Requirements for Dispensing of Compressed Natural Gas Yvonne Espinoza, PE Austin Fire Department Engineering Services
Course Overview Enforcement of code requirements Application of code requirements Hazard analysis of CNG Components, arrangement and operation of CNG fuel dispensing stations Requirements for CNG dispensing stations 2
Jurisdictions Federal Requirements State Requirements Local Requirements Fire Code Amendments Standards 3
City of Austin Fire Code City of Austin Ordinances 2012 International Fire Code NFPA Standards National Standards Technical Reports and Performance Based Designs 4
City of Austin Codes for CNG Installations 2012 International Fire Code Chapter 50 Hazardous Materials Chapter 53 Compressed Gases Chapter 23 Motor Fuel-Dispensing Facilities NFPA 30A Motor Fuel Dispensing Facilities NFPA 52 Vehicular Gaseous Fuel System Code NFPA 70 National Electrical Code ASME/ANSI Standards 5
What is CNG? Colorless, odorless, lighter than air gas. Natural gas supplied via pipeline for consumers requires odorization. Odorized at a level that allows detection of the CH 4 at 20-25% of the lower flammable limit. 6
Properties of CNG Property CNG Molecular Wt. 16.04 Stor. Pressure Stor. State 2500-4000 PSI Compressed Gas Flammable Range 5-15% in air Autoignition Temp. 1003 F Heat of Combst. Odorized 17.8K BTU/lb Yes 7
CNG Fuel Dispensing Stations CNG stations may be designed for fast or slow fills. All fast fill stations have three major elements: Compressor Fuel Storage Containers Dispensers 8
2-4 Stage Compressor Compressor Isolation Valve 3000-5000 PSI Pressure Vessel 30-90 PSI Pressure Vessel Pressure Vessel Gas Shutoff Valve 1st Stage Regulator February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 9 Dispenser
Equipment Location Outdoors or under weather protection 10 ft from building, lot line, public way and sources of ignition 25 ft from nearest railroad track Not beneath power lines 20 ft from flammable/combustible liquids 10
CNG Compressors CNG compressors increase the pressure of the methane. Compressors may be driven by either engines or electric motors. Engine is fueled by natural gas. Can produce flow rates of 1,000 to 5,000 CFM @ pressures to 4,500 PSIG. 11
Pressure Gage for Each Compressor Stage February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 12
CNG Compressor Features Isolation valve at compressor suction inlet. Relief devices that limit stage pressure Automatic shutdown in the event of: High discharge pressure Low suction pressure Compressors must be manually reset upon activation of automatic or emergency shutoff. 13
Compressor Suction Inlet Isolation Valve February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 14
CNG Storage Containers Storage containers for CNG are pressure vessels that must meet the ASME Boiler & Pressure Vessel Code. Vessel storage volumes can be as great as 30,000 cubic feet. Storage pressures range from 3,600 to 5,000 PSI. 15
February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 16
February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 17
National Board of Pressure Vessel & Boiler Inspector ID number. Maximum Allowable Working Pressure February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 18
Pressure Relief Valves Spring loaded safety relief valves are required for CNG service. Must be certified as meeting the ASME BPV Code. To facilitate servicing, a shutoff valve can be installed between the PRV and the pressure vessel. Ensure that the shutoff valve is locked in the open position. PRV set pressure cannot exceed the MAWP of the pressure vessel except when allowed by ASME Section VIII. 19
Conventional Spring Loaded Safety Relief Valve 20
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ASME Certification Stamp Set Pressure Date of manufacture or certification February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 22
Venting of CNG Closed transfer system approved by the local AHJ Atmospheric venting approved by the AHJ Separation Grounding and Bonding Vent Tube Signage 23
CNG Dispensers May have the same appearance as gasoline dispensers. Display normally indicates equivalent gasoline gallons of CNG dispensed. The dispenser may consist of a high pressure hose & nozzle mounted on a vertical post. 24
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CNG Dispenser Location 10 ft from combustible buildings and lot lines Such that vehicle is on the premises 20 ft from fixed sources of ignition Such that the nozzle when the hose is fully extended does not reach within 5 ft of building openings 27
CNG Dispenser Components Conventional CNG dispensers will have the following components: Fuel connection nozzle Fuel hose with a breakaway connection Emergency shutdown device Fuel nozzles, hoses, dispensing equipment shall be listed for CNG service. 28
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Emergency Shutdown (ESDs) ESDs should be located within 75 ft but not closer than 25 ft from the dispensers and shall also be located in the compressor area ESDs are designed to: Stop the flow of fuel at the dispenser. Close the isolation valve at the suction inlet connection of the compressor Close the isolation valve between the container and the dispensers The compressor must be manually reset when a ESD is activated. 31
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Unattended Self Service Dispensing Quantity limits applied to the uninterrupted delivery of fuel or limited in quantity by preprogrammed card Operating instruction and emergency procedure signs required A means to notify the Fire Department shall be provided All users are required to be trained 33
City of Austin Permitting Requirements Storage of any regulated gas over 100 cu. ft. in quantity requires an Aboveground Hazardous Materials Permit 3 yr reporting permit Fee is based on quantity on CNG stored at NTP 34
Repair Garages Must be designed per building code for each type fueled vehicle being repaired Ventilation in accordance with Mechanical Code Continuous ventilation Or activation by gas monitoring set at 25% LFL Ventilation rate no less than 1cfm/sq.ft. 35
Emergency Response Considerations for CNG CNG is a flammable gas. Therefore strategies normally applied for natural gas emergencies are applicable. Isolate the fuel source. Cool exposures High pressure flammable gas fires are jet fires. Release rate is function of the hole diameter. For vehicles, the incident may be over by the time the Engine Company arrives. February 11, 2004 PFC Requirements for Dispensing CNG, LPG & LNG Alternative Fuels 36
CNG Compressor Plant Fire Phoenix, 2004 In January 2004 Phoenix FD responded to a CNG compressor fire. While the cause is unknown this incident confirmed our understanding of CNG: Jet fire that produced a high velocity flame front. Cooling of exposures combined with isolating the gas supply is the safest tactic. 37
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Yvonne Espinoza 512-974-0185 yvonne.espinoza@austintexas.gov QUESTIONS? 39