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As far as is practicable, machine-mounted control devices shall be:

• readily accessible for service and maintenance;

• mounted in such a manner as to minimize the possibility of damage from activities such as material handling.

The actuators of hand-operated control devices shall be selected and installed so that:

• they are not less than 0,6 m above the servicing level and are within easy reach of the normal working position of the operator;

• the operator is not placed in a hazardous situation when operating them.

The actuators of foot-operated control devices shall be selected and installed so that:

• they are within easy reach of the normal working position of the operator;

• the operator is not placed in a hazardous situation when operating them.

The degree of protection (see IEC 60529) together with other appropriate measures shall afford protection against:

• the effects of aggressive liquids, vapours, or gases found in the physical environment or used on the machine;

• the ingress of contaminants (for example swarf, dust, particulate matter).

In addition, the operator interface control devices shall have a minimum degree of protection against direct contact of IPXXD (see IEC 60529).

Position sensors (for example position switches, proximity switches) shall be so arranged that they will not be damaged in the event of overtravel.

Position sensors in circuits with safety-related control functions shall have direct opening action (see IEC 60947-5-1) or shall provide similar reliability (see 9.4.2).

NOTE A safety-related control function is intended to maintain the safe condition of the machine or prevent hazardous situations arising at the machine.

Portable and pendant operator control stations and their control devices shall be so selected and arranged as to minimize the possibility of inadvertent machine operations caused by shocks and vibrations (for example if the operator control station is dropped or strikes an obstruction) (see also 4.4.8).

Push-button actuators shall be colour-coded in accordance with Table 2 (see also 9.2 and Annex B).

The colours for START/ON actuators should be WHITE, GREY, BLACK or GREEN with a preference for WHITE. RED shall not be used.

The colour RED shall be used for emergency stop and emergency switching off actuators.

The colours for STOP/OFF actuators should be BLACK, GREY, or WHITE with a preference for BLACK. GREEN shall not be used. RED is permitted, but it is recommended that RED is not used near an emergency operation device.

WHITE, GREY, or BLACK are the preferred colours for push-button actuators that alternately act as START/ON and STOP/OFF push-buttons. The colours RED, YELLOW, or GREEN shall not be used (see also 9.2.6).

WHITE, GREY, or BLACK are the preferred colours for push-button actuators that cause operation while they are actuated and cease the operation when they are released (for example hold-to-run). The colours RED, YELLOW, or GREEN shall not be used.

Reset push-buttons shall be BLUE, WHITE, GREY, or BLACK. Where they also act as a STOP/OFF button, the colours WHITE, GREY, or BLACK are preferred with the main preference being for BLACK. GREEN shall not be used.

Where the same colour WHITE, GREY, or BLACK is used for various functions (for example WHITE for START/ON and for STOP/OFF actuators) a supplementary means of coding (for example shape, position, symbol) shall be used for the identification of push-button actuators.

Table 2 - Colour-coding for push-button actuators and their meanings

In addition to the functional identification as described in 16.3, it is recommended that push­buttons be marked, near to or preferably directly on the actuators, with the symbols given in Table 3.

Table 3 - Symbols for push-buttons

Indicator lights and displays serve to give the following types of information:

• indication: to attract the operator's attention or to indicate that a certain task should be performed. The colours RED, YELLOW, BLUE, and GREEN are normally used in this mode; for flashing indicator lights and displays, see 10.3.3.

• confirmation: to confirm a command, or a condition, or to confirm the termination of a change or transition period. The colours BLUE and WHITE are normally used in this mode and GREEN may be used in some cases.

Indicator lights and displays shall be selected and installed in such a manner as to be visible from the normal position of the operator (see also IEC 61310-1).

Indicator light circuits used for warning lights shall be fitted with facilities to check the operability of these lights.

Unless otherwise agreed between the supplier and the user (see Annex B), indicator lights shall be colour-coded with respect to the condition (status) of the machine in accordance with Table 4.

Table 4 - Colours for indicator lights and their meanings with respect to the condition of the machine

Indicating towers on machines should have the applicable colours in the following order from the top down; RED, YELLOW, BLUE, GREEN and WHITE.

