Once a DR or Pressure Class has been selected following the pressure design checks, this calculator determines cyclic life of PVC pressure pipe from recurring surge pressures. This was developed based on recent fatigue research by Utah State University. Information on theory of PVC fatigue life can be found by clicking here. Click here for the PVC Forcemain Design Guide (update coming soon).
The user can perform transient modeling to determine peak recurring surge pressures and minimum recurring surge pressures. Hand calculations may be used to approximate these values; existing literature on calculating surge pressures may be used. Note, these maximum and minimum values are based on the surge envelope, not maximum and minimum pressures along the grade line. The average number of surge occurrences per day can be found from knowing pump operations or knowing pump cycle time. An example of using transient model is shown below:
Data from pressure monitoring, along with the average number of surge occurrences per day, can be entered to determine the remaining cyclic life.
Some pipelines may experience multiple transient events with different surge values (ex: multiple pump operations, downstream valve operations). Whether transient analysis or pressure monitoring is performed, different surge values can be added or removed by clicking the “Add Surge Pressure” or “Remove Surge Pressure” button.