NGVConnection Newsletter - August 2012

NGVi Sponsors

Go to the sponsor
digital catalog page,
click here


Natural Gas Vehicle Institute to Exhibit at NACS Show 2012

If you're attending the NACS Tradeshow, you're invited to stop by our booth in the Petroleum Equipment and Services Area (Booth 4935). The tradeshow will be held October 8-10 at the Las Vegas Convention Center.


As gasoline and diesel fuel prices continue to soar, the petroleum equipment and services industry has responded with an interest in compressed natural gas (CNG), priced at an average of only $2.08 per gas gallon equivalent (GGE), as a way to power fleets and consumer vehicles. As the demand for CNG continues to grow, petroleum industry members should look to prepare for the business opportunities to come.

The NACS Show attracts more than 22,000 attendees from more than 60 countries and provides a comprehensive representation of products and services for the convenience and fuel retailing industry. As part of the tradeshow, Petroleum Equipment Institute (PEI) will host its annual convention, beginning on October 7 in the Petroleum Equipment and Services Area.

As a NACS Show/PEI Convention exhibitor, NGVi will have the opportunity to discuss relevant technical training and consulting service options with fellow PEI members and tradeshow attendees. NGVi's curriculum is designed for companies interested in or responsible for designing and building natural gas fueling stations, as well as equipment providers and those involved in permitting CNG stations. 

Defueling NGVs: Ensuring Safety
By Paul Pate, Training Manager, NGVi

For natural gas vehicle (NGV) technicians, there likely will come a time when defueling a vehicle is required. Defueling is necessary when a compressed natural gas (CNG) fuel system component has failed, or when a CNG fuel storage cylinder has sustained level 2 or 3 damage and must be removed from the vehicle for repair or replacement. 

While the term “defueling” might sound simple, it can be one of the more dangerous operations NGV technicians perform, and technicians must be adequately trained on this procedure.  Defueling a natural gas vehicle requires (1) a defueling receptacle on the vehicle; (2) a defueling nozzle and gas pressure regulation system; and (3) a place to put the fuel removed from the vehicle. 

The easiest and safest way to defuel a natural gas vehicle is to use a pre-installed defueling receptacle.  However, the only natural gas vehicles that typically have a defueling receptacle as standard equipment are transit buses.  All other NGVs, unless uniquely specified during the vehicle order process, do not come from the manufacturer with a defueling receptacle.
In the case of a vehicle without a defueling receptacle, the technician must create an alternative method for defueling the vehicle. The technician must disassemble a partially-pressurized fuel line fitting, and while the pressure can be minimized, it cannot be completely eliminated.  The significant risk associated with defueling is that the fitting may have been previously stressed and barely holding together, and when torque is applied to loosen the fitting, it is possible that it will fail, causing it to come apart under pressure, which can be dangerous.

Compounding the problem is that NFPA 52: requires that every natural gas vehicle have two check valves in series in the CNG fuel system.  The purpose of this requirement is to prevent high-pressure gas from escaping through the fueling receptacle in the unlikely event that the fueling receptacle’s check valve fails.  Therefore, the technician must be able to safely bypass the second check valve to defuel the vehicle.

While the following describes the basic processes for defueling a vehicle either with or without a pre-installed defueling receptacle, it is imperative that NGV technicians be fully trained on this procedure.  NGVi includes a “How to Defuel a Natural Gas Vehicle” module in all our NGV Technician Safety Training courses. 

Vehicle Defueling Without a Defueling Receptacle

While there are other options for providing the ability to defuel a natural gas vehicle, one method requires the technician to disassemble a portion of the high-pressure fuel line and install a defueling receptacle. The first step in this method is to remove as much gas as possible.  If defueling is not an emergency situation, the technician should schedule the defueling to occur after the vehicle has consumed the majority of its fuel.