For further distinction or information and especially to give additional emphasis, flashing lights and displays can be provided for the following purposes:

• to attract attention;

• to request immediate action;

• to indicate a discrepancy between the command and actual state;

• to indicate a change in process (flashing during transition).

It is recommended that higher frequency flashing lights or display be used for higher priority information (see IEC 60073 for recommended flashing rates and pulse/pause ratios).

Where flashing lights or displays are used to provide higher priority information, audible warning devices should also be provided.

Illuminated push-button actuators shall be colour-coded in accordance with Tables 2 and 4. Where there is difficulty in assigning an appropriate colour, WHITE shall be used. The colour RED for the emergency stop actuator shall not depend on the illumination of its light.

Devices having a rotational member, such as potentiometers and selector switches, shall have means of prevention of rotation of the stationary member. Friction alone shall not be considered sufficient.

Actuators used to initiate a start function or the movement of machine elements (for example slides, spindles, carriers) shall be constructed and mounted so as to minimize inadvertent operation. However, mushroom-type actuators may be used for two-hand control (see also ISO 13851).

Devices for emergency stop shall be readily accessible.

Emergency stop devices shall be located at each operator control station and at other locations where the initiation of an emergency stop can be required (exception: see 9.2.7.3).

There can be circumstances where confusion can occur between active and inactive emergency stop devices caused by disabling the operator control station. In such cases, means (for example, information for use) shall be provided to minimise confusion.

The types of device for emergency stop include:

• a push-button operated switch with a palm or mushroom head type;

• a pull-cord operated switch;

• a pedal-operated switch without a mechanical guard.

The devices shall have direct opening operation (see IEC 60947-5-1, Annex K).

Actuators of emergency stop devices shall be coloured RED. If a background exists immediately around the actuator, then this background shall be coloured YELLOW. See also ISO 13850.

The supply disconnecting device may be locally operated to serve the function of emergency stop when:

• it is readily accessible to the operator; and

• it is of the type described in 5.3.2 a), b), c), or d).

When also intended for such use, the supply disconnecting device shall meet the colour requirements of 10.7.3.

Emergency switching off devices shall be located as necessary for the given application. Normally, those devices will be located separate from operator control stations. Where it is necessary to provide a control station with an emergency stop device and an emergency switching off device, means shall be provided to avoid confusion between these devices.

NOTE This can be achieved by, for example, the provision of a break-glass enclosure for the emergency switching off device.

The types of device for emergency switching off include:

• a push-button operated switch with a palm or mushroom head type of actuator;

• a pull-cord operated switch.

The devices shall have direct opening action (see IEC 60947-5-1, Annex K).

The push-button operated switch may be in a break-glass enclosure.

Actuators of emergency switching off devices shall be coloured RED. If a background exists immediately around the actuator, then this background shall be coloured YELLOW.

Where confusion can occur between emergency stop and emergency switching off devices, means shall be provided to minimise confusion.

Where the supply disconnecting device is to be locally operated for emergency switching off, it shall be readily accessible and should meet the colour requirements of 10.8.3.

When an enabling control device is provided as a part of a system, it shall signal the enabling control to allow operation when actuated in one position only. In any other position, operation shall be stopped or prevented.

Enabling control devices shall be selected and arranged so as to minimize the possibility of defeating.

Enabling control devices shall be selected that have the following features:

• designed in accordance with ergonomic principles;

• for a two-position type:

position 1: off-function of the switch (actuator is not operated);

• position 2: enabling function (actuator is operated).

• for a three-position type:

position 1: off-function of the switch (actuator is not operated);

position 2: enabling function (actuator is operated in its mid position);

position 3: off-function (actuator is operated past its mid position);

- when returning from position 3 to position 2, the enabling function is not activated.

NOTE The enabling control function is described in 9.2.6.3.

11. Controlgear: location, mounting, and enclosures

    1. General requirements

All controlgear shall be located and mounted so as to facilitate:

• its accessibility and maintenance;

• its protection against the external influences or conditions under which it is intended to operate;

• operation and maintenance of the machine and its associated equipment.

