Cured in Place Pipe (CIPP) Lining
CIPP Lining comprises a resin saturated lining tube that is installed in a pipeline to create what has become known as a close fit ‘pipe-within-a-pipe’ either as a structural or non-structural solution to pipeline deterioration. Installation can be by winching in the liner uninflated through the host pipe, or inverting the liner through the host pipe using either air or water pressure via a scaffold or inversion drum. Once in the pipe the liner is inflated if it is not already by the inversion medium and is maintained under pressure. The resin is then cured (hardened) to leave the liner in place within the host pipe. Possible curing processes vary and include ambient cure; hot water cure; steam cure; UV light cure or high intensity light cure. Ambient cure is commonly used at smaller diameters whilst the hot cure techniques are commonly used for larger diameters. Localised repairs can use this technology as described in the ‘Localised Repair Techniques’ part of this web site.
CIPP Lining has until recently been used to renovate mainly gravity pipelines and culverts for foul or surface water collection and transport. More recently systems have been developed for effective renovation of pressure pipelines such as water, rising mains (sewage) and gas as well as for process effluent pipelines for the food and drink and oil and gas industries. Circular, non-circular, ovoid and box culvert sections can be lined using CIPP with diameter ranges from as little as 50 mm to around 3 m. Installation lengths can vary from short Localised Repair sections to typically 30 m to 200 m (usually manhole-to-manhole) lengths, although specialist operations have achieved up to 900 m.
A CIPP liner can be to designed to withstand the total load imposed on the host pipe by external groundwater pressure, internal service pressure (if any) and ground and traffic loading. Where the host pipe is structurally sound, a thinner lining can be designed as a non-structural lining solution.
Pipeline Preparation removes the deteriorated host pipe from service by overpumping or tankering to handle flows, and cleaning of the section to be lined. Any intrusions must be removed or lateral connection intrusions cut back to ensure the inner host pipe wall is smooth. Other defects may need repairing prior to commencing the lining process. If the host pipeline is deformed by more than 10% of its nominal diameter re-rounded is usual before lining. Large areas of damage, including water infiltration, may require Localised Repair before full renovation.
CIPP liner materials can be non-woven polyester needle felt, glass fibre, or a woven product with additions if required to provide reinforcing for additional strength particularly for pressure pipe liners. Normally they have a coating made from PU, PE or PVC to protect the liner during transportation and installation procedures. Liner resin may be polyester, vinyl ester, epoxy or silicate resin, the chemical make-up also depending on the curing process being used. Impregnation takes place either in the factory or at the job site. Depending on the resin type used it may be necessary to use specific transport capability to accommodate the resin behaviour and curing characteristics. The Shelf-life of an impregnated liner is often curing process dependent. For example Hot cure resins may need to be refrigerated during transport to prevent curing during transit.
Materials are available that will complete straight-line renovation, pipes with bends, pipes with diameter changes within the renovated length and renovation of pipes that handle hot flows.
Post Curing the lining is allowed to cool, the ends are cut to fit the host pipe and usually sealed. A sample of the CIPP liner should be taken from the pipe ends or from a mould cured in the access chamber say, for testing purposes and to verify the liner has met its performance specifications. Service connections and laterals are reinstated once curing has been completed and the pipeline is returned to service. Lined water mains must be disinfected to the appropriate standards before returning to service.