In an important sense, any near-miss incident is an opportunity in disguise, if appropriate corrective action is taken in its wake. However, not all such incidents turn into major events and not all require major corrective action. Typically, plants record near-misses but only perform a root cause analysis (RCA) if an incident appears a potential trouble spot to management. The RCA then leads to corrective action to eliminate or minimize recurrence of such an event.
This approach is fine for near-miss incidents that intuitively are identifiable as trouble spots. However, such an experience-based approach regards risk only in terms of its severity — it fails to take into account the likelihood (expected frequency) of a near-miss incident. As a result, it might ignore some near-miss incidents that could become moderate- or high-risk events.
This article presents an approach based on a risk matrix (RM). In essence, it's an extension of the RM approach used for many process hazard analysis (PHA) or hazard and operability (HAZOP) assessments.
THE BIG PICTURE
Today, operations comprise a mix of automatic and manual or procedural steps. A plant may have hundreds of control loops, interlocks, permissives and safety systems. In addition, numerous procedures rely on human interaction — for instance, opening or closing a block valve, and starting, stopping or ramping a pump or compressor. In view of the large number of operations, it appears reasonable to anticipate that "something" will go wrong someday.
Many factors can contribute to an incident, including:
• inadequate training and poorly written procedures;
• process complexity;
• personnel issues;
• age of the plant and equipment;
• environmental problems such as severe weather; and
• random events (i.e., ones we can't really predict).
From a managerial perspective, the key is to identify near-miss incidents that under slightly different circumstances could become major events with adverse consequences.
Unfortunately, the experience-based approach likely won't spot all such worrisome incidents. That's not surprising because staff may lack sufficient breadth and depth of experience to truly determine which incidents could become big. In addition, in some cases, there's a tendency to disregard existing data on equipment or procedural failures.
THE RM APPROACH
As an alternative, plants should consider using an RM technique. Such a semi-quantitative method can better identify near-misses that could have led to dire consequences under a slightly different set of circumstances. Basically, it screens incidents by likelihood and severity to pick out those with a potential to develop into "large impact" events.
The approach involves estimating the likelihood and consequence of the near-miss and assigning these an index value to use for the risk matrix. Figure 1 shows such a risk matrix while Table 1 provides guidance on how to assign appropriate indices.
Plants with a long history of operations can use near-miss records to estimate likelihood and consequence of relatively similar incidents. New plants should consider data from similar incidents elsewhere in the chemical industry.
In the absence of data, you can turn to plant operations and maintenance personnel for estimates. However, in the long-run, the goal should be to collect relevant data.
The accident data must be arranged in some useful classes. For instance, you might consider the following categories: flammable or toxic gas leak, flammable or toxic liquid spill, dropped object, procedural error, design deficiency, and other.
From the data on near-misses you've collected, estimate the frequency (e.g., times/year) for each category and use these estimates to come up with a likelihood value for the matrix, with 3 being highest likelihood.
Then categorize consequence in three classes: relatively low level of impact (1 on the matrix), moderate level (2), and high level (3). Be as specific as possible — e.g.:
• Category 1: no injury, no lost time, <100-lb gas release, <3-gal spill, no fire, <$1,000 loss;
• Category 2: one injury, lost time; 100–500-lb gas release, 3–5-gal spill, no fire, $1,000–$2,000 loss; and
• Category 3: one lost-time injury, 500–1,000-lb gas release, 5–10-gal spill, no fire, >$2,000 loss.
Once you've placed an incident in the matrix, you're in a position to decide whether it demands corrective action based on your plant's risk acceptance criteria.
POTENTIAL HIGH-RISK INCIDENTS
Risk values in the red area of the matrix should receive top priority for implementing corrective action. Typically, this will involve performing an RCA of the event and then taking appropriate corrective action.
In conducting the RCA, think systemically and address two key issues:
1. What are the "system" deficiencies that led to the incident? For instance, in a near-miss that involved release of flammable gas because of a leaking line, consider which systems could have contributed — e.g., lack of inspections, plant age and failure to upgrade metallurgy, inadequate training, etc.
2. How extensive is the problem? What other units could suffer from similar events in the future?
DON'T MISS OUT
Plants always will have near-misses. However, safety and productivity demand reducing their occurrence as much as possible and minimizing the adverse impact of large events that could happen.
Near-misses can result from myriad causes, including design flaws, badly written procedures, and poor or inadequate training. So, take a systems approach.
While standards and regulations foster robust designs, don't rely exclusively on them. Instead, apply the philosophy of "fault tolerance" and include effective safeguards.
Establish a culture of trust and openness that encourages employees to report all near-miss incidents.
Develop a database and classify near-misses into a number of useful categories. Try to minimize bureaucracy. Near-miss incidents do require record keeping and reporting. However, don't let the paperwork (including electronic record keeping) obscure the key focus — safety, environmental protection and profitability!
G. C. SHAH, PE, CFSE, CSP, CIH, CFPS, CAP, CQE, is a safety, environmental and industrial hygiene professional at Wood Group Mustang Inc., Houston. E-mail him at firstname.lastname@example.org.