EUROPEAN MACHINE DIRECTIVE 89/392

The European Machine Directive 89/392 and its later amendments (91/368, 93/44 and 93/68) came into force in all member states on 1st January 1995.

These directives aim to harmonise the technical norms in machine safety and allow their free circulation within the European Market, respecting both the health and safety of personnel and eliminating administration obstacles to trade due to differing regulations between individual EU states, by replacing them with one set of norms for every member. Under the directives, manufacturers must design and build machines according to the essential safety standards outlined in the Appendix I and ensure that, once finished, the machine carries the CE marking. If the manufacturer believes it necessary, a third party can be called upon to issue a certificate. The manufacturer is responsible for the design and building of the machine and is obliged, without notice, to prove his product corresponds to the safety standards.

Among these essential machine safety standards which the manufacturer must adhere to is "the installation of signalling devices on machines". It is point 1.7 on the Appendix I.

Point 1.7.0 explains in more detail "when a person's health or safety is put at risk by an un-staffed defective machine, this machine must be equipped to transmit an appropriate audible or visual signal".

Point 1.7.1 explains "these signal and alarm devices must be immediately recognised and understood". It continues: "measures must be taken to allow regular maintenance to ensure their constant efficiency". Finally "the colour and safety signals must comply with the directives".

The machine directive establishes the general principles and provides some guidelines on the technical characteristics and the effectiveness of the audible and visual signal devices to be installed on the machine. How the equipment should be designed and what technical characteristic it should have to be "appropriate" and "easily recognised and understood" is defined by the specific technical norms covering acoustic and luminous signalling.

EUROPEAN NORMS EN 457, prEN 842, prEN 981 and IEC 73

The European Norms EN 457, prEN 842, prEN 981 and IEC 73 control the standards of the audible and visual danger signalling and give guidelines on how to interpret them. The type and installation of the signalling device, its suitability and effectiveness must all comply with the norms, regardless of their use.

EUROPEAN NORM EN 457 (safety of machinery: audible danger signalling)

EN 457 specifies the technical, design and functional characteristics the audible danger signalling (which is different from warning and emergency signalling) must have and provides guidelines for the design of signalling which is immediately recognisable and which complies to the Machine Directive.

The audible signal must be designed in such a way that anybody who hears it recognises it and can, therefore, react immediately.

Danger signals have priority over all signals in being recognised except over emergency signals, which have absolute priority.

The characteristics, which make a danger signal effective, are its sound (Audibility), its ability to be recognised immediately (Discriminability) and that there is absolutely no doubt as to what it refers to (Unequivocability).

Audibility

The audible signal is clearly heard when its sound pressure level in dB is at least 15dB greater than that of the noise in the area surrounding the signal, which is no less than 65dB.

The audible signal must be heard clearly, but without causing panic or fear. When the noise around the signal is greater than 110dB, additional signals must be used, including light signals.

Discriminability

The audible signal must be based on frequencies between 300 and 3000 Hz.

The stronger the central frequency where the signal differs from the surrounding noise, the easier it is to recognise the danger signal.

The signal must be sufficiently intense (less than 1500 Hz) to be received and understood by people hard of hearing or those wearing protective ear-pieces.

The distribution and duration of the sound's intensity

Audible signals with pulsating or intermittent sounds are generally more effective than monotone or continuous ones. The intermittent tone must repeat itself regularly between 2 Hz and 5 Hz and must not coincide with the noise in the area where the signals are received.

The distribution and duration of the sound's frequency

Audible signals with varying frequency sound and are more easily recognised than those with fixed frequencies and less likely to be confused with other signals.

Unequivocability

Audible danger signals and signals used for other reasons and with other meanings should never be similar and consequently never confused or misinterpreted.

Signalling manufacturers should be able to supply the following data about their own products after thorough research in an echo-free chamber.

• Maximum value of the level of audible intensity considered (dB A), is calculated by measuring the sound from its source for one metre along the area where the sound is greatest.
• Maximum value of the level per octave band.
• Sound spectrum with the representation of levels per band of a third of an octave included among the base frequencies and of at least 6000 Hz.

EUROPEAN NORM prEN 842 (safety of machinery: visual danger signals)

prEN 842 specifies the technical, design and functional characteristics the visual danger signals (different from warning and emergency signals) must have and provides guidelines for the design of signals which are immediately recognisable and which comply to the Machine Directive.

The visual signal must be designed in such a way that anybody who sees it recognises it and so is able to react immediately.

Danger signals have priority over all visual signals, except emergency signals, which have absolute priority.

To be completely effective, a visual danger signal must be: clearly visible even in strong light (Visibility), distinguishable from other lights and light signals (Distinguishability) and understood immediately (Unequivocability).

Visibility

When the source of the light signal is not small enough to be considered a light point, its visibility is defined by measuring the relationship between the light emitted from the surface of the signal itself and the area lit by the signal.

Visual warning signals must be at least five times brighter than the area where they are used. Visual emergency signals must be at least ten times brighter than the area where they are used.

