NGVConnection Newsletter - May 2015

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Upgrading Your Vehicle Maintenance and Repair Facility for NGVs Series
(Part 4 of 5): Ventilation and Methane Detection

By Annalloyd Thomason, Vice President/General Manager, NGVi 

Methane detectorAdequate ventilation in a natural gas vehicle maintenance facility is critical. It ensures that in the event of a leak, there is an effective system in place to remove leaking gas and bring fresh air into the facility in a very short period of time. It helps prevent an ignitable mixture of natural gas from accumulating inside the maintenance facility in the event of a leak, and helps keep technicians and other employees working in the building, safe.

What exactly are the code requirements for ventilation in a maintenance facility where NGV fuel system repairs are made?

Code Requirements

While National Fire Protection Association (NFPA) 30A does not specify requirements for ventilation for NGV repair facilities, the International Fire Code (IFC) requires continuous mechanical ventilation of major repair facilities at the rate of five air changes per hour. Where natural ventilation can meet this criterion, the authority having jurisdiction (AHJ) must approve its use. Additionally, the IFC provides two exceptions to the continuous ventilation rule: (1) when the ventilation is interlocked to and controlled by a methane gas detection system; or (2) the ventilation system is interlocked to the lighting system for the facility.

Exhaust fanMost existing maintenance facilities will have a ventilation system of some type—including gravity ventilators, a make-up air system or a dedicated heating/ventilation/air conditioning (HVAC) system. Some current ventilation systems may be able to meet the code requirements for ventilation in CNG and LNG vehicle maintenance facilities, provided they (1) are capable to provide ¾ to 1 cubic foot per minute of air flow per square foot of floor space; (2) operate continuously; or (3) are interlocked to the lighting system or a methane detection system.

While continuous ventilation using an existing system sounds like the easiest option, it is possibly the most expensive. The cost of continuously running an existing HVAC system that provides heat in winter or air conditioning in summer can be costly—especially in climates with very cold winters and/or very hot summers.

Methane detection control centerMethane Detection Systems
Currently, the most widely used option to ensure proper ventilation is to install a methane detection system in the NGV repair facility that is interlocked to a power exhaust system—which means the exhaust system is only engaged if the methane detection system detects gas at 25% of the lower flammability limit. There is no code requirement for methane detection systems in CNG maintenance facilities because CNG is odorized, yet it is the most frequently used solution.

For LNG maintenance facilities, methane detection is required because LNG is an unodorized fuel and unlike CNG, human detection of LNG is not possible. Code requires that methane detection systems in LNG facilities must be interlocked with the ventilation system.

Methane detection systems must be listed in accordance with UL 2075 or approved by the AHJ. In addition, they must activate at 25% of the lower flammability limit (1.25% concentration in air) for natural gas. Methane detection systems are also required to activate the mechanical ventilation system, deactivate heating systems and initiate an audible and visual alarm inside the facility.

Exterior AlarmIf the methane detection system itself fails, it is required to activate the ventilation system, deactivate all heating systems inside the facility and initiate a trouble alarm in an approved location. Methane detection systems are required to be tested and calibrated according to the manufacturer’s guidelines and approved by the AHJ.

A final and important note: if you choose methane detection systems as your ventilation solution, make sure the methane detection system in your facility is designed by an engineer with expertise in these systems installed in NGV maintenance facilities. This will help ensure that the system is designed specifically to the needs and requirements of your facility.

Ventilation in Pits

Existing codes do not contain any additional requirements for ventilation in pits for CNG maintenance facilities—primarily because natural gas is lighter than air and rises when it leaks. However, both NFPA 30A and the IFC require methane detection systems in below-grade pits in LNG maintenance facilities.

In our final installment in this series, we will discuss maintenance facilities modifications and practices when performing welding and hot work.

Perspectives With Kevin Collins, VP of Business Development, CP Industries
By Robin Skibicki, Marketing Coordinator, NGVi

CP IndustriesKevin CollinsFor over a century, CP Industries has manufactured and produced large, seamless pressure vessels. In the fall of 1897, the company was founded as U.S. Seamless Tube Works. The plant, called Christy Park Works, began manufacturing seamless steel tubing and small compressed gas cylinders in the spring of 1898. In 1911, the company produced the first heat-treated air flasks for submarines. During WWI, the facility operated as a multi-purpose plant serving the armed forces with shell forgings and torpedo tubes.