If there is an emergency defueling situation, such as suspected Level 2 or observed Level 3 cylinder damage (CGA C-6.4-2007: 7.3.3), the first step is to close the cylinder valve(s) and run the vehicle engine until it dies. This can take up to six minutes or more, depending on the routing and length of the high-pressure fuel lines.

Once the engine dies, the technician should check and double-check that the fuel pressure has been depleted.  To adequately perform this step, a pressure gauge installed in the high-pressure fuel system is required. 

Then the technician can disconnect the most accessible fitting between the second check valve and the cylinder valve(s). Once disconnected, a defueling receptacle can be installed in the disconnected fuel line.

After the defueling receptacle is safely installed, the defueling nozzle can be attached to the receptacle and then connected to the defueling panel or vent stack. There are two commercially available models of defueling nozzles today manufactured by OPW Fueling Components and WEH Technologies.  These nozzles connect to the defueling receptacle and allow the defueling process to be completed.  The accompanying photos above show these products.

Vehicle Defueling With a Defueling Receptacle

The technician must attach a defueling nozzle that is connected to one of the defueling options mentioned below. After this nozzle is connected, the valve that allows system pressure to reach the defueling receptacle must be turned to the “Defueling Enabled” position. (See photo)


Defueling Requirements

Once the vehicle is equipped with the defueling receptacle, there must be an approved place to put the natural gas fuel removed from the vehicle. NFPA 52 sections 6.14.1 – provide a detailed list of requirements to be followed when performing defueling.  The technician must follow these and other applicable rules. 

The following are the three most common defueling options.

Defueling With a Defueling Panel (Atmospheric Venting)
The first thing to check when using this method is whether or not it is legal. There may be local air quality regulations regarding the release of methane into the atmosphere.  If atmospheric venting is acceptable in the area, then a vent stack apparatus that meets the requirements established in either the Uniform Building Code or the International Building Code must be followed. The local authority having jurisdiction—typically the Fire Marshal—should also be consulted.   The vehicle and the fuel system both must be grounded.


Defueling With a Defueling Panel (Compressor Inlet Method)

By far the easiest method, this procedure requires pre-planning and special equipment installed at the CNG fueling station.  If there isn’t a fueling station at the site where the technician is working on the vehicle, towing the vehicle back to the facility for repair will be required after defueling. In this method, the vehicle is connected through the defueling nozzle to the defueling panel and the compressor at the fueling station extracts the gas from vehicle. The vehicle and its fuel system must be grounded.  


Compressor inlet defueling panel


Defueling With a Defueling Panel (Vent –Back to Gas Main Method)

The least common method, venting back to gas main requires pre-planning and specialized equipment. The local gas utility would install special valving, regulation and piping that allows the gas to be put back into distribution system. This process works on the basis of pressure equalization between the vehicle and the utility system, so it is possible that there will still be pressure in the vehicle’s onboard fuel system. As in the other defueling methods, the vehicle and the fuel system both must be grounded during this process.

The bottom line with defueling is that ensuring technician safety requires training and careful attention to using proper procedures. Defueling is not something technicians should “figure out” when it’s time to perform it, but requires significant preparation. Every facility that services NGVs should prepare for defueling ahead of time, especially in case emergency defueling becomes necessary. 

Basic Rules For Defueling

  • Consume as much fuel as possible prior to defueling
  • Notify appropriate nearby personnel prior to defueling
  • Always ground (earth ground) the vehicle and the fuel system being defueled
  • Never defuel indoors
  • Always wear personal protective equipment
  • Be familiar with evacuation routes

>>Back to Top

Examining Certified Fuel System Inspector Standards

An Interview with CSA Group

Recently, NGVi had the opportunity to interview CSA Group’s Peter Ehlers, Program Manager of Alternative Energy. CSA Group, an NGVi sponsor, is a not-for-profit organization with a long history of developing standards that promote trade and competition and also help ensure that the NGVs and the refueling stations are safe to the operators and the people around them. CSA Group has nationally recognized testing laboratories and offers testing and certification services to meet the needs of OEM component manufacturers and system integrators. Additionally, the organization has an ANSI accredited personal certification program for CNG fuel system inspectors.


