Module 3 Process Piping Hydraulics Sizing And Pressure Rating Pdf Better | 2026 Update |

= Mechanical allowances (sum of corrosion allowance, erosion allowance, and thread depth). ToleranceTolerance

Once you know the size, you must ensure the pipe won't burst under pressure. This is where and Wall Thickness calculations come in, primarily governed by codes like ASME B31.3 (Process Piping). The Barlow’s Formula

= Darcy friction factor (determined using the Moody Chart or the Colebrook-White equation) = Length of the pipe = Acceleration due to gravity Minor Losses in Fittings and Valves

t_min = (P × D) / (2 × (S × E + P × Y)) = Mechanical allowances (sum of corrosion allowance, erosion

In industrial process plants, the vast majority of hydrocarbon, water, and chemical flows operate deep within the turbulent regime (

Sizing a piping system is primarily driven by two factors: and allowable pressure drop .

For non-corrosive water, max velocity = 15 ft/s → OK. The Barlow’s Formula = Darcy friction factor (determined

Sudden valve closures or pump trips cause rapid velocity changes, creating high-pressure shockwaves. Water hammer can rupture pipes, strip hangers, and smash instrumentation. Mitigations include slow-closing valves, surge tanks, and pulsation dampeners. Two-Phase Flow Sizing

A superior Module 3 includes a trade-off matrix showing that sometimes going up one NPS size but down to Sch 10 (stainless) is cheaper than forcing Sch 80 through a smaller bore.

Engineers generally follow this five-step sizing methodology: Step 1: Establish Fluid Properties and Operational Criteria Water hammer can rupture pipes, strip hangers, and

| Flow (gpm) | Velocity (ft/s) | Recommended Schedule 40 Pipe (in) | |------------|----------------|------------------------------------| | 20 | 4.5 | 1.5 | | 50 | 5.0 | 2 | | 150 | 6.0 | 3 | | 300 | 7.0 | 4 | | 600 | 8.0 | 6 |

When liquid velocity increases drastically (e.g., across a control valve), local pressure can drop below the fluid's vapor pressure, causing vapor bubbles to form.

Once the diameter is set, the piping must be "rated" to ensure it can safely contain the internal pressure without bursting.