Plastic Pipes Conference Association # 1985 York
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 and it is believed that Specifications should be re-modelled to use fracture mechanics test methods and analyses to demonstrate that only pipes with high toughness are produced.
Examination of any current Specification for PE and uPVC pressure pipe shows that the testing specified and background data required are at levels far in excess of those demanded for more "traditional" pipe materials.
The U.K. pipe industry in particular, carries out in-house quality control testing at a high level of assessinent and it is often argued that those wishing to introduce yet further test procedures are not only a nuisance but are imposing cost penalties on finished products such as to render them uncompetitive c.f. other products.
The view here its that much of the present tesing which is Carried out is irrelevant to service performance of pipe systems and new tests should be introduced to model service more closely, at the expense of 'conventional' procedures which tend to assess properties of 'perfect' pipe under idealised loading conditions. The testing should demonstrate the suitability of the pipe for the purpose for which it is intended. That plastics pipes can be supplied to operate at design limits with assured performance, backed by relevant data should be promoted to challenge the laissez-faire attitude adopted for other materials.
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, 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...
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) : 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) : 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