Are there any new standards related to CNG that you’ve developed or are currently working on? 


CSA Group has issued updates to the NGV3.1 NGV Component Standards and also the NGV2 NGV Cylinder Standard. The NGV3.1 document deals with all of the component performance requirements for the components that make up the NGV’s Fuel storage and delivery system.  The NGV2 standard deals with the performance requirements for all types of CNG fuel storage cylinders. CSA Group also recently published an update to the NGV4.8 standard for CNG Station Compressor Performance Requirements.


We are currently working on releasing the next update of the PRD-1 Thermally Activated Pressure Relief Valve Performance Standard.  This standard will be available near the end of 2012. It will include performance requirements to support the new generation PRDs that are currently being put into service.


Could you share a bit about your certification programs, specifically the CNG Fuel System Inspector Certification program? What are the benefits of this program? Is there a legal requirement to be a certified fuel system inspector?


The CNG Fuel System Inspector Certification was developed to meet the needs of fleets of all sizes that use safe, cleaner-burning natural gas to power their vehicles.  There are currently over 300,000 CNG cylinders in vehicular use in the U.S. marketplace.


CNG cylinders and fuel systems must be visually inspected for external damage and deterioration after a motor vehicle fire or accident and at least every 36 months or 36,000 miles, or at the time of any re-installation.


The inspection is to be performed by a qualified inspector in accordance with the manufacturer's recommendations and the inspection procedures provided in Compressed Gas Association (CGA) pamphlet C-6.4. A CNG Vehicle Fuel System inspector inspects containers, valves, PRDs and other fuel system components, applying appropriate knowledge and skill to assure the safety of compressed natural gas powered vehicles.


The program helps to reinforce the need for candidates to be adequately trained and then tested to levels of competence set by a committee of acknowledged experts.  Procedures are also in place to periodically re-assess certified inspectors to ensure they remain up to date on technical developments and industry changes. Vehicle owners also benefit because the program develops a pool of certified inspectors from whom they can confidently obtain the recommended system inspections. Our CSA Group website contains a national registry of certified CNG Fuel System Inspectors across the U.S. and Canada.


Currently, Utah is the only state that requires that all CNG inspectors be CSA certified. Other states and municipalities are evaluating the Utah model and are considering their own legislation to require inspectors be certified.


What are the qualifications of a certified CNG Fuel System Inspector?


CSA Group’s expert committee defines the minimally qualified candidate as follows:


A qualified inspector will inspect for and document damage or other problems and recommend proper action to assure fuel system safety. The minimally qualified candidate can perform CNG fuel system inspector activities without assistance, including:

  • Knowledge of the types of containers used in CNG Vehicle Fuel Systems and damage allowances for each type
  • Understanding of inspection requirements, tests and procedures
  • The container manufacturer’s current inspection guidelines readily available


What preparation for the CNG Fuel System Inspector Certification Program exam do you recommend?  


There are no prerequisites for the program in order to take the exam. We do however recommend training prior to writing the test. There is a list of CSA affiliated training organizations on the CSA Group Website. Check our website for a list of training organizations and resources.


How often does CSA update its CNG Fuel System Inspector Exam?


We are constantly scanning the industry and as the technology changes, the exam content is updated.


How does CSA obtain information to include in its CNG Fuel System Inspector Exam?


Our company works closely with a group of industry experts including manufacturers, technical support staff, system integrators and regulators. This is a volunteer group that brings its expertise to ensure pertinent content to determine the minimally qualified level of inspector. 


What is the linkage, if any, between the organizations that offer a CNG Fuel System Inspector course and CSA in terms of course content or areas to focus on during the course? 


As a third party certification administrator, CSA Group does not contribute any content directly to training organizations. The test blueprint, available in the complementary certification guide and developed by the group of experts, is available to training organizations as an outline. 




