Securing the installations of an important gas site. A risky subject !

Leading hydrocarbon group in Africa

The first hydrocarbon group in Africa, our Client operates a large natural gas field near the Libyan border. Since the 1970s, this facility has been processing 1.2 million tons of gas annually.

Our Client has undertaken a significant project to completely re-instrument the site. This project includes a high level of safety requirements through the compliance of the installation with international industrial safety standards and in particular with the IEC61511 standard (known as the “SIL” standard). SPC took charge of this specific aspect of the studies.

Securing a gas site with major fire and explosion risks

Securing a gas site with major fire and explosion risks requires the use of appropriate methods implemented by experienced personnel. The studies are carried out in successive stages :

1. A detailed risk analysis which studies each of the possible risk scenarios by analyzing the possible deviations of the process. A probabilistic approach of the risk leads to define the SIL (Safety Integrity Level) for each instrumented safety function used as a risk reduction barrier;
2. The design of the architecture of each safety function and the definition of preventive maintenance requirements (periodicity and modalities of periodic tests);
3. The drafting of requirement sheets for each safety function (SRS sheets: Safety Requirement Specification);
4. The drafting of detailed functional analyses of the safety functions which integrate the functional and operating requirements of the installation.

A strong expertise and an equipped know-how

SPC has been carrying out industrial site security projects for over 25 years. SPC has brought to the project the fruits of its many years of experience, its expertise in process safety and its know-how in conducting studies of such magnitude and criticality.

SPC conducted the studies using a range of tools dedicated to these tasks:

• An industrial risk analysis tool based on the HAZOP standard (IEC61882) and which integrates a LOPA approach (Layer Of Protection Analysis: probabilistic risk approach) in accordance with the IEC61511 standard. The criticality or risk acceptability matrix defined by or for the Client is integrated into the tool. It facilitates the strong preparation of the scenarios studied upstream of the review sessions in working groups.
• A Safety Instrumented Systems Analysis tool: a suite of tools dedicated to reliability calculations (PFDavg) for each safety function. Quantified justification of its design and tests to be implemented. Integrated functions for optimizing preventive maintenance and its cost.
• A tool to assist in the creation of SRS sheets for each safety function.

A complete and documented site security file

• More than 600 risk scenarios studied in close collaboration with site specialists.
• More than 200 instrumented safety functions studied, with justification of the architecture and test period requirements for each. Production of the associated SRS sheets.
• A renovated installation with an adapted level of safety (the methods used make it possible to define and limit to what is necessary).
• Detailed justification of each of the decisions taken through the site safety file.