A number of major process industry accidents have involved SIMOPS. Company conducted construction (modifications) activities inside its own plant during the period from November 2017 to May 2018. The Group Risk Acceptability Criteria Guidelines have been defined by Company for the purpose of providing Senior Management with quantitative information about the risk profile during SIMOPS activities and to help them in taking informed decision about the execution strategy to ensure safe operations. A DNV-GL Phast based model of the plant has been used to assess the risk level. Using Group Risk guidelines for On-site personnel based on the FN (Frequency – Number of Fatalities) Curve, Company evaluated and compared several SIMOPS options prior to the actual works to identify the optimal manning level and schedule to ensure the overall Group Risk laid in the ALARP region. The quantitative risk assessment served as a tool to derive the optimal manning levels and shutdown schedule during the SIMOPS activities. The manning levels were controlled through additional administrative measures to ensure its implementation. Moreover, the overall SIMOPS Risk (FN Curve) for the current activity was compared with the risk undertaken during similar previous activities conducted in 2015 and 2016. After the successful completion of the activities, the Risk Assessment was updated to take into consideration the actual manning and schedule inputs for the Pre-Shutdown and Partial Shutdown phases. The actual overall Group Risk (including Pre and Partial Shutdown) was within the Company Group Risk Acceptability Criteria. Additionally, valuable Lessons Learned were identified such as purging (with inert gas), rather than just the depressurization of the equipment in the units during Shutdown, can contribute to a significant risk reduction. This paper presents a novel approach to evaluate SIMOPS risk on personnel using a Group Risk criteria based on FN Curve. This provides an additional re-assurance to stakeholders involved in the activity to take informed decisions based on a quantitative risk analysis rather than a qualitative assessment.

In line with ADNOC Codes of Practice, areas where fatal H2S concentrations could exist must be classified as ‘Red Zones'. Personnel in these zones should always be under air. Al Hosn Gas facilities in the Shah field have large areas categorized as Red Zones. This presents a challenge as personnel working in these areas have to traverse long distances under air and on foot from the Red Zone perimeter to the units within, and back. Al Hosn Gas has overcome this challenge with the development and implementation of an innovative Red Zone Vehicle. These specialized vehicles are suitable for all terrain movement and have been fitted with breathing air cylinders that can provide up to 1 hour of breathing air for up to 5 occupants, a gas monitoring screen that displays various parameters in real time, a flammable gas permissive start option and a permanent monitoring system that continuously compares the flammability of surrounding air with stored calibrated air to de-energise vehicle if a certain limit (i.e. 10% LEL) is breached, a special valve to automatically shut-off the air intake to the diesel engine if the engine accelerates rapidly in flammable atmospheres, a spark arrestor and flashing strobes & beacons which activate upon toxic or flammable gas detection. With the implementation of the above innovation and safeguards, travel time in the plant Red Zone has been reduced by 82% (also reducing heat exposure) and up to 71% breathing air is now conserved and available to personnel in their personal SCBA sets when travelling the longest route in the Red Zone (approximately 1.5km). The breathing air system and the flammable gas protection systems are relatively inexpensive to install and are easy to upgrade individually as and when newer technologies are made available. This would not require replacement or a complete overhaul of the existing vehicle. Further, the same systems have been fitted across a wider range of industrial vehicles e.g. cranes, forklifts, trucks, etc. thus enabling an increased range of safe maintenance activities in the Red Zone. At present, 20 existing vehicles (consisting of pick-ups, cranes, fork-lifts, cherry pickers, and a delivery truck) in the Shah Gas Plant have been successfully converted into Red Zone vehicles to allow for safe, efficient movement and smooth maintenance activities within the red zones.