Explosion at a methanation reactor

The day before the incident, the outlet pipe of the methanation reactor started leaking gas containing hydrogen. The leak was temporarily eliminated by a pressurised plug. On the day of the incident, the pipe leaked again, and the same plugging method was still used to stop the leak. This occurred without shutting down the unit and taking safety measures. Approximately one hour later, a sudden explosion occurred at the repaired line .

The INITIATING CAUSE was hydrogen corrosion of the pipe, which brought to its cracking and to a gas release. The welded joint of outlet pipe was operating for a long time in an hydrogen containing medium at high temperatures. Under this condition, hydrogen embrittlement took place, producing local defects and eventually opening up. The released hydrogen ignited and exploded.

According to the source reporting the event, the company did not implement the safety operation procedures prescribed by the "Pressure Pipeline Management Regulations", and specifically the "Special Equipment Safety Technical Specifications" (TSG D0001-2009 Pressure Pipeline Safety Technical Supervision Regulations-Industrial Pipelines) and "General Specifications for Standardization of Hazardous Chemical Business Units" (AQ3013-2008). The decision to try plugging the leak without stopping the reactor and the lack of additional safety measures put in place were definitively part of the ROOT CAUSE.

oulet pipe

The outlet pipe from the methanation reactor was leaking and had been temporary repaired by a pressurised plug.

4 fatalities, 2 persons injured. Reactor destroyed, direct economic loss of over Euro 0.78 million.

According to the source (See reference), in the petrochemical industry, the corrosion problems caused by the poor processing raw materials are increasing, as well as leakage in production, storage and transportation. On top of that, the operating periods of materials and systems are getting longer. To ensure uninterrupted long-term operation of the process systems, the use of pressure plugging technology is also increasing. However, plugging under pressure is characterised by a poor working environment (generally high temperature, high pressure, flammable and explosive, toxic and harmful, and coexistence of various harsh conditions): therefore accidents are very likely to occur during the operation.
How to ensure safe conditions? It is important to investigate how to quickly and effectively stop leaks under pressure, and standardize the plugging technology under pressure to form national standards or industry standards.
Suggested measures
• Increase investment in safety, strengthen detection, and investigate and control potential safety hazards.
• Strengthen safety education and training for employees to improve safety awareness. Further implement the unit's safety production rules and regulations, special equipment inspection and maintenance plan and safety production target responsibility system, and strictly implement special equipment operating procedures.
• Strengthen supervision, form a working mechanism combining safety production supervision and industry supervision and guidance, strengthen cooperation, and further strengthen safety education, guidance, supervision and inspection of enterprises.
• Carry out research on the safety application of hot air plugging technology and standardize it.