15 May 2006

Explosion Oxygen Injection Line

Safety Incident Topic : Explosion Oxygen Injection Line
Location Of Incident : Netherland
Date Of Incident : 8th March 2006

Brief Account of Incident
A small explosion occured during commissioning of temporary 2" oxygen line in use for catalyst regeneration on catalytic reforming unit. No injuries occured. A part from a total loss of the injection line there was no significant damage but delay in the regeneration process. After safeguarding the unit catalyst regeneration was progressed with air as opposed to pure the oxygen.

The stainless steel line is only used for catalyst regenerations which are carried out roughly ance every 18 months. In between times the line is fullt segregated from the rest of the unit and spaded off at valve connection at the unit. This to prevent ingress of dirt and/or hydrocarbon. Both precursors for violent reaction with pure oxygen. At the time of the incident one of the connection turned out to be still in place with no spade installed and with the valve closed. This was noted during the unit check up before the regeneration period and was reported but people did not realised the possible consequences. It turned out that the valve had leaked hydrocarbons over 1.5 years after the previous - and had built up in the line, sufficient to cause the explosion upon commission the oxygen flow.

Potential Outcome
Serious injury or fatality as the incident happened close to a unit walkway.

What When Wrong
. Oxygen System connection not segregared from the process line after the previous catalyst regeneration (at the end of a cycle ending turnaround)
. Nobody inticipating the inherent risk of possible hydrocarbon ingress into the oxygen system

Immediate Causes
. Violation by group: the procedure for de-spading was not followed properly.
. Lack of judgement: people did not realised the possible consequences of the connected line
. Routine activity without thought: sign off the spading list assuming the line would have been disconnected and the assumption that the hydrocarbons would never enter the line.
. Inadequate isolation of process: no spool removed / spade present.
. Defective equipment: passing valve

System Caused
. Emotional overload: pressure to immediate start up after turnaround.
. Inadequate identification of critical behaviours doing check ups.
. Inadequate development of PSP's: spading list did not mention the removal of the spool piece.
. Inadequate communication between the people doing the work after the TAR and the acceptors of that work.

Corrective Actions
. Remove the valves at the connection point - this will force removal of the spool piece and spading after regens.
. Improve spading list and procedures for catalyst reformer regenerations.
. Adjust training program contents to make people more sensible for risks that are not so obvious.

No comments: