CNG Fuel System Inspection Requirements

Inspection Intervals Defined by Code:  3 Years/36,000 miles/After Any Fire/After Any Accident

  • Federal Motor Vehicle Safety Standards (FMVSS) Standard 304 requires that CNG cylinders be inspected every three years or 36,000 miles, whichever comes first, or after any accident or fire.
  • ANSI NGV-2 also requires CNG cylinders to be visually inspected at least every three years or 36,000 miles.
  • Manufacturers may have inspection intervals that are more frequent.

Four Types and Intervals for Inspections

Inspection TypeWhen Performed?Inspection LevelWhat is Inspected?Who Performs?
Pre-Service InspectionPrior to placing vehicle in serviceDetailed Visual InspectionThorough inspection of all high pressure components, including cylindersA certified or qualified CNG Fuel System Inspector
Driver Pre- and Post-Trip InspectionBefore and after each trip in a CNG vehicleCursory Visual InspectionAll visible components and cylinder shieldsDriver
General Visual InspectionDuring any preventive maintenance/serviceGeneral Visual InspectionAll visible components, with special attention to cylinder shieldsTrained Vehicle Technician
Detailed Visual InspectionAt manufacturer’s specified intervals, or 3 years/36,000 miles (whichever comes first); after any fire or accidentDetailed Visual InspectionThorough inspection of all high-pressure components, including cylindersA certified or qualified CNG Fuel System Inspector

What Is Covered in the Detailed Visual Inspection?

In 2008, the NGV industry adopted a best practice to inspect not just the cylinders, but the entire high pressure CNG fuel system.  This includes:

 

  • Fuel Receptacle
  • Secondary Check Valve
  • Defueling System
  • Fittings, Tubing and Lines
  • Cylinder(s)
  • Cylinder Shields and Mounting System
  • Cylinder Valves
  • PRDs, Vent Lines and Caps
  • Fuel System Isolation Valve
  • High Pressure Coalescing Filter
  • Fuel Shutoff Solenoid
  • Pressure Gauge
  • Pressure Regulator
  • Components/Labels

What Records are Required?

For each Detailed Visual Inspection, a completed CNG Fuel System Inspection form and accompanying photos should be retained.  Inspection records are not required to be submitted to any regulatory agency or manufacturer.

At the conclusion of each Detailed Visual Inspection, a “Passed” or “Failed” inspection label should be affixed to each cylinder installed on the vehicle.  

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