Module 3 Process Piping Hydraulics Sizing And Pressure Rating: Pdf [updated]

This guide is structured to serve as a study outline or a technical summary for engineers and designers.

3.2 Economic Pipe Diameter

Use pressure drop per 100 m (e.g., 200–500 Pa/m for liquids). Oversizing → high capital cost; undersizing → high pumping cost.

2. Pipe sizing methods

Objective: choose pipe diameter to meet required flowrate with acceptable pressure drop, velocity limits, and economic considerations. This guide is structured to serve as a

3.2 Wall Thickness Calculation (ASME B31.3, Eq. 3a)

For straight pipe under internal pressure:

[ t = \fracP \cdot D2(SEW + PY) ]

Where:

• ( t ) = minimum required wall thickness (inches or mm)
• ( P ) = internal design pressure (psig)
• ( D ) = outside diameter of pipe (in)
• ( S ) = allowable stress from ASME B31.3 Table A-1 (psi)
• ( E ) = quality factor (1.0 for seamless pipe; 0.85 for ERW)
• ( W ) = weld joint strength reduction factor (usually 1.0)
• ( Y ) = coefficient for wall thickness (0.4 for ferrous materials up to 900°F)

After calculating ( t ), add:

• Corrosion allowance (often 1/16" to 1/8")
• Manufacturing tolerance (e.g., -12.5% for seamless)

Then select the nearest schedule number (Sch 10, 40, 80, etc.) such that the nominal wall thickness ≥ calculated.

3. Pipe Sizing

Sizing is the intersection of hydraulic requirements and economic optimization. ( t ) = minimum required wall thickness

3. Pipe Sizing Methodology

Pipe sizing is an economic decision. A smaller diameter pipe costs less to purchase and install but incurs higher pumping costs (high friction). A larger diameter pipe costs more upfront but reduces operating costs.