray currents in soil.
Himaya provides protection through three aspects:
A thick organic layer of HDPE, density greater than 910 kg/m3, provides “passive protection” as it forms a crack-resistant organic barrier against the corrosiveness of soil and ground water aggressiveness.
A metallic layer of zinc-aluminum 85/15 alloy, with a minimum surface density of 400g/m2 provides active protection in case of damages to the primary HDPE barrier.
The pipe end surfaces not covered by the HDPE layer (spigot, front end of socket and internal section of socket) are coated with epoxy paint or other suitable coating(s). Pipe joints will be externally protected by the application of dedicated Saint-Gobain PAM rubber sleeves, or traditional heat shrinkable sleeves, depending on the type of joint.
1) Double protection: Himaya provides protection with double layers of HDPE and zinc aluminum alloy.
2) Strict quality control: The layer of crack resistant HDPE is applied by flat dielateral extrusion in spiral multi layers to produce a tightly bonded seamless coating. HIMAYA ensures that pipes are continuously protected and the HDPE layers fully welded.
3) Damage proof: Impact tests and scratch test are carried out at different temperatures to simulate extreme field conditions. The HDPE layer with a density greater than 910 kg/m3 provides superior anti-scratch property.
4) Fast laying process: Pipes are ready to install without any further treatment on site which save time and energy for installation process.
GB/T 13295，EN 14628
PAM technical teams carry out soil surveys at customers' request in order to recommend the most suitable protection.