Testing and Processing
Plastic Pipes Conference Association # 1979 Brigthon
A survey is given of suction press on PVC pipes Discussed are buckling of elastic materials, the deviations of existing theories occurring because of non circular, visco-elasticity of PVC, forced deformation and support of the soi 1 Some design criteria for short- and long-term loading are discussed.
Product characteristics such as permissible internal pressure and the resistance to soil loading have to play a part in the basic design of PVC transport pipelines Besides, particularly in the case of pipelines which are put out of use during certain periods the permissible internal depression must be taken into account On the one hand depressions of short duration could occur through water-hammer phenomena, while on the other hand it is also possible for (semi)-permanent depressions to occur through differences in elevation.
Little has been published with regard to the design criteria concerning the permissible depression, compared to that relating to positive pressurisation.
On the basis of an investigation on pipes overground a theory has been developed, according to which the permissible depression is derived from a stability criterion, for which pipe rigidity, creep properties (time) and pipe deformation are the most important parameters An assessment of the soil support, a pipe has underneath in practice is 1 ikewise undertaken.