CASE STUDIES
Figure 5. Arrival of the everted liner into the test sample pipes.
flexural modulus 8,775 MPa and thickness of 7.8mm.
The design values for the liners were 250 N/mm, 8 bar, 6,000 MPa and minimum thickness of 8.3mm respectively. The desired operating life of the liner was designed for 80 years.
Figure 4. Arrival of the everted liner into the test sample pipes.
approximately 10 hours and each main was pressure tested once cured.
Several twin wall plastic bends led the liner up above ground into a system of straight pipe, to provide test samples for indicative mechanical property testing (Figure 4). These were conveyed to a laboratory in Germany, where Bateman Consultants Pty Ltd, specified tests to align with his pressure main designs.
Tests and results
Four tests were carried out post-installation of the CIPP liner – CCTV survey to visually inspect the liner, pressure test, burst testing and mechanical property of the liner samples. The acceptance criteria is that the measured value to be equal to or greater than the design values.
The CCTV inspection showed few wrinkles around the bends as expected, but within the limits. The wrinkles along the mains were also within ISO 11297 limitations. The ends of the liner were sealed with a Weko seal end finish.
Figure 6. Initialcircumferentialtensile wallstrength, initial failure pressure test and thickness results from IKT, Germany.
The rising mains were pressure tested for 1 hour at 5.4 bar, 1.9 bar higher than the current MOP.
Both mains passed the test without any variances.
Figure 7. Flexural modulus results from IKT, Germany. 30
The mechanical properties of the liner were tested in Germany, IKT Laboratory. The test samples were cut into smaller specimens and were tested for initial circumferential tensile wall strength (σc), initial failure pressure (P0), flexural modulus testing (E1) and thickness testing (t). These tests were carried out using ISO 10467:2018 and ISO 11296-4:2018 standards. The results shown in Figure 6 and 7 are the mean value of five specimens for one of the mains. The tensile wall strength measured was 257 N/mm, the initial failure pressure 11 bar, the
| July 2021 |
www.draintraderltd.com Conclusion
During all steps in the process safety was of paramount importance – protection around working close to the river, the potential for flooding and falls, risk assessments and internal negotiations were undertaken. No instances arose which caused any concern during the works. All H&S legislation and CDMprocedures were recognised. All aspects of legislative compliance were addressed from colleagues across Wessex Water and OnSite Ltd.
Good working relationships were also established with the lining contractor OnSite, lining supplier Norditube, lining designer Ian Bateman Consultants, Wessex Water construction and sewerage operations teams.
The test results came back all satisfactory and the liner exceeded all the design parameters. The second phase of the project (lining works) were completed on programme over a period of 3 weeks in October 2020. The submarine eversion technique used to overcome the highly fluctuating tidal threat is believed to be the first in the UK water history.
This solution had been estimated with a range of £540k - £660k and was delivered within the budget. It saved the company approximately 40% compared to original proposal of horizontal directional drilling.
The Authors would like to thank the following:
Richard Wortley, Contracts Manager , Onsite Ltd
Roland Waniek and Dr Iain Naismith, IKT Laboratories
Julian Britton, Critical Sewers Manager, Wessex Water
Steve Robbins, Technical Manager, Pressurised Pipelines, WessexWater
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