1. A recent serious incident occurred that involved the catastrophic failure of a shell and tube heat exchanger, and there is a potential risk of failure to heat exchangers of the same, or similar, design. This notice describes the incident and outlines the action that should be taken by dutyholders.
2. The incident on an offshore gas production platform occurred when a shell and tube production cooler suffered a catastrophic failure. Seawater was being used to cool High Pressure (HP) hydrocarbon gas. The shell, tubes and titanium cladding sheet were torn from the steel tube sheet and propelled across the deck with sufficient force to rupture an adjacent exchanger. The cooling water pipe work and vent pipe work were torn off the shell and the tube sheet and channel end were ripped off the supports. There was a significant and immediate gas release followed by ignition and an explosion. Fortuitously there were only two relatively minor injuries, but under slightly different circumstances there could have been significantly more serious casualties.
3. The heat exchanger operates with sea water on the shell side and HP hydrocarbon gas plus condensates and water on the tube side. The tube sheet had been manufactured from carbon steel with an explosively bonded, 13mm thick titanium cladding plate on the sea water side to provide corrosion protection. A key feature of this design is that it allows the HP hydrocarbon gas, condensates and water to come into contact with the steel tube sheet/titanium interface, thus creating the potential for in-service degradation mechanisms as detailed in paragraph 4 below.
4. Based on the results of an ongoing forensic investigation, the current evidence suggests the following sequence of events:
5. HSE considers that the emerging findings of this investigation are significant enough to require immediate action by dutyholders in the light of the sudden and possibly catastrophic nature of this type of heat exchanger failure. Therefore, dutyholders should:
6. The main legal requirements include:
There are legal duties on both the owner and the operator of the plant.
Any queries relating to this notice should be addressed to:Team Leader - OSD3.4 Mechanical Systems
This guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance as illustrating good practice.