Heat - Control of the temperature in work place

Physical hazards - heat

It means the rise in ambient temperature on the extent that human beings can not bear that subjects it to the many risks of death may be its final phase, and measured the amount of heat is called calorimetry unit price or a quantity of heat required to raise the temperature of kilograms of material one degree Celsius

And heat in the work environment is one of the forms of energy and can produce heat in the work environment from natural sources such as sunlight or artificial, such as furnaces and others. Where heat is exchanged between these sources and objects in ways that work into the known heat exchange (radiation - Seek - pregnancy).

Heat exchangeThe human body is an important source of production and exchange heat with the surrounding environment where the heat exchange between man and the surrounding environment through 

four ways, namely

 exchange symbolized her pregnancy-C: a method of heat transfer by air where the hot air moves up and down the cold air

C = 8.3 V 0-5 (Ts - Ta)

As:

Skin temperature Ts m

 Air temperature Ta m

V air speed m / s

 exchanges have to seek symbolized k: is the heat transfer through direct contact between the surfaces of molecules and hot surfaces and L particles less heat and continue this exchange to get the balance

 exchange by radiation have symbolized R: It is a source of heat transfer to the surrounding medium generated by energy

R = hr (Ts - Tr)

 As:

Skin temperature Ts m

Tr the temperature of the surrounding surfaces M

hr radiant heat exchange coefficient (see Table (

 exchanges have symbolized evaporation E: is the heat by sweating

E = he (Ps - Pa)

As:

 Water vapor pressure Ps of the skin

 Pa water vapor pressure of the air

 he coefficient of evaporation

To calculate the amount of heat which the body stores them S (+ warm in the work environment, - the work environment in the cold) we must calculate the following:

 -Cresp: the exchange rate of convection heat through breathing

 - Eresp: rate of heat exchange by evaporation through the respiratory

:And the amount of heat is calculated by the following relationship

S = (M + W) + R + C + K + (Cresp + Eresp) + E

But in the industry and the small heat exchange rates of respiration dependent relationship the following:

S = (M + W) + R + C + K + E

:Principles of control of the temperature

:Control - on metabolism

Automation of work - post work between individuals - increased rest periods -

:Control of the radiation heat transfer

Isolate the source of heat - wear protective clothing from the heat (cover body)

Control - the convection heat transfer:

If the temperature is above 36: decrease the temperature - increase the speed of the air - reducing the clothes

Control - the transfer of heat by evaporation:

Increased sweating increased air speed - reduce the moisture

But is enough to identify sources of heat exchange and ways to find out the amount of heat that human exposure does not, of course, there are other factors affecting the heat balance

 Factors affecting the heat balance:

The thermal equilibrium state and reflect the character of neutrality towards feeling heat or cold, several factors affect the achievement of thermal equilibrium, namely:

: levels of heat

And reflects the levels of heat by:

 air temperature is called the degree of dry heat§

 the degree of radiant heat§

 Temperature wetlands and explain the percentage of moisture the air§

 metabolism and work Harirat

The human nature produces heat and this heat production increase as a result of professional activities practiced by the worker and the process is called Balastqlab a result of exchange calories. Which is determined in a realistic way by taking the following considerations:

- Determine the value of the primary metabolism of the human person. Which calculates the reference person:

By 90 kcal k / h

- Determine the effectiveness of professional Harirat ins (Harirat work). Which are calculated in several ways depend heavily on identifying metabolism caused by both: modes of work - stress effectively and work style

Effective stress pattern of work Example calories expended

Rest 90

Light work of hand and arm - convicted of writing - a car 100-200

Work average work hand and arm

The work of the arm and leg

Drive a truck body work

Weeding

Clean the floor 200 to 300

Heavy work of digging the work of the body - hand harvesting - a quick walk from 300 to 400

The work of a very heavy body works the same activities faster than the previous 300 to 400

:  Air movement

It is a natural air speed or the industrial or the result of convection currents

: to adapt

Could be more ordinary people coping with temperature fluctuations as a result programs are adapted according to the nature of each work

: Dress

Constitute an additional barrier of appropriate clothing to insulate the skin from the center hot or cold

: Personal factors

Personal factors affecting the effective thermal balance, such as: color of skin - sweating - Gender - Age - the health status and psychological

: time of exposure

When the exposure time can be small to achieve thermal equilibrium, but this balance varies with the length of time

