NGVConnection Newsletter - February 2016

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CNG Fuel System Inspection Requirements Revisited: NGV Industry Working Group Tackling Modifications

By Annalloyd Thomason, Vice President/General Manager, NGVi 

Last October, NGVi published an article titled “CNG Fuel System Inspection Challenges for Heavy-Duty Fleets” which turned out to be our most widely read article ever. In the article, we discussed the challenges for heavy-duty fleets with the current CNG fuel system inspection interval of every three years or 36,000 miles, whichever comes first.

The article outlined several issues that require clarification—including the language used in the National Highway Transportation Safety Administration’s (NHTSA) FMVSS 304, which states that CNG containers “should be visually inspected after a motor vehicle accident or fire and at least every 36 months or 36,000 miles, whichever comes first, for damage and deterioration.” Most NGV users treat FMVSS 304 as law, and most heavy-duty users find the interval unrealistic and costly because many heavy-duty vehicles reach 36,000 miles every 12 weeks or less.

An additional challenge is that FMVSS 304 calls for inspection of cylinders—not the entire fuel system—while industry best practice calls for inspection of the entire CNG fuel system. This is because other fuel system components can have equally serious safety impacts.

The good news is that since last October, the NGV industry, through its national trade association NGVAmerica, has established a special working group to take on the task of addressing CNG fuel system inspection issues. NGVi’s Executive Director, Leo Thomason, was asked to serve as chairman of that working group, made up of a broad cross section of industry members including CNG cylinder and fuel system manufacturers, vehicle manufacturers, and end users. NHTSA is also represented on the working group and has indicated its support for the process.

The major tasks that the working group is undertaking include (1) inconsistencies that need to be addressed between current codes and standards that govern CNG fuel system inspections; (2) what components should be included in a CNG fuel system inspection; (3) how frequently inspections should be conducted; and (4) qualifications of a CNG fuel system inspector.

In commenting on the working group, Leo Thomason noted “The tasks being undertaken by the working group are long overdue. I am pleased that NGVAmerica has assembled an experienced group of industry members—especially including the cylinder manufacturers—to develop recommendations to be adopted by NHTSA and other organizations that will help ensure safety and meet the current operational needs of NGV users.”

The bottom line and ultimate goal for CNG fuel system inspections is safety. Inspections must be conducted frequently enough to detect potential in-use safety issues or installation code problems and that’s the real issue on the table. While many in the industry encourage one year/100,000 mile inspection intervals for heavy-duty trucks, NGV users currently using the 36,000 mile interval often find safety or installation issues that need to be corrected.

As the working group progresses, we will keep our readers informed. In the meantime, if you have input you’d like to share, email us at

Training Technicians Smarter Through E-Learning
By Kasia McBride, Marketing Manager, NGVi

NGV fleet and dealership safety starts with comprehensive CNG and LNG training, and managers face the challenge of selecting the right training delivery method for their technicians and support staff.

Technicians are often kinesthetic learners, which means they absorb information better when given the opportunity to manually practice the skills being taught through hands-on exercises. Though this form of training can be highly effective, and in some circumstances necessary, recently many organizations have added e-learning to their training delivery mix as a scalable, economical alternative. Determined in cost savings alone, the value of e-learning can be substantial.

For years, traditional classroom training was the most practical option available. But for some organizations, scheduling this type of training can be more difficult, especially when staff are geographically dispersed.

Since the launch of our first e-learning program in 2014, NGVi has seen tremendous growth in the popularity of e-learning among our clients. Every month more and more NGV organizations recognize that e-learning can deliver excellent safety training to their employees at low cost.

“Because of its convenience and flexibility, e-learning allows us to address many of the training needs of our maintenance associates,” said Matt Krasney, Director of Alternative Fuels at Penske Truck Leasing, and one of NGVi’s customers. “With more than 231,000 vehicles operating across nearly 1,000 locations, it is essential that Penske provide high-quality training that is conveniently available to all of our technicians. While hands-on, in person training remains the foundation of our training program, NGVi has been instrumental in developing a custom e-learning solution unique to Penske that addresses the specific needs of our growing natural gas fleet.“

E-learning has many benefits compared to traditional classroom training, and can produce great results by decreasing costs while still improving employee performance. Key factors:

24/7 Accessibility
E-learning courses are accessible to technicians around the clock. This makes it possible for them to learn the content at their own pace and in comfortable settings. Unlike instructor-led training, participating in e-learning ensures that faster learners may complete their training sooner, which enhances their productivity. In turn, slower learners can still master the subject matter without the stress of falling behind. With e-learning, employees can receive training anytime and anywhere—at work, home, or even while commuting. Also, in large organizations where employees work in different time zones, e-learning makes it possible for an employer to offer training without time constraints on resources.

