Monday, September 26, 2022

RISING MAIN REHABILITATION

Sanivar recently completed a 750 m long pipeline refurbishment of a 250 mm diameter Rising Main in Matlock, Derbyshire, UK. The project was promoted by Severn Trent Water (STW) following a number of asset failures that had resulted in 10 reactive repair interventions in recent years. The project was delivered through STW’s delivery alliance CSP and lining contractor Colus Specialist Projects.

The 250 mm diameter cast iron main was found to be badly corroded over a section that ran along the High Street and into a discharge chamber in the riverside park. Originally installed in 1970 the pipe had eroded from the inside and grit had worn a groove along the base of the pipe making it susceptible to bursts.

Challenges
The project posed a number of challenges including:
• The main ran the length of the High Street which, due to local topography, is an essential throughfare meaning that traffic management and lane occupation were major considerations.
• The main operates at near capacity due to recent housing developments meaning that tankering was required to maintain serviceability for the duration of the works prompting the need for a quick installation.
• The liner had to navigate a number of bends along the length of the main some of which were in close proximity to each other providing a navigable challenge.

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Outcome
Working with Sanivar and CSP, STW selected SaniTube as the optimum repair solution. A 250 mm diameter SaniTube was selected with an outside diameter of 246 mm providing the opportunity to inflate to 250 mm under 3 bar pressure so providing a close fit to the internal diameter of the host pipe. To mitigate risk, it was decided to excavate and replace one of the 45o bends and for other logistical reasons install the liner in three 250 m long sections.

The liner was winched through the host pipe at a rate of 6 m/minute at a torque of 5.9 kN meaning that each section was completed in under 45 minutes.

The sections were then joined using back-to-back flanged SaniGrip couplings which were also used to connect onto the host pipe via a conventional flange adaptor.

Sanitube provided the only viable solution for this project due to:
• Cost efficiency – reducing mitigation measures and allowing for a quick restoration of
service
• Flexibility allowing for navigation of bends and chambers
• Durability – through a pressure rating in excess of 16 bar, accommodating existing
and future operating pressures
• Efficiency – rapid installation enabled by lack of curing or wetting out processes
• Sanivar’s commitment to collaborative working and on-site support

“The Sanivar solution, supported by Colas, was a great solution with the tube folded
prior to installation and with the cleansing and survey work being undertaken via a
night shift to enable the liner to be pulled through during the day and pressurised and
put back into service.” said Andrew Warren – Network Operationalist Specialist Severn
Trent Water

Sanitube Installation – Step by Step

The process started with a Desktop Evaluation to scope project and identify the route
and configuration of pipeline including indicative diameters and potential access
points. This informed the initial proposal and selection of liner. A Site and CCTV Survey
was then undertaken to verify the desktop evaluation and assess the condition of host
pipe. A final proposal was then presented including connections.
Enabling works followed including excavation and establishment of bypass
arrangements, cleaning of the pipe (typically using high-pressure jetting) and a final
survey was conducted.

The liner was then prepared, shackles fitted and winch cable attached. The liner was
then pulled through host pipe typically at 6 kN force to achieve an installation rate of
6m/minute until the liner appeared in the reception pit.
Inserted end stops hold the inserted liner in place whilst the liner is inflated. The liner
fully inflates within host pipe with application of some 3 bar working pressure using
compressed air.

End couplings are fitted using SaniGrip bespoke couplings to achieve NP16 flanged
connections to the existing or new infrastructure. Thereafter, a pressure test is
undertaken to confirm the integrity of liner. A post-installation CCTV survey is optional
at this stage. Finally the lined section(s) are connected to existing infrastructure and
reinstatement of the excavations is completed.

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