All items of controlgear shall be placed and oriented so that they can be identified without moving them or the wiring. For items that require checking for correct operation or that are liable to need replacement, those actions should be possible without dismantling other equipment or parts of the machine (except opening doors or removing covers, barriers or obstacles). Terminals not part of controlgear components or devices shall also conform to these requirements.

All controlgear shall be mounted so as to facilitate its operation and maintenance from the front. Where a special tool is necessary to adjust, maintain, or remove a device, such a tool shall be supplied. Where access is required for regular maintenance or adjustment, the relevant devices shall be located between 0,4 m and 2,0 m above the servicing level. It is recommended that terminals be at least 0,2 m above the servicing level and be so placed that conductors and cables can be easily connected to them.

No devices except devices for operating, indicating, measuring, and cooling shall be mounted on doors or on normally removable access covers of enclosures. Where control devices are connected through plug-in arrangements, their association shall be made clear by type (shape), marking or reference designation, singly or in combination (see 13.4.5).

Plug-in devices that are handled during normal operation shall be provided with non- interchangeable features where the lack of such a facility can result in malfunctioning.

Plug/socket combinations that are handled during normal operation shall be located and mounted so as to provide unobstructed access.

Test points for connection of test equipment, where provided, shall be:

• mounted so as to provide unobstructed access;

• clearly identified to correspond with the documentation (see 17.3);

• adequately insulated;

• sufficiently spaced.

Non-electrical parts and devices, not directly associated with the electrical equipment, shall not be located within enclosures containing controlgear. Devices such as solenoid valves should be separated from the other electrical equipment (for example in a separate compartment).

Control devices mounted in the same location and connected to the supply voltage, or to both supply and control voltages, shall be grouped separately from those connected only to the control voltages.

Terminals shall be separated into groups for:

• power circuits;

• associated control circuits;

• other control circuits, fed from external sources (for example for interlocking).

The groups may be mounted adjacently, provided that each group can be readily identified (for example by markings, by use of different sizes, by use of barriers or by colours).

When arranging the location of devices (including interconnections), the clearances and creepage distances specified for them by the supplier shall be maintained, taking into account the external influences or conditions of the physical environment.

Heat generating components (for example heat sinks, power resistors) shall be so located that the temperature of each component in the vicinity remains within the permitted limit.

The protection of controlgear against ingress of solid foreign objects and of liquids shall be adequate taking into account the external influences under which the machine is intended to operate (i.e. the location and the physical environmental conditions) and shall be sufficient against dust, coolants, and swarf.

NOTE 1 Requirements for protection against electric shock are given in Clause 6.

NOTE 2 The degrees of protection against ingress of water are covered by IEC 60529. Additional protective measures can be necessary against other liquids.

Enclosures of controlgear shall provide a degree of protection of at least IP22 (see IEC 60529).

Exceptions:

1. Where an electrical operating area is used as a protective enclosure for an appropriate degree of protection against the ingress of solid bodies and liquids.

2. Where removable collectors on conductor wire or conductor bar systems are used and IP22 is not achieved, but the measures of 6.2.5 are applied.

NOTE 3 Some examples of applications, along with the degree of protection typically provided by their enclosures, are listed below:

- ventilated enclosure, containing only motor starter resistor and other large size equipment IP10

ventilated enclosure, containing other equipment IP32

enclosure used in general industry IP32, IP43

and IP54

enclosure used in locations that are cleaned with low-pressure waterjets (hosing) IP55

enclosure providing protection against fine dust IP65

enclosure containing slip-ring assemblies IP2X

Depending upon the conditions where installed, another degree of protection can be appropriate.

Enclosures shall be constructed using materials capable of withstanding the mechanical, electrical and thermal stresses as well as the effects of humidity and other environmental factors that are likely to be encountered in normal service.

Fasteners used to secure doors and covers should be of the captive type. Windows provided for viewing internally mounted indicating devices shall be of a material suitable to withstand mechanical stress and chemical attack (for example toughened glass or polycarbonate sheet of not less than 3 mm thickness).

It is recommended that enclosure doors be not wider than 0,9 m and have vertical hinges, with an angle of opening of at least 95°.