Renovation & Rehabilitation
Plastic Pipes Conference Association # 1998 Gothenburg
Marshall, Morley, Pearson
The Water Industry in England and Wales has responsibility for an approximate length of 300,000km of water main, ~nuchof which was laid over 70 years ago using cast iron.
Subsequently, asbestos cement, PVCu and cement lined ductile iron have been used. The old iron pipe systems that were installed in many of the world's great conurbations between 1870 and 1930 are now nearing the end of their useful life. The cost of renovation is enormous and in situations where burst frequency and modest leakage are 'tolerable'. criteria to assist in the decision as to whether to repair mains or alternatively consider wholesale replacement are needed.
The decision to re-line a pipe or use 110-dig tecllniques to rehabilitate the system with new pipes capable of withstanding all structural loadings depends not only on the present burst frequency but also on the predicted lifetime that remains. It makes no sense to line pipes in wliich corrosion is so advanced that a cement Inortar lining will offer little benefit as regards extending the life. To expend far greater sums to structurally line pipes that have suffered little deterioration, also makes no economic sense.
During the last eight years, the UK water companies have spent large sums of money on pipe systems (approximately £600 million per year) in a drive to improve water quality. It would be wise to use this experience as a basis for a common approacli towards renovation choice.
Historically, there has not been one nationally agreed procedure, but a mixture of options and approaches that are suited to the different needs of different companies.
However, there is noN a developing beliel'that the structural condition of the pipework. plus factors affecting leakage. liydraulic performance and water quality need to be combined in an 'holistic' approach towards the renovation problem.
Related papers
Author(s) : Peter Hubbard, Linqing Luo, Andrew Yeskoo, Kenichi Soga, Krista (Moita) Araica, Gus Cicala, Marshall McLeod
Seismically active faults pose a risk to buried water pipelines that can be complicated to quantify. Fault type, slip rate, pipeline geometry, and soil conditions all factor into a complex soil-pipeline interaction. For critical pipelines that cross faults, high-density polyethylene (HDPE) has become an attractive...
Author(s) : Dr. Dane Chang, Dr. David Marshall, Chris Cox
Plastic pipe applications often require polymers to have adequate abrasion resistance during usage. Although typical polyethylene resins have reasonably good resistance to abrasion and can be broadly used with a variety of chemicals, there are some demanding applications that require a resin with enhanced abrasion...
Author(s) : Marshall, Brogden, Shepher
Many early brittle failures in PVC water and sewerage pipelines, where repeated surge events are thought likely to induce embrittlement, were attributed to fatigue. The concerns of pipeline engineers led to the adoption of the British Standard Code of Practice CP 312 (ref. 1) by the UK water industry, which gives...
Author(s) : Marshall, Hepburn, Netherwood
The adoption of polyethylene as a pipe material by both the gas and water indusmes has undoubtedly led to several sigruf~cant economic and operational advantages. The development of narrow trenching techniques and insertion refurbishment methods only became viable once a complete fusion jointed polyethylene system...
Author(s) : Marshall, Ingham, Brogden
When clients purchase plastics pressure pipes, they have frequently made that decision because they know that plastics do not corrode and they assume that if they do not exceed the pressure rating then a long lifetime should be assured. (Low cost has also been known to be a factor). It is thus of concern for the...
Author(s) : Marshall, Birch, Morley
Many UK Water Companies are now using PE pipe systems because it 1s believed that use of an all-welded pipe will minimise the number of mechanical fittings employed and therefore will reduce potential sources of leakage. With pipes such as ductile iron and PVCu, which are joined in short lengths, it is often...
Author(s) : Marhsall, Harry, Ward, Pearson
Existing test methods used for the characterisation of long term strength properties of plastic materials for use in pressure pipe duties have been reviewed. A notched "C" ring type test has been developed to define the long term crack resistance and strength properties of a CPE modified PVC. Since materials of this...
Author(s) : Lowe, Marshall
A Rotating Pipe Drum Test has been developed to assess the abrasion performance of plastics pipes to an extpnt where most test variables are understood. The procedure involves the rotation of relatively short pipe lcngths containing slurry on a conventional bail mlll. In the rest, the pipe surface repeatedly passes...
Author(s) : Marshall, Birch-Kisbenyi, Youd
A complete analysis of the Charpy impact system has been made to relate measurements of impact toughness to the geometry of samples. Using data obtained on pipe grade polyethylenes, Gc values at 20°C and 3°C have been found to correlate wel! with measurements of resistance to fast fracture in pressurised pipe...
Author(s) : Young, Thomas, Marshall
Within the Water Industry in England and Wales, there is an estimated length of 295,000 km of water main, much of which was laid in unlined cast iron prior to 1940. Subsequently, asbestos cement, UPVC and cement lined cast/ductile iron has been uscd. It is kn-that a substantial number of...
Author(s) : Marshall, Birch
It is proposed that present Specifications for PE Pressure pipes are essentially undemanding and tests do not simulate service conditions. Perfect pipes are assessed rather than pipes which have sustained handling and installation ‘damage’. Flaws and defects have caused many problems with other thermoplastics pipes...
Author(s) : Lowe, Marshall
A new test has been developed to evaluate the abrasion performance of different pipe materials. The Rotating Pipe Test simulates sliding bed flow of a slurry and gives quite excellent data reproducibility. The influence of sample geometry and slurry changing frequency and particle size have been assessed. The effects...
Author(s) : Marshall, Taylor, Dickinson
A study has been carried out which has sought to establish the influence of processing conditions on the properties of medium and high density polyethylene. Residual stress and fracture toughness measurements have been carried out on hdpe pipe, from which predications of the influence of diameterlwall thickness on...
Author(s) : Birch, Marshall
The mechanics of failure of uPVC pipe materials have been investigated using fracture mechanics test methods to induce brittle failure. It has been found that brittle failure can be quantified and test procedures have been developed which are capable of being used as quality control methods for classifying pipe. High...
Author(s) : Birch, Howarth, Marshall
The paper is a brief resum of a large project which has sought to investigate the use of fracture mechanics in evaluating the failure properties of a number of common thermoplastics pressure pipe materials. In this outline, the results of tests made on uPVC and YDPE pipes are described. Pre-notched pipes have been...
Author(s) : Marshall, Williams
During the last ten years, it has often been predicted that plastics will be used in increasing quantities as true engineering materials, Whilst there has been an increased acceptance of GRP as a positive alternative to metals in many applications, the use of thermoplastics for major load bearing structures has been...
Members of the Association
