By: Joe Antony, Principal Engineer – Controls and Components
At UL, we prioritize science and safety. We develop principles that secure safety from potential hazards that can harm anyone or anything when products are being produced or when products are being used. This article will focus on a particular safety science that helps keep the world safe and that is hazard-based safety engineering (HBSE). HBSE can best be described as a key component and building block of safety science, consisting of two components: inherent safety and functional safety. Inherent safety is safety related to the inherent design of the product where the safeguards against potential hazards are not relied upon for the correct operation of embedded functions. Functional safety is related to safety resulting from a loss or malfunction of a function, either within the product or in the overall system. Both of these components are based on hazard-based safety principles that are discussed later in this article.
Unfortunately, safety science is not taught in engineering schools as part of an academic curriculum and therefore it is not well understood in the field. As a result, implementation of reliable and robust safeguards in product designs, to prevent the risk of potential hazards especially with new and emerging technologies, are missed during the design stage of a product.
For a hazard to manifest, three events must take place. First, there should be an energy source capable of providing the hazardous energy continuously. Secondly, there should be a transfer mechanism that transfer the energy from the source to the output and lastly, the body susceptibility to the available level of energy. The three-block hazard transfer model, noted below, illustrates the above point.
This tool can be applied in product design, certification and development of safety standards. It involves a systematic and analytical approach to safety by identifying all hazardous sources and implementing measures to either reduce or mitigate energy transfer to the human body.
Outlined below are some guiding thoughts on how one should proceed with this activity:
- Identification of the energy source.
- Determine if the energy source is hazardous or nonhazardous based on consensus standards of safety or industry norms
- Determine the specific type of hazards, i.e., electric shock, fire, casualty injury, etc., that can occur from this energy source both in the intended operation and foreseeable misuse of the product
- Determine the various paths that this energy can be transferred in the product
- Identification of the transfer mechanism and safeguards
- Determine event sequence leading to the hazardous events by applying hazard and risk analysis techniques such as fault tree analysis (FTA) and failure mode effect analysis (FMEA) to identify the transfer mechanism and possible safeguards
- Examine each energy transfer mechanism to determine if the energy can be reduced or mitigated by using appropriate safeguards
- Identify the protective measures/safeguards
- Determine the suitability of the safeguard with respect to the severity of the hazard
- Evaluate the safeguard for its effectiveness, robustness and reliability to perform its intended safety function
By implementing this thought process, product designers can design safety into their products even though the relevant safety standard may not address the anticipated hazards. Consensus standards lag behind technology and application, so the safety community should utilize HBSE techniques in their work.
For over three decades, UL has implemented these safety principles in the development of their standards, which, of course, provides the safeguards to reduce or mitigate anticipated hazards, and continues to do so, especially with the advancement of technology. With emerging technology and advanced connectivity of products, new faults emerge that must be addressed to maintain the safety level of the product. Consequently, UL plays a leadership role in technical committees, both international and domestic, involving the areas of functional safety and cybersecurity.
UL offers public and private seminars regarding the above topic, including the principles of functional safety and cybersecurity. Please contact [email protected] or click the following links below for addtional information and trainings: