THE DETERMINATION AND APPRECIATION OF PROFESSIONAL MICROCLIMATE AT A WORKPLACE

Transcription

1 THE DETERMINATION AND APPRECIATION OF PROFESSIONAL MICROCLIMATE AT A WORKPLACE Oana CHIVU,, Claudiu BABIS, Andrei DIMITRESCU, Dan Florin NIŢOI Univ. Politehnica of Bucharest, virlan_oana@yahoo.co.uk ABSTRACT:The microclimate at work is a very important element that puts a mark on worker health. The paper presents the methodology for determining and appreciating the professional microclimate through its components: air temperature; Relative air humidity; Airflow velocity; Caloric radiation; The working surface temperature at work. The aim of the paper is to educate in order to obtain an appropriate microclimate to avoid overworking of the visual analyzer, stimulate higher nerve activity processes, increase working capacity, prevent occupational diseases, work accidents and chronic fatigue. Keywords: microclimate, temperature, humidity, air currents Introduction By microclimate we understand all the physical factors of the air from a bounded space (workplace), which exerts its action on the thermoregulation function. The microclimate components [1], [2], [3] are normalized in relation to heat release in the human body due to physical effort. The constituent factors of the professional microclimate are the following: air temperature (measured in degrees Celsius C); Relative humidity (expressed in percentage); Air velocity (measured in m / s); Calorific radiation (measured in horsepower / cm2 / min); And the working surface temperature (measured in C). The temperature [4] is determined with the following devices: globtermometers, Assman psychometers, digital psychometers and thermographs. With globtermometer, the temperature is expressed in degrees Celsius. The Assmann Psychrometer is an apparatus that consists of two identical mercury thermometers. The two metal tubes join in a central tube at the upper end of which a vacuum cleaner is installed. One of the thermometer tanks is covered with a cotton sleeve that moistens with a pipette. Thus, Assmann's psychrometer has a dry bulb thermometer and another with a wet reservoir. The Assmann psychrometer can also be used in the absence of globtermometer. The dry tank thermometer indicates the air temperature. Reading is done after 5-6 minutes, determining first the wet thermometer, then the whole degree. The dry bulb thermometer is also read. The wet tank thermometer, due to the heat lost by evaporating the water on the cloth covering the wet bulb, depending on the air saturation deficit for that temperature, indicates a lower temperature than the dry tank thermometer. The apparatus shall be kept suspended during the suspension, vertically, on a rod holder at the place where it is to be determined. The digital psychrometer now replaces Assmann's psychrometer and determines dry temperature and relative humidity directly. With the help of thermographs, continuous temperature recording can be made for 24 hours or more. The temperature of working surfaces or varied surfaces is measured with adaptive thermometer (flat bulb). 206

2 To measure the humidity in the working atmospherethere are used: Assman psychometers, hydrographers to record humidity continuously for 24 hours or more and digital psychometers. Air velocity is determined using anemometers and catatometer meters as devices. Anemometer with blades or cups is used for speeds above 0.1 m / sec. The airflow speed in m / s or m / min is read directly on the dial. Anemometers can also be digital. The Hill Catameter is an alcohol thermometer made up of two tanks, one larger at the bottom and one smaller at the top, joined by a capillary tube. The capillary tube has two divisions: 350C and 380C. Cooling heat loss from 380 C to 350 C is always the same and specific to each appliance, which is the catafactor, denoted F (eg F = 493). Note the time at which the alcohol column drops from 380C to 350C in seconds ("t"). The calculation formula is used to determine the velocity of the air currents. "Air cooling power" and "air heating power" are measured as the temperature is below 350 C or above 380 C, with the time required for the alcohol in the capillary tube (alcoholic meniscus) of the cataterometer to drop from 380 C to 350 C, Respectively, to rise from 350C to 380C. At each point studied three measurements are made and their arithmetic mean is used. Caloric radiations are determined with the globtermometer. It consists of a mercury thermometer whose tank is centered inside a metal sphere, with a matt black surface. The wall thickness of the sphere is mm, the diameter of the sphere varies between 10 cm and 15 cm, and the metals used are copper and aluminum. Description of the appliance For the assessment of microclimate, you can use the Casella Anemometer M12900X, which measures both the airflow speed and the temperature, humidity or pressure according to the exact model. This appliance is ideal for on-site measurements of air exhausts due to the small size of the anemoscope (30 mm). It can also be used for more general wind and wind current measurements as specified. The M12900X anemometer is shown in Figure

3 Fig.1 Anemometer of the range M12900X for Casella The anemometer shown in Figure 2.1 consists of the following elements: 1-button HOLD and RECALL; 2-button ESC (Escape) and REC (Record); 3-button MAX, MIN and AVG (Average = Average); 4-button automatic closing and arrow "up"; 5-button ENTER and change unit; 6-button Power and arrow "down"; 7-button SET and background light; 8- display (display) and background light; 9-pin sensor connector to the device; 10-cell compartment; 11-cell battery cover; 12-probe connector; 13-handle probe; 14-sensor sensor (temperature / humidity); 15-propeller; 16-pressure internal sensor (M only). The characteristics of the poster are shown in Figure 2. Fig. 2 Characteristics of the poster 208

