Progress: Addressed, Monitoring
DOT Relevance: 172 Subpart G
This key area pertains to the availability of appropriate information resources needed by first responders to potential emergencies (e.g., accidents) involving hydrogen stored and transported as a compressed gas in steel cylinders. The emergency response information must be applicable to tube trailers and/or any other compressed hydrogen steel cylinder packaging. In particular, the emergency response information resources must apply to operations such as the transfer of hydrogen from tube trailers to stationary pressure vessels at vehicle fueling stations, temporary parking of tube trailers to provide the hydrogen source at a fueling station, delivery of hydrogen-filled steel cylinders to fueling stations, and the use of hydrogen mobile fuelers with steel pressure vessels.
This key area will be critical if hydrogen fueling infrastructures evolve that utilize hydrogen transported as a compressed gas in steel cylinders. Examples include hydrogen transported in tube trailers from central production plants to fueling stations (with the gas transferred to permanently installed high-pressure vessels at the fueling station, or, as is more common, parking of the tube trailer at the fueling station to serve as a temporary gas supply) and mobile fuelers (some of which utilize compressed hydrogen stored in steel cylinders). Both of these examples are in common use at this time to support hydrogen-fueled vehicle demonstration projects. However, neither of these infrastructure scenarios are economically viable, nor are they likely to be part of a widespread hydrogen-fueled vehicle deployment scenario. They are not economically viable because, for example, a truck-transported tube trailer (which can hold up to 350 kg (772 lb) of hydrogen at up to 21.4 MPa (3100 psi)) consumes more energy than it delivers for distances greater than roughly 1610 km (1000 miles).
As discussed below, emergency response resources applicable to accidents involving compressed hydrogen steel pressure vessels (e.g., as used in tube trailers) are well developed for current applications, which are generally limited to restricted-access industrial sites and trained personnel. These same resources are probably appropriate and adequate for supporting current tests and demonstrations of hydrogen vehicles, which are few in number, have limited access, and are closely managed by trained personnel. A possible exception may be associated with current and future use of mobile fueling stations that store hydrogen in steel vessels. These units involve a relatively unusual combination of components (e.g., unlike tube trailers, they are not addressed specifically in the DOT ERG2004) and their application straddles two jurisdictions (i.e., DOT when they are transported on highways and OSHA/local AHJs when they are parked and operated as vehicle fueling stations).
If hydrogen-fueled vehicles commercialize with a fueling infrastructure that involves tube trailers and/or the use of any other steel pressure vessels in DOT-jurisdiction applications (which is judged to be unlikely), then new and specifically focused emergency response resources will be needed to enable first responders to deal effectively with potential accidents in environments such as public-access fueling stations.
Progress toward providing the technical basis to support development of emergency response information applicable to a potential hydrogen fuel infrastructure involving compressed hydrogen stored in steel vessels is rated as Addressed, monitoring. This is because considerable resources are already available, and although these resources were not developed to apply specifically to environments like public-access fueling stations, it is unlikely that steel pressure vessels will be a significant element of the fuel-delivery infrastructure supporting commercialized hydrogen vehicles.
For example, in the DOT ERG2004, compressed hydrogen is assigned ID Number 1049 and covered by Guide Number 115 (GassesFlammable, Including Refrigerated Liquids). Emergency response guidance pertaining to tube trailers (which are designed, manufactured, tested, and marked consistent with DOT-3A or -33A specifications in 49 CFR 178.36 and 178.37, respectively) that might transport hydrogen is also contained in literature produced by industrial gas companies (e.g., Safetygrams) and other sources. Emergency response resources are also readily available for compressed hydrogen in individual steel cylinders.
In 2005, the NASFM and DOTs RITA established the Hydrogen Executive Leadership Panel (HELP). HELPs mission is to bring together emergency responders, government regulators, scientists, consumers and experts from the automotive and energy industries to facilitate a safe and orderly transition to hydrogen and other alternative fuel sources. HELP will focus on issues involved in training, educating, and mobilizing emergency responders to work with government, industry, and community groups to facilitate and ensure hydrogen transport, storage and distribution, and the safety of vehicles and environs.
ASME's Boiler and Pressure Vessel project team on hydrogen tanks is addressing high pressure gas storage in metal and composite tanks. The work plan includes a proposed new article KD-10 to Section VIII-3, a code case on composite tanks for Section VIII-3, and a revision to code case 2390 on metal lined composite reinforced circumferentially wrapped pressure vessels under Section VIII-3. Transport tanks may also be included in Section XII.
Currently available emergency response information resources are adequate for current low-vehicle-number and controlled-access hydrogen vehicle demonstration projects that sometimes utilize compressed hydrogen delivered in tube-trailers or individual cylinders. More research is needed to develop emergency response resources applicable to mobile hydrogen fueling stations with steel pressure vessels, especially if the use of such mobile fueling stations increases.
Comprehensive emergency response resources applicable to compressed hydrogen steel pressure vessels employed as part of a commercialized hydrogen vehicle fueling infrastructure will probably not be needed, because steel pressure vessels are not anticipated to be a significant part of the fuel-transport aspects of such an infrastructure. However, hydrogen fueling infrastructure evolution should be monitored, and work to develop appropriate emergency response resources should be initiated if it appears that steel pressure vessels will in fact be part of this infrastructure.