Design of hydrogen fueling components is critical for safety and reliability. Intensive usage of such components in urban public environment is expected in the near future. Any leakage of gas or failure of equipment will create potential hazards. Materials for such category of equipment must have specific mechanical characteristics, including hardness (influence on the durability of the equipment and on the resistance to hydrogen) and be easy to machine. Air Liquide has developed a test program for qualifying equipment representing the present state of the art. Studies on the susceptibility of various steels to hydrogen embrittlement have been done. Test specimens were exposed to static and cyclic loads with hydrogen and an inert gas, the inert gas representing a reference. Various tests are described here. As a result, the importance of further development in the design and selection of appropriate materials for critical hydrogen components is required. Various options are presented and discussed.

It is expected that hydrogen will serve as a nonpolluting carrier of energy for the next generation of vehicles, and guidelines for its safe use are required. Hydrogen-gas service stations for supplying fuel-cell vehicles will have to handle high-pressure hydrogen gas, but safety regulations for such installations have not received much investigation. In this study, we experimentally investigated the flame characteristics of a rapid leakage of high-pressure hydrogen gas. A hydrogen jet diffusion flame was injected horizontally from convergent nozzles of various diameters between 0.1 and 4 mm at reservoir over pressures of between 0.01 and 40 MPa. The sizes of the flame were measured, and experimental equations were obtained for the length and the width of the flame. Flame sizes depend not only on the nozzle diameter, but also on the spouting pressure. Blow-off limits exists and are determined by the nozzle diameter and the spouting pressure. Furthermore, the radiation from a hydrogen flame can be predicted from the flow rate of the gas and the distance from the flame.

The European Community requires a vehicle-level bonfire test for vehicles using plastic fuel tanks for conventional fuels (ECE R-34, Annex 5). A similar test could be applied to hydrogen-fueled vehicles. It would test a realistic vehicle with its complete fuel and safety systems. An advantage of such a test is that the same test could be applied independent of the hydrogen storage technology (compressed gas, liquid, or hydride).

There are currently standards for bonfire testing of a bare Compressed Natural Gas (CNG) tank and its Pressure Relief Device (PRD). This standard is FMVSS 304 in the U.S. and ISO 15869-1 in Europe. Japan has a similar standard. It requires that a bare tank and its associated PRD be subjected to a propane flame for 20 minutes. The tank must either survive or safely vent its contents. No modern composite wound tank is expected to survive for 20 minutes – so this is not a tank test but really a PRD test. The test procedure requires the PRD to be shielded from direct impingement of the flames – but the shield is not well specified. If it shields the PRD too well, the PRD will not activate and the tank will burst. This paper describes the results of a CNG and a hydrogen tank burst from such tests. The mechanical energy released is enormous. It is simply unacceptable to allow the tank to burst – the PRD and venting system must work. Organizations in the U.S, Europe, and Japan are in the process of modifying the CNG tank bonfire test for compressed hydrogen storage.

A bare tank with a single PRD is not a good simulation of a hydrogen fuel systeminstalled in an actual vehicle. There will usually be multiple tanks plumbed together at either the tank pressure or at the intermediate pressure (after the pressure regulator). There may be more than one PRD. The tank may be shielded (from debris) or insulated to protect it from an underbody pool fire. Also the heat transfer from the simulated pool fire (propane flame) will be very different when mounted in a vehicle versus the bare tank test. A vehicle-level pool fire test will alleviate these problems.

It is therefore recommended that the bare tank test be replaced by or augmented with a vehicle-level bonfire test similar to ECE R-34, Annex 5.

In the last years different Italian hydrogen projects provided for gaseous hydrogen motor vehicles refuelling stations. Motivated by the lack of suitable set of rules, in the year 2002 Italian National Firecorps (Institute under the Italian Ministry of the Interior) formed an Ad Hoc Working Group asked to regulate the above-said stations as regards fire prevention and protection safety. This Working Group consists of members coming from both Firecorps and academic world (Pisa University). Throughout his work, this Group produced a technical rule covering the fire prevention requirements for design, construction and operation of gaseous hydrogen refuelling stations. This document has been approved by the Ministry s Technical Scientific Central Committee for fire prevention (C.C.T.S.) and now it has to carry out the Community procedure for the provision of information . This paper describes the main safety contents of the technical rule.

