Importance of safety through design

In the modern world of engineers, there are some fashionable words that are often used: Safety, Health and Environment commonly called SHE problems.

Each year, unintentional injuries cost our society in excess of $399 billion in the US alone (National Safety Council’s report). This figure includes lost wages, medical outlays, vehicle damage and other expenses.

Worldwide, billions more are lost. The cost of human misery is incalculable: unintentional injuries are the fifth leading cause of death. Most of these incidents result from interaction between machines and their environment and the way people live and work. Thus, these unplanned and unwanted accidents could be avoided if someone, especially engineers, think more about the safety of the users. A deal has to be found between suppliers and users engineers so as to improve safety on all the steps, could it be professional or private use. Only a common conscientious work could help to decrease the rate of user’s accident.

“Every accident should be avoided’: this is the way of thinking of the leading team of Du Pont de Nemours society: it’s the way of progress we have to think about together.

The main reasons why we should more care about safety are:

  • Time - the design cycle is under ever increase pressure to compress
  • Costs – there are significant opportunities for productivity gains and cost efficiencies
  • Competition – reducing costs and increasing productivity through safety through design can provide an attractive competitive advantage
  • International Influences – through the CE mark, the European Union (EU) explicitly requires an analysis of the hazards in accordance with the hazard elimination and control hierarchy
  • Capturing knowledge – a completed risk assessment can be used to capture much of the knowledge pertinent to that design and applicable to similar designs.
  • Product liability – risk assessment help reduce exposures to hazards and can assist in building a successful defense against a product liability claim

Safety analyses are fundamental tools in the safety community. They help make an implement decisions regarding product safety, simultaneously preventing accidents, improving product safety, and reducing a manufacturer’s liability exposure by systematically identifying and evaluating hazards concerning the product design, its uses, and potential “failures”. Safety analyses should advance designs rather than solely reviewing and checking past decisions. Particular focus should be given to areas in which the designer has not been able to concentrate, and where safety problems are often overlooked.

Although some safety analyses are formal and extensive analytical efforts, many of the techniques should be adapted to a product’s specific needs. This ensures the analysis advances the design and remains focused on the critical safety issues.

Hazard analysis and Risk assessment: What is it?

Objectives:

A risk assessment is a tool for engineers and safety practitioners to identify possible hazards, to provide an evaluation of the risks and to prompt alternative design solutions to mitigate or control the risks to an acceptable level.

This safety step identifies hazards of a product or a process before an injury occurs.

Definitions:

Hazard:A potentially dangerous condition, which is triggered by an event. This event is often called the cause of the hazard. Any hazard will have to be existent for a period of time before it will become dangerous.

Risk:A hazard that is associated with a severity and a probability of occurrence.

Hazard analysis: Identify all possible hazards potentially created by a product, process or application.

Risk assessment:It is the next step after the collection of potential hazards. Risk in this context is the probability and severity of the hazard becoming reality.

When performed:

This safety process must be done before the design begins. It brings profits in the time, the cost, and in liability.

Information used:

  • Literature
  • Scenarios,
  • Expert opinions,
  • Personal experience.

Method:

Many industries have developed methods in risk assessment. However, a general risk assessment protocol can be presented.

Figure 1 General Risk Assessment Process

1. Establish the analysis parameters.

The first step in the risk assessment process is to establish the parameters of the analysis. These parameters can be limits of the machine or design, limits on uses, limits on the scope of the analysis, or other limits.

2. Identify hazards

The next step is to identify hazards associated with the product or process design. The nature of this step lends itself to a team approach such as brainstorming.

  1. Assess risks using two or more risk factors

Once hazards have been identified, the risk assessment effort begins. Generally, two risk factors (severity of injury and probability of occurrence) are used.

  1. Derive risk rating

Once the risk factors are assessed, a risk rating is derived from a risk matrix. The risk matrix is the combination of the risk factors mapped to various risk levels. One example of a risk matrix is presented in Table 1.

Table 1Example Risk Matrixfrom MIL-STD-882D (6)

Probability Level / Severity of injury
Catastrophic / Serious / Slight / Minimal
Probable / High / High / Low / Negligible
Possible / High / High / Low / Negligible
Unlikely / Moderate / Moderate / Low / Negligible
Negligible / Negligible / Negligible / Negligible / Negligible

The risk assessment process yields a level of risk. If the risk is determined to not be acceptable, it is necessary to reduce that risk by implementing protective measures.

5. Reduce risks

Risk reduction activities begin after the risk rating is derived. Remedy actions are taken to reduce risks following the hazard hierarchy. The hazard hierarchy is shown below.

Hazard Elimination and Control Hierarchy

  • Eliminate hazards through the design
  • Protect or guard against the hazard
  • Warn the user about the hazard
  • Train the user(s) to avoid the hazard
  • Personal protective equipment

6. Verify the risk reduction effectiveness

Once the risks have been reduced to an acceptable level, most risk assessment protocols call for a second assessment of the risk factors after the risk reduction remedies have been selected. This assessment verifies that the remedy actions have reduced the risks to an acceptable level, risk, which is accepted in a given context, based on the current values of society.

7. Document the results

After risks have been reduced to an acceptable level, the risk assessment activities should be documented. The documentation can be added to a technical file for future use.

When to stop:

There is no possibility of zero risk in most processes. Therefore some level of residual risk always remains. One definition of residual risk is: “Risk remaining after protective measures have been taken”. If the residual risk is acceptable, then the risk assessment process is completed. The minimal acceptable level should prevent irreversible injury or death under single fault conditions.

Caution:

Any hazard, which is not identified, will not be addressed by safety measures and will not be detecting during testing. It is crucial to be aware of this vulnerability, because it requires paying close attention to detail and completeness of the hazard analysis.

Hazard not identified during this analysis can create substantial risk to users of the design.

An efficient tool:

A new computer tool, named Designsafe, specially designed to speed the hazard analysis process has become available. It uses a task-based method to ensure all hazards to users are identified.

What are the next steps …

  • Fault Tree Analysis (FTA) is a powerful diagnostic tool for analyzing complex systems. FTA begins with selecting the “top event”. Then, analysis built the tree of contributory events using logic symbols. Repeating this process at successive levels using standardized symbols identifies primary and secondary faults.
  • Failure Modes and Effects Analysis identifies potential product modes which could lead to accidents. It breaks down designs into components or subcomponents, then systematically evaluates the potential for and effects of individual failures, focusing on how they can lead to hazards or unreliability in design. Results of the analysis are used to evaluate and implement preventive measures to eliminate or control hazards.