Having spent 28 years in the water industry I have come to understand the importance of training and on-going competency, product design, installation methods and the constant need for R&D. Over the years, I have been involved in Trenchless Technology and the rehabilitation of both water pipes and sewers using various technologies from cleaning, spray lining, coating, localised repairs (CIPR), cured-in-place pipes (CIPP), engineer training, product development, international standards and specifications.
Regarding the rehabilitation and renovation of pipes there are numerous systems, materials and resin systems in the market place that can be used, however, most contractors only use 1 or 2 repair methods and therefore subject to a higher risk of failure or installation problems due to the performance envelope of the systems they use.
As part of the design and selection of the repair system you need to understand and consider these key points:
Pipe diameter, pressure rating, depth and length
Pipe location, ground conditions and location of 3rd party services
Existing condition and serviceability history
External conditions – ground water level, ground and traffic loads, effects of tidal changes, access issues, down time
Reason for the repair – prevent leakage (exfiltration, infiltration, tree roots), improve flow, stop pipe corrosion, structural repair to withstand external loads
Pipe preparation systems – drag scraping, pigging, rack boring, water jetting, air scouring, electro-mechanical
Rehabilitation systems – flexural modulus (short and long-term properties), wall thickness of the coating / lining, cure time, curing method (ambient, warm water, hot water steam, Ultraviolet Light (UV), Blue Light (LED), air cured
Installation – pre-works, installation time, materials, cure time, over pumping, traffic management
Secondly you must ensure that the engineers who are installing the system and/or product are trained / qualified to do so. It is not uncommon for training to be handed down from engineer to engineer, however, this inevitably leads to the adoption of bad practices and an increased risk of failure. This can be reduced by undertaking work in progress audits or site visits, then following up with further coaching and if required additional training.
So, just a quick thought, when you take your car or motorbike to the garage for a repair does the motor mechanic only have one or two tools to work with, or does he have access to a toolbox full of different types of tools backed up with a range of analytical systems!
Let’s consider the rehabilitation of a gravity sewer using a CIPP system. Depending on the long-term design requirements you can select different:
Types of felt (i.e. polyester, glass reinforced plastic, carbon fibre)
Coating (i.e. PVC, PE)
Construction (i.e. glued, stitched, knitted)
Wall thickness (i.e. 3mm, 4.5mm, 6mm or greater)
Resin System (i.e. Polyester, Vinylester, Epoxy, Silicate)
Installation method (i.e. drag-in, inversion (fixed water column, inversion drum (air or air & water), shooter, gun, cannon, single point of entry, manhole to manhole), dual inversion
Curing method (i.e. Air, Water, Steam, UV, LED)
Some lining systems can only be used in straight pipes
whilst others can accommodate changes in diameter, navigate multiple bends or changes in direction. In some cases, lined connections may have to be re-opened using mechanical cutters.
Like the motor mechanic at the garage it is important for contractors to have access to a “No-Dig Toolbox” which should include a range of pipe cleaning, preparation and rehabilitation systems to renovate all types of pipelines and diameters. The more forward-thinking companies invest in innovation to enable them to improve product performance, increase productivity, reduce installation costs or develop new products.