Risks considered when refueling with hydrogen

Refueling with hydrogen involves more risks than refueling regular fuels. The transshipment of gaseous hydrogen can take place under (very) high pressure, such as at (multi-fuel) filling stations. As such it is somewhat similar to refueling LNG.

Hydrogen fuel stations

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Sources of ignition during loading

Hydrogen is highly flammable and can easily ignite when exposed to sparks or high temperatures. The risk of fire and explosion is greater during loading and unloading operations due to the possible presence of open flames or hot surfaces in the area.

When hydrogen gas is released during loading, it can more easily ignite in the air due to its wide flammability range and low ignition energy. This increases the risk of fire and explosion during loading and unloading.

Controlling ignition sources is important during hydrogen loading. Consider proper connection, grounding and ensuring that electrical equipment meets the applicable classification requirements for hazardous areas. Weather conditions, such as the risk of thunder, must also be taken into account.

Overpressure scenarios when hydrogen is loaded

When loading hydrogen, exceeding the maximum permitted pressure is a safety risk. If early intervention is not taken and with insufficient safety measures (high alarm or automatic technical intervention), an overpressure scenario can escalate to rupture (leakage) or tank failure.

The design must take into account a safe layout of the site, so that the knock-on effects of explosions and fire can be reduced. For example, safety-critical and heavily manned areas are best kept separate.

Gas leakage of hydrogen during loading

Hydrogen gas accumulation is a major safety risk. In the case of hydrogen transport via tankers, gas accumulation due to leaks can occur in environments such as covered loading stations. Efficient ventilation in such environments is crucial to prevent incidents.

Causes of leakage of hydrogen gas under high pressure include defects in flanges, equipment and through valves. A deformed seal or gasket can also be the cause of a hydrogen gas leak. During loading, an additional cause is the incorrect connection and/or mechanical failure of the unloading hose connection.

The loading point for hydrogen gas is best closed (aligned) and covered (capped) when the system is not actively used to prevent unwanted leakage.

Operational risks when loading hydrogen

A leak of hydrogen gas is difficult to see. As indicated earlier, hydrogen ignites more quickly when released under high pressure, also during loading. The hydrogen flame that occurs as a result of this leak is colorless and difficult to detect.

In addition, the human factor also plays a role when working with hydrogen gas. When using compressed hydrogen safely, it is important to pay sufficient attention to the prevention of human error through an inherently safe design principle, for example so that the unintentional incorrect opening of valves cannot simply occur.

It is therefore important that personnel involved in the loading and unloading process receive good training to handle hydrogen safely, such as properly checking, flushing and ventilating a loading point for hydrogen gas before and after work.