Vehicle Maintenance Facilities Requirements for CNG and LNG Vehicles

Transcription

1 Vehicle Maintenance Facilities Requirements for CNG and LNG Vehicles Presented by: Leo Thomason Executive Director Natural Gas Vehicle Institute (NGVi) at NFPA Conference and Expo, June 11, 2014 Leo Thomason S. Durango Drive, Suite 304, Las Vegas, NV

2 About Leo Thomason Over 30 years of experience in the NGV industry Conducted over 20 vehicle maintenance and repair facility evaluations Delivers code and technical training to fleet owners, managers, and vehicle technicians Co-founder of Natural Gas Vehicle Institute (NGVi) Established in 1989 North America s leading provider of technical training and consulting on natural gas vehicles and fueling The only ASE CASE accredited training provider for CNG and LNG Topics Discussed in This Presentation Properties and characteristics of natural gas and how it compares with liquid fuels Vehicle maintenance facilities requirements for natural gas vehicles Properties of Natural Gas Is a gas like oxygen Composed of methane, ethane, propane, butane 85-96% methane Simplest hydrocarbon (CH 4 ) Diesel C 14 H 30 Gasoline C 8 H 18 Propane C 3 H 8 Health Hazards of Natural Gas Non-toxic Simple asphyxiate Above 7% will displace oxygen Inhalation is primary route of exposure Overexposure symptoms Shortness of breath Unconsciousness Two Forms of Natural Gas for Transportation CNG Compressed to +/ psi Stored onboard vehicles at F Remains a gas LNG Liquefied by cooling to -260 F Heavier-than-air in liquid state Lighter-than-air in gaseous state 2

3 Comparing Fuels (Table of Properties) CNG and LNG Comparisons CNG Odorized Gaseous state Lighter-than-air Always travels upward Simple asphyxiate Non-cryogenic Cylinders only vent under abnormal conditions LNG Un-odorized Liquid state Can be heavier-or-lighter-than-air depending on temperature Can pool on ground Simple asphyxiate Cryogenic (-260 F) Tanks will vent under normal conditions (may be frequently) Why Are NGV Maintenance Facilities Different? Existing facilities built to codes for gasoline/diesel Heavier-than-air fuels Natural gas Lighter-than-air Stored onboard vehicles at high pressures Classified areas are exactly opposite for CNG Code Development Developed over three decades Performance documents not design documents Based on primary assumed hazard Unintentional release and ignition of natural gas while a vehicle is inside a facility Based on historical experience Slow Release of Low-Volume CNG Usually caused by: Loose fitting Leaky valve Expected to dissipate rapidly Total volume of leak expected to be less-than-air volume inside the building Leo Thomason leo@ngvi.com 3

4 Rapid Release of CNG Usually caused by: Catastrophic failure of high-pressure tubing Gas discharge through PRD Malfunction Thermal fusible plug failure Rupture disk failure Expected to release a large volume of gas which would pose a hazard if released inside a building Slow Release of LNG Usually caused by: Loose stainless steel tube fitting Leaky valve Vaporized gas leak from heat exchanger or downstream stainless steel tubing Expected to dissipate rapidly Not anticipated to pose significant hazard due to low volume Rapid Release of LNG Usually caused by: Catastrophic failure in stainless steel tubing connecting tank to heat exchanger Liquid discharge through PRV or PRD Malfunction Thermal fusible plug failure Expected to release a large volume of gas which would pose a hazard if released inside a building Natural Gas Hazards Flammable gas that ignites in concentrations between 5% and 15% in air Ignition temperature 900-1,080 F Ignition sources must be controlled where an ignitable mixture may be present Should not be allowed to accumulate in an enclosed space Simple asphyxiate 4

5 Major Codes Governing NGV Facilities NFPA 52 NFPA 30A NFPA 88A NFPA 70 IFC IMC IBC IEC Code Inconsistency Some of the codes conflict Example: Ventilation in Pits IFC 1.5 cfm/sq. ft. NFPA 1.0 cfm/sq. ft. AHJ will determine which is applicable Major vs. Minor Repair Facilities Addressed by both IFC and NFPA 30A IFC is more stringent IFC Major vs. Minor Repair Facilities Definitions for Lighter-Than-Air Fuels Major Repair Facility: Repair garages where work is performed on the fuel system and may require open flames or welding Minor Repair Facility: Repair garages where work is not performed on the fuel system and is limited to exchange of parts and maintenance requiring no open flame or welding What Is the Fuel System? Includes any component between the receptacle and the fuel injector NFPA 30A and International Fire Code Exempt Minor Repair Facilities from all code requirements specific to CNG except for ventilation requirements required for all fuels Only non-cng fuel system maintenance and repair can be performed and no open flames or welding No LNG powered vehicle may be parked or repaired within an unmodified vehicle maintenance facility (LNG will vent and is non-odorized) 5

