Relining
Relining of underground pipelines
The proposed rehabilitation system is based on a “No Dig” technology, known also as CIPP (Cured In Place Pipe).
The system is based on internal relining of the pipe to be rehabilitated using a felt liner (hose), impregnated by thermosetting resin, that is inserted into the host pipe and squeezed against its wall.
The system may be applied to any type of pipes: concrete, steel, plastic, etc.
After the resin polymerization, the hose forms a solid pipe placed inside the original one.
The internal pipe surface, that is in contact with flowing product (water, sewer, oil, etc.) is covered by a this layer of plastic material (mainly PE of PU), that is not affected by contact with the flowing product.
In this way the surface on which the product is flowing will be very smooth.
Thickness of the liner and type of impregnating resin will be selected case by case.
In case of water contaminated with hydrocarbons (as for waste water networks in refineries) vinyl-ester or epoxy resins are used.
The liner is inserted into the pipe under rehabilitation using a system called “inversion”.
Introduction can be made either by air pressure or by water pressure, depending from size of pipe and length of the stretch to be treated.
In both case the advancing speed is continuously controlled; advancing speed will be 1 to 3 m/min depending on circumstances.
After insertion, the liner is subjected to a computer controlled heating cycle to achieve a complete resin polymerization: heating by circulation of hot water (in case of insertion by water push) or by steam.
At the end of the heating (and cooling) cycle the hose has become a solid pipe in itself with adequate static resistance.
In case of pipes working under pressure, a layer of fibreglass reinforcement is inserted between two felt layers to increase the polymerized hose strength.
Before liner insertion the pipe has to be completely cleaned (by pressure water and/or mechanical brushing) and an accurate video inspection is executed.
After hose polymerization the liner is cut at the end pits and its extremities are sealed using special resin or mortar or by application of special collars.
A tightness test under pressure and a final video inspection are made.
