5.5 Engineering calculations on artificial lighting/ noise protection/ ventilation etc.)

Calculation of artificial lighting

Purposes: For calculation of parameters of artificial lighting. To define intensity of sources of a sound to intensity levels and to find the general noise level for all sources. All coefficients are taken from a leaf of data

We consider, a task - lighting, it provides standard levels of illumination indoors and working platforms out of buildings. The ultimate goal consists in defining type of lamps and quantity of lamps. As the minimum purpose of discrimination during the work with the pixel personal computer - one point of light, and his size makes 0.28mm, he has to deal with visual work of very high precision, the level II of visual work. And depending on the used software can be considered as directly, and at the return contrast and compare nature of object and character of a background can be any: easy, average, dark. It is also necessary to note that duration of visual work makes more than a half of the working day. On the basis of these data, we come to a conclusion that visual work has the II level with a subclass "in the region". The general lighting the 500th luxury and 2000 luxury of lighting in a combination, including the 200th luxury of lighting.

As operation of the personal computer doesn't belong to category very well, to choose system of the general lighting.

Bulb Type LTB40; lamp power Pl = 40 W

Luminous flux Fl = 2200 lm

Lamps from tubular luminescent lamps are placed parallel to a wall with windows. Lamps are located ranks, joining with each other.

Plans location of fixtures and their vertical orientation:

hn hp - defined; hn = 3 m hp = 0.8 m

The distance from the floor to the fixture

hc = 0,2 (hn-hp) = 0.44 m; (5.1)

The distance from the working surface to the lamp

hcp = hn - hp - hc = 1.46 (5.2)

l = 1,5 (for fluorescent lighting fixtures);

lc= l×hcp (5.3)

lc = 1.5 * 1.46 = 2,19 m - the distance between the centers of the lamps.

The calculation of the required number of lamps finds by the formula

Nсв=Sn/lc2, where Sn - The illuminating the room;

Nсв = 6 * 3/4, 79 = 3,76 ≈ 4 (5.4)

Used the method of utilization of luminous flux:

i= a×b/( hp(a+b)), (5.5)

i - Index of premises; a, b, hp - length, width, height of the room, if m i <0.5 or i> 5, the corresponding but-or i = 0.5 i = 5.

Our i = 6 * 3 / (0.8 * (6 +3)) = 2.5.

The coefficient of uneven lighting for fluorescent lamps z = 1.1. The safety factor for media containing less than 1mg/m3 dust and smoke, provided cleaning fixtures at least 4 times a year kz = 1.8

The reflection coefficient of the ceiling P = 0.5

Wall reflectance Pc = 0.3

The coefficient of luminous flux at a given index premises and reflection coefficients of the walls and ceiling ŋ = 0.48

Number of lamps:

N = (E * Sn * z *kz)/(Fl * Nсв * ŋ) (5.6)

N = (500 * 18 * 1.1 * 1.5) / (2200 * 4 * 0.48) = 14850/4224 = 3.52

Calculation of noise workplace laboratories

In "Institute of Space Equipment and Technologies" laboratory 10 personal computers and one server the Average level of noise makes 40 dB of one personal computer, 60 dB of the server. To define the actual intensity of sources of a sound to levels of intensity and to find the general noise level for all sources [29].

The actual intensity of sound determined by the formula

L = 10*lg(J/J0) (5.7)

where J - the actual value of the power of sound, W/m2

J0 - the threshold values of sound power, W m-2 (J0 = 10-12 W/m2)

lg - logarithm of the decimal.

L = 10 * lg (J/ J0) = 10 * (lgJ - lg J0) = 10 * lgJ - 10 * lg J0

10 * lgJ = L + 10 * lg J0

lgJ = L/10 + lg J0

PC lgJ = 40/10 + lg10-12 = 4 - 12 = -8 W/m2

For the server lgJ = 60/10 + lg10-12 = 6 - 12 = -6 W/m2

the actual sound intensity for each PC -8 W m-2, the actual intensity of the sound server - 6 W/m2

The total noise from several sources with the same level of sound intensity or sound pressure L1 (dB) can be determined from

L = L1 + 10lgn (5.8)

where n - the number of noise sources;

L1 - a source of noise, dB

L = 40 + 10lg10 = 40 + 10 = 50 dB

The noise level from all of the computers is 50 dB.

To determine the total noise level using a formula

L = Lb + ∆ (5.9)

Where Lb - the larger of the folding noise sources dB.

Δ – “additive" at addition levels from two sources dB

L1 - L2 = 60 - 50 = 10dB (5.10)

If the noise is 10dB difference, Δ = 0,45

L = Lb + Δ = 60 + 0.45 = 60.45 dB

The total noise level in the laboratory “Institute for Space Applications and Technologies” is 60.45 dB. This is the optimal level of noise exceeds the laboratory.

5.6 Conclusion of Safety

Biological factors play a large role in the called rooms because a large number of people can lead to an infection and spread of viruses.

The harmful and dangerous factors connected with use of the computer it can be minimized at the correct organization of a workplace which include the correct arrangement of the employee and use of system of grounding.

Other possible problem with health in operating time at office is musculoskeletal frustration and weakening of eyes sight.

Many recommendations can be found in sanitary and epidemiologic the rules developed by official establishments of the Republic of Kazakhstan. The computer on a workplace has to be are properly organized, and it also demands that users for performance of simple actions, to, in time and after work. These actions help to avoid dangerous situations, violations of health, and also the equipment of breakage.

Numbers with a high density of technological details create a constant risk of fire. In this regard, the people working with computers have to be ideally prepared what to do in case of fire detection and how to eliminate potential economic losses. Rooms have to be equipped also with special fire-prevention devices and systems for fast fire and a smoke to respond to the requests.

Other big problem on a workplace is lighting. There are standard and recommendatory descriptions about light, and from calculation has been established that the office conforms to requirements in artificial lighting. Industrial noise can be the cause of psycho physiological frustration and shouldn't exceed norms.

At institute of space equipment and technologies of office operating conditions at which or completely to eliminate influence of dangerous and harmful factors are created, or are in the acceptable range.