1          Additional aspects regarding the selection of risk reduction measures for electrical lighting

1.1      Introduction

Reducing the occupational risks associated with integral electric lighting equipment of machines at the machine design stage is mainly associated with the use of appropriate luminaires for local lighting and their appropriate position within the machine. Therefore, the designer must take into account the following electric lighting parameters:

–           operational illuminance;

–           uniformity of illumination;

–           occurrence of direct glare;

–           occurrence of reflective glare;

–           flickering and pulsating light;

–           stroboscopic effect;

–          colour rendering index.

The size of these parameters are generally presented in PN-EN 1837+A1: 2009 E Safety of machinery. Integral lighting of machines. Further detailed values of these parameters, varying depending on the type of machine and the visual work performed, are provided in PN-EN 12464-1:2012 Light and lighting. Lighting of workplaces. Część 1: Indoor workplaces.

The provisions of PN-EN 1837+A1: 2009 E pertain to an integral lighting system of a machine consisting of light sources, luminaires (luminaire) linked with mechanical and electrical control devices, which are integral with the machine, designed to provide lighting on or inside the machine.

1.2      General lighting requirements

Ergonomics and lighting techniques need to be taken into account when designing machinery lighting. Visual tasks which are to be performed on/inside a machine vary when it comes to their sizes, contrast, position, speed of movement, etc. In order to provide optimum lighting conditions, detailed analysis of a given visual task needs to be conducted in the first place. For special tasks follow the guidance provided in PN-EN 12464-1:2012. Lighting requirements of PN-EN 1837+A1: 2009 E are based on the average level of a visual task difficulty.

1.2.1    Illuminance

The required illuminance depends on the type of a visual task and should be sufficiently high and uniform in order to allow safe and comfortable perception of visual task details. In general, average illuminance should be maintained at the level of at least 500 lx, with the minimum uniformity of UO = Emin/Eav = 0.7 within the work area. In the immediate surrounding area of a visual task, average illuminance should be at least 300 lx, with a uniformity of UO = 0.3.

When the use of a guard or a protective screen is required on the machine, lighting intensity needs to be multiplied by the reciprocal value of light transmittance factor for additional guards. If the light transmittance factor of the guards in place is not known, illuminance shall be increased at least by 50%.

1.2.2    Glare

Integral lighting system shall not cause direct glare, both for the operator of a machine and for other employees working in adjacent work places. Reflective glare must be minimised as much as possible.

Glare limitation is possible due to the relevant arrangement and orientation of luminaires, the application of correct shielding mounted at luminaires, and illuminated surfaces being given a matt finish. Excessive luminance of lighting can be reduced by covering it with semi-transparent (e.g. opal or mat lampshade) or opaque (e.g. louver) materials. In the design practice it involves the choice of appropriate luminaries and positioning them in a way that prevents the occurrence of discomfort glare. The occurrence of interfering or, especially, blinding glare is unacceptable. It is assumed that reduction of discomfort glare reduces the possibility of occurrence of interfering glare. Fig. 1 shows examples of a local lighting luminaire, using components capable of restricting the luminance of the light source. This can be a louver with a small mesh size or a metal cover used for halogen lamps.

a) louver                                                         b) metal light source cover

Fig. 1. Examples of a local lighting luminaire with components capable of restricting the luminance of the light source

1.2.3    Orientation of lighting

The lighting system shall be designed and orientated in such a way that there is no area of shadow likely to cause nuisance within the visual task area. The orientation of lighting shall ensure correct perception of a form for a given visual task.

1.2.4    Quality of lighting colour

The colour rendering and the colour of the light emitted by the luminaire should make it possible to distinguish correctly the colour of the visual task and provide visual comfort during work. In practice, for local lighting luminaires light source with a colour rendering index (Ra) greater than 80 should be used.

1.2.5    Stroboscopic effect

The lighting system shall be designed in such a way that stroboscopic effects which may lead to dangerous situations due to alternating the perception of movement, rotation or reciprocating motion, or a piston movement of machinery are eliminated. This can be achieved, for instance, by the use of incandescent light sources – halogen lamps, LED lamps, direct current for the supply of luminaires, or powering gas-discharge lamps (fluorescent light) using high-frequency current (use of electronic ballast systems).

It is equally important to prevent flickering and pulsation of the luminous flux emitted by discharge lamps.

