David Becerril García, Jacinto Cortés-Pérez, Ian D. Moore
Papers # 2016 Berlin
Joint performance of joints in gravity flow buried pipelines is very important since joint failure could produce structural or service limits to the system. Standards have been developed to evaluate that joints have the necessary structural and leakage capacities which specify test methods that are not clear and do not seem to evaluate real conditions. In this paper the test methods specified by a European and an American standard are presented and discussed. Then their tests are compared with results of large scale laboratory tests and from simplified design equations. Finally, test methods for plastic pipe joints intended for gravity flow applications are proposed along with a testing apparatus.
SEVERAL AUTHORS HAVE POINTED OUT THAT THE PERFORMANCE OF JOINTS IN BURIED PIPELINES EMPLOYED IN GRAVITY FLOW APPLICATIONS IS VERY IMPORTANT, SINCE JOINT FAILURE CAN PRODUCE STRUCTURAL OR SERVICE LIMITS TO THE SYSTEM, REDUCING ITS LONGEVITY. TO VERIFY THAT JOINTS HAVE THE NECESSARY STRUCTURAL AND LEAKAGE CAPACITIES, STANDARDS HAVE BEEN DEVELOPED WHICH DEFINE TESTS TO EVALUATE JOINT PERFORMANCE FOR SEVERAL PIPES AND JOINTS. NONETHELESS SOME OF THE TEST METHODS AND CONDITIONS SPECIFIED IN THESE STANDARDS ARE NOT CLEAR, AND DO NOT SEEM TO EVALUATE REAL CONDITIONS.
This paper discusses the methods and conditions specified by the UNE-EN-1277 and the ASTM D3212 standards for testing leaktightness of joints in plastic pipes that feature elastomeric seals employed in gravity flow applications. The selection of the standards was made since the Mexican norm NMX-E-205 specifies two methods based on these procedures. The discussion focuses on a comparison made between the conditions evaluated in the European and American standards and addresses the sequence and the manner in which these conditions are imposed to the system. Furthermore, the conditions examined in the standards are compared with the demands observed in large scale laboratory tests on buried pipes, and with the demands calculated employing analytical methods when the jointed pipeline is subjected to earth and live loads. Finally, the paper proposes alternative test methods and devices for evaluating the structural and hydraulic performance of joints in plastic pipes, based on tests performed employing a testing apparatus that generates joint demands similar to those observed in the buried pipe tests under internal and external pressures.