1 Scope
This document specifies the requirements and information on the use of interceptor key interlocking devices and systems. This document applies to security-related interceptor key interlocking devices and systems.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of normative references in the text. Where a reference is dated, only the version corresponding to that date applies to this document; where a reference is not dated, the latest version (including all amendment sheets) applies to this document.
GB/T 14048.1-2012 Low voltage Switchgear and Controlgear Part 1: General
GB/T 14048.3-2017 Low voltage Switchgear and Controlgear Part 3: Switch Isolators, Disconnectors and Fuse Combiners
GB/T 14048.5-2017 Low voltage Switchgear and Controlgear Part 5-1: Control Circuit Apparatus and Switching Elements Electromechanical Control Circuit Apparatus
GB/T 15706-2012 General Principles for Mechanical Safety Design Human Risk Assessment and Risk Reduction
GB/T 16855.1-2018 Safety Related Components of Machinery Safety Control Systems Part 1: General Principles for Design
GB/T 16855.2-2015 Safety Related Components of Machine Safety Control System Part 2: Confirmation
GB/T 18831-2017 Safety of Machinery - Interlocks Related to Protective Devices - Design and Selection Principles
GB/T 41,108.1 Safety Requirements for Interlocks of Machinery - Part 1: Direct Disconnect Position Switch
GB/T41108.2-2021 Safety Requirements for Interlocks of Machinery - Part 2: Interlocks with Protective Locks
3 Terms and definitions
The terms defined in GB/T 15706-2012, GB/T 18831-2017 and GB/T 41108.1 and the following terms and definitions apply to this document.
3.1
trapped key interlocking system
A system containing at least two trapped key interlocking devices, with one or more security functions achieved by the transfer of keys.
Note: The trapped key interlocking system mainly implements two sub-functions: isolation control and access control, the intermediate transfer sub-function is optional.
4 Symbols
The following symbols apply to this document.
Note: The symbols given in this document do not state any performance level (PL) or safety integrity level (SIL) in relation to the safety function. The corresponding connections between contacts are therefore given by dashed lines, independent of the contact type.
5 Requirements for interlocking systems with intercepting keys
5.1 Composition of the interlocking system for intercepting keys
The interlocking system shall consist of at least the following components:
a) switch or switch with protective locking mechanism
b) a key;
c) a protective locking mechanism.
To enable intermediate key transfer, the interlocking system may be supplemented by key exchange devices, time delay devices, etc.
5.2 Functional breakdown of the interlocking system
5.2.1 Overview
A typical complete truncated key interlocking system consists of three sub-functions (see Figure 4):
a) Isolation control (e.g. key-operated switch), see 5.2.2;
b) intermediate transfer (e.g. key exchange device), see 5.2.3; c) access control (e.g. authorised door lock), see 5.2.4.
Note: The intermediate transfer function is not a necessary sub-function of the interceptor key interlocking device. For simpler tasks, one or more security functions can be achieved by relying only on the two sub-functions of isolation control and access control.
5.2.2 Isolation control
5.2.2.1 General requirements
The purpose of isolation control is to enable the power or movement to reach and maintain a safe state. Examples of interceptor key interlocking devices for isolation control include latch locks (to operate valves or isolation switches), key-operated switches, etc.
When the key is removed from the interceptor key interlocking device, the power or movement should be maintained in a safe state. The power or movement can only be restored to its original state if the key is retrieved and inserted in an unlockable or truncated state.
Isolation control can be divided into:
Power interlocking, i.e. isolation by direct mechanical action.
Control interlocks, i.e. isolation by indirect mechanical action.
5.2.2.2 Power interlocking
For interlocking systems where isolation is achieved by means of a power interlock, the power is directly locked out by means of a direct mechanical action of the interlocking device. This is usually achieved by means of an isolating switch with a latch lock (see Figure 5) or by means of a switch assembly as a key-operated switch for the isolator. The disconnect switch should meet the requirements of GB/T 14048.3-2017. The key can only be removed from the interceptor key interlocking device if the power has been isolated and locked in the off position.
