Overview
The Brae Alpha platform is a single, integrated platform consisting of drilling rig,production, utility and accommodation facilities. Production commenced in July 1983 and is very much active today, however as the site ages the concentration level of oil drops and the amount of produced water increases. As part of Marathon Oil environmental policy the existing water treatment plants were to be replaced by two independent skids.
The objectives for the project were as follows:
1. High availability - greater than 90%
2. Time for change over
3. Safety Integrity Level
4. Intutative operator information
Design
Applied Integration UK Ltd was chosen as the contractor to supply the ESD design and software configuration. The design was based on the client's requirements - High availability, Safety integrity level and ease of use. The solution that was offered was a Siemens S7-417 HF PLC system with a 12" operator display. This solution allowed Applied Integration UK Ltd to offer high speed bump-less PLC redundancy, redundant networks and the ability to process both Safety (Up to SIL3) and non safety in the same PLC.
The clients 'cause and effect' diagrams were used as the formal method of describing the client's requirements, the 'cause and effect' diagrams were also included in to the operator display so allowing personnel to quickly diagnose any issues on the system.
The design was fully compliant to IEC 61508 using the Siemens Safety PLC and Applied Integrations 'Safety Life Cycle Model' which involves independent safety assessment.
Commissioning and Installation
Testing of the system included full I/O hardwired simulation of functionality and involved both client engineering personnel and site operations. After clients acceptance the system was then released for installation on to the Alpha. The installation process was completed with-in the allocated time, no modifications have been required to the system since installation.
Maintenance
Full diagnostics of hardware were displayed on the operator display, and the use off an active backplane allowed for the replacement of hardware with shutting down the system.
Conclusion
Applied Integration UK Ltd believes that open and full dialogue with the client is the main factor for a successful project, this not only delivers the solution but also gives the client confidence from the start of the project. Our approach to quality assurance is also a major factor in ensuring that what we design and build is what the client wants. This project not only fulfilled the clients requirements but was fully compliant with IEC 61508 (Safety Systems) and was applicable for use in a SIL level 3 environment.