6 NFPA 30A and International Fire Code Minor Repair Facilities perform Chassis Lubrication Transmission Repair Engine Tune-ups Parts Replacement Oil Changes Break System Repairs Tire Rotation Similar Routine Maintenance Work Facilities Can Be Separated Some facilities can be separated into major and minor repair areas This can significantly reduce the cost of modifications Each facility is unique Separation can be accomplished through the use of fire walls, partitions and other methods all of which must be pre-approved by the AHJ Vehicle Maintenance/Repair Facility Evaluations Performed by an experienced professional Include a detailed visual inspection of the entire facility Documentation includes Recorded measurements Observations Photos Recommended modifications Facility Areas That Must Be Evaluated Building Envelope Ventilation System Heating System Lighting and Electrical System Pits/Floor Drains/Below Grade Surfaces Welding, Grinding and Hot Work 6

7 Building Envelope Ceiling geometry - should not promote collection of gas pockets Roof trusses - open design to allow thorough ventilation Enclosed rooms or spaces must prohibit the transmission of gases from the vehicle maintenance area Internal doors/windows must be closed when not in direct use Ventilation Option 1 Continuous Ventilation Each facility likely will have either Gravity ventilators (approved by AHJ) or power vents Make up air system Dedicated HVAC system If any of the three deliver ¾ to 1 cfm/12 cf. of room volume and operate continuously or are interlocked to lighting system, the 18-inch space from the ceiling becomes unclassified Ventilation Option 2 Interlocked with Methane Detection Power exhaust system interlocked with methane detection system Set to provide five air changes per hour Also capable of manual operation Detect at 25% LFL Methane detection must be able to: Initiate visual alarm Sound audible alarm Turn off heating system Turn on exhaust ventilation system Sound alarm at the control panel if the methane detection system fails to be operational plus turn off heating system and turn on exhaust ventilation system Heating Code prohibits open flame heaters or any heating systems with a skin temperature > 750 F Can be replaced with low pressure steam, hot water, infra-red or Class 1 Division 2 Group D rated heaters with a surface temperature < 750 F Lighting/Electrical Classified space CNG is from the ceiling 18 down LNG (in its liquid state) is from the floor 18 up If Option 1 for Ventilation is NOT selected All electrical equipment within the classified area must be: Class 1 Division 2 Group D or Moved below the classified area 7

8 Electrical Conduit Any Class 1 Division 2 Group D compliant electrical conduit that extends into the 18 inch classified space from an electrical device (transformer, electrical sub-panel, etc.) below the 18 inch classified space must be sealed within 10 feet of entering or exiting the classified space (has to be at the first conduit fitting) Electrical conduits that pass through a wall within 18 inches from the ceiling and extend from the maintenance and repair bays into other areas of the building must be sealed The Class 1 Division 2 Group D compliant electrical conduit connected to any classified device (electrical box, junction box, convenience outlet, etc.) located within the classified space must be sealed within 18 inches of entering or exiting the classified device Methane Gas Detection Not required by code except for LNG maintenance facilities Is frequently used to control the operation of the ventilation system when ventilation is not operated continuously or interlocked with the lighting system Welding, Grinding or Hot Work None of the codes require specific modifications Industry best practices call for: Using welding blanket or other protective device over all fuel system components Defuel vehicle to at least half of the rated pressure or more depending on the nature of the work LNG Maintenance Facilities All facility modifications required for CNG involving building envelope, ventilation, heating, lighting, electrical, and methane detection must be completed PLUS Any floor drains in the vicinity of the LNG maintenance bay must be sealed or otherwise modified Space 18 inches above the floor is Class 1 Division 2 Group D classified Below grade pits Require methane detection system interlocked with ventilation system inside the pit Methane detection system must be capable of all functions described earlier Suggested Plan of Action Conduct maintenance facility evaluation Develop preliminary plan of modifications Meet with the AHJ to discuss recommended plan of modifications Use the codes as reference Explain rationale behind recommendations Obtain conceptual approval before finalizing plans 8