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Hazardex 2018 Conference - 6. When the lights go out

30 January 2018

Roger Stokes – Principal Engineer, BakerRisk. 
Weds 14.45 – 15.25: Main conference room

Processing facilities require a reliable supply of electrical power. The consequences of a sudden power loss ranges from an inconvenience to a major incident with consequences including damage to equipment, failure of emergency systems, loss of containment, fires, explosions and environmental impact. Damage during restart can also be a major issue. The increasing reliance on automated systems for control, emergency shutdown and mitigation means that power supplies and back-up systems must be much more reliable than in the past.

There have been many incidents where loss of external power has been a key factor and there are opportunities to learn from these events when assessing the design criteria and maintenance requirements of supplies and back-up systems. Typical facilities that require a reliable supply of power include offshore platforms, oil refineries, petrochemical, chemical, pharmaceutical, plastics, glass and nuclear industry facilities.

Power is not only required for process control and for driving the plant and machinery; it is also a crucial link in the chain for provision of services including steam, air, process water, cooling water, nitrogen, lubrication and emergency systems. There have been several instances where even a brief power loss has led to the cascade failure of services, which has then resulted in a major incident.

Causes of power supply failure include: Fires in substations and switch-houses, faults/ human error when working on switchgear, underground cable faults, excavations and other works damaging underground cables, vehicles striking overhead cables, lightning strikes and storm/ flood/ tsunami.

Typical protection from power loss include uninterruptible power supplies (UPS’s), emergency power generators, services back-up (stand-by boilers, nitrogen back-up for air, gravity fed cooling water/ lubrication). These don’t always work.

Procedures are written to include “load-shedding”, manual activation of valves and critical safety systems. In a real situation, some of these may literally require working in the dark. There is a lot to do, few staff and little time to act.

Planning for power outage requires a thorough assessment of the scenarios that may occur, the possible consequences and the design and reliability of the measures that are in place. Novel ideas for low frequency/ high risk scenarios may need to be considered.
This presentation reviews some examples of incidents that have occurred to encourage operators to reconsider the potential impact of a sudden loss of power at their facility and how they would deal with such an event.


Roger Stokes graduated from UMIST as a Chemical Engineer in 1982 and joined ICI’s Mond Division where he initially worked in a technical capacity on various plants and projects including chlorine/ caustic, chlorinated solvents and chlorinated paraffins.

In 1987 he moved into plant management, first on a chlorinated rubber resins plant and then PVC.  In 1992 he joined a firm of Loss Adjusters dealing with commercial insurance claims including fires, explosions and machinery breakdown on chemical, petrochemical, food processing and other manufacturing facilities.  This took him to various parts of the globe where he encountered numerous types and sizes of incidents. 

He joined Baker Risk in 2015 and works out of the UK office as part of the Process Safety Group, where his work is currently focused on accident/ incident investigation and insurance risk engineering.



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