Cs Vessel Over Pressurisation
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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
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Transcript of Cs Vessel Over Pressurisation
Vessel Over PressurisationCase 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
For more information on Major Hazards Awareness:
• BG Group Major Hazards Awareness eLearning Course, via the Learning Management System
• Contact the Asset Integrity Group in BG Advance, [email protected]
• BG Group Asset Integrity Standards, via the BG Portal
• BG Safety Engineering and Asset Integrity Community, via BG Connect
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ASSET INTEGRITY Vessel Over Pressurisation
Case Study 1 – Risk Awareness
! Permanent deformation of the horizontal vessel
Maintenance There was no evidence of prioritised maintenance and inspection plans for the temporary equipment.
Risk Perception There were a number of warning signs of over pressurisation which were not recognised or reacted to.
• Liquid-level sight glasses had broken due to pressure in the past, although this was not recognised as over pressurisation and the issue was solved by up-rating the sight glasses only to avoid future cracking
• Repeated closure of the ESDV in the plant indicated that the risk of potential over pressurisation happened regularly
• Overall, there was a tolerance of non-functioning equipment such as level-instruments. Operational work-arounds were therefore normal and accepted
• Further failure to recognise the full scale of the risks occurred when the equipment was re-started after the over pressurisation event
Lesson to be Learned (L2BL) If the operators had really understood the risks associated with Temporary Equipment then it would have:
• Been assessed under the MoC process
• Had a maintenance and inspection plan in place
• Been realised that over pressurisation was occurring (liquid-level sight glasses breaking and repeated ESDV closure)
• Shut down and not re-started after the over pressurisation event
MAJOR HAZARDS AWARENESS
