Hydrogen release from a gas reycle compressor

A release of hydrogen occurred at the gas recycle compressor of a heavy oil desulfurization unit of a refinery.
An earthquake induced oscillations in the lubrication and sealing oil system of the compressor. This triggered the oil pump to start, bringing the pressure in the oil circuit from 135 to 137 bar. A section of the oil pipe to the compressor shaft bearing was corroded and could not stand the pressure, releasing the full oil content. Due to the leak, also the oil supply to the seal ring stopped, which could not anymore contain the hydrogen. The alarm was triggered by the hydrogen detector of the compressor room.

No personnel injuries. 3 000 l of lubricating oil and 2 109 m³ of hydrogen (180 kg) were released.

The INITIAL CAUSE was a combination of two factors. The earthquake started a sequence of event which brought a pipe already heavily weakened by external corrosion to rupture.
External corrosion of the pipe caused a leak from the bearing area of the compressor. The pipe had an external insulation made of rock wool, which absorbed moisture for a long period of time, creating the conditions for an accelerated corrosion.
Because of the insulation layer, visual inspection could not detect corrosion onst and progress.

The Chiba earthquake occurred the 14th of March 2012.
[Wikipedia: https://en.wikipedia.org/wiki/2012_Chiba_earthquake]

The unit was a naphtha reformer, providing various oil streams: heavy oil, heavy diesel oil, light diesel oil, and naphtha.

DETAILED ACCIDENTAL SEQUENCE
19:28 – An earthquake (M ≈ 4, epicentre in the northeast of Chiba ken) - the seal oil pump of compressor automatically started.
19:29 – While performing a routine walk around, the operator heard a sound resembling the actuation of a safety valve.
19:30 – Alarm of the gas detector in the control room .
19:34 – Emergency stop (ES) of the the desulphurisation unit initiated.
20:30 – On site oil leakage confirmed.
20:50 – Emergency stop of the unit completed.

External corrosion inspection beneath insulation is very difficult to be detected by inspections based only on visual observations. Non destructive examinations especially of the areas more at risk (e.g. the moisture prone ones) is required.

Despite the fact that this incident had very limited consequences, it revealed inadequacy in disaster response capacity of the plant, which failed to initiate the intervention of the internal emergency team. Regular training and education were required to improve preparedness.

1. Expert workers with equipment maintenance knowledge will perform regular external appearance checks.
2. The insulation on the affected pipe was removed.
3. All carbon steel oil pipe insulation on the affected unit and on other units will be reviewed and unnecessary insulation will be removed.
4. Where insulation was still required, it will be dismantled for visual and non destructive testing.
5. Neutron moisture meters will be used to check the water content of insulation materials.
6. Same process pipe inspection procedures will be applied to all oil pipes.