Lining Techniques are used to rehabilitate lengths of pipeline which have deteriorated to a point where leakage or structural instability has become an issue mainly in water, sewer, culverts and gas networks. It should be noted that lining of pressure networks is complicated by the requirement for the lining to withstand internal pressures as well as external loads and that connection issues may be challenging but not impossible. The systems may be used to line cable or other ducting where perhaps infiltration is a problem but this would appear to be a rare use.
Lining techniques are available for a wide range of diameters (as little as 50 mm up to around 3 metres although a small amount of lining over 3 m has been undertaken) depending on the system being utilised. Most if not all pipe materials now have available lining techniques that will suit including asbestos cement, clayware, brick, concrete, GRP and most plastic pipes.
The length of rehabilitation is dependent on the type of lining process being utilised. In most commonly experienced circumstances, i.e. between existing manholes on a typical utility network, lengths from 30 m up to 200 m have been lined.
Limitations on use generally depend on the type of rehabilitation/lining process being used, accessibility, and availability of infrastructure such as for example water supply.
Lining systems can be non-structural, semi-structural or fully structural depending on the degree to which the method used will improve the structural integrity of a pipeline. Anyone wishing to look at the structural aspects of various linings and their categorisation should reference the following documents:
• Gravity Pipes: Standard BS EN ISO 11296 – Plastics piping systems for renovation of underground non-pressure drainage and sewerage networks
o Part 2 Lining with continuous pipes
o Part 4 Lining with CIPP
o Part 7 Lining with spirally-wound pipes
• BS EN ISO 11295:2017 – Classification and information on design and applications of plastics piping systems used for renovation and replacement
• Categories of lining for pressure pipes, specifically water, are outlined in AWWA Manual M28 and ISO Standard 11298-4.
Lining techniques offer pipeline engineers the option to extend significantly the life expectancy of an existing pipeline without the need to remove the old pipeline from its route, whether this is a buried pipe, a surface network or a pipeline within an industrial or building setting. Lining can eliminate infiltration add strength to a pipeline, prevent pipe delamination/scaling and prevent corrosion. The generally smoother finish of lined pipes also has the effect of reducing friction losses and therefore increasing (potentially) the operating capacity of a pipeline even though lining does usually mean a slight loss in cross section. By lining pipes rather than replacing with traditional excavation techniques the rehabilitation operation tends to be quicker and less disruptive to the locality in which the work takes place.
The most modern lining systems also offer higher environmental operating standards with reduced fumes, dirt, noise, site traffic and interference/impact with local infrastructure. These techniques also, when correctly utilised, tend to be safer as they tend to reduce the need for the workforce to enter trenches or other hazardous work spaces provided the correct procedures are followed. This does however depend on the technique being used and the experience of the contractor.
Costs for lining techniques tend to be less (often significantly less) than those of traditional pipe laying/replacement methods and may be on a par with more modern trenchless pipe replacement options. Ensuring the selection of the correct lining technique for the job in hand may also reduce costs even more significantly, so potential users should investigate the range of options available before making a final selection to take full advantage of the systems available.
Over the past 40 years several technologies have been developed that can be used for lining and rehabilitation of existing pipelines including those following – hover the cursor over the technique to see more details.
In all cases more detail on each option is available from experienced contractors and industry consultants, either or both of which should be consulted before any final lining choice is made by those less familiar with the technologies. By use of the various methods of installation, pipes of diameter 150 mm to 3,000 mm can be relined.
Within non man-entry pipelines, lateral connections are located by measurement and after lining remade by cutting through the lining using robotic equipment, ensuring that a watertight reconnection is made with a standard trenchless technique. For man-entry pipelines, this can be achieved by manual methods however the sealing of the connection against external water ingress is just as important and necessary.