Author(s) : Peach 1985 York
ABS has been used for pressure pipework systems for over 30 years and although it is not one of the major tonnage polymers for this application, it has become a popular engineering material, particularly in process areas, where high purity is required. The ductility of the material has also resulted in it being used...
Author(s) : Zefrin, Scholten 1985 York
The gas industry in the Netherlands uses not only PE and metal but also unplasticized and impact modified PVC as pipe material for the distribution of natural gas. For a number of years the phenomenon of crazing in PVC and impact modified Pvc gas pipes caused by the combined action of mechanical stresses and certain...
Author(s) : Lustiger 1985 York
Since 1980, samples of field failures in polyethylene pipe for gas distribution have been collected and analyzed at Battelle in a field failure library. The majority of these failures were found to occur from slow crack growth as a result of a secondary load. Most often, the location of these failures were at points...
Author(s) : Rahmann, Banks, Tooth 1985 York
The equations governing the behaviour of circular cylindrical GRP pipes under a variety of loading conditions are derived. The pipes are assumed to be fabricated as a layered anisotropic system with through thickness symmetry. The well known Fourier expansion methods, used extensively in the analysis of isotropic...
Author(s) : Menges, Schmachtenberg 1985 York
The mechanical properties of thermoplastics are determined by strong. non-linear structures which are primarily functions of time,-temperature and degree of multiaxial loading. With the help of simple approximation-functions an exact description of this non-linear relationship between stress and strain is possible...
Author(s) : Usclat 1985 York
Electrofusion is uncontestahly a reliable assembly technique with much higher performances than conventional techniques such as hurt or socket fusion.The studv of the parameters involved in electrofusion process has enabled Gaz de France to define rules for the design and implementation of electrofused joints....
Author(s) : Filer 1985 York
CPVC piping systems have found wide use in many market segments due to its ability to meet a wide range of temperatures and pressure needs as well as excellent chemical resistance. Thermoplastic piping systems are capable of being the most cost effective solution to the problem of transporting corrosive fluids....
Author(s) : Godwin, Kilty, Matthews 1985 York
A programme of tests has been carried out to study the behaviour of bolted GRP pipe flanges under pressure. The influence of bolt tension has been established, and the information acquired in this way has been used to validate a Finite Element model of the flange. This model may be used to predict leakage behaviour of...
Author(s) : Pitman 1985 York
A relatively recent innovation in the field of plastic pipes and pipeline systems is the development of electro-fusion as a means of joining pipes and fittings. For this technique special fittings are manufactured which incorporate a heating element close to the surface to be welded. Welding takes place by locating...
Author(s) : Britton, Houseman 1985 York
British Gas has an interest in alternative pipework materials for wet central heating systems, and has been studying candidates, including a number of plastics, for more than 10 years. Performance requirements are outlined. A significant aspect is that of compatibility with other components of the system, and a novel...
Author(s) : Harnett, Wilson 1985 York
Notched ring sections of extruded pipe and injection moulded fittings have been tested to induce brittle failure which can be described by LEFM theory. Failure times have been measured at a range of applied stress intensity factors for each material tested at 23~C. The influence of processing, batch/batch variation...
Author(s) : Ifwarsson, Eriksson 1985 York
Hot water pipes made of cross linked polyethylene have been studied at Studsvik Energiteknik A6 since 1973. The work has mainly been concentrated to studying different evaluation and extrapolation methods. The results show that today the best method of lifetime extrapolation for hot water pipes is based upon...
Author(s) : Morgan 1985 York
During talks with personnel from Redlands Reinforced Piastics Ltd. (part of the Redland Group of Companies), the process of machining plastic reinforced pipe end-forms was discussed with a view to improving manufacturing efficiency. Traditionally Redlands manufacture 65% to 70% glass reinforced plastic pipes which...
Author(s) : Greig 1985 York
As polyethylene pipes increase in size above 250 mm, the avoidance of high-speed brittle fracture propagation becomes of overriding importance. More stringent operating and test pressures have had to be introduced. A full scale test programme on a variety of pipe sizes is being conducted by British Gas. In this paper,...
