1 / 23

Clean Vehicle Education Foundation

11/3/2011. www.cleanvehicle.org. 2. Purpose. To inform vehicle maintenance organizations about the need to safely prepare fuel systems for maintenance repairs or disposal of cylinders and the specific issues that should be addressed using approved facilities and only the vehicle or equipment suppli

yamal
Download Presentation

Clean Vehicle Education Foundation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. 11/3/2011 www.cleanvehicle.org 1 Clean Vehicle Education Foundation Defueling and Disposal of CNG Cylinders CTA Conference & Expo November 3, 2011

    2. 11/3/2011 www.cleanvehicle.org 2 Purpose To inform vehicle maintenance organizations about the need to safely prepare fuel systems for maintenance repairs or disposal of cylinders and the specific issues that should be addressed using approved facilities and only the vehicle or equipment supplier’s maintenance procedures.

    3. Why the Fuss? Airborne Tank Injures Worker By Mary K Reinhart, East Valley Tribune A compressed natural gas tank turned into a missile Monday, launching out of a … service bay, soaring more than 500 feet, crashing down through the roof of a nearby body shop and critically injuring a longtime employee… The employee had bled the tank, as is standard practice, and believed the tank was empty when he began removing the valve, Cameli said. "The valve went one way and the tank went another direction”, she said, "The tank hit the vehicle, and then shot into the air." 11/3/2011 www.cleanvehicle.org 3

    4. CNG Cylinders are Different Cylinders hold flammable gas at very high up to 4,500 psi. Maintenance may be unfamiliar with some of the hazards from the high fuel pressures. Modern CNG systems and components combine sophisticated design features to maximize operating safety but this same sophistication requires carefully developed maintenance procedures. Buses often have cylinders equipped with individual solenoid valves that require very specific defueling procedures. CNG cylinders serve for a limited life and then must be emptied and destroyed. This is a major enabler of the safe use of visual in-service inspection. 11/3/2011 www.cleanvehicle.org 4

    5. What are the Special Hazards? One hazard is similar to any fuel, the potential for fire if fuel is spilled or released. While CNG does not pool and spread on the floor like gasoline or diesel, it does float upwards and can accumulate near the ceiling of an unventilated garage. Safe venting procedures make sure that the CNG is released outdoors and upward into open air so that it can easily disperse without ignition. 11/3/2011 www.cleanvehicle.org 5

    6. Hazards Cont’d Although not a hazard per se, CNG is odorized just like domestic natural gas distributed to homes to make it easy to detect a leak. If the CNG is not properly released it can result in nuisance reports of gas leaks in the neighborhood. Another hazard is from the high pressure of the fuel. This makes it very important that procedures are followed to be sure that joints are not disconnected before the fuel pressure is released. Different system and component designs on different buses require different specific procedures for pressure venting and verification that the pressure is gone. 11/3/2011 www.cleanvehicle.org 6

    7. Hazards Cont’d Since cylinders or other high-pressure components may be replaced during the vehicle lifetime, leak testing the repaired system without the use of air is a critical safety issue. Though not exactly related to defueling or decommissioning, the safety issues merit inclusion. The last safety issue is to make sure that any CNG cylinders that are no longer safe to use are destroyed in a way that makes it very unlikely they will be returned to service after disposal. There have been instances in which unscrupulous sellers concealed damage from a buyer or even removed part of the cylinder composite to hide the fact that it was damaged. 11/3/2011 www.cleanvehicle.org 7

    8. Solenoid Tank Valves Some fleets have high rates of solenoid failure and no fuel is released from the cylinders. Solenoid valves have fine pilot orifices that can be plugged with debris or ice. A solenoid valve can vent gas for a while and then stop. The cylinder may be empty or the valve may be iced up. Intuition is not adequate to know how to open a solenoid valve. Manufacturer’s knowledge is necessary. Special tools are necessary for safe and sure venting of solenoid valve equipped cylinders. 11/3/2011 www.cleanvehicle.org 8

    9. Solenoid Tank Valves 11/3/2011 www.cleanvehicle.org 9

    10. Manual Tank Valve 11/3/2011 www.cleanvehicle.org 10

    11. Manual Valve + Solenoid Valve 11/3/2011 www.cleanvehicle.org 11

    12. So How to Safely Defuel Cylinders? Bad News There is no known single source for all of the information needed for a safe defueling process. Facilities must be approved according to local codes and defueling procedures must be specific to the vehicle system design. Organizations will probably have to assemble their own documented procedures for safe defueling and disposal, and train personnel. 11/3/2011 www.cleanvehicle.org 12

