CNG Fleet Safety Depends on These 2 Inspections
Compressed natural gas (CNG) vehicles are engineered with high-pressure fuel systems that must meet the appropriate industry codes and standards. Their level of complexity requires vehicle manufacturers and fleets to inspect these systems for quality control and safety. For manufacturers, this takes the form of a pre-delivery inspection; for fleets, it’s pre-service. Are you aware of both of these inspections, and — more importantly — do you know that they aren’t the same? Let’s explore the key differences between pre-delivery and pre-service CNG inspections, and why you need to learn about them.
Why CNG Fuel System Inspections Matter
CNG vehicles must comply with FMVSS 304, NFPA 52, ANSI 6.1, and OEM-specific requirements for fuel system installation, labeling, and cylinder protection. This makes it incumbent upon both manufacturers and fleet managers to establish dependable records and accurate baselines for all of their vehicles — especially when all parties can be held liable for those vehicles should any of them ever be involved in an incident.
What Is a Pre-Delivery Inspection?
A pre-delivery inspection is conducted by a vehicle manufacturer before a CNG vehicle is delivered to a customer. It represents the final step in the assembly phase that acknowledges a vehicle meets all installation and performance expectations, including fuel system component installation and safety requirements.
What Manufacturers Evaluate
Pre-delivery inspections include:
- Confirming proper installation of CNG cylinders, cylinder mounts, valves, pressure relief devices (PRDs), fuel lines, and other components according to codes and standards.
- Noting cylinder protection against impact, abrasion, and heat sources.
- Performing a leak test per OEM procedures.
- Checking CNG labels, safety decals, and system documentation.
- Reviewing the structural and mechanical integration of a fuel system.
- Preparing the vehicle for over-the-road transport.
What Is a Pre-Service Inspection?
Once a vehicle arrives at a fleet facility, technicians should perform a pre-service inspection before placing it into operation. This creates the fleet’s own baseline fuel system record for that vehicle in terms of its components, features, and safety requirements.
Why is this so important? Not all CNG vehicles are designed the same way in terms of their fuel systems and cylinder placement, which means that they’re susceptible to different types of wear and tear over time. Reviewing these unique qualities in advance helps teams better prepare for what types of maintenance will be needed.
In short, technicians have a clear understanding and documentation of each vehicle’s condition at the beginning of its service life, which makes it easier to track component aging, cylinder expirations, and future inspection intervals.
What Technicians Evaluate
Pre-service inspections include:
- Recording cylinder serial numbers, expiration dates, and placement.
- Performing a detailed visual inspection of every component of the CNG fuel system from the receptacle through the regulator.
- Examining mounting brackets, PRDs, covers, and protective structures.
- Performing a fleet-standard leak check after transport.
- Documenting the environmental condition of components (temperature, dust, vibration exposure).
- Adding the vehicle to the fleet’s inspection cycle per maintenance policy.
- Establishing baseline photos and records for future comparison.
The Key Differences Between Pre-Delivery and Pre-Service CNG Inspections
Although both inspection types relate to safety and system readiness, they are performed by different parties for different reasons.
1. Different Stakeholders
- Pre-delivery: Vehicle manufacturers.
- Pre-service: Fleet management.
2. Different Objectives
- Pre-delivery confirms that a CNG fuel system vehicle is engineered and installed in conformance with appropriate codes and standards.
- Pre-service establishes internal baseline documentation for the fleet’s lifespan of maintenance.
3. Different Inspection Environments
- Pre-delivery happens in controlled conditions.
- Pre-service happens after transport, where technicians may note environmental effects from shipping or storage.
4. Different Roles in the Vehicle Lifecycle
- Pre-delivery closes out the build process.
- Pre-service begins the operational phase.
Together, these inspections maintain accountability and quality control throughout the production and delivery of CNG vehicles.
How AFVi Training Supports Fleets During Pre-Service Inspections
AFVi provides industry-leading training for CNG fuel system inspectors, helping fleets adopt inspection practices that are consistent and safe. We teach technicians how to properly identify CNG components, recognize cylinder expiration dates and PRD placement, evaluate protective structures, strengthen their knowledge of NFPA 52 and other industry standards, build fleetwide confidence in natural gas safety, and follow predictable, repeatable inspection procedures that support long-term operational readiness.
By understanding the differences between pre-delivery and pre-service CNG inspections and why these inspections are needed, technicians are better equipped to support fleet operations and safety.
Do Your Technicians Need Training?
AFVi is here to help your technicians master this process. See when our next live online course for CNG fuel system inspections is available, learn more about our on-demand e-learning version, or contact us directly to talk about a customized training program.