Author(s) : Lancashire 1985 York
In order to determine whether uPVC pressure pipe performance is affected by time in service, sections of uPVC water mains of ages up to 16 years have been exhumed and tested. From a combination of quality and mechanical property tests it is shown that initial pipe quality is the overriding influence in determining...
Author(s) : Eriksson, Ifwarson 1985 York
Since 1978 STUDSVIK has been testing a PEMoD-grade from Unifos Kemi AB for applications in the temperature range 30 - 60 C. The aim has been to study the long term properties of the material and thus to enable its life to be determined. Pressure testing has show; that the material is expected to last for 50 years at...
Author(s) : Alferink, Blom, Venema, Wolters 1985 York
Joints in PE casings of district heating pipelines are made by extrusion welding, butt welding or sleeves in which sealing is obtained by an adhesive. To set up guidelines for making these joints a lot of research has been performed, part of which is described in this paper. Joints of a good quality are obtained if...
Author(s) : Fischer, Worthberg 1985 York
Modern extrusion will in future mean computer control. Even the mere introduction of a microcomputer-based wall thickness measuring apparatus helps to save 1-2 % of material in pipe manufacture. Automatic centering of the die, in conjunction with wall thickness measurement and with gravimetric feed of the extruder,...
Author(s) : Lustiger, Markham 1985 York
In developing optimum polyethylene resins for gas distribution piping, it is important to maximize resistance to slow crack growth (SCG) which is the most common mode of material-related field failure in this application. It is proposed that SCG resistance is related to both tie molecule concentration and the...
Author(s) : Maine, Stafford 1985 York
Since 1969, when polyethylene pipe systems were first used to distribute gas in the U.K., the vast majority of joints have been constructed using heated tool fusion techniques. The jointing processes involved require a high level of operator participation. The paper describes the development of fusion jointing...
Author(s) : Bush, Harland, Bilgin 1985 York
In an earlier paper the principle of extruding short (c. 5 mm) glass fibre reinforced polypropylene in pipe form, using a rotating mandrel and stationery outer die, was described, together with the results shown in the first section of the Table below. Generally, desirable increases in both hoop strength and hoop...
Author(s) : van Dijk 1985 York
A method has been developed to obtain plane-strain fractures in ductile plastics materials. This was done by adhesion of stiff and hard layers to the free surfaces of 3-points bending samples. The plane-strain fracture toughness, K,., was derived from the force-displacement curves in two wad§ : via a finite elements...
Author(s) : Transue 1985 York
In the late 1960's and early 1970ts, polyethylene piping was gaining an early foothold in American gas distribution piping systems. Early usage centered around service lines as gas companies experimented with this new type of piping material. During this period there was little need for plastic valving as companies...
Author(s) : Ball 1985 York
Polybutylene's basic physical properties are briefly reviewed with reference to its unique balance within the range of polymers used in the production of plastic pipes. Pipe standards are discussed and examples given of pipe characteristics required to meet the recently introduced German DIN norm. Polybutylene's pipe...
Author(s) : Dilley 1985 York
The characteristics of PVDF are derived from its essential features. It is a semi-crystalline thermoplastic fluoropolymer This leads to the properties High burst resistance Long-term reliability - virtually no ageing Easy processability Chemical resistance No scaling 0 Service temperature up to 140 C Examination of...
Author(s) : Parker, Wydle) 1985 York
A small nunber of premture failures have occurred in PVDF pipe system carrying chlorimted mcals. A proposed explanation of such failures is that the observed deterioration in the physical properties of mF is a result of at-& by atanic chlorine produced under service conditions. Evidence is presented showing that...
Author(s) : Wolters 1985 York
The modified Robertson test is a test method by which ina rather simple and quick way crack arrest and (limited) crack propagation are distinguished, provided that crack speed over the crack length is measured. Rather large variations in rapid crack propagation (RCP) behaviour of different PE types have been found....
Author(s) : Moore, Prediger, Stephenson 1985 York
Fracture mechanics techniques are applied to UPVC pipe compositions in order to obtain quantitative and credible toughness results. The influence of polymer molecular weight and pipe age-in-service is then examined. The techniques are also applied to considerations of material toughness and pipe toughness. Plastics...