6 Requirements for the interceptor key interlocking device
6.1 Structural requirements
6.1.1 Key-operated switch
6.1.1.1 General requirements
Only direct break control switches or load break switches shall be used for the switching components in the safety circuit of the interceptor key interlocking device. Other types of switch may also be used for auxiliary signals (non-safety signals).
6.1.1.2 Direct break control switches
Direct break control switches should meet the requirements of GB/T 41108.1.
6.2 Strength requirements
6.2.1 Key holding force
Measures shall be taken to prevent keys trapped in the lock from being easily extracted. A force of less than 250 N should make it impossible to pull the key out of the lock. All components used for key retention, including the key itself, shall be capable of withstanding a torque of at least 5 N-m.
In addition, for torque values greater than 5 N-m, it shall be ensured that the key does not exert a shearing force on the lock that would result in loss of security function (e.g. by design measures such as pre-determined breaking points).
6.2.2 Protective locking force for authorised door locks
An authorised door lock in the closed locked position shall remain in the locked position without permanent deformation of the elements when subjected to a force of more than 1.3 times the protective locking force (Fa) given by the manufacturer.
Note 1: 1.3 is a safety factor.
Note 2: Fa is given by the manufacturer in the operating information, see chapter 7.
6.2.3 Swivel actuator for authorised door locks
The blocking mechanism of the rotary actuator should be able to withstand a torque of at least 5 N-m acting on the actuator.
In addition, for torques greater than 5 N-m, it should be ensured that the actuator does not exert a shearing force on the lock that would result in loss of safety function (e.g. through design measures such as predetermined breaking points).
Note: This differs from the holding force of the key.
6.3 Average number of cycles to failure at risk (B1oD)
The B1op value for interceptor key interlocking devices should be at least 2 000 000 cycles.
6.4 Prevention of foreseeable abandonment in a simple manner
6.4.1 General requirements
In addition to the requirements of chapter 7 of GB/T 18831-2017, the interceptor key interlocking device shall also meet the requirements of 6.4.2 to 6.4.4. Note: There is a clear difference between the key code and the code of the actuator in the interlocking system.
6.4.2 Key code
Keys for interlocking devices shall be coded and only the corresponding coded lock shall be operated.
The key shall not be easily reproducible by persons other than the manufacturer (e.g. by means of hand tools or domestic locksmiths).
6.5 Electrical clearances and creepage distances
The electrical clearances and creepage distances between adjacent electrical components shall meet the requirements of 7.1.4 in GB/T 14048.1-2012 and shall be maintained during operation of the switch.
6.6 Enclosure protection class
If the interceptor key interlocking device has an enclosure, the enclosure shall have a protection class of at least IP65.
6.7 Electromagnetic compatibility (EMC)
The electromagnetic compatibility of the interceptor key interlocking device shall comply with the requirements specified in 7.3 of GB/T 14048.5-2017.
7 Use information
7.1 Marking
7.1.1 General requirements
Interceptor key interlocking systems shall be permanently and clearly marked (character height not less than 2 mm) in accordance with the requirements specified in 7.1.2 to 7,1.7.
7.1.2 Interceptor key interlocking devices
7.1.2 Interlocking devices for intercepting keys
The interceptor key interlocking device shall be clearly marked with the following information:
Name of manufacturer;
Product name (e.g. key change interlocking device)
Date of manufacture;
The standard to be implemented.
7.1.3 Switching elements
The switch components should be clearly marked with the following information:
Name of the manufacturer
System identification number (e.g. serial number).
7.1.4 Switch components with locking mechanism
Switch elements with locking mechanism should be clearly marked with the following information:
Manufacturer's name;
System identification number (e.g. serial number);
the performance parameters of the electromagnetic locking mechanism (if available, these can be marked anywhere)
Terminal connection diagram with terminal assignment (if any).
7.2 Operating instructions
The interlocking system should be supplied with the information required for correct connection and commissioning.
The information provided to the user and its presentation shall be in accordance with 6.4 of GB/T 15706-2012.
Note:For further information on information for use, see ISO 20607;2019.
Bibliography
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Requirements for interlocking systems with intercepting keys
6 Requirements for the interceptor key interlocking device
7 Use information
Bibliography
