Hydrogen explosion in a foundry.

The event occurred in the continuous casting of hot metallic melt of the plant.
Cooling water leaked through a crack in the cooling water inlet pipe of a secondary cooling line and directly into the hot melt (temperature > 1500 °C). This resulted in the formation of hydrogen which ignited on the hot surface.
The pipe in question had been in operation for a prolonged period. The material analyses of the component showed that the rupture occurred as a consequence of fatigue. The annual visual inspection had revealed no signs of imminent failure.

The INITIATING cause was the leaking of cooling water onto the melted metal, which produced hydrogen by thermolysis, followed by its ignition.
The root cause was probably a design or inspection deficit, because the cooling pipe failed due ageing due to fatigue.

casting unit, water cooling pipe

The annual visual inspection had revealed no signs of imminent failure.

(database ProcessNet)
In order to effectively avoid such an event in future, the following points should be remembered:
(1) The discussion of potential hazard sources should include a sufficiently wide range of possibilities to ensure the safe management of the process.
(2) Cooling water connection points should be fitted with a splash protector, if hazardous conditions can be created by escaping leakage water.
(3) In presence of fatigue stress, it should be critically evaluated whether components are suitably designed and monitored.
(4) Fatigue-affected components should be inspected for fatigue damage by means of dye penetration method or ultrasound.