When the visual signal is small enough to be considered a luminous point, visibility is the amount of light emitted from the signal which reaches the eye, compared to the lighting in the area.

A flashing light signal is generally more effective than a continuous light signal. The flashing must occur between 40 and 180 times per minute with regular intervals between the light coming on and going off.

A signalling device which is both visual and audible is usually more effective. It is not necessary to synchronise the light with the sound, but it can improve the signal's effectiveness even more.

The visual signals must be installed where any danger is possible, so people working in or using that area, or those about to enter it, will immediately be aware of the impending danger. If necessary, extra visual signalling could be installed just outside the danger zone.

The visual signals must be installed in positions which reach all the area designated to them and their message must be clearly understood - whether it regards a machine, a group of machines, a production line or a complete department.

Distinguishability

Once a visual signal has been seen, it must be understood immediately.

Visual signals can differ according to the colour of the light, its position and the position of two or more lights.

Colour: The visual danger sign must be either Amber or Red. Warning signals have Amber or Red lights depending on the degree of urgency they represent.

Visual emergency signals are Red. If it is necessary to distinguish between a Red emergency signal and a Red warning signal, the emergency signal light must be twice as intense, flashing and, ideally, accompanied by an audible signal.

Position: The visual danger signal must be positioned so that people can easily see it and understand the nature of the danger and so be able to take necessary measures.

Position with more than one light: If two or more luminous signals are used, the red light should always be over the yellow and if two red lights are used, they should be next to each other.

Reflection: The recognition and perception of a visual danger signal should not be confused by reflections from other sources of light within the signal area (sunlight, for example).

Distance: The distance between the signal and where it reaches the eye must be minimal in order to reduce the amount of light the visual signal has to produce to be effective.

Where visibility is reduced due to fog, rain, snow, smoke, dust or steam, the effectiveness of the visual signal is clearly reduced, too. A light signal here is frequently less useful and must be replaced by an audible signal.

Duration: Once a dangerous situation has been recognised and necessary measures taken, the visual signal should be turned off.

Unequivocability

Visual danger signals and signals used for other reasons and with other meanings should never be similar, and consequently not confused or misinterpreted.

The IEC 73 Norm establishes the meanings to give to the different colours of luminous indicators and pushbuttons. The deegee® range of visual products includes Rotating Flashing, Xenon Strobe, Pulsed Filament/LED and Static Filament/LED and conforms to every aspect of the technical and functional requirements of Norm EN 842. Products are available to meet the norm's requirements for the degree of brightness, frequency of flashing and colour.

There are varying degrees in effectiveness between the four different families of visual signals: Pulsed Filament/LED beacons are normally more effective than Static Filament/LED (non-flashing) Beacons, Rotating Flashing Beacons are more effective than Pulsed Beacons and Xenon Strobe Beacons are even more effective than Rotating Beacons.

Non-Rotating Beacons have standard visual diffusers. Models with Fresnel lenses, able to increase the intensity of the light compared to ordinary diffusers, are also available.

Rotating Flashing Beacons create piercing beams of light by either a revolving mirror or an array of sequenced LEDs. They are more effective than Pulsed Beacons, and are particularly effective where dust and smoke are experienced.

Xenon Strobe Beacons are more effective signals compared to Rotating Beacons due to their high intensity flashes of light. The short-duration high-intensity flash demands attention and is noticeable, even in peripheral vision.

Full specification details of all deegee® Beacon Lamps are contained in the ‘Beacon Lamps and Hazard Warning Products’ catalogue which is available on request, or on our website http://www.deegee.com

The colours available in the deegee® Beacon Lamp range are the same as those required by the Norm IEC 73, Red, Amber (dark Yellow or Orange), Green, Blue and Clear (Neutral – No Colour).

The material used in the manufacture of all visual diffusers in the deegee® Beacon Lamp range is in line with the requirements of the norms. Only high-quality UV-stable polycarbonate is employed, which does not fade or noticeably discolour during the working life or routine use for which they are designed.

Where as luminous signalling is concerned, installation of products from the deegee® Beacon Lamp range onto machines conforms in every detail with the safety standards required by the European Machine Directive.

EUROPEAN NORM prEN 981 (safety of machinery: danger or absence of danger signals, both audible and visual)

prEN 981 controls the varying types of audible and visual signals to use on board a machine so that they can be clearly recognised and understood, as required by the directive.

The Norm defines messages used for different degrees of urgency: from an extremely serious situation to one of normality and safety and generally requires a quick but correct recognition of both audible and visual signals in any possible environmental condition.

Credibility and respect for a signal is essential for anybody it might concern or effect. The lack or absence of these greatly reduces a signal's effectiveness.

Because of the physical aspects affecting the diminishing intensity of both sound and light over a distance, audible and visual intensity are not aspects which are regulated by this norm. The technical, design and functional characteristics of audible and visual signals are found in Norms EN 457 and prEN 842.

The norm defines the meanings, which must be conventionally given to different audible and visual signals installed on machines, according to varying sounds and colours.

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23/06/09