Characteristics of the background and contrast of the object of distinction with the background by sub-categories of visual work (for categories IV)

Practical work No. 3

Calculation of lighting Purpose of work: Calculate the total fluorescent lighting of the workshop using the method of luminous flux utilization factor, based on the standards for the category of visual work and labor safety, according to the following initial data:

  1. shop height H=3 meters,
  2. lighting network voltage=220W,
  3. luminaires use LB-20-4 fluorescent lamps with a luminous flux Fl = 1180 lm and power Wl = 40 W
  4. Length – A, (m)
  5. Width – B, (m)
Initial data Options
A, (m)
B, (m)
Rank and sub rank IIc IIIb IV IIa IIIa IVa IIg IIId IVg IIc

A simplified technique was adopted to solve the problem.

Characteristics of visual work The smallest size of the object of distinction, mm Discharge and sub-discharge of visual work Illumination, LC, under general artificial lighting
highest precision less than 0.15 I BUT
B
AT
G
Very high precision from 0.15 to 0.3 II BUT
B
AT
G
high precision over 0.3 to 0.5 III BUT
B, C
G
Medium precision over 0.5 to 1 IV BUT
B, C
G
Low precision over 1 to 5 V BUT
B, C
G
rough over 5 VI
Working with luminous materials and products in hot shops over 0.5 VII
General supervision of the production process VIII permanent
periodic about 40

Characteristics of the background and contrast of the object of distinction with the background by sub-categories of visual work (for categories IV)

Sub-categories of visual work The contrast of the object of distinction with the background background characteristic
a small dark
b small average
average dark
in small light
average average
large dark
G average light
large light
large average

Using the initial data and an extract from SNiP 2305-95, calculate the required number of fixtures N; the total power of the workshop lighting system W (for selecting the supply cable); draw up a sketch of the plan of the workshop, where to show the location of the fixtures.

Give written answers to the following questions:

  1. What is the stroboscopic effect?
  2. What is the category and sub-class of your visual work when distinguishing the smallest objects? Indicate the characteristics of the background and contrast of the object of difference with the background. According to these data, select according to the extract from the table. 1 SNiP 23.05-95 required illumination (LK) with general artificial lighting of your workplace.

The calculation of the total required luminous flux F (lm) is carried out according to the formula

where En – normalized illumination, Lux, is selected according to the category and order of visual work in Table. 1 SNiP 2305-95

S – area of the room, m 2

Z u003d 1.15 – coefficient of uneven illumination

K 3 – safety factor (dust content) according to the level of indoor air pollution is selected from Table 3 of SNiP 23.05-95.

Take for discharge lamps K 3 = 1.5

η – use of the luminous flux, determined by the formula

where i is the index (indicator) of the room, taking into account its configuration

where h is the estimated height of the lamp suspension above the working surface

h u003d H – h rp – h s

where h rp = 0.8 m, the height of the working surface above the floor

h c u003d 0.5 m, distance of the light center of the lamp from the ceiling (overhang)

where n is the required number of lamps, the resulting value is rounded up to the nearest higher even integer.

In fixtures where fluorescent lamps are combined in two, the stroboscopic effect is eliminated.

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