In recent years, federal and state safety authorities have worked to bring emergency planners and responders together with industry, the scientific community and consumers to ensure high levels of safety with gas and liquid pipelines, and more recently, with liquefied natural gas terminals. The U.S. Department of Transportation (DOT) is the federal authority on the safe transportation of energy, and the National Association of State Fire Marshals (NASFM) represents state-level safety authorities. Together, they have produced firefighter safety training materials, technical guidance and information for use in communities considering new energy infrastructure, and conducted research to support these activities. In 2004, the DOT-NASFM partnership established the Hydrogen Executive Leadership Panel (HELP) to ensure a safe transition from fossil fuels to hydrogen fuel cells. HELP brings together senior policy-level experts from all sectors to understand and recommend mitigation strategies for the risks associated with the transportation and use of hydrogen in motor vehicles. The initial group includes experts from the United States, Canada, and Europe. HELP will be supported by an advisory committee of emergency planners and responders individuals well-equipped to describe real-world scenarios of greatest concern and by a second advisory committee of engineers and scientists who will help translate the real-world scenarios into useful technical solutions. By September 2005, HELP expects to define the initial real-world scenarios of greatest concern, and bring together teams of experts to collaborate with automakers, energy producers, government authorities, consumers and public safety officials. Much work lies ahead, including creating guidance for hydrogen powered automobiles, emergency response safety training, establishing test methods to reflect real-world incident scenarios, and modifying state and local building and fire codes. The HELP leadership will present its strategic plan and first report at the International Conference on Hydrogen Safety in September 2005.

An essential problem for the operation of high pressure water electrolyzers and fuel cells is the permissible contamination of hydrogen and oxygen. This contamination can create malfunction and in the worst case explosions in the apparatus and gas cylinders. In order to avoid dangerous conditions the exact knowledge of the explosion characteristics of hydrogen/air and hydrogen/oxygen mixtures is necessary. The common databases, e.g. the CHEMSAFE database published by DECHEMA, BAM and PTB, contains even a large number of evaluated safety related properties, among other things explosion limits which however are mainly measured according to standard procedures under atmospheric conditions.Within the framework of the European research project SAFEKINEX and other research projects the explosion limits, explosion pressures and rates of pressure rise (KG values) of H2/air and H2/O2mixtures were measured at elevated conditions of initial pressures and temperatures by the Federal Institute of Materials Research and Testing (BAM). Empirical equations of the temperature influence could be deduced from the experimental values. An anomaly was found at the pressure influence on the upper explosion limits of H2/O2 and H2/air mixtures in the range of 20 bars. In addition explosion pressures and also rates of pressure rises have been measured for different hydrogen concentrations inside the explosion range. Such data are important for constructive explosion protection measures.Furthermore the mainly used standards for the determination of explosion limits have been compared. Therefore it was interesting to have a look at the systematic differences between the new EN 1839 tube and bomb method, ASTM E 681-01 and German DIN 51649-1.

Safety is a high priority for a hydrogen refueling station.Here we propose a method to safely refuel a vehicle at optimised speed of filling with minimum information about it. Actually, we identify two major risks during a vehicle refuelling: over-filling and over-heating. These two risks depend on the temperature increase in the tank during refuelling. But the inside temperature is a difficult information to get from the station point of view. It assumes a temperature sensor in a representative place of the tank and an additional connection between the vehicle and the station for data exchange. The refuelling control may not depend on this parameter only. Therefore, our objective was to effectively control the filling, particularly to avoid the two identified risks independently of optional and safety redundant information from the vehicle. For that purpose, we defined a maximum filling pressure which corresponds to the most severe following conditions: if the maximum temperature is reached in the tank or if the maximum capacity is reached in the tank. This maximum pressure depends on a few filling parameters which are easily available. The method and its practical applications are depicted.

