CRITICAL BARRIERS

On April 20, 2010, at a deepwater oil rig in the Gulf Of Mexico, a surge of natural gas blasted through a concrete core installed to seal an oil well.? Once released, the natural gas traveled up a riser to the platform of the oil rig, ignited, and killed 11 workers and injuring 17.? It also resulted in the largest environmental impact to a marine environment within the nation's history. (BP Macondo Deepwater Horizon Oil Spill April 20, 2010)

On a typical oil rig there are hundreds of devices and equipment to prevent or limit the consequences of a major incident.? Of the many that may not have worked in this incident, there were a significant few safeguard and control systems that needed to absolutely work when needed in this operation:? ?

• Cement/mud in the casing and tie-back systems
• Automated isolation valves
• Blowout preventer
• Mud-gas separator
• Pressure Controller
• Well seal pressure detection
• Vent Fans automated shutdown (upon gas detection)

?And of these few, arguably the cement/mud in the casing & tie-back systems and the blowout preventer would have prevented or at least mitigated the pressure event – the initiating event.

Various means are employed to achieve safe operation and prevent an operational incident.? They include engineering and administrative controls, safeguards, safety control systems, safety instrumented systems and other such safety measures.? All of these are Barriers --- as in barriers to a failure that will lead to a significant or catastrophic event.

In every process safety incident, you can find a critical barrier that was either not in place or did not function as required when needed.

When a Process Hazard Analysis is conducted properly, all the barriers are identified.? Of those, a critical few will come to the forefront.? That is, if no other barriers are maintained, then above all else these critical few barriers must always be in place and always work when needed - essentially have integrity and reliability.

Knowing those critical barriers, the organization or operation has a very powerful tool in which to protect against a significant or catastrophic event. A powerful tool for:

• management to laser focus their energy on monitoring and measuring those critical barriers;
• the management systems maintaining the operational equipment to achieve asset integrity and reliability;
• the organization to use its limited resources, time, money, people, on what will provide the biggest impact;

Barriers are measures that reduce the probability of releasing a hazard and reducing the consequence of a released hazard. Barriers can be hardware, human intervention, or a combination. These equipment and devices can be in any of the categories:

• Structural Integrity
• Process Containment
• Ignition Control
• Detection Systems
• Protective Systems /Suppression / Extinguishment
• Safety Instrumented Systems
• Shutdown System
• Emergency Response / Life Saving

?For example, let’s look at just one potential hazard – overpressure.? Barriers employed to reduce the probability of an overpressure event may include:

• High Pressure alarm/ operator response;
• Pressure regulator
• Equipment & piping design
• Automatic high pressure interlock;
• Pressure relief valve/device
• Burst discs / pressure plates
• Bypass systems

?Of all these barriers, if the alarm/operator response, the pressure regulator, and/or the pressure interlock fail, then the last resort to preventing an overpressure incident is that Pressure Relief Valve.? That critical barrier must always, unquestionably, have integrity and reliability.

All barriers must be maintained for reliability, but that critical barrier must have the laser focus of the organization, the monitoring and measuring of its performance, and the application of sufficient resources to maintain its integrity and reliability.? There is protection from overpressure, and you always know it is there.

Of the many definitions of Process Safety, I will argue that Critical Barrier integrity and reliability is the singular objective for Process Safety.