Asset Integrity ManagementOct 2025
Risk Assessment for GTM CNG Storage Module
A technical risk assessment for a 10-feet CNG transport module, focused on composite-cylinder integrity, corrosion exposure, and inspection strategy.
Executive Snapshot
A faster way to understand the engagement
Project Overview
What this project covered
This assessment addressed the operating risk of a Gas Transport Module (GTM) using composite Type 2 cylinders for compressed natural gas storage. The work reviewed design basis, applicable standards, likely degradation modes, and inspection strategy to provide clearer integrity visibility for repeated transport and operating cycles.
Technical Facts
Structured data pulled from the project basis
Cylinder TypeType 2
Liner Material30CrMo Steel
Wrap MaterialGlass Fiber
Hydrotest Pressure375 bar
Actual Head Thickness7.11 mm
Minimum Thickness6.10 mm
Work Scope & Method
How the assignment was executed
Verify design and inspection data
The risk study started by validating design references, wall-thickness records, field observation notes, and the GTM 10-feet technical layout.
Apply RBI Level 1 logic
The report evaluates the module using API RP 581 Level 1 by combining damage factor, generic failure frequency, management factor, and area-based consequence.
Translate results into inspection planning
The technical output was converted into focused inspection scopes for head areas, exposed zones, and composite-wrap condition monitoring.
Context and delivery pressure
The system combined metallic and composite components, which meant the assessment had to account for different degradation mechanisms, inspection access limits, and operating realities without oversimplifying the actual risk picture.
How the work was structured
We structured the analysis around risk categorization, head-area corrosion exposure, composite wrap condition awareness, and interval recommendations so the client had a practical inspection and monitoring basis for continued operation.
Key Findings
Important technical takeaways
The main technical concern is concentrated at the cylinder head
The report points to thinning and atmospheric exposure at the head area as the primary technical risk, while the shell is protected by composite wrap.
No major damage indication was found during inspection
The module still operates at 250 bar with measured thickness above the design minimum and without significant physical damage noted during inspection.
Deliverables
Key outputs from the engagement
- 01Design basis and standards review
- 02Risk category and integrity summary
- 03Inspection interval recommendations
- 04Condition monitoring recommendations
Recommendations
Practical follow-up priorities
Keep operating pressure at or below 250 bar according to the design basis.
Perform UT inspection on the cylinder head at a maximum interval of 4 years.
Run visual and tactile inspection on the wrap shell to detect abrasion, delamination, or transport-related damage.