Author(s) : Thompson 1985 York
Over the past three years the Authority has been examining materials used for the laying of mains and services. With the introduction of MDPE to the Water Industry this has given the opportunity to examine this new material and compare i t with the more traditional pipelaying materials. In order to carry out this work...
Author(s) : Rice 1985 York
A market awaits the Plastics Industry with the renovation of deteriorating sewers. Plastic pipes feature strongly in small diameter renovation techniques. To successfully exploit this market it will be necessary for civil engineers to understand more about polymers and polymer...
Author(s) : Marshall, Birch 1985 York
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) : Koch, Meldt 1985 York
Trials to investigate the deformation and buckling behaviour of HDPE pipes with profiled outer wall and smooth bore are reported. Results show that the deformation and stability check can be carried out in the same way as for solid-wall pipes. However, an additional check on circumferential compressive stresses is...
Author(s) : Lowe, Marshall 1985 York
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) : Dibbo 1985 York
Thermoplastic valve design and moulding technology is a dynamic situation responding to market demands with new and improved products. The wide range of valves currently available in the different thermoplastics will be reviewed and compared. Particular emphasis will be given to actuation and control as well as...
Author(s) : Answell 1985 York
The electrofusion technique far polyolefins, and in particular, polyethylene pipe and system assembly has many advantages aver heated tool fusion or mechanical jointing methods of assembly, not least of...
Author(s) : Dukes 1985 York
The dynamic fatigue performance of a new high strength, oriented, uPVC (HSPVC) pressure pipe is compared to the conventional as-extruded uPVC product under similar test conditions. Results obtained by cycling the hydraulic pressure in lengths of standard production pipe and by applying cyclic circumferential tensile...
Author(s) : Parmar, Bowman 1985 York
The performance of aligned and controlled misaligned butt welds in 63 and 90mm polyethylene pipe systems was determined under fatigue loading conditions designed to induce brittle failure. The results showed a significant reduction in fatigue lifetime for butt welds having fractional misalignments greater than 10%...
Author(s) : Hooning 1985 York
The main characteristics of filament wound GRE (= glass reinforced epoxy) piping are discussed and some comparisons with other materials are made. It is conclud~d this system's excellent mechanical properties combined with its outstanding chemical resistance make it very suitable for all conditions where materials...
Author(s) : Lawrence 1985 York
Polyethylene gas supply systems are designed for a minimum of 50 years life, but as long term data, both laboratory and field is difficult to obtain, long term assessments are based on an extrapolation of Quality Control and other short term tests. An essential requirement is that Polyethylene should be highly...
Author(s) : Selwood, Parson, Gray 1985 York
The process of die-drawing has been investigated as a means of producing oriented polyethylene pipe. Two materials, one homopolymer and one copolymer, have been successfully drawn into pipe. When compared with isotropic pipes the oriented products exhibit enhanced mechanical and physical properties and produce a novel...
Author(s) : Brown 1985 York
Slow crack growth in polyethylene involves one of the most complex fracture processes in the field of fracture mechanics and especially; very little is known about the initiation mechanism. It is generally believed that there is a critical value of the stress intensity, K, below which crack growth does not occur in...
Author(s) : Rice 1985 York
The Polymer Engineering Directorate of SERC has piayed a major part in sponsoring research and development of plastics pressure pipe systems over the past eight years. Since its inception PED has been involved with both thermoplastic and GRP pipe programmes and to date has invested approx. £2 million of Government...
Author(s) : Sanders 1985 York
A surge in industrial development in Richards Bay over the past three years prompted the Government to establish the Nllatuze Water Board with powers to control water supply and effluent disposal over a 20 !a wide coastal strip stretching 50 km from Mtunzini in the south to Kwambonambi in the north. The applications...
Author(s) : Cooke 1985 York
There is now considerable pressure on pipe producers to improve efficiency and to automate to meet the ecconomic pressures that have increased over the past...
Author(s) : LeHunt 1985 York
The behaviour of UPVC pipes exposed to natural weathering for periods up to 51 months has been evaluated in terms of colour change, surface behaviour and low speed mechanical properties and the influence of CaCO,/Tj;0, substitution and gelation variations has been investigated within the programme. As part of a...
Author(s) : Murphy 1985 York
Author(s) : Mc Dowell 1985 York
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