The European Standard prEN "Safety related parts of control systems" deals with these aspectsIt lays down a "language" of five categories for benchmarking and describing the performance of SRCSsTable is a summary of the categoriesSUMMARY OF REQUIREMENTSSYSTEM BAHAVIOR.

Category Main Safety Functions (, , and Refer to safety category .) .Fail safe design keeps the safety door locked when power fails.Foolproof design prevents incorrect operation.Input redundancy using switches Two channel input with limit switches SW and SW in positive

safety functions risk reduction through implementing the safety function, and ensuring that the safety function performs as intendedAll functional safety activities must be managed during the lifecycle of the machine.

The CategoriesThe cat­egor­ies are used to describe sys­tem archi­tec­tures for safety related con­trol sys­temsEach archi­tec­ture car­ries with it a range of reli­able per­form­ance that can be related to the degree of risk reduc­tion you are expect­ing to achieve with the sys­tem.

[] Safety of machinery Gen­er­al prin­ciples for design Risk assess­ment and risk reduc­tionISO Stand­ard [] Safety of machinery Func­tion­al safety of safety related elec­tric­al, elec­tron­ic and pro­gram­mable elec­tron­ic con­trol sys­temsIEC Stand­ard .

Safety integrity level (SIL) is defined as a relative levels of risk reduction provided by a safety function, or to specify a target level of risk reductionIn simple terms, SIL is a measurement of performance required for a safety instrumented function (SIF).

Guide to Safety Relays and Safety Circuitsby peter September , Safety relays are a special type of relay you can use to build a safety circuitSafety is a critical issue in machine designIt is crucial to have a good basic understanding of the principles behind safety relays and safety circuits.

categories The most important single concept to understand about the standards is the Overvolt age Installation CategoryThe standard defines Categories I through IV, often abbreviated as CAT I, CAT II, etc(See Figure .) The division of a power distri bution system into categories is based on the fact that a danger ous high energy transient

Chapter Safety Related Control Systems, Additional Considerations Overview, Categories of Control Systems, Undetected Faults, Component and System Ratings, Fault Considerations, Fault Exclusions, Stop Categories According to IEC EN and NFPA , U.SSafety Control System Requirements, Robot Standards U.Sand Canada

However, the safety function may fail between the test phases if a fault occursBy appropriate selection of the test intervals (e.gonce per shift), an appropriate risk reduction can be achieved when apply ing category In categories and , the occurrence of an individual fault cannot lead to the loss of the safety functionIn category