Manifold

Barlow's formula, t = PD/2S, is a simplified calculation that relates the thickness to the pressure, diameter, and allowable stress of the pipe material. The length is irrelevant unless thermal expansion/contraction are in play. The allowable stress is the material's tensile strength divided by the safety factor, which is often 5:1 for pipe, but may vary with the service.

thanks the material in this case will be just ordinary carbon steel

If it's A-53B (or API 5L) pipe, I think the tensile stress is 55,000 psi. If the safety factor is 5:1, the allowable stress S would be 11,000 psi. I haven't checked these figures recently, so this is just for illustration.

Use any pipe schedule for >7 barg at that diameter.

The thickness will be given in the tables schedule.

70m ≈ 230ft ≈ 100psi ≈ 6.81bar; thus the 7bar figure is a good choice.

If it's metal pipe - e.g. steel or ductile iron - at 70m head the pipe wall stress is negligible, even for 1200mm dia. If wall is 5mm thick stress is only 84MPa.

More of an issue are the pipe connections, correct flange rating and take account of thrust forces if pipe couplings (VJ, Teekay) are used.

Cheers..........Codey

Gibson,

Since this obviously, is the first piping system you have ever designed, I suggest that you should hire a piping design engineer.

This is large pipe, under pressure and a lot of money can be wasted and people could be hurt

Have the piping engineer design the system in accordance with a Design Code ( just like the way buildings are designed) ensure that the system is fabricated, inspected and tested in accordance with that code. Have the newly-hired piping engineer develop an inspection and installation plan. Design and/or select pipe supports. consider internal/external coatings for you carbon steel piping system

Develop dimensioned drawings and make as-builts.

Consider valve selection, instrumentation in your design.

You can use the formula of ASME B31.3 to calculate the pipe wall thickness, t = P D/2 (SE+PY). Please find attached herewith an excel spread sheet, showing use of that equation, just substitute for parameters for a carbon steel pipe material like A106 Grade B or API 5L or A53 Grade B: ASME_B313_Calculator.

Note. Take into consideration that the example was done for stainless steel pipe material A312 Gr TP310, and not carbon steel as required for your case.