    13. Where Can We Get the Information? NFPA 52 requires: Written procedures and trained personnel Approval of any method for atmospheric venting Control of the venting flow Grounding to prevent ignition Slow discharge of Type 4 cylinders Cylinder restraint during venting An unobstructed 2” vent pipe 11/3/2011 www.cleanvehicle.org 13

    14. More Information 11/3/2011 www.cleanvehicle.org 14

    15. Information Sources The Vehicle Manufacturer NFPA 52 – Vehicular Fuel Systems Code – National Fire Protection Association, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101, 617-770-3000,www.nfpa.org. Compressed Natural Gas (CND) Cylinders: Tips for General Visual Inspection and Care, GRI-96/0426, (Report & Poster), Gas Technology Institute, 1700 South Mount Prospect Road, Des Plaines, IL 60018-1804, 847-768-0500, www.gastechnology.org. 11/3/2011 www.cleanvehicle.org 15

    16. More Information Cylinder Care and Maintenance Handbook, GTI-01/0119, Gas Technology Institute, 1700 South Mount Prospect Road, Des Plaines, IL 60018-1804, 847-768-0500, www.gastechnology.org. CGA C-6.4 - Methods for External Visual Inspection of Natural Gas Vehicle and Hydrogen Vehicle Fuel Containers and Their Installations - Compressed Gas Association, 14501 George Carter Way, Suite 103, Chantilly, VA 20151, 703-788-2700, www.cganet.com. Natural Flo Internal Solenoid CNG Tank Valve Removal & Installation, or Technical Specifications and Description of Operation, External CNG Cylinder Solenoid Tank Valve, GFI Control Systems, 100 Hollinger Crescent, Kitchener, Ontario, CanadaN2K 2Z3, 519 576 4270, gfikitchener@gfics.eu 11/3/2011 www.cleanvehicle.org 16

    17. Safe Defueling Requires: Approved venting facility (NFPA 52 and Fire Marshal) GTI handbook also provides specific guidance Manufacturer’s venting procedures for vehicles and valves Complete Written defuel procedure and trained personnel 11/3/2011 www.cleanvehicle.org 17

    18. Typical Defueling Steps Exhausting fuel by running out of gas Depressurizing the piping by shutting off cylinder valves and venting (Vehicle/valve OEM) Determining if solenoid valves are working (Vehicle/valve OEM) Connecting the vent point to the vent stack (Vehicle OEM) Valve-specific defueling procedure for each cylinder in turn (Vehicle/valve OEM) 11/3/2011 www.cleanvehicle.org 18

    19. More Typical Defueling Steps Verifying that cylinders are empty (Vehicle or valve OEM) Removal of cylinder valves (Vehicle or valve OEM) Dismounting cylinders (Vehicle OEM) Purging of cylinders (CGA C-6.4) Destruction of cylinders (CGA C-6.4) Disposal of cylinders (Local disposal sources) 11/3/2011 www.cleanvehicle.org 19

    20. Vehicle Defueling Specs Convenient and safe defueling capability should be specified as part of the purchase specification. Defueling should not require dismantling the system. Defueling systems should be designed to allow safe defueling even if some components have failed such as solenoid and Ľ turn valves. Service manuals should provide clear and safe instructions for defueling under any circumstances, including after an accident. 11/3/2011 www.cleanvehicle.org 20

    21. Safe Leak Testing High-pressure compressed air must never be used to leak test CNG cylinders or piping systems. Use only natural gas, nitrogen or a nitrogen-helium mix to leak test the CNG system. Two very serious accidents resulted from air leak testing: A triple fatality in Quebec A very serious personal injury when a filter housing on a bus exploded 11/3/2011 www.cleanvehicle.org 21

    22. Why Air is Unsafe High-pressure can mix with residual CNG and form an explosive mixture. Many ignition sources exist and the explosive pressure can 10x the starting pressure. Plastics or other non-metallic materials can provide the fuel for an explosion even if there is no CNG present, just air. Plastics absorb CNG and are very easy to ignite. Residual oil films also facilitate ignition. Compression shock or static charge can ignite. 11/3/2011 www.cleanvehicle.org 22

    23. “One More Thing” A failed solenoid tank valve can cause its cylinder to be over-pressurized. Failed valves have been implicated in cylinder failures in Italy and Korea. Solenoid valves should be periodically checked for proper operation. Some fleets have experienced multiple failures. Buses should not continue in service with a failed solenoid tank. Bus OEMs should provide a diagnostic procedure. 11/3/2011 www.cleanvehicle.org 23

More Related