What is Functional Safety? | Functional Safety Standards
The Essential Guide To Functional Safety Standards
The safety of equipment often depends on a control behaviour that is the result of deliberate design intent. This has been the case for many years and across many sectors and product types. Where the behaviour is to some degree reliant on programmable logic, i.e. computers, then the software that dictates the computer behaviour is also of great interest to the designer. This is true regardless of the energy type being controlled i.e. mechanical, pneumatic, electronic, hydraulic, electrical or programmable electronic. The designer must therefore consider not only all the elements within an individual system, i.e. an interlock switching signal de-energising and stopping the dangerous actuators prior to access but also all the safety-related systems making up the total combination of safety-related systems such that the overall effect of all systems can be validated as an effective safety concept.
The term functional safety embraces the whole process of risk assessment and the technical realisation that achieves this objective. Perhaps the most important output of this procedure is the development of the safety requirements specification necessary to achieve the required functional safety level for safety-related systems. This will include not only the intended function but also consideration of hardware failures, human error, wear-and-tear, systematic errors and environmental stresses.
Why Functional Safety
Functional safety is important because it provides a workable method of protecting lives in the workplace, as well as the reputation of your business. Functional safety processes and standards are implemented to mitigate risks of system or component failures that would otherwise cause harm or interrupt business continuity.
Businesses are increasingly turning to software-based solutions and automation processes to provide algorithmic functional safety to a wide array of sectors, including aerospace, automotive and oil and gas but also less technology-driven sectors such as food and pharmaceutical. The switches, signals software and automation processes, upon which safety depends, must be the result of deliberate design intent and in proportion to the risk and complexity. The functional safety standards provide a method for identifying where functional safety is relevant by identifying the potential for dangerous failure and then adopting a risk-based approach to determine the safety integrity levels (SIL) or performance level (PL) of the safety functions during the safety requirement specification. In this way, designers and specifiers can verify meeting these objectives by the calculations that take into account relevant characteristics of the system such as demand rate, hardware fault tolerance, diagnostic coverage and sensitivity to common causes of failure.
Functional Safety Standards and Regulations
When designing a new system that relies on functional safety, or modifying an existing system, then it is necessary to work to current standards in order to presume you are meeting the guidance in relevant statutory codes of practice, e.g. PUWER. There are different standards that businesses could use to demonstrate that a device, product or process is correct in terms of its functional safety. Care should be taken to select the correct standard for your product/industry.
The General/Umbrella Standard - IEC 61508
The basic international standard of functional safety, known as the “umbrella standard”, IEC 61508 can be applied to any kind of safety-related electronic, electric and programmable-electronic product.
Machinery Standards - EN ISO 13849-1
EN ISO 13849-1 is the relevant safety standards governing the functional safety of all systems and technologies including hydraulic, pneumatic and mechanical products.
Machinery Standards - IEC 62061
The IEC 62061 standard of safety covers the machinery industry; covering electronic, electric and programmable-electronic safety control systems. This standard seeks to lower risk by accessing processes and products against the Safety Integrity Level (SILs) system.
Automotive - ISO 26262
ISO 26262 is the standard applying to electric and electronic systems consisting of software and hardware components in production vehicles. Using Automotive Safety Integrity Levels (ASILs) to determine automotive-specific safety risks and catalogue the level of risk according to an A – D standard.
Medical Devices Software - IEC 62304
The medical device industry’s safety standard is IEC 62304 and it covers software lifecycle processes. Safety assessments are classified into three categories (A-C) which will then detail the recommended requirements based on the risks detected.
Medical devices are also concerned by other safety regulations, including:
Nuclear - IEC 60880
Covering safety function software, IEC 60880 is the safety standard for use in nuclear power plants.
Railway - EN 50128
Covering electric and electronic protection software and railway controls, EN 50128 is the rail industry safety standard. Safety standard requirements are measured in Software Safety Integrity Levels (SSILs) via 0 – 4 categorisations.
Functional Safety for Certification and Functional Safety Management
As a user, receiving certification of the product where they incorporate functional safety as a part of the safety concept is vitally important. The certification is a pillar upon which you rely to establish suitability and only then can you have confidence that the products and processes are safe to put into use, continue to use or put on the market. As you develop this asset over time by modification or integration to other items, then it is necessary to manage functional safety through a robust change management procedure that incorporates the necessary steps to achieve and evidence functional safety. If you fail to implement a functional safety management plan then the engineering changes that naturally occur over time will deteriorate the integrity of the product and leave you, your employees and the business exposed.
Similarly, if you are writing logic blocks for safety-critical software that dictates safe behaviours of machines then the certification of the functional safety of your software can be easier when you utilise the right software development tools that may assist in identifying risks, fulfilling compliance and providing traceable compliance documentation.
Functional Safety Specification & Design Risk Assessment (DRA)
The certification process and its design risk assessment (DRA) should begin early in the development stages so that it can inform design. If you are designing new or modifying safety-critical control systems then your business is attempting to get a product certified or avoid damaging the existing certification. This is done by development of a functional safety specification and verifying/validating where all relevant parties are involved to ensure that functional safety specification is suitable.
The aim of functional safety design risk assessment is to define the safety specification to be achieved during the design so that it can be verified to that design intent later on. Collecting the evidence that your product and its software demonstrate compliance with functional safety requirements such that you can demonstrate why and how you are correct to apply certification. Certification service providers can provide advice to your business regarding changes and revisions necessary to achieve functional safety certification.
Certification Software for Functional Safety
By using the right design risk assessment (DRA) tools that incorporate intuitive development of the safety requirement specification, your functional safety development will be coherent and clearly derived from the risk identified during the design of the machine or modification giving an overall benefit of quality and productivity in your certification procedure. With the right tools, you can ensure that the functional safety solutions you develop are safe, well documented and reliable. RiskMach may assist you in:
- Ensuring complete compliance with the regulations and achieving certification more quickly
- The identifying and analysing of risks
- Recognising which devices are safety-critical
- Developing a safety specification
- Transparent compliance and documentation of standards based on the risks
The RiskMach Certification module and its Certification Vault can assist you greatly in your functional safety obligations. Gain commercial clarity and peace of mind in the knowledge that your compliance tracking and documentation are correctly structured and contain all the necessary information – all stored securely, able to be presented to industry regulators upon request.