Fire at a hydrotreater of a refinery

This incident occurred at a unit designed to convert heavy oil residues into refined products. It involved a fluidized bed reactor and the related hydrogen supply system serving the optimisation of the catalytic conversion insider the reactor.
Note: there are two versions of the events. eMARS and MARSH (see references). They agree in identifying triggering event the trip of a hydrogen compressor. They diverge however about the following steps and their causes. The version presented here is the one provided by the European eMARS database, because based on the results of an investigation.
The accident was probably triggered by a mechanical failure of regulation of a secondary supply line from the compressor which was providing the reactor with hydrogen. The supply line providing the reactor with hydrogen gas was at 160 bar and 500 °C. The rupture caused a hydrogen leak, which ignited and formed a horizontal jet fire. The flame was located at an elevation of about 8 m from ground level that affected other components and equipment.
The rupture occurred close to a valve in the hydrogen pipe with clamp connectors, in the vicinity of the reactors. The causes of the rupture were identified as being the result of anomalous operation of the facility due to reduced/non-existent hydrogen flow that led to cooling by natural convection and consequent thermal stress. The loss of flow in the pipe occurred because of a compressor becoming blocked and a second compressor reducing to minimal flow.
The fire then caused some other components in the facility to rupture, leading to a partial release of hydrocarbons. This was also the result of the malfunctioning of a cut-off valve when operated manually, probably because of a power cut owing to the power supply panel being affected by the fire.
There was also a fire near the air coolers that broke out when the facility was depressurised rapidly because of stresses in excess of those designed for.
The quantities involved were 70 t of hydrocarbon and 0.3 t of hydrogen.

The INITIATING/direct cause was a mechanical failure, which caused a series of additional failures. Two sources diverge on the exact reasons of these failures, but are bot pointing at the same type of causes.
Human errors and procedures and management shortcoming are the root cause, because procedures had not been followed and incorrect mitigating operations were undertaking on a series of failing components.

hydrogen compressor, flidised bed reactor

The hydrogen supply line was at 160 bar and 500 °C.

DESCRIPTION OF THE INDUSTRIAL PROCESS
The hydrocracker was a prototype, aiming at refining crude oil rest. It was of the type 'ebullated bed reactor' , i.e. a type of fluidized bed reactor that utilizes ebullition, or bubbling, to achieve appropriate distribution of reactants and catalysts. Hydrogen and feedstock enter at the bottom of the reactor, thereby expanding the catalyst bed.

The facility suffered such major damage that it had to be rebuilt. According to another source, the 325 M$ of 2016 can be converted into 401M$ of 2021.

There is no record of the event having consequences for human health, the environment or non-company property. The data recorded by the air quality monitoring network did not reveal significant increases in the concentration of the pollutants measured.

Two managers were found guilty of contributing to the incident through negligent and imprudent conduct.

adopted concerned both redesigning parts of the facilities and implementing additional management measures to monitor critical equipment. Unfortunately, the sources do not provide details.