The Industry-proven tool for determining retirement limits of process piping.
Introduction
Many oil and gas companies are faced with maintaining 10,000+ miles of 100+ year old piping networks supporting multi-billion dollar/year processing operations. There is rarely a simple solution to immediately shutdown a process pipe - as these shutdowns more often than not impact other units and cost companies millions in time and resources.
In mechanical integrity engineering, we are frequently asked the hard question - do we have to shutdown the pipe immediately, or do we have time? Pipe retirement requires rigorous analysis. You must find the perfect balance - such that one isn't squandering company time/resources but also holding personnel safety paramount.
This is more than a python package, it is a comprehensive engineering decision support system for critical infrastructure safety and operational continuity.
The Challenge
Cross-section of Pipe Wall Thinning Over Time
Every day, mechanical integrity engineers face decisions that can cost millions of dollars or risk catastrophic failure. When a pipe shows signs of thinning, the clock starts ticking. You need answers fast:
- Can this pipe continue operating safely?
- How much time do we have before retirement is mandatory?
- What are the consequences of immediate shutdown vs. continued operation?
- How do we balance operational continuity with personnel safety?
These aren't theoretical questions - they're real decisions that affect production, safety, and the bottom line. TMIN was built by engineers, for engineers, to provide the analytical rigor needed for these critical decisions.
Understanding Pipe Retirement Limits
Imagine a pipe wall gradually thinning over a 10-year span, slowly approaching a critical red line - the retirement limit. This is the minimum acceptable wall thickness that ensures safe operation. When the actual thickness hits this line, the pipe must be retired or replaced immediately.
The Two Minimum Thickness Requirements
Pipe design involves two distinct minimum thickness calculations. The pressure design minimum ensures the pipe can contain internal pressure safely using ASME B31.1 equations that consider design pressure, temperature effects, and material properties. The structural minimum ensures the pipe can support its own weight and external loads according to API 574 Table D.2 requirements, which becomes critical for per-code pipe spans. However, this package does not account for fluid weight, insulation, heat tracing equipment, pipe hangers, and other per-application basis.
The limiting thickness is whichever of these two values is more restrictive. TMIN automatically determines which factor controls your design and provides clear guidance on current status, remaining life, and required actions.
Corrosion Allowance and Remaining Life
The difference between your actual thickness and the retirement limit is your corrosion allowance - essentially your safety margin. This allowance, combined with your known corrosion rate from inspection reports, determines how much time you have before retirement becomes mandatory.
This analytical approach transforms the complex retirement decision into a clear, data-driven process that balances operational needs with safety requirements.
Overview
TMIN is a sophisticated pipe thickness analysis tool designed for mechanical integrity engineers, reliability specialists, and operations teams in the oil and gas industry. It provides automated analysis of pipe wall thickness against multiple design criteria and generates professional reports with actionable recommendations.
Example Output of Reports and Visuals
A folder called "Reports" will be automatically generated in the user's root directory and populated with .txt reports and helpful visualizations of the TMIN analysis. The report will show both the measured thickness, the inspection year, and the calculated present-day thickness.
All files are automatically named with timestamps:
Reports/
├── 20250712_181928_TMIN_report_TMIN_20250712_181928.txt
├── 20250712_181928_TMIN_summary_20250712_181928.txt
├── 20250712_181928_thickness_analysis_number_line.png
└── 20250712_181928_thickness_comparison_chart.png
The comparison chart displays a bar chart comparing all relevant thickness values (measured, pressure design minimum, structural minimum, and retirement limits) to quickly identify which factor controls the pipe design.
Install
It is recommended to use a virtual environment:
python -m venv venv
source venv/bin/activate # On Windows use: venv\Scripts\activate
Then install TMIN with pip:
pip install tmin
How It Works: Time-Based Corrosion Adjustment
TMIN allows you to supply both the measured thickness and the year that measurement was taken. If you also provide a corrosion rate (in mpy), TMIN will automatically calculate the present-day (current) thickness by accounting for the metal loss since the last inspection.
Calculation:
present_day_thickness = measured_thickness - (corrosion_rate × years_elapsed × 0.001)
measured_thickness: The thickness measured during the last inspection (inches)corrosion_rate: Corrosion rate in mils per year (mpy)years_elapsed: Years since the inspection (current year - inspection year)0.001: Conversion factor from mpy to inches per year
If you do not supply an inspection year or corrosion rate, TMIN will use the measured thickness as the present-day thickness.
Example
Run as a CLI Tool
tmin
Follow the prompts to analyze your pipe and generate reports. You will be asked for:
- Measured thickness during inspection (inches)
- Year when thickness was measured (e.g., 2022)
- Corrosion rate (mpy, optional)
TMIN will calculate the present-day thickness and use it for all analysis and reporting.
Or Use as a Python API
from tmin.core import PIPE
# Create a pipe instance
pipe = PIPE(
schedule="40",
nps="2",
pressure=50.0,
pressure_class=150,
metallurgy="CS A106 GR B",
corrosion_rate=10.0 # mpy (optional)
)
# Analyze with time-based corrosion adjustment
results = pipe.analysis(measured_thickness=0.060, year_inspected=2023)
print("Present-day thickness:", results["actual_thickness"])
# Generate full report with visualizations
report_files = pipe.generate_full_report(measured_thickness=0.060, year_inspected=2023)
Industrial Standards Featured
Pressure Design (ASME B31.1)
- Calculates minimum wall thickness for pressure containment
- Considers temperature effects via WSRF (Weld Strength Reduction Factor)
- Uses Y-coefficient for high-temperature applications
Structural Requirements (API 574)
- Evaluates minimum thickness for structural integrity
- Considers pipe deflection and weight loading
- Based on API 574 Table D.2 requirements
Retirement Limits
- API 574 Retirement Limit: Code-mandated minimum thickness
- Table 5 Retirement Limit: Company-specific maintenance limits
- Custom Limits: User-defined retirement criteria
Corrosion Analysis
- Life Span Prediction: Based on corrosion rate and thickness excess
- Corrosion Allowance: Thickness above retirement limits
- Monitoring Recommendations: Inspection frequency guidance
Supported Pipe Specifications
Schedules
- 10, 40, 80, 120, 160
Nominal Pipe Sizes (NPS)
- 0.5" to 24" (varies by schedule)
Pressure Classes
- 150, 300, 600, 900, 1500, 2500
Metallurgies
- CS A106 GR B (Carbon Steel)
- SS 316/316S (Stainless Steel) - Coming Soon
- SS 304 (Stainless Steel) - Coming Soon
- Inconel 625 (Nickel Alloy) - Coming Soon
Testing
Run the comprehensive test suite:
python -m pytest tests/test_core.py -v
The test suite includes:
- Basic analysis functionality
- Time-based corrosion adjustment
- Report generation
- Multiple pipe scenarios
- Corrosion rate analysis
- Edge case handling
Contributing
This project is designed for the mechanical integrity engineering community. Contributions are welcome, especially for:
- Additional metallurgy support
- New retirement limit standards
- Enhanced visualization features
- Additional analysis criteria
License
MIT License
Disclaimer
TMIN is a decision support tool designed to assist qualified engineers in making informed decisions about pipe integrity. It should be used in conjunction with professional engineering judgment and should not be the sole basis for critical safety decisions. Always consult with qualified personnel and follow applicable codes and standards.
