Calculators›Gas Pipe Sizing
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Gas Pipe Sizing Calculator

Comprehensive Analysis · Erosional Velocity · MAOP Evaluation · ASME B31.3 & B31.8

Comprehensive Line Sizing Calculator
Evaluates optimal pipe size based on flow rate, pressure drop, velocity limits, and MAOP requirements. Compares multiple pipe schedules with economic analysis per API RP 14E and ASME B31.8 standards.

Flow Conditions

MMscfd
psig
°F

Design Parameters

psia
°F

Design Requirements

psig

Manufacturing Details

Note: For B31.8, tolerance is already included in design factor. This setting only applies to B31.3 calculations.

Calculated Parameters

Flow Analysis:
Actual Velocity (ft/s), Erosional Velocity Limit (API 14E), Reynolds Number, Friction Factor.
Pressure Design:
MAOP (Maximum Allowable Operating Pressure), Design Factor (F), Location Class.
Pipe Selection:
Optimum Diameter, Schedule (STD, XS, XXS), Wall Thickness, D/t Ratio, Pipe Weight.

📚 Learn the Theory

Understand flow equations, pressure drop, erosional velocity, and economic optimization

Read Engineering Guide →

📋 Calculation Methodology

Comprehensive Analysis

Evaluates all pipe size and material combinations simultaneously, analyzing both velocity constraints per API RP 14E and pressure requirements per ASME B31.3/B31.8.

Results show viable options ranked by safety margin, velocity status, and overall suitability for your application.

🔬 Key Formulas

Erosional Velocity (API RP 14E)
Ve = C / √ρ
C = Service constant (60-125)
ρ = Gas density (lb/ft³)
MAOP (B31.8)
P = (2St/D) × F × E × T
S = SMYS | F = Location factor | E = Joint factor | T = Temp factor
MAOP (B31.3)
P = 2SEt / (D - 2Yt)
S = Allowable stress | E = Joint factor | Y = 0.4 (ferritic steel <900°F)

⚠️ Important Notes

  • Uses real gas calculations with Papay compressibility correlation
  • Erosion Status Criteria:
    • Safe: V < 50% erosional limit AND < 50% critical velocity
    • Caution: V between 50-80% of erosional limit
    • Erosional Risk: V > 80% of erosional limit (API RP 14E)
    • Critical Flow Risk: V > 50% of sonic velocity
  • Manufacturing Tolerance: For B31.8, tolerance is already included in design factors (F). For B31.3, 12.5% tolerance is applied per code requirements
  • D/t ratio limited to 96 per ASME B31.8
  • Results are for preliminary design - verify with licensed engineer

Standards & References

  • API RP 14E
    Erosional Velocity Guidelines
  • ASME B31.3
    Process Piping
  • ASME B31.8
    Gas Transmission Systems
  • CFR 49 Part 192
    Pipeline Safety Standards

Frequently Asked Questions

How do you calculate gas pipe size?

Gas pipe size is calculated by determining the minimum diameter required to handle the flow rate without exceeding velocity limits (erosional velocity) or pressure drop constraints. This calculator iteratively checks standard pipe sizes against API 14E and ASME B31.8 standards.

What is erosional velocity in pipelines?

Erosional velocity is the flow speed at which the gas stream may begin to erode the pipe wall. Per API RP 14E, it is calculated as Ve = C / √ρ, where C is a service constant (typically 100 for continuous service) and ρ is gas density.

What is the difference between ASME B31.3 and B31.8?

ASME B31.3 covers Process Piping (refineries, chemical plants, compressor stations), while ASME B31.8 covers Gas Transmission and Distribution Piping Systems. This calculator supports both standards for MAOP verification.

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