I am determining the schedule for A106 Gr B Seamless pipe for the following conditions:
Operating Pressure: 70 bar
Temperature: 120 Farenheit
NPS: 3 inch
Service: Hydrogen
How may i convert my operating pressure into design pressure???
If 70 barg is the maximum operating pressure then it would not be unreasonable to add 10% to this to use as design pressure. But you need to evaluate with due consideration of the means of pressure control of the system, and whether upset conditions can peak above the stated operating pressure.
As a rule of thumb if the design pressure cannot be calculated by Process Engineer due to known conditions a figure of +25% of operating pressure is added as a safety factor and commonly this figure or another is stated in client specifications. If not stated anywhere client should be consulted.
You really need to include additional wall thickness for corrosion (internal and external)over the expected life and certain dynamic wave effects e.g. water hammer and (in some cases) bubble collapse. Develop and review a list of these possible internal and external dynamic effects. Also include factor for seamless pipe, and seam welded (or spiral welded) pipe.