1.1 This document is applicable to the product family of escalators and moving walks used in residential buildings, offices, hospitals, hotels, industrial plants, etc. This document covers those aspects that need to be addressed when programmable electronic systems are used to carry out electric safety functions for escalators and moving walks (PESSRAE). This document is applicable for escalator and moving walk safety functions that are identified in escalator and moving walk codes, standards, or laws that reference this document for PESSRAE application. The safety integrity levels (SILs) specified in this document are understood to be valid for PESSRAE application in the context of the referenced escalator and moving walk codes, standards, and laws in the Bibliography.

1.2 This document is also applicable for the application of PESSRAE that are new or deviate from those described in this document.

1.3 The requirements of this document regarding electrical safety/protective devices are such that it is not necessary to take into consideration the possibility of a failure of an electric safety/protective device complying with all the requirements of this document and other relevant standards.

This document:

a) uses safety integrity levels (SIL) for specifying the target failure rate for the safety functions to be implemented by the PESSRAE;

b) specifies the requirements for achieving safety integrity for a function but does not specify who is responsible for implementing and maintaining the requirements (for example, designers, suppliers, owner/operating company, contractor); this responsibility is assigned to different parties according to safety planning and national regulations;

c) applies to PE systems used in escalator and moving walk applications that meet the minimum requirements of a recognized escalator and moving walk standards, such as EN 115, ASME A17.1/CSA B44 or The Japan Building Standard Law Enforcement Order For Elevator and Escalator;

d) defines the relationship between this document and IEC 61508 and defines the relationship between this document and ISO 22200;

e) outlines the relationship between escalator and moving walk safety functions and their safe-state conditions;

f) applies to phases and activities that are specific to design of hardware and software but not the phases and activities which occur post design, for example sourcing and manufacturing;

h) provides requirements relating to the hardware and software safety validation;

i) establishes the safety integrity levels for specific escalator and moving walk safety functions;

j) specifies techniques/measures required for achieving the specified safety integrity levels;

k) defines a maximum level of performance (SIL 3) which can be achieved for a PESSRAE according to this document and defines a minimum level of performance (SIL 1).

1.4 This document does not cover:

a) hazards arising from the PE systems equipment itself such as electric shock etc.;

b) the concept of fail-safe that can be of value when the failure modes are well defined and the level of complexity is relatively low. The concept of fail-safe was considered inappropriate because of the full range of complexity of PESSRAE that are within the scope of this document;

c) other relevant requirements necessary for the complete application of a PESSRAE in an escalator and moving walk safety function, such as system integration specifications, temperature and humidity, the mechanical construction, mounting and labelling of switches, actuators, or sensors that contain PESSRAE.

d) foreseeable misuse involving security threats related to malevolent or unauthorized action. This document can be used in cases where a security threat analysis needs to be considered, provided that the specified SIL has been reassessed.