Safety is a High Priority and People Make it Work
Published on : Thursday 04-02-2021
The question of how to avoid incidents has been a top priority for industry safety professionals for over half a century, says Mark Sen Gupta.
Industry works diligently to increase the level of safety in process operations. Standards such as IEC61511, IEC61508, and ISA 84 provide practitioners direction and goals in the form of best practices for implementing safety technologies. Technology suppliers have addressed these standards head-on with sophisticated relays and logic solvers that have an outstanding record.
On the human side of the safety equation; most end user organisations have placed appropriate safety practice reminder signs in the workplace at every turn in the corridors, offices, and control rooms; but catastrophic industrial events still occur. While the event can sometimes be traced to a fault in a piece of equipment, often it is a human-induced problem (or a problem amplified by a human) resulting from a decision with unfortunate consequences. So, what can we do to reduce the occurrence of hazardous incidents to zero?
Safety is a high priority
Most process manufacturers have an unwavering concern for plant safety. Many have embraced a ‘safety culture’ that describes their efforts to instil the importance of acting in a safe manner in everything every employee does. Overall, industry has made tremendous progress to make processes safe, with zero tolerance for accidents and incidents. The company’s safety culture provides a constant reminder for everyone to work safely.
Layers of protection, beginning with the DCS, PLC, or other ‘basic process control system’ (BPCS), have been engineered into the safety design. End users add interlocks and safety instrumented systems (SIS) as increased layers of protection to handle something dangerously abnormal or unexpected.
However, despite the best efforts to engineer appropriate system- and equipment-based safeguards into the overall design, things can and do still go wrong. Quite often, this is because of a failure in judgment, a flaw in the plant practices, inadequate training/experience, or simply that practices are taken for granted.
Tragedy is a harsh reminder
Incidents like the explosions at BP’s Texas City refinery, at the UK’s Buncefield oil storage facility in 2005 (the largest fire in the UK since WWII), or the recent tragic explosion in a corn processing plant in Wisconsin; heighten companies’ concern about plant safety. These incidents also increase governmental scrutiny and lead to increasingly tougher environmental regulations. These have helped drive the adoption of reliable SIL-rated safety instrumented systems (SIS) to mitigate the risk of such catastrophic events.
The ASM Consortium keeps a running list of incidents around the globe. It is filled with incidents occurring almost daily. These events serve as a potent reminder of the stakes involved.
What can be done?
The question of how to avoid these incidents has been a top priority for industry safety professionals for over half a century. The answer remains elusive. As long as people and equipment process flammable and/or explosive materials there is always the potential for something to go wrong. Depending on the process, mistakes can result in explosions.
On the equipment side, industry continues to improve both the processing equipment and the control and safety interlock systems. Theoretically, the combination automatically monitors the process conditions and takes actions if limits are violated. Standards such as IEC61511, IEC61508, and ISA 84 provide direction toward detailed practices for implementing safety technologies in industry.
The human side of the problem is inherently different. Where machines can be designed to always react the same way given a set of circumstances, the same cannot be said for humans. Humans can simply have a bad day, which may lead to bad decisions when unexpected events occur. Owner/operators in the process industries have almost universally attacked this in two ways: training operating personnel and developing operating procedures.
State nature of procedures and safety
Unfortunately, most procedures handle a specific set of process conditions. For example, procedures for startup, shutdown, or normal operation recognise the specific state of the process. If the procedure is for normal operation, it assumes that all other conditions about the operation are as it has been in the past. If the procedure is about startup or shutdown, it assumes a certain sequence of events have or will take place.
Just like the procedures, the control system needs to be able to handle the conditions based on the state of the process. For example, some processes – particularly exothermic reactions – need to control the rate of change that can occur in the normal operation so as not to cause a run-away of the reactor temperature.
From the human perspective, operators must monitor the current state of the process to be sure that the proper conditions for safe operation are in place. They need to know that startup and shutdown state transitions are typically the most dangerous conditions for a plant and its personnel. Finally, they need to be trained to react properly to the conditions and plant state from both a safety objective and operating objective point of view.
Recommendations
Explosions and other tragedies have heightened the intensity with which safety is practiced. Despite this, other tragic events will most likely continue to happen. Machines can be made to be nearly perfectly repeatable in adverse conditions. The operative word is ‘nearly’, since there is always a statistical probability of failure. Humans are inherently fallible. They will do what they believe is best to get the job done, regardless of its legitimacy.
Safety practices must be more rigidly enforced during start-up and shutdown events and spelled out in terms of the process state at the time. During these events, however, the humans in the plant are already stressed to get the job done as quickly as possible. The fact that people do not often experience these transient plant states aggravates the situation. High-fidelity process training simulators can help build experience in the workforce, especially as the older workers retire and plant run times increase.
Since the humans can become, in effect, the last interlock, they must be trained to fully understand the current state of the process, the best practices for operating under that state, and the true meaning of ‘work safely’.
Mark Sen Gupta is Director of Research at ARC Advisory Group, USA. Mark assists clients with their Digital Transformation initiatives, providing a particular focus on how digital transformation affects people and the organisation. He also leads ARC's research of process automation, process safety, SCADA, and terminal automation.
