Proper sizing balances flow performance with capital costs. Key considerations include:
This diagram illustrates how the three core disciplines of process piping design are integrated in a real-world engineering workflow:
Piping components like flanges, valves, and fittings are categorized into standard pressure classes according to (for sizes up to NPS 24) and ASME B16.47 (for sizes larger than NPS 24). Pressure Classes Proper sizing balances flow performance with capital costs
To ensure a seamless workflow from hydraulics to mechanical integrity, follow this engineering step checklist:
Compare with allowable ΔP. Adjust diameter if needed. Adjust diameter if needed
lbft3the fraction with numerator l b and denominator f t cubed end-fraction ). Crucial for pressure drop calculations.
t=PD2(SEW+PY)t equals the fraction with numerator cap P cap D and denominator 2 open paren cap S cap E cap W plus cap P cap Y close paren end-fraction = Pressure design thickness ( = Internal design gage pressure ( kPak cap P a = Outside diameter of the pipe ( t=PD2(SEW+PY)t equals the fraction with numerator cap P
The final pipe inside diameter (ID) is a function of the chosen schedule. This true ID is often different from the initial tentative ID used in the hydraulic calculation. The engineer must now re-run the hydraulic analysis (steps 1 and 2) using this final ID to confirm that the velocity and pressure drop are still acceptable. Only when both the hydraulic and mechanical requirements are satisfied is the design considered complete.
Size a carbon steel pipe for water flow Q = 150 m³/h (≈660 gpm), length 500 m, allowable ΔP = 250 kPa, T = 80°C.
Re=ρvDμ=vDνcap R e equals the fraction with numerator rho v cap D and denominator mu end-fraction equals the fraction with numerator v cap D and denominator nu end-fraction = Fluid density ( = Fluid velocity ( = Internal diameter of the pipe ( = Dynamic viscosity ( = Kinematic viscosity ( : Laminar Flow : Critical/Transition Zone : Turbulent Flow 2. Pipe Sizing Methodology and Criteria
hf=f⋅LD⋅v22gh sub f equals f center dot the fraction with numerator cap L and denominator cap D end-fraction center dot the fraction with numerator v squared and denominator 2 g end-fraction = Darcy friction factor = Length of the pipe = Inside diameter of the pipe = Fluid velocity = Acceleration due to gravity Finding the Friction Factor ( For , is solely dependent on the Reynolds number: For Turbulent Flow , depends on both and the relative roughness of the pipe (