Code of Practice for Cured in Place Pipe Technique Suiting Indian Conditions
Water and sewage infrastructure and other utility services represent a significant investment on the part of most municipalities. For well over 100 years, the distribution networks for utility services have been located underground in pipes or ducts that are laid, repaired or replaced by trenching from the surface. In cities and urban areas, these distribution networks are located underneath roads. This often makes access difficult, particularly in areas congested with traffic and buildings. When pipeline infrastructure is not well maintained, inefficiencies occur. For example, in water distribution systems, this can lead to leakage and possible water shortages. In sewage systems, cracked and damaged pipes can cause wastewater seepage, leading to contamination of groundwater. These problems often give rise to related health and environmental impacts.
Perhaps the largest share of the trenchless market is represented by the requirement to rehabilitate defective pipelines with some residual structural and physical life, which can be used as a structure for the new line. Examples of rehabilitation techniques include Cured-in-Place Lining (CIPP), Close-Fit Lining, Slip-lining, and Spray Lining, all with their own-patented variations, as well as various other localised repair techniques. Variations relate to the material used, wall thickness provided to offset structural or physical defects, the rate of rehabilitation, and the minimum time of shut-down for the existing service.
The rehabilitation of small diameter underground pipes is a new area where the cost competitiveness of Trenchless Technologies is well recognised. Many utility pipelines, sewage in particular, become defective due to the corrosiveness of modern effluents. They also suffer from overloading and loss of capacity. One of the advantages of rehabilitation is that the new lining materials have a much lower surface friction coefficient, thus it is often possible to increase the capacity of the refurbished pipe without increasing its diameter.
In CIPP, a fabric impregnated with polyester or epoxy resin is inserted into the defective pipe and inflated to fit against the pipe wall. It is then cured by hot water, steam or ultraviolet light. The system has many variants and can be designed to provide different wall thicknesses to meet particular needs. One advantage is that the lining adjusts to variations in the size of the pipe. It is widely used for the rehabilitation of gravity sewers, including laterals, and usually results in no loss of capacity.
The Code of Practice for Cured-in-Place Pipe suiting Indian conditions has been developed to assist the project owner and the service provider in attaining the desired outcome of the rehabilitation process. The conditions proposed would help in developing the pipeline with desired properties and strengths if followed properly. The conditions have been developed with the assistance of the working committee members and are an attempt at standardizing the technique so that procurement process could be more transparent and the product could be economic in the long run.
As with all codes of practices, this would be reviewed and updated with times and the user/reader is invited to send their comments for a further development of the code.
Prof. Niranjan Swarup