From 1920 through 1940, Christy Park Works continued to pioneer work in the development of technology utilizing cylinders for the storage and transportation of compressed gasses. In the mid-1980's, the company was sold to Stanwich Partners and renamed CP Industries. At that time, 60% of the business was comprised of military projects, with few international sales. In 2008, CPI was sold to Everest Kanto Cylinder Ltd (EKC) with operations in Dubai, China and India.

NGVi had the opportunity to speak with CP Industries' VP of Business Development, Kevin Collins, about their involvement in the natural gas vehicle market.

When did your company begin manufacturing storage vessels for compressed
natural gas (CNG), and what vessel sizes do you offer?
CPI was on the forefront in offering products for storing and transporting CNG. As far back as the 1970’s, CPI provided trailers and ground storage to New Zealand. Our website lists some of the sizes, pressures and specifications that we design and manufacture to. It’s important to realize that CPI vessels are customized to meet the requirements of our customers, and vary in operating pressures, wall thickness, length and outside diameter (OD).

Can you explain your applied manufacturing process, and which processes are
used for your CNG products?

CPI spin forms large, OD seamless pipe. The vessels are heat treated to attain specific properties and machined, cleaned, assembled and tested. The following video depicts our manufacturing processes:

What are the testing methods for your CNG storage vessels?
CPI vessels undergo strenuous testing to pass the requirements of the ASME, DOT, ISO/UN, ANSI NGV 2, and FMVSS304 specifications. It is important to mention that CPI ASME ground storage vessels must pass a final ultrasonic test to a 5% notch criteria. This test is not required by the ASME code but is performed by CPI to assure safe CNG storage. Tests are monitored and approved by third party inspection agencies.

Which manufacturing standards do you design in accordance to, and which
third party approvals have you received?

For transportation, our tubes are manufactured in accordance with DOT and ISO 11120. Our ground storage vessels are manufactured to meet ASME Section VIII Division 1. The cylinders for on-board storage are certified to ANSI NGV2-2007 and are compliant to FMVSS-304. Our approvals include TPED, KGSC, China SELO, DNV, PED and Canada.

CPI makes ASME Section VIII Division 1 pressure vessels. Please share with
us the primary differences between your vessels and ASME Section VIII
Division 2 pressure vessels offered by your competition?
Division 1 is the most commonly used division and contains rules for the basic design of unfired pressure vessels. Division 2 contains alternative rules for the design of more complicated or specialized vessel designs. Division 2 vessels require that the vessels be designed for a specific usage and for a specific installation. Further, the usage of Division 2 vessels must be monitored following installation. There is also a Division 3, which contains rules specific to the design of vessels for pressures above 10,000 psi.

Are your manufacturing plants eco-friendly?
CPI monitors our water outtakes and air quality constantly and are in full compliance. We have also operated CNG fueled forklifts since the 1970’s.

How has the demand for natural gas vehicles and fueling shaped your company’s production? Has it changed its priorities?
CPI has been innovative in bringing new designs for the storage and transportation of CNG. We introduced a longer ASME vessel that is capable of storing more CNG than a “traditional” three pack. The dollar value per standard cubic foot (SCF) of CNG stored is significantly lowered. We have also introduced larger 24” OD ASME vessels that reduces the space required for CNG storage at NGV stations. In addition, CPI manufactures a line of Type IV composite cylinders for on-board storage applications. These cylinders are ideal for use on passenger and commercial vehicles in the heavy-duty, medium-duty and light-duty markets.

Why should natural gas fueling customers choose CP Industries? What are your competitive advantages?
CP Industries is well known in the high-pressure storage market as manufacturers of high-quality products, offering flexible and expandable design options. We are well positioned in the Industrial Gases and Alternative Fuels marketplace given our vast industry knowledge and technical expertise. We’ve established market channels worldwide through our parent company, EKC. Operating as a LEAN manufacturing facility, productivity is high and our lead times and delivery are timely and consistent.

Tech Series on High-Pressure CNG Fuel Systems: Part 3- Pressure Relief Devices

By Kasia McBride, Marketing Manager, NGVi 

Pressure relief deviceWhile CNG fuel systems are extremely safe, due to stringent manufacturing requirements, it is essential that NGV technicians fully understand the specific standards that apply, and know how each component within the fuel system should operate. This article explores pressure relief devices (PRDs), and is the third in our series on the high-pressure side of the CNG fuel system.

