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Hydrogen Ventilation and Deflagration Venting Analysis for Indoor Storage and Dispensing Facilities


By Bob Zalosh

Introduction

Current and future anticipated use of hydrogen-fueled vehicles entails using special facilities for storing hydrogen, compressing it to the pressures needed for on-vehicle storage, and dispensing it during refueling operations. Some of these facilities are unenclosed, so there is no opportunity for accidentally released hydrogen to accumulate. Other facilities are partially or completely enclosed such that hydrogen accumulation and ignition of the accumulated gas layer are a significant concern.

Similar concerns exist for compressed natural gas (CNG) vehicle refueling facilities. National Fire Protection Association (NFPA) Standard 52, entitled “Compressed Natural Gas Vehicular Fuel Systems,” provides guidance on the minimum ventilation rates to prevent/limit methane accumulation and ignitions in indoor facilities. One way of approaching the issue for hydrogen is to develop analogous guidelines to those for CNG. This is the approach being followed by a committee currently in the throes of drafting such a standard. One difficulty is the lack of any explanation of the technical basis for the ventilation rates in NFPA 52.

The specific approach followed in this report to suggest analogous ventilation rate guidelines is as follows:

Another guideline addressed in this report is the deflagration venting requirements to prevent significant damage if a flammable hydrogen-air mixture were ignited in a confined structure. Available test data and existing NFPA guidelines on hydrogen deflagration venting are reviewed following the discussion of ventilation.

[Note: Only the introduction to this paper is included here.]

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