The final step is selecting a standard commercial pipe schedule (e.g., Schedule 40, Schedule 80, Schedule 160) that meets or exceeds this nominal value. 4. Fitting and Valve Losses (Minor Losses)
A typical Module 3 problem will give:
Piping components must safely contain internal pressure without yielding. Wall thickness calculations are strictly governed by industrial design codes. Codes and Standards Overview
) is the sum of frictional losses in straight pipes and minor losses in fittings/valves. Frictional Loss (Darcy-Weisbach Equation)
What are you sizing for (e.g., liquid water, steam, hydrocarbons)? The final step is selecting a standard commercial
The primary equation for frictional pressure drop is:
Identify fluid properties, mass flow rates, operating temperatures, and maximum operating pressures.
The behavior of fluid in a pipe depends heavily on the Reynolds Number (
In process plants, piping networks are the lifelines that transport fluids between equipment. Designing these systems requires a precise balance of fluid mechanics, mechanical strength, and safety compliance. The primary equation for frictional pressure drop is:
t=P⋅Do2(S⋅E⋅W+P⋅Y)t equals the fraction with numerator cap P center dot cap D sub o and denominator 2 open paren cap S center dot cap E center dot cap W plus cap P center dot cap Y close paren end-fraction = Pressure design thickness ( = Internal design gage pressure ( MPacap M cap P a Docap D sub o = Outside diameter of pipe (
Piping must be designed to withstand the "most severe condition" of coincident internal/external pressure and temperature.
): Flow fluctuates between laminar and turbulent conditions. Turbulent Flow (
Understand when you can exceed design pressure (e.g., 33% for short durations) per code standards. 3. Critical Design Considerations 🔍 and pharmaceutical plants).
= Wall thickness coefficient (dependent on material type and temperature) Pipe Schedule Selection Once the minimum thickness (
| Fluid Type | Velocity Range (m/s) | Velocity Range (ft/s) | |------------|----------------------|------------------------| | Pump suction (low NPSH) | 0.6 – 1.5 | 2 – 5 | | Pump discharge (general) | 1.5 – 3.0 | 5 – 10 | | Steam (low pressure) | 20 – 40 | 65 – 130 | | Compressed air | 10 – 25 | 33 – 82 | | Erosive fluids (slurries) | < 3 | < 10 | | Corrosive fluids | < 1.5 | < 5 |
(sizing) and how design pressure and temperature dictate the wall thickness (pressure rating). 1. Hydraulic Pipe Sizing
| NPS | OD (in) | Sch 40 ID (in) | Sch 80 ID (in) | Sch 160 ID (in) | |-----|---------|----------------|----------------|------------------| | 2 | 2.375 | 2.067 | 1.939 | 1.687 | | 4 | 4.500 | 4.026 | 3.826 | 3.438 | | 6 | 6.625 | 6.065 | 5.761 | 5.187 |
Apply the continuity equation to find the initial inside pipe diameter.
Process Piping (Refineries, chemical, and pharmaceutical plants).