In addition to being offered around the clock, e-learning can be completed in short chunks of time that fit around a technician’s work schedule. Unlike day-long instructor led training, a technician does not need to be out of the shop an entire day to get effective training. Instead, e-learning offers a set amount of learning, typically divided into modules, which allows technicians to be trained around their other daily duties without a major interruption.

Reduced Training Costs
Generally speaking, the more training your employees need, and the more geographically dispersed they are, the greater the training costs. If technicians must travel out of town to receive training, often a significant portion of the costs are due not to the cost of the training itself, but to employee travel expenses such as airfare, lodging and meals. With e-learning, these costs are eliminated since there is no longer a need for them to leave their place of work.

Condensed Delivery Time and Rapid Deployment
E-learning takes less time than instructor-led training because there are no interactions with fellow students, student questions to be answered or breaks required. A traditional two-day instructor led curriculum can often be delivered in about 10 hours of e-learning, thus saving the employer in lost production costs.

In addition, e-learning can be delivered quickly and conveniently, so that technicians are able to acquire new information or skill sets almost immediately.

Learn at Their Own Pace
With e-learning, every learner proceeds at his or her own pace. When learners have control over the amount of content they cover at one time, they are better prepared to retain the information. Technicians who have access to online training don't have to rush through content presented in a classroom setting or move at the pace of the rest of the students. They are given the opportunity to fully absorb what is taught before they progress with additional course material. There is also the ability to revisit or replay sections of the e-learning training that might not have been mastered the first time around.

Multiple Languages
E-learning material can be easily translated into other languages. This facilitates delivery of training to diverse or multilingual workforces. A case in point is Waste Management, which employs drivers and technicians who speak not only English, but also Spanish and French. NGVi has developed customized training for Waste Management’s drivers and technicians that is translated into those languages.

“Waste Management’s commitment to providing quality safety and technical training is unparalleled in the industry, going far beyond the standard safety training programs,” said Neil Allison, Manager of Fleet Training at Waste Management. “These e-learning courses are a convenient way for our technicians and drivers to gain the knowledge and skills needed to do their jobs safely and effectively, without having to send them off site. A big plus: we were able to have teams trained in French, Spanish, and English, supporting sites all over North America.”

The unique fuel properties, components and inspection requirements of NGVs demand specialized maintenance knowledge, making technician training vital. Adding e-learning to the NGV training delivery mix gives managers just another tool to provide NGV technicians with the knowledge and skills they need to perform their jobs, but with more focus, in less time and at a significantly lesser cost.

CNG Fuel System Inspections: Technician Training is Key

By Kasia McBride, Marketing Manager, NGVi

This article was originally published in the October issue of Government Fleet.

CNG fuel system inspections are complex processes, during which technicians must be able to properly identify and determine the extent or significance of any damage discovered to system components, including cylinders, and be clear on what specific actions must be taken. Whether any damage or other concerns about fuel system integrity are due to accidents, misuse of system hardware, or simply through long-term wear and tear, the damage is not necessarily easy to identify for those unfamiliar with the components involved.

To conduct CNG fuel system inspections correctly, safely, and accurately, with the obvious goal of averting any unsafe driving or maintenance situations, technicians must be trained on the entire process of fuel system inspection, all related components, and safety practices specific to NGVs.

There are two different kinds of CNG fuel system inspections: the general visual inspection and the detailed visual inspection. General visual inspections are the industry recommended best practice. These are basic inspections of the system’s visible elements that should be conducted regularly as part of the vehicle’s routine maintenance schedule. During these inspections, technicians must look for any signs of obvious or gross external damage to the cylinder shields, loose or damaged mounting brackets, and any damage to the high-pressure components of the fuel system. If evidence of damage is found during the general visual inspection, then a detailed visual inspection becomes necessary.

In addition to conducting the detailed visual inspection when damage is found, this higher level inspection is required every three years or 36,000 miles (whichever comes first) of vehicle use, and after any fire or accident, according to standards ANSI/NGV-2 and FMVSS 304.

The detailed visual inspection covers the entire high-pressure fuel system, including cylinders, and must be conducted by sufficiently trained technicians. It should adhere to the cylinder manufacturer’s maintenance and inspection requirements, or secondarily to CGA C-6.4. – (Methods for External Visual Inspection of Natural Gas Vehicle and Hydrogen Vehicle Fuel Containers and Their Installations.) Because the manufacturer’s requirements cover information and guidance for specific types and brands of the cylinders installed on the vehicle, they are more stringent, always take precedence, and should be the primary source for information.

Before the detailed visual inspection can begin, technicians must gather information such as the vehicle history, previous inspection records, any vehicle records of collision damage, or any accidents, VIN, license plate number, and other potential identifiers. This information becomes the foundation of the inspection and the documentation.