If you are interested in becoming a CNG Fuel System Inspector or need preparation for the CNG Fuel System Inspector Certification Program exam, please consider NGVi’s CNG Fuel System Inspector Training Course.


This two-day training course provides technicians the information and skills required to knowledgeably inspect CNG fuel systems, detect and assess damage and determine necessary next steps.


For additional information or to register for the upcoming course in Chicago, IL on October 17-18, visit

Oil Change Due Already?

By Dave Crowley, NGVi Instructor

Technician A says, “You should normally change the oil based on the engine manufacturer’s recommended schedule.”

Technician B says, “Oil that looks that clean doesn’t need changing yet.”

Which technician is correct?

While that exact question hasn’t shown up on an ASE test yet, it seems that whenever CNG-fueled engines are being discussed, eventually the discussion leads to engine oil life.

Visual comparisons between oil dipsticks pulled from diesel, gasoline, and CNG-fueled engines show dramatically different results. For diesel and gasoline engines, we know appearance is not a reliable method for evaluating oil condition. But is appearance a valid indicator of CNG engine oil?

For economic reasons and responsible resource usage, oil should only be changed when necessary. If the oil is still doing its job, leave it in! However, when the oil is no longer able to protect the engine, it has passed its useful service life and should have already been changed. For fleet operators, this decision can lead to even more detrimental consequences.

“But it still looks clean…”

So how do you know when it’s time to change the oil in a CNG- fueled engine?

If you are relying solely on the visual appearance of the oil, you will most likely leave the oil in too long between changes. When it comes to CNG vehicles, there is much more to consider than the concept “less carbon in the fuel equals clean, longer oil life.”

This is where questions arise.  Can the oil look clean, but be degraded? Is it possible that the oil in an engine is no longer able to do its job even though it still looks clean on the dipstick? Yes, on both counts.

Even though it may appear “clean,” the oil is not in the same condition as when it was put into the engine thousands of miles prior.

“But I thought oil didn’t wear out…”

While the base oil doesn’t “wear out,” it changes chemically over time, and critical additives are depleted. Some of the changes include:

Viscosity increase: Oil viscosity changes with use. As lighter parts of the oil burn off, viscosity will increase. In gasoline and diesel engines, some fuel dilution is normal, which lowers viscosity, so there is some balancing between the two tendencies. However, using CNG eliminates fuel dilution of oil, so the oil thickens as miles and operating hours accumulate. This has a negative effect on a lubricant’s ability to protect a CNG- fueled engine.

Oxidation: Oxidation is caused by the reaction of oil combined with oxygen, particularly as oil temperatures increase above 200°F (95°C). Oxidation occurs in all lubricated systems and also contributes to an increase in the oil’s viscosity. Engines that run on CNG experience higher temperatures in the combustion chamber and upper cylinder than gasoline or diesel engines,, which increases the rate of oxidation.

pH Balance: Base number (BN) is an indication of the reserve alkalinity contained in an engine oil. It is an indicator of the level of the detergent/dispersant additive package’s ability to counteract acids. While formation of acids is normal in internal combustion engines, some natural gas can bring additional acidity. Natural gas composition can vary by region and source. For example, where natural gas containing high sulfur or landfill gas is in use, the acidity of the engine oil can increase more rapidly. This would not be possible to detect without having oil analysis done.

“So when should we change the oil?”

In addition to viscosity increase, burning any fuel creates by-products that ultimately end up in the oil.  With CNG, they won’t be as visibly noticeable because of the lack of carbon in the fuel. Nonetheless, the oil will still oxidize, acids will be produced, the pH will drop, and additives will be depleted. How many thousands of miles can be driven before this occurs? It depends. How rapidly this occurs is contingent upon the engine, loads applied, and the daily duty cycle. But it still applies whether the vehicle is a Honda GX, taxi, or refuse truck. One option some fleet operators choose is to collect oil samples from some of their vehicles and send them out for laboratory analysis. Obtaining this data can be used to help determine an oil change interval that balances cost of maintenance with reliable, long engine life. Short of doing oil analysis, the best recommended practice is to follow Technician A’s advice, and refer to the manufacturer’s intervals for oil and filter change.

