Functional safety considerations on modification projects

Improved drilling techniques and better access to subsea wells has resulted in the extension of the lives of many oil and gas platforms, which require modification to allow them to accept and process product. 

For example, to allow one North Sea oil platform to start to receive and process product from two subsea wells, modifications to the platform are currently being planned. An Emergency Shutdown (ESD) system is being developed, as part of the modification programme, by Hima-Sella, a specialist Safety Instrumentation Systems provider. 

The platform’s new ESD will be implemented using a HIMA HIMax, a Programmable Electronic System (PES) designed for use in production processes where downtime is not acceptable. HIMax has virtually unlimited expansion potential making it a scalable solution suitable for such applications. For this particular project the PES will, initially, have more than 300 I/O fully redundant channels, which will interface with a variety of sensors and actuators.

HIMax delivers SIL3 protection and hardware and software changes can be made without interrupting the functionality of the system. It also offers scalable redundancy for operation in quad, triple, dual or single mode.

Eddy Turnock, Hima-Sella’s sales & marketing director, said: “HIMax is proving popular within the oil and gas sector due to its flexibility, scalability and non-stop performance. Hima-Sella’s engineering capabilities are also helping ensure continued compliance with IEC 61508 which requires functional safety to be managed throughout the entire lifecycle of a platform. It is important that the ESD and other safety systems keep pace with any and all modifications.”

IEC EN 61508 defines functional safety as ‘freedom from unacceptable risk of physical injury or damage to the health of people, either directly or indirectly, as a result of damage to property or the environment’. This is, typically, achieved by good design, which eliminates the hazards or detail changes to the current operation of an existing plant. Any remaining residual risk then needs to be addressed with additional measures including the use of Safety Instrumented Systems (SISs) that are able to automatically place the plant into a safe condition and raise alarms. 

With so many oil and gas plants now being modified to help extend their operating lives, it is important to consider the safety implications of any modifications from a functional safety perspective.

The ESD is currently being built at in the UK  with the system functionality being created using HIMA’s SILworX programming tool. In addition, the development and verification of the ESD’s functionality is being overseen by Hima-Sella’s Functional Safety Management Team, on which only engineers certified to TÜV FSEng or FSP are able to work.