Safety Control Circuits

Safety systems Ltd employ a range of techniques to reduce the level of risk, many of which will not involve the use of safety-related control systems.  For example, the use of fixed guards will prevent access to dangerous parts, and the provision of platforms and walkways will reduce the risk of falls from height.  However, in many cases risks cannot be reduced to acceptable levels without incorporating safety-related control systems.  In this case, the designer needs to understand and assess the contribution that these systems make to the reduction of risk, and the consequential reliability and fault tolerance that the systems will need.  The more critical the role played by the safety-related part of the control system, the more reliable and resistant to faults it must be. This property is known as the safety integrity of the system, which is a measure of how well the safety-related control system will perform the required safety function(s) under all stated conditions within a stated period of time when required to do so.

A control system in a machine should be regarded as being safety-related if it contributes to reducing the occurrence of a hazardous situation or if it is required to function correctly to maintain or achieve safety. The functions carried out by a safety-related control system are termed ‘safety functions’.  Generally safety functions either prevent the initiation of a hazard or detect the onset of a hazard. Safety-related control systems should be designed and configured to be reliable enough (bearing in mind the consequences of any failure) and to perform the necessary functions to achieve or maintain a safe state or mitigate the consequences of a hazard.

A designer or assessor must decide which of the three main standards that address the design of safety-related control systems to use: EN62061, EN13849 or EN 954-1. Safety Systems expert engineering knowledge includes vast experience in electro technical safety-related systems that use programmable technologies and those that use electromechanical components.