Programmable electronic systems in safety related lift applications

With the advent of programmable electronic systems (PESs) or computers, in safety related lift systems, need has arisen to clarify those areas covered by the `safety rules for the construction of lifts´, where PESs may or may not, be applied. The article is based on the guidelines prepared by the National Association of Lift Makers. The guidance applies if one or more of the safety related systems associated with a plant is a PES. It does not apply if an adequate level of safety is assured by one or more conventional systems, separate from the controlling PES, of conventional safety integrity or better. The conventional system will need to adequately cater for, amongst other things, failures of the controlling PES itself