Minimising offshore arc flash risks
Offshore oil and gas operations require the highest standards of safety. Managing arc flash risks in this environment calls for a comprehensive, engineering-led approach.
There are few more demanding industrial environments than offshore oil and gas facilities. The combination of remote location, challenging weather conditions, and the inherently hazardous nature of the materials and processes involved mean operators must seek to understand and manage risks by the best available means. The complexity of that work is compounded for companies responsible for multiple, widely distributed assets.
We recently helped one North Sea oil and gas operator to tackle a specific category of risks in its operations: the potential of arc flash incidents during the operation and maintenance of the electrical equipment installed on its on- and offshore gas collection, compression and processing facilities.
The company’s highest priority was the reduction of potential arc energy levels by engineering means. Achieving that goal, however, required a detailed understanding of the electrical distribution systems on each of its assets, which included three major offshore platforms, several satellite facilities as well as a large onshore processing plant.
Our engineers started their work with a comprehensive programme of site surveys to gather the information required to produce a computer model of the electrical distribution system on each asset. That model quantified the potential fault currents throughout each installation, together with the protection clearance times at arcing current. We used that information to calculate the arc flash incident energy levels and flash protection boundaries in accordance with IEEE 1584.
Once we understood the precise nature of the arc flash risks, we could recommend appropriate engineering methods to reduce overall arc energy levels. On eight main distribution boards across the client’s asset portfolio, we suggested the installation of new overcurrent protection relays incorporating instantaneous high-set overcurrent elements. At the same time, we conducted a comprehensive electrical protection coordination study, and suggested revised protection relay settings that would ensure optimal fault clearance performance and supply integrity. That work achieved the customer’s key goal of reducing arc incident energy from more than 40 Cals/cm2 to less than 25 Cals/cm2 across all its assets.
The next step in the process was a qualitative risk assessment, based on the revised arc energy levels, the design of the installed switchgear and the customer’s operating and maintenance procedures. That study showed a greatly reduced residual risk, meaning the use of additional personal protective equipment (PPE) was required in relatively few situations or procedures.
For our customer, this work didn’t just deliver a substantial reduction in arc energy levels. The company also has a much more comprehensive understanding of the remaining arc flash risks across its assets. That has significantly reduced the requirement to wear inappropriate or burdensome PPE during many of their operational procedures, simplifying and streamlining its operations. The remaining high risk situations and procedures, meanwhile, have been clearly identified allowing the adoption of revised operating procedures and/or appropriate PPE where necessary.
Following completion of this study the company also now has up to date records and a comprehensive computer model, allowing it to demonstrate appropriate strength and capability of their fault rated electrical apparatus under short circuit conditions in accordance with statutory requirements, and simplifying the ongoing management of arc flash risks during the life of its assets.