Inherently Safe Designs for Hydrogen Use

The hydrogen industry is developing fast and safety experts have to keep up the pace integrating hydrogen specificities. A sensible approach is to adapt practices that has already been developed for other industries. However, time is of the essence when dealing with hydrogen safety cases, therefore incorporating effective mitigation strategies and inherent safety concepts at the start of the project can avoid surprises and costly re-designs later on. This paper will present a number of strategies based on Gexcon’s experience within the hydrogen industry, which have been quantified and illustrated thanks to the use of CFD modelling.

Early isolation is key to limit the released quantity of hydrogen which could potentially lead to a vapour cloud explosion in case of delayed ignition. Relying on a detection system is thus a requisite but is sometimes not sufficient to prevent hazardous conditions. It is thus necessary to implement safety measures that follow simple concepts making the equipment inherently safer.

The first concept deals with the largest inventory, namely the hydrogen storage. The use of automatic shut-off valves right at the bottles would instantly stop the hydrogen feeding to the system.

The second notion relates to the size of the available free volume. The larger it is, the larger the hydrogen cloud might become. Partitioning to limit the free volume before releasing to a vent mast is proved valuable and effective.

The third proposition relies on hydrogen natural high buoyancy. Considering sloping ceiling would allow rapid evacuation of any release and avoid any accumulation. Different designs present different features which could be relevant depending on the use and restrictions (space etc).

When considered early on, inherently safe design would benefit the whole project without the need to investigate and invest in sophisticated equipment or procedure.