Practical work 3. Design of industrial lighting. The method of calculation

Practical work 3

Design of industrial lighting

 

The calculation of the system of general uniform lighting is made by the method coefficient of use luminous flux that allows providing the illumination of the surface in view all the falling on it fluxes both the direct and reflected. It is used for the calculation of general uniform lighting of horizontal working surfaces.

 

The method of calculation

 

Considering the characteristics of visual work (the minimal size of object of distinction, the characteristic of the background and contrast of object of distinction with the background according to table 3.1) is determined the category of visual work and also normed light level in the workplace.

Then is determined the number of lamps and its distribution of floor space. Uniform illumination of the horizontal working surface is achieved in case the certain attitude of the distances between the centers of lamps L to the height of its suspension above the work surface H_p  and is determined by formula:

                        L=1,75∙H                                                     (3.1)

The number of lamps is determined by the formula:

,                                             (3.2)

where S – the area of the room, m²; M – the distance between the parallel rows on condition that M≥ 0,6 H_p (the optimal values M =2...3 m.)

For achievement of uniform horizontal illumination is recommended to place the lights with LL by continuous ranks, parallel to the walls and windows or the long sides of the room.

 Luminous flux from one incandescent lamp or group of lamps luminaire when fluorescent lamps is determined by the formula:

,                              (3.3)

where Е_N – normed minimally admissible lighting, lx (table 3.1); К_з – the safety factor that incorporate dusting the lamps and the decrease the light output in the process of operation is depending on the type of technological process, is performed indoors and recommended standards SNiP 23-05-95 [13] (table 3.2); S_f – the area of the lighted room, m²; Z – the coefficient of irregularity lighting that depend on the type of lamps (for incandescent lamps and arc mercury lamps – 1,15, for fluorescent lamps – 1,1); η – the utilization rate of luminous flux of lamps, that takes into account the portion total luminous flux that  is attributable to the calculated plane and depends on the type of lamp, reflection coefficient of ceiling ρ_c, walls ρ_w, and floor  ρ_f, the height of suspension of lamps, the size of the room, is determined by the index i of the room, table 3.3; N_c – the number of lamps in the room; γ – the shading coefficient which is introduced in the calculation only in the presence of large equipment that shadows the workspace.

Table 3.1

Lighting standards (extraction from SNiP 23-05-95) [13]

 

Feature of visual work

The smallest size of the observed object , mm

Rank of visual work

Subclass of visual work

The contrast of object of distinction with the background

Background
characteristic

Artificial lighting

Illuminance, lx

In the combined lighting

In the total lighting

Average precision

Over 0,5 to 1

IV

а

Low

Dark

b

<<

Average

Average Dark

в (c)

Low Average High

Light Average Dark

г (d)

Average High

Light Average

–

Minor

precision

Over 1
to 5

V

а

Low

Dark

b

<<

Average

Average

Dark

–

в (c)

Low Average High

Light Average Dark

–

г (d)

Average High

Light Average

–

 

Rough
(very low precision)

More 5

VI

 

Regardless of the characteristics of the background and contrast of the object with the background

–

The end of the table 3.1.

General monitoring of the production process:

–

VIII

 

Regardless of the characteristics of the background and contrast of the object with the background

 

 

the permanent stay of people in the room

а

 

–

 

 

 

b

<<

 

–

periodic at periodic stay

 

 

в (c)

<<

 

–

general supervision of engineering services

г (d)

<<

 

–

 

Table 3.2