Safety: Part 1 - Functional Safety Trend

The concept of safety in electrical, mechanical and electronic equipment and systems with or without software has long been an aspect of interest in specific application sectors. Among the pioneering sectors in the application of Safety concepts we have Space and Nuclear. Consequently, also the training of specialized figures in the field of Safety were mainly professionals who had gained significant experience in the aerospace or nuclear sector. The only university courses that guaranteed an educational offer with safety-focused courses were precisely the Nuclear Engineering Courses.

The growth of the avionics market first, and then the rail market, required the need to guarantee an ever higher level of safety and consequently also the diffusion of competent figures in the safety sector have spread.

Nowadays, the concept of Safety, with specific declinations for each sector, are widely applied also in the medical, military, automotive, industrial and even household appliances sectors.

The legislation, the guidelines, the standards have multiplied and specialized in the various sectors in order to achieve specific safety levels for the different types of users. In addition to the specific standards to analyze and guarantee the level of safety necessary for the specific application, regulations, guidelines and standards have also been created to guide the processes of design, development, verification and approach to certification of the various products.

The creation of common markets with the sharing of the same rules for the certification of products such as the European Community and the Eurasian Community have allowed the diffusion of directives for the certification of products such as CE and EAC certification. These directives (machinery directive, low voltage directive, etc.) have been joined by a series of standards and regulations of different levels which regulate or outline common approaches to demonstrate compliance with the reference directives for the specific product.

MIL-STD-882, ARP 4761, ARP 4754, ISO 26262, ISO 13849, IEC 62304, EN 5012x, IEC 62061, IEC 61511, IEC 61513, ISO / PAS 21448, DO 178, DO 254, DO 257, DO 330, DO-278, and IEC 61508 are only some of the standards and guidelines currently used.

The Safety is leterally defined in the dictionary as "the condition of being protected from or unlikely to cause danger, risk, or injury."

A product that performs a certain function can be made in many different ways based on the judgment, competence and level of safety that the designer thinks he must guarantee. Relying on the designer's judgment alone can lead to a product that can be far too complex and economically unacceptable or that it has been conceived too simple to be economical and therefore not such as to guarantee the necessary level of safety.

At the basis of the theories for the study of Safety is the idea that a product cannot be conceived with a level of quality and robustness such as to have an infinite duration of time without ever damaging itself and without ever deteriorating. With the full awareness that a product can be damaged at any time in its life, being able to generate dangerous conditions for people who use it or who are in the immediate vicinity, techniques for analyzing the level of safety that a product is able to guarantee were born. It is understood that these techniques use Probability Theory as a basic tool.

It is therefore clear that when we talk about Safety we are not referring to an absolute guarantee but to a certain level of safety.

The Level of Safety that statistically can be achieved is commonly defined by the different standards as Design Assurance Level (DAL), Safety Integrity Level (SIL) or Automotive Safety Integrity Level (ASIL).

The DO 178 was published in each first issue by the RTCA on 1982 and it was organized to define the basic concepts of Software Design Assurance for Avionic Application by means of 3 different levels of SW Safety. With the second update published as DO 178B, the levels of SW Safety was splitted in 5 different levels from A to E.

The DO 254 was published by the RTCA on 2000 to be a guideline for the Design Assurance for Airborne Electronic Hardware and it is based on 5 different Design Assurance Level from A to E.

The System Safety in the Space sector is managed bu the ISO 14620 and the ISO 14300. In particular, the ISO 14620 is the standard used to define safety program and the technical safety requirements implemented to protect flight and ground personnel, the launch vehicle, associated payloads, ground support equipment, the general public, public and private property, and the environment from hazards associated with space systems.

In the other sector, it was published the ISO 61508 as general standard for safety-related products. Specific standards were published to cover the safety-related products for specific sector: ISO 26262 for the Automotive equipment, ISO 60730 for Household equipment, IEC 61131-6 for Programmable Controller, IEC 61800-5-2 for Variable Speed Drives, IEC 62061 and ISO 13849 for Machinery, IEC 60601 for Medical, IEC 61513 for Nuclear, EN 50128 for Railway, and IEC 61511 for Process Industry.

With the increasing on the complexity of the equipment ans systems, it was envisaged the necessity to have a regulation adjusted for the specific market or tipology of equipment to define the minimum list of safety requirement to be implemented and verified.

In the European Union, the process of unification and harmonization in regulation has led to the birth of several European directives and community regulations that govern the minimum requirements that products must have to be marketed in the union market. Sometimes, these European directives also define the organizational structure of the company that designs, manufactures and markets products on the European market. Often these directives and regulations rely on a series of standards collected in a list called harmonized standards. Harmonized standards are those standards identified by the European community as a means of demonstrating compliance with the requirements defined by the European directive.

The mechanism has different facets based on the specific sector of reference and the relevant European directive taken into consideration.

All the aspects mentioned above could be considered driving factors in the proliferation of regulations and standards for product safety as well as the greater understanding of the risks deriving from use and the need to protect the end user from potential health damage caused by a malfunction of a product.