Workshop # 1998 Gothenburg
Jointing Methods for Plastics Pipeline Systems AL Headford (Durapipe S & LP, UK) ee Introduction The basic requirements for pipe Jointing are common to all pipe systems made from any material (including traditional materials), whether they be for sealed pressure usage or non-pressure usage. These are
a) minimal detrimental effect on the performance of the remainder of the system, and b) acceptable cost :a) Minimal detrimental effect on the overall pipe system, in terms of key properties, embracing factors such as the following :
- life expectation
- physical strength
- resistance to internal pressure
- handling and flexibility
- resistance to physical abuse
- able to accept expansion / contraction / axial loading - forces / movement
- influence on flow properties
- influence on fluid quality
- chemical resistance and corrosion
b) Optimum cost combination of any materials or components plus labour.
For example : - component or material cost
- associated assembly equipment costs - ease of use
- time for assembly / make-up
- skills / training requirements
- traceability / ownership cost
- reliability / quality
- replacement / repair cost
- transport costs
- health and safety considerations -environmental effects For different pipe materials, types of pipe system, and operational conditions, some of the above factors will be more important than others, and this will influence the choice of jointing method.
However there are fundamental reasons why certain jointing methods are the norm for particular pipe materials.
A limiting factor, influencing the choice of jointing metnod, comes into place when it is necessary to connect together entirely different types of materials, for example thermoplastics to metals, when fusion is not feasible. In these cases mechanical methods are used (adhesive bonding is also possible but rarely favoured — except for GRP).
Author(s) : Shepherd, Headford, Jordan, Reeves, Walton
In Europe polyethylene (PE) has been chosen almost exclusively for gas mains for many years because of economic, technical and safety reasons but in the water industry a number of different materials are still used for pressure water mains. Indeed at sizes above 355mm (14 inch) most new large diameter water mains are...
Author(s) : Headford, Hill, Wilson
The United Kingdom is the most highly developed PE pressure pipe market in the world. Following pioneering work done in the USA and Germany, it was the UK that was first to adopt PE on a large scale for gas, and then for water distribution. The 100% PE policy of British Gas, and wide range of sizes used (at low...
Author(s) : MacKellar, Headford, Ingham
This paper provides an overview of the basic properties of plastic pipes, in the range 50mm to 400mm, and how these should be used in the design of above ground process pipe systems made of PE and PVC. It covers the basic properties of plastics, examples of the determination of load cases and describes the basic types...
Author(s) : Hill, Wilson, Headford
Butt fusion welding is the most reliable and unobtrusive method of joining PE pipes (and spigot fittings) of virtually any size-except perhaps the smallest where other methods are usually preferred. It is the dominant method of jointing both medium and large pipe sizes, but for different reasons. In medium pipe sizes...
Author(s) : Headford
A novel polyethylene stub flange adaptor is described which allows size-for-size connection, in terms of the respective bores, to iron pipes or fittings. The end load performance of this product is significantly superior to that achieved with conventional polyethylene flanges, especially at large pipe diameters, and...
Author(s) : Boot, Headford
This paper summarises current design practices for buried thermoplastic pipelines subjected to combined gravity and internal pressure loadings. It suggests that accurate predictions of stabilised deformations are neither possible nor necessary, but that appropriate structural design methodologies should instead...
Author(s) : Beech, Headford, Hunt, Sandilands
The guldeUnes g h n in BS CP 312 :Pwt 2 : 1973 w e recommended to the UK toater industryfor the deslgn of polyethylene pfpeline systems to toke inin account the effects of tmnsient [surge) pressurejluctuatlons with respect to fatigue (ref.1). These guIdelInes we based on earlier experience wlth PVC-Usewer h i n g...