ISO/TC 199/WG 7 - Interlocking devices

ISO/TS 19837:2018 specifies principles for the design, selection and application of trapped key interlocking devices and systems for machinery applications, independent of the type of energy used to control them or that they control. The requirements of this document apply to the safety related aspects of trapped key interlocking devices and systems. ISO 14119 always applies unless an exception is given in this document. ISO/TS 19837:2018 is intended to be used in conjunction with ISO 14119. ISO/TS 19837:2018 does not provide testing requirements. NOTE Documents addressing testing requirements can be found in the Bibliography.

ISO/TR 24119:2015 illustrates and explains principles of fault masking in applications where multiple interlocking devices with potential free contacts (B1 to Bn) are connected in series to one logic unit (K) which does the diagnostics (see Figures 1 to 7). It further provides a guide how to estimate the probability of fault masking and the maximum DC for the involved interlocking devices. This Technical Report only covers interlocking devices in which both channels are physical serial connections.

ISO 14119:2013 specifies principles for the design and selection ? independent of the nature of the energy source ? of interlocking devices associated with guards.It covers the parts of guards which actuate interlocking devices. It does not necessarily provide all the specific requirements for trapped key systems. ISO 14119:2013 provides measures to minimize defeat of interlocking devices in a reasonably foreseeable manner.