Vessel Over Pressurisation Case Study 1 – Risk Awareness What happened? In February 2007, a temporary hydro-cyclone unit was installed into the condensate system on an onshore terminal. The unit was a temporary modification being trialled to remove fine sand in the condensate. In August 2008 a valve downstream of the condensate system closed and the pressure in the hydro-cyclone unit rose. However, the emergency shutdown valve (ESDV) in the hydro-cyclone unit failed to close and the pressure relief valves (PRVs) on the unit also failed to open. As a result the unit was subjected to a pressure of over two and a half times the unit design limit – which would have resulted in rupture of the unit if an operator had not noticed a pressure gauge and manually closed the ESDV. There was no release or rupture of equipment, but the vessel on the hydro-cyclone became distorted or barrelled due to the overpressure and was assessed to have been very close to rupture. Problems The key problems that led to this incident were: Design Temporary equipment was required in the first place because the original facility was not designed for sand production. Sand blockages therefore rendered much of the plant’s instrumentation unreliable. Sand had also caused erosion and valves had been replaced in the past due to this erosion. Temporary Equipment Management Due to urgency, installation of the temporary equipment was completed without the normal Management of Change (MoC) process and associated risk assessments. Whilst deemed to be temporary, the equipment had been on site for 15 months at the time of the incident. When August 2008 Impact • Permanent deformation of the vessel • Potential for significant injury or even multiple fatalities • Potential for plant shutdown and loss of production Key messages It is vital to understand the risks associated with temporary equipment. This type of equipment requires that risks are assessed and control measures put in place. All key personnel, operators, supervisors and technical personnel must be aware of the risks associated with the activities they perform. Defective equipment cannot be tolerated and warning signals must be recognised and acted upon. ! Temporary hydro-cyclone unit ASSET INTEGRITY MAJOR HAZARDS AWARENESS