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THE MAGAZINE FOR THE DRAINAGE,WATER &WASTEWATER INDUSTRIES


MAIN FEATURE


Over the life of a liner, theworst case is likely to occur at some point several years or decades after installation. In particular, once the host pipe has finally fully deteriorated and the liner experiences a high groundwater event or themaximumexternal loads. Also, as CIPP liners aremade fromthermosetting materials theywill creep gradually and continually deflectingwhen under permanent load. So, froma design point of viewthe flexuralmodulus or tendency for amaterial to resist bending, relating to expected deflection after 50 years is used to calculate the required CIPP liner thickness. Confirming this value has been achieved after each installation is fundamental to confirming that the load bearing capacity of the installed liner.


Should the actual flexuralmodulus of the CIPP liner be less than expected, the linermay not have adequate structural capacity to withstand theworst-case loading events that could occur at some time in the liner’s life. To put this in perspective, if such understanding of creep had been available in the 1950’s when pitch fibre pipeswere introduced they would never have been accepted into the market.


As a consequence of performance considerations like these, standards exist for the performance ofmost technologies and for undertaking replicable testing of them. These takemany forms.


There is a hierarchy of standards and it is important to understand that this hierarchy is generated at the local, national or international level These standardsmay apply to any givenmaterial, product or service depending on its use or application. Theymay be official or self-imposed, voluntary or compulsory andmay include:


■ Company – instructions for installation/use


■ Industry – e.g., GSTT (German Society for Trenchless Technology) standard for


pressure sewers


■ Customer – e.g.,Water Industry Specifications (WISs) and Industry


Guidance Notes (IGNs) fromWater UK


■ National – e.g., British Standard (BS), German Standard (DIN), US Standard


(ASTM) ■ Regional e.g., European – EN


■ International – ISO (International Organization for Standardization)


These evolve over time and following publicationmay be updated such as in the following:


Example of howstandards develop FOLLOW US


■ WIS 4-34-04 – original standard designed around the first CIPP lining entrant to the


market


■ WIS 4-34-04 - 1995 update – reflecting a wider range of CIPP lining systems


available on themarket


■ BS EN 13566 - 2002 – updated version of theWIS to a BS EN reflecting European


wide range of lining systems available


■ BS EN ISO 11296-4 – 2011 – updated international standard to reflect


worldwide lining systems available


It isworth at this point consideringwhether therewill be any changes that affect the trenchless industry post-Brexit. BSI, the UK’s National Standards Body’s,membership of CEN and CENELEC,which have responsibility for European standards, is continuing. It has been the UKs policy to seekwherever possible to develop international standards first, involving UK leadership or influence and BSI states itwill continue to promote and enable UK stakeholder leadership in international and European regional standardisation. But it also states it recognises the need for flexibility where standards are used to support compliancewith national regulation. Therefore, probably no change is likely on the immediate horizon but this is something to keep an eye on.


TESTINGMATERIALS ANDPRODUCTS


Testing ofmaterials and products is normally undertaken as part of a quality assurance programme andmay take place at any point during development, production, installation and use. Tests can be self-administered,which is useful during development or for internal purposes, but these can be challenged, or can be independentlywitnessed or undertaken by a third party for verification.


Is testing compulsory? The general answer is no, unless there is a specific requirement in law. In reality the decision is often down to the end user and the requirements theymake of their supply chain, and that depends on their level of knowledge about the relevant quality assurance, standards and testing requirements that apply to a given technology or product.


Is there accreditation for testing? Anyone can undertake a test on amaterial or product that is devised by in-house, suggested by a manufacturer/supplier or against a common standard or procedure. However, the correct construction of apparatus, conduct of a test and production of consistent, comparable results is a QA issue in its own right. So, accreditation bodies exist that can check and certify the capability of an organisation and


audit ongoing performance against national/ international requirements. In the UK this is undertaken by UKAS and in Germany by DiBt for building products. The provision of accredited testing requires investment in facilities, equipment, qualified staff, internal QA and external accreditation. Consequently, it is usually undertaken by dedicated Test Houses.


The IKT Test Centre for Building Products is a testing, supervisory and certification body accreditedwith the German Institute for Construction Technology (DIBt) in accordance with European Standards (DIN EN ISO/IEC 17025 (Accreditation)). This covers selected mechanical and technical tests for polymeric components of pipe and CIPP liner systems, and for GRP laminate.


At themost basic level enforcement is the responsibility of the customer, but to do that theymust be informed customerswho fully understand requirements and have the time and resources to do it. Often, this is dealtwith collectively through amaterial/product/ service ‘approval scheme’ or ‘certification scheme’ such as theWRASMaterials and WRAS Products scheme for buildingwater supplies and the Regulation 31 Scheme for hygiene in publicwater supplies.


For Approval/Certification schemes thesemay be created by:


■ a customer – e.g. aWater Company


■ a trade association – e.g, as a condition of membership or on behalf ofmembers


■ an industry – e.g., theWRAS Approvals


■ an industry or private organisation, that has recognised status.


■ Government – e.g., DrinkingWater Inspectorates Regulation 31, formaterials


used in contactwithwater in the public supply


An approval or certification scheme provides a userwith a simpleway of checking that a material or product has been independently evaluated against a specific set of criteria. However, just because a product has an approval/certificate the end user still needs to make sure that the evaluation criteria cover the performance attributes they need from the product for the specific application they are using it for. An Approval also only provides reassurance if the product is then correctly supplied and installed.


QUALITY ASSURANCE FOR TRENCHLESS REHABILITATIONOF PIPES


As previouslymentioned, testing and approvals/certifications are tools that are used


February 2021 | 9


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