The growing attention being paid by car manufacturers and the general public to hydrogen as a middle and long term energy carrier for automotive purpose is giving rise to lively discussions on the advantages and disadvan-tages of this technology also with respect to safety. In this connection the focus is increasingly, and justifiably so, on the possibilities offered by a probabilistic approach to loads and component characteristics: a lower weightobliged with a higher safety level, basics for an open minded risk communication, the possibility of a provident risk management, the conservation of resources and a better and not misleading understanding of deterministic results. But in the case of adequate measures of standards or regulations completion there is a high potential of additional degrees of freedom for the designers obliged with a further increasing safety level.For this purpose what follows deals briefly with the terminological basis and the aspects of acceptance control, conservation of resources, misinterpretation of deterministic results and the application of regulations/standards. This leads into the initial steps of standards improvement which can be taken with relatively simple means in the direction of comprehensively risk-oriented protection goal specifications. By this it s not focused on to provide to much technical details. It s focused on the context of different views on probabilistic risk assessment. As main result some aspects of the motivation and necessity for the currently running pre-normative research studieswithin the 6th frame-work program of the EU will be shown.

The CEP (Clean Energy Partnership) – Berlin is one of the most diversified hydrogen demonstration projects at present. The first hydrogen fuelling station serving 16 cars is fully integrated in an ordinary highly frequented Aral service station centrally located at Messedamm in Berlin. Hydro has supplied and is the owner of the electrolyser with ancillary systems. This unit produces gaseous hydrogen at 12 bar with use of renewable energy presently serving 13 of the cars involved. The CEP project is planned to run for a period of five years and is supported by the German Federal Government and is part of the German sustanaibility strategy. During the planning and design phase there have been done several safety related assessments and analyses:

• Hydro has carried out a HAZOP (HAZard and OPerability) analysis of the electrolyser and ancillary systems delivered by Hydro, Electrolysers.
• Hydro arranged with support from the partners a HAZOP analysis of the interface between the electrolyser and the compressor, an interface with two different suppliers on each side.
• A QRA (Quantitative Risk Assessment) of the entire fuelling station has been carried out.
• Hydro has carried out a quantitative explosion risk analysis of the electrolyser container supplied by Hydro Electrolysers.

The aim in the CEP-Berlin project was to follow the guidelines from the European Integrated Hydrogen Project, phase 2, (EIHP2) [1] when planning and designing a new hydrogen fuelling station. These guidelines focus on installation and operation of hydrogen refuelling stations, and were based upon best practice and knowledge from the industrial partners in EIHP 2. The explosion risk analysis for the CEP-Berlin facility demonstrated that the safety risk was acceptable if certain design modifications were carried out. Both Aral/BP and Hydro accepted the results from the quantitative risk assessments. These companies have also their own standards regarding safety acceptance criteria, which have to be complied with. The fuelling station was opened November 12 2004, and was put in normal operation during winter 2005.

Introduction and commercialisation of hydrogen as an energy carrier of the future make great demands on all aspects of safety. Safety is a critical issue for innovations as it influences the economic attractiveness and public acceptance of any new idea or product. However, research and safety expertise related to hydrogen is quite fragmented in Europe. The vision of a significant increased use of hydrogen as an energy carrier in Europe could not go ahead without strengthening and merging this expertise.

This was the reason for the European Commission to support the launch on the first of March 2004 of a so-called Network of Excellence (NoE) on hydrogen safety: HySafe [9].

With its 6th Framework Programme the European Commission has introduced these NoE’s as a new tool to facilitate collaboration within organisations with expertise in a given topic (hydrogen safety for instance). Ultimately, this collaboration should turn into integration of research programs and eventually integration of resources. Technical excellence and optimised research are tangible outputs of this integration.

Besides the development of an integrated, competitive scientific and industrial community in Europe on hydrogen safety, HySafe intends to be capable of jointly addressing the challenges presented by the safe transition from current fuels to a regular use of hydrogen in daily life. Technical expertise and activity encompass hydrogen release, ignition, fires, explosions, risk assessment and mitigation techniques.