1.3      Lighting equipment

1.3.1    Light sources

Use only light sources which ensure operational safety and are not hazardous to the machine operator. It is recommended that light sources be shielded in order to protect operators against injury, e.g. in the case of a lamp bursting, excessive heat, or emission of UV radiation. Standard glass can act as a shield and a UV radiation filter. As far as halogen light bulbs are concerned, they shall be marked with the following notice: UV STOP or Low Pressure, which means that their manufacturer has ensured the limitation of UV radiation.

1.3.2    Local lighting luminaires

These luminaires shall be designed so as to:

a)    ensure sufficient illumination for the visual task;

b)    minimise the accumulation of dust and dirt on light sources and optical surfaces;

c)    limit premature ageing of optical elements;

d)    ensure comfortable operation;

e)    be compatible with the machine, e.g. resistant to vibration, radiation, appropriately IP rated, etc.

1.3.3    Mounting method of local lighting luminaires

These luminaires shall be mounted so as to:

a)    ensure the required level of illumination for the visual task;

b)    avoid colliding with the visual task or posing a hazard to the operator;

c)    minimise the accumulation of dirt on light sources and luminaires;

d)    ensure easy/comfortable operation.

Fig. 2 shows examples of proper lighting of a milling machine and a turning lathe.

a)                                     b)

Fig. 2. Proper lighting of a milling machine (a) and a turning lathe (b)

Fig. 3 shows examples of a local lighting luminaire with long flexible arms (a) and a two-piece luminaire with three joints (b)

a)                                                         b)

Fig. 3. Examples of luminaires with long arms

Examples of luminaires intended for additional lighting of turning lathes are shown in Fig. 4 and 5. Fluorescent lamps with outputs from 11 to 36 W are used with the IP 67 rating. The characteristic feature of this family of luminaires is the special design louver covering the entire light source, which virtually eliminates the glare, even when looking directly at the luminaire. The use of such luminaires in an automatic turning lathe is shown in Fig. 6.

Fig. 4. The view of a luminaire louver designed for additional lighting of turning lathes

Fig. 5. A family of a luminaires designed for additional lighting of turning lathes

Fig. 6. Lighting of a closed automatic lathe with a fluorescent lamp in a shaded luminaire; easy to clean housing protects the light source against dirt and damage; the visible louver reduces personnel exposure to glare

A separate group of luminaires designed for various types of machines are LED light source luminaires. They use single LEDs – as point sources for additional illumination of a small area (Fig. 7, 8 and 9), or multiple (a dozen or so) LEDs to illuminate larger surfaces (Fig. 10).

Fig. 7 shows a LED luminaire with the power of 11 W or 18 W and the angle of the beam of 70° or 100°, and Fig. 8 – a LED luminaire with the power of 3 W and the angle of the beam of 6° or 25°.

Fig. 7. Example of a LED luminaire for additional lighting of machines with a LED module with the power of 11 W or 18 W

Fig. 8. Example of a LED luminaire for spot lighting of machines with a single LED
with the power of 3 W

The luminaire in Fig. 9 shows a sample application of the luminaire with three LEDs with the power of 3 W and the angle of the beam of 10° or 40°.

Fig. 9. Example of a LED luminaire for additional lighting of machines
with a long arm and three LEDs with the power of 3 W.

Fig. 10 shows various types of LED luminaires designed for mounting within various types of machines. These luminaires may have a power of several dozens of watts and they are equipped with light beam dispersing optics. Owing to a large area of lighting surface they can illuminate significant parts inside the machine. The luminaires are IP 67 rated.

Fig. 10. Examples of LED luminaires for additional lighting of large areas within machines.

1.4      Ensuring availability of lighting

Where risks may increase as a result of failure of the integral lighting system of the machine, the lighting system shall comprise more than one light source. One of the light sources shall be provided with a separate power supply.

1.4.1    Electric power supply

The lighting system shall be connected to a power supply source so that it can function even when the machine is powered off.

1.5      Verification procedures (assessment of local lighting)

The manufacturer of a machine with integral lighting should:

a)    measure the illuminance and check its uniformity in the visual task area and the immediate surrounding area. The illuminance should be measured with the use of an illuminance meter with a cell correction featuring spectral luminous efficiency V (ƛ) and the cosine curve;

b)    check subjectively the glare reduction, the correct orientation of the luminaire onto the visual task area, the correct colour rendition and elimination of the stroboscopic effect;

c)    provide a report on the assessment of the lighting system;

d)    provide the inspection and maintenance schedule.

1.6      Information on the use

The operation of the lighting system should be checked regularly, at least once a year, and depending on the results appropriate action should be taken. The lighting system should be cleaned and maintained in accordance with the machine maintenance schedule.