Article 39 -Escalator Electric Hazards
Escalator Electric Hazards due to Direct or Indirect Contacts with live parts:
Electrically Live Parts, in escalators, moving walks, or any other machines, involve the energized conductive components of that machine or device. In case a competent person unintentionally touches or approaches the unguarded electrically live parts of an escalator, it could lead to serious injuries and even death. Contacting with live parts of an escalator could occur directly or indirectly as follows:
- Direct contact refers to a person contacting a conductor, which is live in normal conditions.
To protect against direct contact with the live parts, the EN 60204-1:2006, 6.2 requirements must be followed as well as utilizing sockets with the following specifications:
- Socket Outlets type 2 P+PE (2 poles + earth conductor), 250 V, which are directly supplied by the mains
- The socket outlets which are supplied at a safety extra-low voltage based on HD 60364-4-41:2007
Protection against direct contact can be achieved by the insulation of live parts, which can only be removed by destruction. Such insulation must be capable of withstanding the mechanical, chemical, electrical, and thermal stresses to which it can be subjected under normal operating conditions.
- Indirect contact occurs when a person contacts with any part of an electric circuit, which is not normally live, but has become live due to an accidental insulation failure or some other fault.
To prevent the hazardous situations resulting from indirect contact, the insulation resistance tests, according to EN 60204-1:2006, 18.3, must be done so that the resistance insulation between conductors and between conductors and the earth is measured.
Also, electric supply and the electric protection requirements (e.g. electric shock, short circuit; overload), must be negotiated and agreed between the owner and the manufacturer. Moreover, the installation must be either based on EN 60204-1:2006, or based on the requirements of the national rules of the country where the machine is installed.
To prevent the hazardous situations resulting from indirect contact with live parts a protective device must interrupt the power supply in a short time to reduce the effect of touch voltage, through which the automatic disconnection of the supply of any circuit affected by an insulation fault is possible.
In addition, disconnecting the socket outlets, i.e. switching off the power supply to individual socket outlets by the use of Residual Current protective Devices (RCD) means to limit the effects of possible electric shock when using e.g. electric hand-held tools, connected to the socket outlets on the machine.
Note: RCD with a maximum 30 mA must be connected to the wall socket outlet in the equipment to protect persons.
Escalators electric hazards due to inadequate emergency stops:
There could always be emergencies regarding escalators in which a manually operated stop device plays a vital role to prevent such hazardous events. In case the stop device is not installed appropriately and based on the required standard, the actuator of the stop device might not be activated, which could lead to a hazard. Therefore, the location of an actuator in obvious and reachable positions (from an area outside the step/pallet band) especially at both landings is very important.
Escalators electric hazards due to the wrong assembly of electric components:
To prevent this hazard, EN 60204-1:2006, 13.4.5 requirements except c), d) and i), are necessary to apply when utilizing Plug socket combinations. In addition, it is essential to design and place the connectors and devices of plug-in type, which are placed in the circuits of electrical safety devices, in a way that they cannot be inserted in a position that could cause a hazardous situation.
Escalators electric hazards due to electrostatic phenomena:
Such charging of insulation materials can be seen every day. You have definitely experienced it when pulling your sweater over your head and heard the familiar crackling. It happens because your hair has rubbed against your sweater. Such a phenomenon could also happen in escalators causing that the passenger gets an electric shock by touching the handrail of an escalator. Even though the handrail rubber is an insulator, this phenomenon is possible to happen because the constant motion charges the rubber through friction. Electrostatic charges must be reported and investigated immediately since the spark created by such energy could lead to fire or explosion. This hazard can be prevented by installing a device called anti-static-brushes to discharge electrostatic loading. Additionally, all the escalators and moving walks are provided with an Anti-Static Brush which is located within the escalator steps.
Escalators electric hazards due to external influences on electric equipment:
Such a danger is possible when false signals appear due to the effects of switching at the outputs of safety devices. To prevent such signals, the construction and arrangement of the internal power supply units must be based on the required standard. Also, based on EN 12015:2014 and EN 12016:2013, voltage peaks arising from the operation of the escalator or other equipment on the network must not create inadmissible disturbances in electronic components (noise, immunity). Considering 3 mm air gaps and 4mm creep distances if the protective enclosure is not at least of type IP 4X is necessary.