Plastic Pipes Conference Association # 1979 Brigthon
The properties of HDPE pipe materials necessary to satisfy processing and performance requirements are considered. Methods of predicting pipe performance are discussed, and experimental data are presented to support the predictive technique.
High density polyethylene is now well established as one of the major materials for pipe systems.
The term high density is being used here to describe the rigid polyethylenes and includes the medium density materials introduced more recently. HDPE has been used for more than 20 years in a wide variety of applications ranging from pressure pipe in water distribution schemes and chemical plant to very large diameter non pressurised drain and effluent pipe installations. PE pipe is, however, still very much a growth industry as shown by the rapid development in recent years of MDPE pipe systems for natural gas distribution.
In the early days the design of pipe systems was based largely on empirical relationships obtained from pipe pressure tests. Nevertheless, these ideas have proved to be soundly based, as can be seen in the many successful, diverse applications. Today however there is emerging a better understanding of material properties. and design methods and this seems a good time to review the current state of knowledge on the selection and tailoring of PE materials and the design of pipe systems. This better understanding is vital to the development of markets for PE materials in the more demanding applications such as gas distribution now and in the future.
For many years too, it has been recognised that articles in plastics should be rationally designed in the same way as in traditional engineering materials. Pipe systems are one of the first applications where plastics are load bearing for much of their life and the design principles available for pipe systems should serve as a model for other applications of plastics materials.
Author(s) : Gray, Powell, Bonner
Aliphatic polyketones are a family of polymers prepared by the polymerisation of olefins and carbon monoxide in a perfectly alternating sequence. BP Chemicals produces these materials using a proprietary palladium catalyst in a continuous polymerisation process. They are crystalline thermoplastics which offer a unique...
Author(s) : Selwood, Parson, Gray
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) : Gray, Frye
Long term failure of plastics pipes is governed by very slow crack propagation. Assessing pipe materials' resistance to this slow growth is time consuming and in the case of recent very tough medium density polyethylenes is difficult using constant load tests. It is shown that fatigue tests can achieve comparative...
Author(s) : Gray
Pipework constructed in glassfibre composites is now used in many Process Industries. The design methods derived for these materials have shown that they exhibit characteristics not usually considered in general engineering design. These concepts are briefly described together with their relevance in the overall...
Author(s) : Gray
The Paper considers some of the fundamental problems in the design of reinforced plastics, out lining the major engineering concepts which are applied when designing pipework, or plant in such materials. To be able to demonstrate the major differences between conventional materials and reinforced plastics, the...