Last edit: 26/06/2023
5.3.2.1 Classification of ESPE
IEC 61496-1 defines 3 “types” of ESPE. The types differ in their performance in the presence of faults and under influences from environmental conditions.
Type 2 ESPEs employ a periodic test to reveal failures to danger. Type 2 are unlikely to be suitable for applications demanding a medium or high risk reduction.
Type 3 ESPEs are designed to not fail to danger die to a single fault but can fail to danger due to an accumulation of faults. Type 3 can be suitable for applications demanding a medium to high risk reduction when their sensing technology is appropriate.
Type 4 ESPEs are designed to not fail to danger due to a single fault or an accumulation of faults. Type 4 can be suitable for applications demanding a medium to high risk reduction when their sensing technology is appropriate.
not be reduced by a start interlock
5.5 a start interlock shall be provided except where risk analysis has shown that the probability of injury is not reduced by the presence of a start interlock.
5.6 a restart interlock must be provided except where the risk analysis has shown that the probability of injury is not reduced by the presence of a restart interlock. A restart interlock must be provided where a protective device, with a stop function, is used for perimeter protection (trip device).
A restart interlock must have a time ≤ 0.5 s between manual reset and resumption of safety functions.
5.7 Muting
The muting function should be provided only when strictly necessary for the production process.
The parts of the control system that perform the muting function must have an appropriate performance level (SIL or PL) and must not reduce the safety performance level of the safety function.
When the muting function is provided, the following requirements apply:
– The muting function must be initiated by two or more muting signals so that a single fault does not cause a muting condition
– The muting function must stop when one of the muting signals is disabled
– Use of timers and/or sequences to control the muting signals
– Protection against tampering
5.7.2 The muting function can be used to allow operator access only:
– During non-hazardous portions of the operating cycle
– When safety is assured by other means
5.7.3 The muting function may be used to allow material access only when safety is assured by other means.
The following measures, where applicable, must be provided:
– Selection, positioning, and configuration of muting sensors to distinguish people from material
– Selection and positioning of muting sensors so as to detect the load being carried but not the pallet or conveyor unit
– Install muting sensors sufficiently close to the ESPE
– Designing access to the hazardous area so that it cannot be accessed undetected