Epoxy Resin Lining Systems
Epoxy Resin lining of pipes with a thin lining of resin (typically 1 mm thick) requires that the main being rehabilitated is thoroughly cleaned and prepared before application. Generally the aim of this technique is to isolate the host pipe from the conveyed medium.
This technique can be applied to both man-entry and non-man-entry sized pipes. In man-entry sized pipe the application is usually achieved by hand-held spray guns but this does require the use of specialist PPE by the operator, and high levels of ventilation or the use of breathing gear to ensure the safety of the operator.
In non-man-entry pipe sizes, remotely controlled spray systems are utilised once the pipe has been cleaned and prepared. The thickness of coating in these cases is established by calculating the resin flowrate and speed of movement of the spray head through the pipe to provide the required thickness of application. In both man-entry and non-man-entry sized pipes the effective length that can be lined will depend on the availability of pumping systems that can present the lining material to the spray head over the distance required. In most cases the resin mixture is a two part system which is mixed only as it reaches the spray head so the potential for resin setting in the feed tubes before is it applied is very small.
Practically, in pipes that are utility based, lining is completed on a manhole-to-manhole distance which limits the length that is lined in one run. For both options there may be some potential for these techniques to be used to reinforce the structural capabilities of the host main if a lining thickness of sufficient depth is used and the lining is cured effectively.
There is however a question over the status of this type of renovation as a structural option. In the USA in 2016 AWWA revised its M28 Water main rehabilitation manual and changed the landscape with a very clear statement much as follows: “To meet AWWA Class IV structural criteria, polymeric material must have the ability to essentially replace the host pipe in the event of a structural failure, and continue to perform on a long-term basis. Should the host pipe fracture, a Class IV spray-applied lining must separate from the host pipe much as Class III materials but have sufficient structural strength to function as an independent pipe under load and full working pressures. At the time of publication, there are no conclusive tests that demonstrate this ability for a commercially available spray applied lining.” This does not apply in Europe and the UK where there is no particular standard requiring this type of lining to perform in this way and to be considered structural.