:Environmental factors

Factors that we have measured to study the effect of thermal environment on the human body

 air temperature- 

 Humidity-

 air movement-

 radiant heat-

The following table shows the role played by these factors in heat exchange 

processes

Air temperature of pregnancy - evaporation

Air movement Pregnancy - evaporation

Radiant heat - seek the radiation -

Relative humidity evaporation ---

Thresholds for temperature:

Thresholds for temperature radiation wetlands:

Period of work and rest temperature affecting C - the type of effort

Effort, light effort, average effort, hard

Work in progress 30.0 26.7 25.0

75% -25% relief work 30.6 28.0 25.9

50% work - 50% 31.4 29.4 27.9 comfort

25% work - 75% 32.2 31.1 30.0 comfort

:Thresholds for extended periods of exposure to low temperatures

C maximum temperature period was allowed in the day

From to

18-1 - There is no maximum period as long as the worker properly and wearing protective clothing and appropriate sufficient

35 to 19 - total time of exposure does not exceed (4) hours alternately

            (Hours of work there would be an hour break)

57 to 36 - Total hours of daily work does not exceed one hour to two half-hour interval of four hours of rest

74 to 58 - total time of exposure per day with only five minutes to dress and special protective

The effects of heat on man!

 physiological and psychological effects-

 Lack of effectiveness - irritability - anger

 the effects of illness-

Heat shock

: The high relative humidity or high temperature leads to a sudden failure of thermoregulation in the body which causes a lack of heat exchange by evaporation (sweating) and is forced to occur in the circulatory system.

Heat stress

When you work in an environment with high temperatures for long periods occur a state of collapse due to the increase of the body expands blood vessels and the lack of effective circulation and a lack of blood pressure and lack of effectiveness of the heart and the lack of blood given to the college and increase the proportion of salts in the blood

Thermal contraction-

When you work in an atmosphere of high temperature and relative humidity low, perspiration increases, leading to the loss of the body to large amounts of salts, especially NacL and this is what causes involuntary spasms in the muscles

Work where workers are exposed to the harmful effects of heat are

 Work in the open under the influence of the sun's heat§

 work underground mines and tunnels§

 work next to the ovens, stoves, such as iron and steel industry and foundries in metal smelting operations and in the distillation§

 In the petroleum industry, fertilizer

 work next to the boilers and furnaces, in front of bakeries§

Damage suffered by the workers when exposed to high temperatures

 is forced to psychological and neurological and sense of malaise is reflected in the form of increased errors in the work and increase the likelihood of injury and lack of ability to concentrate at work§

 feeling of tiredness and fatigue§

 contractions of the voluntary muscles in the legs and abdominal wall§

 thermal stress and the cause of the aneurysm and skin rush of blood to and increase the number of heart beat, dizziness, headache, vomiting and fainting§

 heat stroke arise from exposure to high degrees with high humidity, which disrupts the body get rid of the temperature and feel the injured headaches and severe dizziness and then begin the body temperature to rise is followed by convulsions nerve and loss of consciousness and if not ministering patient treatment, death occurs§

 infections of the skin, eyes and occurs as a result of chronic exposure to high temperature§

:Methods of prevention of heat

 protect workers from exposure to high temperatures with the dimensions of the need of employees with heart disease and kidney from working in places with high temperature

isolate the source of heat or the production process from which a heat from the rest of the production processes and personnel in order to minimize the effect of temperature on the rest of the workers and the workplace.

 absorption of heat or reversed out of the workplace through the establishment of protective barriers for this purpose taking into account that these barriers do not block vision.

 good ventilation of the workplace in order to improve the atmosphere and reduce the temperature

 increased intake of salt to compensate for the salts that the body loses race

 the work of a system for the exchange of personnel who are exposed to heat in the workplace for example, are set in front of furnaces and then transported to work in workshops and working group workshops in front of furnaces and thus underestimate the rate of exposure to heat

 Use personal protective equipment for workers for the prevention of high-temperature

 the work of primary medical examination and periodic on workers exposed to high temperature

He was taken to a cool place and the work of first aid to him in the case of heat stroke

Measuring devices used:

 measure air speed-

 hygrometer: Albesekoumtr-

 dry thermometer: a thermometer ordinary liquid (mercury or alcohol)-

 radiation thermometer: a thermometer has a black ball-

 wet thermometer: a thermometer to him and put the pot in which distilled water and filter-

But now there is a digital device contains all of these thermometers measure the relative humidity and calculates the index directly moist heat radiation