Title: Over Pressurization of Pipeline Causing Busting of Pipe Spool

Title: Over pressurization of pipeline causing busting of pipe spool

Location: Production Installation

Activity Type (Result/outcome): Injury and Property damage

What happened:

PCV of HP separator connected to the flare header was taken up for stroke test to ensure that PCV is fully seated and there is no passing of gas to the flare header. While carrying out this operation, the manual isolation valve after the PCV was closed by operation person. PCV was opened 10% from CCR resulting in the over pressurization to the pipeline causing busting of pipe spool. One person suffered injury. Pipe spool on the HP flare line between PCV and manual valve was completely ripped off. The ripped off pipe spool hit and damaged the adjacent piping and structures. Instrument cable trays, electrical fittings and grating in the nearby area also got damaged.

What caused it:

1.  The design of the pipeline from HP separator towards HP flare is such that the pressure specification of the piping changes immediately after PCV. The upstream section of PCV is rated at 900 # and downstream section of PCV is rated at 150 #. Downstream isolation valve of lower rated pipeline was not marked Lock Open in P&ID and in field also it was not locked open physically.

2.  Operator closed the lower rated downstream valve before stroking of PCV thus pressurizing pipe section designed for 150 # (19 bar) to 110 bar.

Corrective actions:

1.  Competence level of field operator should be improved to understand the intrinsic design of the process.

2.  Design should be reviewed to make process safer. Options include pipe spool and downstream isolation valve to be upgraded to higher pressure rating; isolation valve to be marked lock open in P&ID and kept lock open in field, etc.

3.  To physically check valves in plant, which are marked LO on the P&ID are locked open in field.

4.  System of JSA should be strengthened.

It is provided for information purpose. This information should be evaluated to determine if it is applicable in your operations, to avoid reoccurrence of such incidents.