The next step is to prepare the vehicle for inspection. This includes gaining access to the cylinder area by removing shields that cover the cylinders (if at all possible) as well as cleaning all of the cylinders. It is very important that the surface of each cylinder be free of dirt and other debris prior to conducting inspection so that the inspector can visualize any damage.

The equipment required to conduct a detailed visual inspection includes:

  • Telescoping inspection mirror or go-pro camera (or similar device) and flashlight which are helpful when inspecting cramped, awkward, or hard-to-reach areas.
  • Measuring tape or ruler to measure the length and width of any cylinder damage.
  • Leak-check solution to check for leaks in fittings, valve packing and seals, pressure chambers, and other leak points. A portable methane detector may also be used to detect the general location of gas leaks.
  • Depth gauge, a precision instrument used to measure the depth of any damage to the cylinder
  • A camera to document the inspection, including any discovered areas of damage
  • “Failed Cylinder Inspection” sticker
  • “Passed” inspection sticker
  • Inspection form and pen

After all necessary information and equipment are gathered and the vehicle has been prepared, the technician can proceed with the detailed visual inspection of the CNG fuel system.

While conducting this inspection, NGV technicians will examine all components of the high-pressure system including cylinders and shields, brackets, PRDs, valves, fittings, lines, hoses, regulator, coalescing filter and fuel receptacle. These components should be inspected for damage, obstructions and that they are properly seated. Technicians should also leak check all fuel system connections and fittings including all solenoid valves, high-pressure coalescing filter, quarter-turn valves, high-pressure regulators and PRDs. They should make sure that the O-ring is present on the receptacle, is free of debris, and is not torn, punctured, or otherwise damaged.

PRDs must be checked for any visual signs of damage, including gouges, scratches, corrosion, rust, bulging, or plugged channels. Technicians must verify that the PRDs are properly attached to the cylinder and are not deformed, bent, or corroded. Also during the inspection process, they should inspect the interface between the PRD and cylinder valve and make sure it is tightly seated with no gaps or evidence of being loose.

During the cylinder inspection, technicians must be able to verify any damage to the cylinder and assess its type and level. The potential damage sources can include heat, impact, corrosion, abrasion and chemical attack (for example, battery acid or solvents). Correct assessment of the damage source is extremely important because, for example, in the case of heat damage, it is impossible to determine the amount of heat to which the cylinder was exposed, nor the extent of potential internal damage within the cylinder’s protective layers. In a case such as this, the cylinder would have to be condemned.

Next, the technician must measure the depth and length of any damage found, including cuts, scratches, indentations, punctures, or abrasions observed on each cylinder. The damage must be photographed and recorded on the inspection form, which will later help technicians assess the level of the damage, and to consequently determine the final disposition.

CNG cylinder damage is formally classified into three levels:

  • Level 1 damage is defined as no damage or damage depth of less than or equal to .010 inches. In this case the cylinder does not require any repair and can be returned to service. Note that some manufacturers have different limits for cylinder damages, therefore technicians should always consult the manufacturer of the cylinder if damage exceeds .010 inches for their specific requirements.
  • Level 2 damage includes any scratch, gouge, or abrasion with a damage depth of .011 to .050 inches. This damage requires repair, a more thorough evaluation, testing or destruction. The manufacturer’s guidelines will determine the final outcome.
  • Level 3 damage is defined as damage of a depth greater than .050 inches or any damage sufficiently severe that the cylinder shall not be repaired and must be condemned.

Once the inspection is complete, the inspector must determine the outcome of the inspection.

  • If all cylinders exhibit Level 1 or no damage and all high-pressure fuel system components are undamaged, do not leak, and show any signs of needing repair or replacement, the vehicle can return to full service immediately.
  • If any cylinders exhibit Level 2 damage or one or more components of the high-pressure fuel system need repair or replacement, or any cylinders exhibit Level 3 damage or any components of the high-pressure fuel system need repair or replacement, the vehicle has to be removed from service and the technician must report their findings to management or the vehicle owner.

CNG fuel system inspections require a high level of accuracy and precision, especially since measurable differences between the three levels of damage assessment are very small. Failure to properly assess and diagnose damage can jeopardize the safe operation of the vehicle, and increase the risk of accident both in the shop and on the road. With proper training, including not only theory, but applicable hands-on practice, technicians can obtain actual experience before they begin inspecting CNG fuel systems on the job.

Technicians who perform CNG fuel system inspections must have sufficient knowledge of all of the codes and standards governing CNG fuel system installation and CNG fuel system components, be able to interpret them, and apply that knowledge routinely in practice. They also must understand the mandated inspection requirements, and know how to properly apply the cylinder manufacturer’s maintenance and repair guidance and recommendations during their inspections.

CNG fuel system inspections allow technicians to identify unsafe conditions which could result in life-threatening situations. To do their jobs adequately, technicians need not only classroom training (the theory), but also the hands-on practical skill-building essential to measure, record, document, and to accurately assess any damage found within the context of the manufacturer’s written specifications. As a result, technician training is the single most important key to reducing risk and maximizing operational safety.

CNG Fuel Price Report
From Clean Cities Alternative Fuel Price Report published by National Renewable Energy Laboratory (NREL) for DOE's Clean Cities Program

Overall Average Fuel Prices (as of October 2015)


Nationwide Average Price for Fuel This Report

Nationwide Average Price for Fuel Last Report

Change in Price This Report vs. Last Report

Units of Measurement

Gasoline (Regular)




per gallon





per gallon





per GGE

NGVs and CNG in the News


Annual NGV Sales to Reach Almost 4 Million Units in 2025 -- NGT News
New Freedom CNG Fueling Station for Houston -- NGV Global News

Love's Travel Stops acquires Trillium CNG --

Peterbilt, Toyota team up to produce natural gas-powered car hauler -- CCJ Commercial Carrier Journal

New Mid Mon Valley Transit buses run on natural gas -- Herald-Standard

Shell to Run Ryder LNG Trucks in Louisiana and Texas -- NGV Global News

Upcoming Training from NGVi

NGV Essentials and Safety Practices CNG Fuel System Inspector Training
February 23, 2016 Fort Worth, TX
March 15, 2016 Toronto, ON
March 22, 2016 High Point, NC
April 26, 2016 Sacramento, CA
May 24, 2016 Chicago, IL

With a focus on safety, this one-day course teaches technicians the fundamentals of natural gas, CNG and LNG fuel systems and maintenance practices for NGVs.

February 24-25, 2016 Fort Worth, TX
March 16-17, 2016 Toronto, ON
March 23-24, 2016 High Point, NC
April 27-28, 2016 Sacramento, CA
May 25-26, 2016 Chicago, IL

Two-day session that provides you with the proper techniques for inspecting CNG fuel systems, including on-board compressed natural gas fuel storage cylinders.

Heavy-Duty NGV Maintenance
and Diagnostics Training

Heavy-Duty NGV Maintenance and Diagnostics Training

NGVi Cylinder Fuel System Inspector Training
May 10-13, 2016
(Combo class with CNG Fuel System Inspector add-on)
Scottsdale, AZ
May 10-11, 2016
(Single class)
Scottsdale, AZ

Prepare your NGV technicians to safely and cost-effectively maintain and diagnose the components of all CNG fuel systems, as well as the Cummins ISL G and ISX12 G engines.

This comprehensive, two-day course includes operational theory and diagnostics, with more than a dozen hands-on exercises.


CNG Fueling Station Design Training 

April 4-5 , 2016 Spring Valley, NV

Two-day course that offers the detailed technical information needed to successfully size, design and specify a CNG fueling station.

CNG Fueling Station Operation and Maintenance Training

April 6-7 , 2016 Spring Valley, NV

Two-day session that provides you with the proper techniques for operating and maintaining CNG fueling stations to help avoid oil carryover and water in the natural gas stream.

NGVi CNG Fueling Station Operation and Maintenance Training

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Upcoming Training

Level 1: NGV Essentials
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August 21, 2018
Atlanta, GA

Level 2: CNG Fuel System
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August 22-23, 2018
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Level 1: NGV Essentials
and Safety Practices

September 11, 2018
Boothwyn, PA

Level 2: CNG Fuel System
Inspector Training

September 12-13, 2018
Boothwyn, PA

Essentials of CNG Station Planning,
Design and Construction

September 24-25, 2018
Las Vegas, NV

Essentials of CNG Station
Operation and Maintenance

September 26-27, 2018
Las Vegas, NV

Level 1: NGV Essentials
and Safety Practices

October 2, 2018
Sacramento, CA

Level 2: CNG Fuel System
Inspector Training

October 3-4, 2018
Sacramento, CA


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About NGVi

Natural Gas Vehicle Institute is North America’s leading provider of training and consulting on natural gas as a transportation fuel.

Our services address the full range of natural gas vehicle and fueling issues, including:

Technical consulting services – Sizing and designing compressed natural gas fueling stations, vehicle assessments and technical assistance for fleets, CNG fueling station troubleshooting, natural gas vehicle maintenance facilities upgrades, liquefied natural gas fleet and fueling management.

Technical training – NGV Essentials and Safety Practices, CNG Fuel System Inspector Training, Heavy-Duty NGV Maintenance and Diagnostics Training, Light-Duty NGV Maintenance and Diagnostics Training, CNG Fuel System Design and Installation Training, Essentials of CNG Station Operation and Maintenance Training, Essentials of CNG Station Planning, Design and Construction Training and CNG/LNG Codes and Standards Training for Fire Marshals and Code Officials.


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