Laboratory evaluation of plastic pipe from a gas service field‐test installation

Abstract

his paper presents the background and the results of T the first two years of a long-term field exposure of various types of plastic pipes in a gas-distribution system. The study is part of a program to establish the suitability of plastic pipes for gas-distribution uses. The work was initiated at Battelle in 1960 by the American Gas Association for the purpose of developing improved plastic pipe for gas-distribution service. It was soon apparent that, before an improved plastic pipe could be developed, the limitations of existing pipes had to be defined. The methods for defining these limitations ultimately became a major part of the program at Battelle. Information resulting from an earlier study at Battelle for the Thermoplastics Pipe Division, now the Plastic Pipe Institute of the Society of the Plastics Industry, Inc., indicated that the establishment of the long-term stress-rupture behavior with natural gas would be needed to demonstrate the potential use of plastic pipes for this application. This study became the major part of the laboratory work. Subsequently, however, it was deemed necessary to investigate other methods of evaluating plastic pipe that would be useful to the gas-distribution industry for detecting changes in mechanical properties. Thus, a considerable part of the program was involved in the development of test methods that could be used in defining those parameters of interest to the gas industry. A greater understanding of fatigue, permeability of the pipe, as well as resistance to impact, aging, and the effects of environments were some of the objectives of the laboratory work.Editor's Note: Actual tabular data used to construct graphs nre available from authors upon request. 111 the course of this work, the long-term stress-rupture tests with natural gas showed that the behavior with gas was essentially equal to that with water. The fatigue study showed that secondary stresses that might be encountered in the use of plastic pipe for gas distribution were not likely to be a serious factor in its long-term performance, provided the pipe was properly installed. The permeability studies demonstrated that none of the plastics currently used in the program would be expected to be eliminated as a potential material because of its permeability.About mid-1962, the activities of the A.G.A. Subcommittee on Plastic Pipe Standards revealed that several serious operational failures had occurred with plastic pipe in the gas-distribution industry. Most of these failures could be attributed to faulty installation but, in at least three serious failures, the plastics themselves appeared to be a factor. About this time, laboratory studies indicated that the fracture behavior of the pipes in the stress-rupture testing varied with both the stress-rupture life and temperature of the test. After available information on the three field-failure incidents was examined, it was concluded that the failures were aggravated by the presence of constituents other than methane in the gas. However, it was recognized t...

Effect of Inner Cavity’s Gas Flow Rate on the Extrusion Forming of Plastic Micro-Pipe

“…Plastic micro-pipe [1] is a kind of important plastic product mainly applied into the medical diagnosis. In general, plastic micro-pipe can be produced by the continuous extrusion forming [2,3] in the production line. Since there a hollow cavity existed in the plastic micro-pipe, the mandrel should be designed and manufactured in the extrusion die of plastic micro-pipe [4].…”