Release of hydrogen during hydrogenation

The event occurred at the hydrogenation unit of a pharmaceutical company.
145 kg of hydrogen were released at the atmosphere at the gas circulation pump, due to a maintenance error. A specialist company (third-party company), had replaced the cylinder head of pump, but during assembly they did not re-installed the prescribed temperature sleeve for the thermometer (the temperature sleeve is the pressure-bearing element).
The safety flare of the affected plant was triggered, the plant operations management and plant fire brigade were called on duty, the hydrogen supply to the neighbouring hydrogenation unit was stopped and the system was switched to circular operation.

The INITIATING CAUSE was an error during re-assembling of the system after maintenance.
A possible contributing CAUSE could be a lack of maintenance instructions, or their shortcoming.

hydrogen recirculation pump

Maintenance works had been completed by a third party.

Only operative costs due to loss of hydrogen and production stop.

The safety flare was triggered, so that the leaked hydrogen could be released safely.
Factory fire brigade and factory operations management were called on site.
The hydrogen supply was stopped at the neighbouring hydrogenation plants and the system was operated in closed-loop mode.

To develop an assembly checklist together with the external (third party) company.