Each CNG cylinder must have at least one PRD. PRDs are mandatory safety devices located at one or both ends of a CNG fuel cylinder. They are designed to protect a CNG cylinder from catastrophic rupture by activating (opening) at a specified temperature or pressure, and thereby relieving the CNG cylinder of its contents if the pressure becomes excessive.

The PRD type and location, determined by the cylinder manufacturer, is part of the certification process for the cylinder, and cannot be changed without the manufacturer’s approval.

PRDs can be activated by pressure, temperature, or a combination of both. The most common type of PRDs used in North America are thermal PRDs. These PRDs use a fusible alloy material that melts at a specific temperature (the alloy itself has a set melting point between 212°F-230°F). In the event of heat build-up, the material melts, opening a path for natural gas to release safely through a vent. CNG cylinders must be installed in such a way that their PRDs are not thermally shielded in likely fire scenarios.

PRD with hairline crackThe key point to remember is that PRDs are
one-time use only devices. If they open due to excessive temperature or pressure, they will stay open. They are also not serviceable in any manner and if they are activated, they must be replaced. If a PRD is damaged (bent, corroded, etc.) it must be removed from service, destroyed, and a new approved PRD installed in its place. If for any reason a PRD is removed, but is not damaged, it may be reinstalled--but on the same exact cylinder it was removed from (no swapping).

Because ensuring the integrity of the CNG fuel system is the core of NGV safety, routine inspections of the CNG fuel system, including examining all PRDs, are required at least every three years or 36,000 miles, whichever comes first, and after any accident or fire.

During the CNG fuel system inspection, NGV technicians should check PRDs for damage, including gouges, scratches, corrosion, rust, bulging, and plugged channels. They should verify the PRDs are properly attached to the cylinder and are not deformed or corroded. Also during the inspection process, NGV technicians 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.

One of the biggest causes of PRD failure is moisture. According to NFPA 52, PRDs must be designed in such a way that moisture cannot collect and freeze in a manner that would affect their performance.

caps on PRD vent lineDuring CNG fuel system inspections, technicians should visually determine whether the vent tube is routed or bent in such a way that water hasn’t accumulated and filled the PRD. Technicians also should verify and record whether there is a cap on the end of each PRD vent line. These caps are installed to prevent water or debris intrusion. If caps are missing, technicians should check for evidence of water, including water marks in the vent tube or the PRD, for loose fittings on the outlet side, or loose or stretched PRDs.

Finally, PRDs should be carefully checked for leakage, using a liquid leak check solution and possibly a gas detector. This includes leak checking each PRD connection to each cylinder valve, between the PRD and cylinder port, and the vent side of the PRD.

Assuring the CNG fuel system’s integrity is crucial for NGV fleet safety and requires specialized training on the entire CNG fuel system, including all high-pressure components such as PRDs. For more information about NGVi’s CNG Fuel System Inspector Training, click here.

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 January 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


RTA Unveils Brand New Compressed Natural Gas Buses Tuesday

Natural Gas Refueling Station Opens in

Republic Services Goes

Potential Buick Regal CNG Caught Testing In

Upcoming Training from NGVi

NGV Technician and Fleet Operations Safety Training

June 23, 2015
Clearwater, FL
July 7, 2015
Northern California East Bay

One-day session that teaches you the elements involved in the safe maintenance practices, fueling procedures, and operation of NGVs.


NGV Technician and Fleet Operations Safety Training

NGVi Cylinder Fuel System Inspector Training

CNG Fuel System Inspector Training

June 24-25, 2015
Clearwater, FL
July 8-9 , 2015
Northern California East Bay

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


CNG Fueling Station Design Training 

August 24-25, 2015
Las Vegas, NV
November 30-December 1
Spring Valley , NV

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


NGVi CNG Fueling Station Training

NGVi CNG Fueling Station Operation and Maintenance Training

CNG Fueling Station Operation and Maintenance Training

August 26-27, 2015
Las Vegas, NV
December 2-3, 2015
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.


Heavy-Duty NGV Maintenance
and Diagnostics Training

August 11-13, 2015
Downey, CA
September 1-3, 2015
Clearwater, FL

This intensive three-day training course prepares technicians to understand the operation, maintenance, diagnosis and repair of heavy-duty natural gas vehicles and covers all natural gas heavy-duty manufacturers’ systems, including CNG and LNG, with major emphasis on Cummins ISL G-equipped vehicles.


Heavy-Duty NGV Maintenance and Diagnostics Training


Register Now

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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 »

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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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