In a future article, we’ll explore oil analysis and see what lab results are revealing about CNG engines and predictive maintenance.

Mansfield Gas Equipment Systems Announces Job Opportunity: Manager of Engineering

Mansfield Gas Equipment Systems, Corp. Ontario, CA announced today that Bruce Buckner, Sr. Engineer, has retired after a long and distinguished career in the CNG fueling infrastructure industry according to MGES President Larry Ozier.

Bruce began his industry career with Wilson Technologies in 1990, joining the MGES team in 2005.  Bruce’s diversified experience included CNG compressor technology design, Project Management and station infrastructure construction. He also participated in the construction of the first hydrogen re-fueling station facility at SCAQMD and as a Project and Site Manager for LNG and LCNG projects at Los Angeles International Airport.

According to Ozier, the MGES HR Department has just begun a search to fill this important company position.   Interested candidates should apply by following the link below.


To Apply, Please visit:

CNG Fuel Price Report
From Clean Cities Alternative Fuel Price Report published by Argonne National Laboratory for DOE's Clean Cities Program

Overall Average Fuel Prices (as of July 2012)


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

How to Fuel a Natural Gas Vehicle  


NGVs & CNG in the News

CA Waste Company Brings On More Than A Dozen Mack TerraPro CNGs--NGT News

Republic Services' CNG Truck Takes to Speedway, Honors State's Firefighters--Kent Reporter

Cummins: Play On Cheap Natural Gas--Seeking Alpha

Norwich to Receive $2 Million Grant for Alternative Fuel Station, New

Ryder and Fresh & Easy Receive LQ Magazine’s Best 3PL Performer in Sustainability Award--Herald Online

To read more, click here.

Upcoming Training from NGVi

CNG Fuel System Inspector Training

October 17-18, 2012 | Chicago, IL

Training for technicians on the information and skills required to knowledgeably inspect CNG fuel systems, detect and assess damage and determine necessary next steps.

Driver & Technician Safety Training for CNG Powered Vehicles

October 16, 2012 | Chicago, IL

Training for drivers and technicians on safe driving, fueling and maintenance of today's natural gas vehicles.


Click here to Register

>>Back to Top


Email Newsletter icon, E-mail Newsletter icon, Email List icon, E-mail List icon Sign-up for NGVConnection eNewsletter
Email address:
For Email Marketing you can trust



Upcoming Training

Level 1: NGV Essentials
and Safety Practices

August 21, 2018
Atlanta, GA

Level 2: CNG Fuel System
Inspector Training

August 22-23, 2018
Atlanta, GA

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


Register Now »

NGVi Newsletter

Receive NGVi updates directly to your inbox

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.


Read more about NGVi »

Find NGVi on Follow NGVi on LinkedInFollow NGVi on TwitterFollow NGVi on FaceBookFollow NGVi on YouTube



Participating Sponsors of Natural Gas Vehicle Institute
  • ANGi
  • CPI
  • HandyTube
  • Mack
  • Oasis
  • OPW
  • Parker
  • SensorElectronics
  • Trillium
  • Volvo
  • WEH US
  • CNGcylindersinternational
HomeAbout NGViTrainingConsultingResourcesNews & EventsSponsors Contact UsBack to Top

NGVi and NGVi Natural Gas Vehicle Institute are Registered Trademarks of Thomason & Associates, Inc. NGVi reserves the right to refuse registration to our training classes or purchase of NGVi products based on customer applicability or other standards determined by NGVi.

© 2018 Natural Gas Vehicle Institute - Site Designed by 454 Creative - Site Produced by Perkolate Marketing Las Vegas

3120 S. Durango Drive, Ste 304, Las Vegas, NV 89117

800-510-6484 l