APPENDIX D – Wave Speed
Surge Analysis and the Wave Plan Method
Supplementary Material: Example Problems and Solutions
Appendix D – Problem 9
D.9 Thousands of pipe-burst events are reported each year in US and Canadian water utilities (see Section 2.3). You were asked to do a surge analysis study for one such water utility.
After a thorough investigation into the existing steady state model, you realized there were several burst events in a certain pressure zone that has predominantly low-celerity PVC and HDPE pipes, and that the utility has replaced short sections of burst-pipe with metallic pipes. For example, a 3m section of burst PVC pipe was replaced by a 3m section of DI pipe of roughly the same internal diameter.
Though this was marked as a note on the corresponding model pipe element, the model itself was not updated to reflect the change in pipe material. That is, if a small pipe section PVC pipe on a 200m long pipe element between two junction nodes was replaced by a DI pipe, the pipe element in the model was NOT split into 3 different elements (one shorter DI pipe element sandwiched between two longer PVC pipe elements). Instead, it remained as one 200m long PVC pipe element with a note indicating that there was a pipe burst event and a small section of pipe was replaced with DI pipe. This was done to reduce the complexity of the model. Besides, it was determined that such changes have practically no effect on steady state and quasi-steady state model results.
Would it be necessary to update the model by carefully dividing the longer pipe elements into multiple elements accounting for all sections of replaced pipes, for dependable surge analysis results?
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