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Document Update: SAE J2578, Recommended
Practice for General Fuel Cell Vehicle Safety
by Karen Miller
Vice President of the National Hydrogen Association
The Society for Automotive Engineering (SAE) is making terrific
progress on the development of industry recommended practice
documents for fuel cell vehicles. The group has been around
for only two years, but with the input of vehicle manufacturers,
fuel cell developers, certification agencies, and industry trade
associations (including the NHA), the group has developed six
working documents, one of which has successfully been balloted
and is in publication. This article focuses on the Safety Working
Group, in which the NHA has had the most interest and participation.
This working group met on January 8-10, 2002 in Troy, Michigan
to work out remaining technical details, present the draft to
the full SAE Fuel Cell Standards Committee, and incorporate
comments from this walk-through.
The document covers integration of fuel cells into vehicles,
and is applicable to all fuel cell vehicle fuels. It addresses
unique aspects of the vehicle design associated with the fuel
cell. A companion document is the fuel system safety standard,
still under development by this same working group.
Glenn Scheffler, UTC Fuel Cells, chairs the working group. He
has granted permission to reprint the foreword of the document
for information purposes.
Foreword: Vehicles manufactured with liquid hydrocarbon as fuels
have a long history of creating appropriate safety countermeasures.
With the onset of new hydrogen fuel cell systems, new mechanical
and electrical system safety design parameters will need to
be provided to vehicle developers. These SAE reports are an
initial attempt to formalize a list of important safety items
for fuel cell vehicle and subsystem developers.
The purpose of this document is to identify the criteria for
the integration of fuel cell systems into vehicles. This document
relates to the overall design, construction, operation and maintenance
of fuel cell vehicles including the integration of the Fuel
Cell Systems (and other systems containing fluids with hazards
as defined in SAE J2579) into the vehicle.
SAE draft documents are available only to working group members,
or those parties who may offer technical input to the development
of the document. Once the document is published, it will be
available to the public through the SAE. If you believe you
can contribute to the development of this document, please contact
Glenn Scheffler at +1-860-727-2259, Glenn.Scheffler@UTCFuelCells.com.
The public can access general information about the SAE Fuel
Cell Standard committee and its activities on the Internet
at the SAE website, www.sae.org/fuelcells.
The basic outline of the document is shown here:
* 1.0 Scope
* 2.0 References
* 3.0 Definitions
* 4.0 Guidelines for Design and Construction
* 5.0 Operation 6.0 Emergency Response
* 7.0 Maintenance
The working group members participate on a number of other
related codes and standards efforts, including the International
Code Council ad hoc Committee on Hydrogen Gas, and the National
Fire Protection Agency’s (NFPA’s) Vehicular Alternative
Fuel Systems Committee (VAFSC). This collaboration is intended
to minimize duplication of effort and potential incompatibility
between developing codes and standards.
Hazardous conditions addressed in the document include:
Fuel
Flammability
Toxicity
Pressure (High)...Extreme Temperature
Electric
High voltage
Intermediate voltage
Three types of releases are covered:
1. Releases to the exterior
2. Releases to the passenger compartment
3. Releases within the vehicle into other compartments
During the walkthrough with the full committee, a number of
issues came up. Some of the issues that may be of particular
interest to the hydrogen community are as follows:
* Compressibility of hydrogen changes with pressure. CNG documents
used 0.8 because that is the compressibility within the range
of interest. With hydrogen, the range of interest is broader
(includes 10,000 psi), and so a compressibility curve may
be needed in the document.
* Parking in garages. SAE looked at codes for guidance –
there is currently not consensus. This SAE document provides
for vehicle testing and prohibits fuel concentrations in garages
above 25% lower flammability limit (LFL).
* Pressure Relief Devices (PRDs) present a potential single
point failure. In case of PRD activation, 25% LFL is exceeded.
Precautions are recommended to reduce this to a low probability
or have manufacturers address the risk.
* Water discharge must not create a hazard. Fuel Cell vehicles
expel approximately 6 fluid ounces of water per mile. In sub-zero
temperatures, this could create a hazardous condition, particularly
with large numbers of fuel cell vehicles on the road. There
is an energy cost to ensure the discharge is in the form of
water vapor. This issue should be addressed by the vehicle
manufacturers.
Following the presentation of the document, the full committee
gave permission to go directly to balloting following incorporation
of the committee comments. It will then be made available
to committee members for a 28-day voting period.
“The working group plans to present the content of this
effort to the appropriate international standards bodies,
including IEC TC 105 and ISO TC 22/SC 21 for consideration,”
says Scheffler. “There is great interest in utilizing
the information and data contained in this document for the
development of international standards. Starting with an international
group of experts in the SAE committee provides some confidence
that the document may be internationally acceptable.”
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