4 The component parts of the poster are: 1 main display; 2-sided display; 3-zone display symbol in operation; 4-battery indicator discharged; 5-symbol auto lock indicator; 6 main units displayed; 7 secondary units displayed. The general device specifications are shown in Table 1 Table 1 General device specifications Display (display) 42 mm (W)*33 mm (L) monochrome LCD with backlight Maximum operating current Battery Type Lifetime battery Dimensions Weight 25 ma 1 piece type - PP3 (6F22 zinc carbon) Aprox. 100 ore Apparatus: 130 (L)*56 (W)*38 (H) mm Sonde: 195 (L)*47 (W)*30 (H) mm Cable length about 1 meter Apparatus: aprox. 160 g Sonde: aprox. 100 g Accessory User Manual, Carrying Case, 9V battery, probe Operating conditions Temperature: 5 C ~ 40 C Humidity: 0% ~ 80% RH Temperature: -10 C ~ 60 C Terms of use storage Humidity: 0% ~ 70% RH The speed variation range is shown in Table 2. Table 2 Range of speed variation Humidity Field Rezolution Accuracy m/s 0,4 ~ 25 0,1 ±2% + 0,2 Km/hr (kph) 1,5 ~ 90 0,1 ±2% + 0,8 Mph 0,9 ~ 55 0,1 ±2% + 0,4 Knots (kts) 0,8 ~ 48 0,1 ±2% + 0,4 Ft/min (fpm) 79 ~ ±2% + 40 Beaufort 1 ~ The range of flow variation is shown in Table

5 Table 3 Flow variation Humidity Field Rezolution Accuracy CMM 0 ~ CFM 0 ~ The range of temperature variation is shown in Table 4. Table 4 Variation temperatury Humidity Field Rezolutio Accuracy C -20 ~ 60 0,1 ±1 C F -4 ~ 140 0,1 ±1,8 F The range of humidity variation is shown in Table 5 Tabele 5 Variation umiditatii Humidity Field Rezolutio Accuracy %RH 20 ~ 80 0,1 ±3,5%RH %RH <20,>80 0,1 ±5%RH Limitele de variatie ale presiunii sunt prezentate in tabelul 6. The pressure variation limits are shown in Table 6. Tabelul 6 Variatia presiunii absolute Humidity Field Rezolutio Accuracy hpa 35 ~ ,1 ±2hPa mmhg 263 ~ 825 0,1 ±1,5mmHg inhg 10,3 ~ 32 0,1 ±0,1 Experimental determinations Experimental determinations should consist of two phases: determination of determination sites and determination of determination times. The setting of the microclimate determination points should include the following: places with the maximum degree of harm (eg in front of the oven, near steam boilers, etc.); Jobs where most workers are grouped; At the opening of the room (right of doors, windows); With regard to the establishment of vertical microclimate points, it should include the following: at 0.5 m, 1.0 m and 1.5 m in order to appreciate any differences in heating (cooling) between different parts of the workspace; - to establish the comfort microclimate (operating temperature) will be done 210

6 determinations and at a height of 0.1 m and 1.1 m respectively, which corresponds to the ankle and cervical region of a worker working in the seated position. The determination of determination times should be based on determinations made during the day of work (start, middle, end): in the peak periods of the technological process; in hot and cold weather; During and without the operation of the ventilation system Interpretation of results Appreciation of cold microclimate is done by using minimum thermal limits. For determining the normative values of temperature, the metabolic class (physical strain or heat release intensity) and the velocity of air currents are used as variables as shown in Table 7.. Table 7 Minimum thermal limits admitted to workplaces. Globtermometer temperature Class of metabolism ( C) (W) Speed of air currents (m/sec.) M ,2 117 < M ,3 234 < M ,4 M ,5 The maximum thermal limits are used to appreciate warm microclimate. In order to establish the maximum allowed temperature values from hot microclimate workplaces, the metabolic class (physical strain or heat release) is used; The existence of air currents (air mobility); The worker's acclimated or unconditioned quality and the location of the workplace with or without exposure to the sun. The WBGT (wet, bulb, globe, temperature) index used to estimate the maximum thermal limit is measured or calculated with relation 1 for indoor and outdoor activities without solar exposure and with relation 2 for outdoor activities with sun exposure. WBGT = 0,7tun + 0,3tg 1 WBGT = 0,7tun + 0,2tg + 0,1ta 2 Where ta is your dry air temperature, in C, tg is the globothermometer temperature, in C, and the cannon is the natural wet temperature, C. The calculated value of the WBGT index, according to the above formula, compares with the value in Table 8. This should not be exceeded, otherwise the risk of illness would be affected. 211

7 Table 8 Maximum allowed thermal limits at work Class of metabolism Index WBGT( C) (W) A person acclimated to heat Unaccounted person to heat Rest (0) Reduced metabolism (1) Medium metabolism (2) Intensive metabolism (3) Very metabolic Intense (4) No move Perceptible a air 25 With movement Perceptible a Air 26 No move Perceptible a Air 22 With movement Perceptible a Air Regarding comfort microclimate, the following conditions must be ensured in workplaces (offices, control rooms, video-rooms, social rooms, etc.) where the professional activity requires thermal comfort. For the summer season: Operating temperature between C; Vertical difference of air temperature values at 1.1 m and 0.1 m above ground (head and ankle) less than 3 C; Relative air humidity between 30-70%; Average air flow rate between m / s. For winter: Operating temperature between C; Vertical difference of air temperature values at 1.1 m and 0.1 m above ground (head and ankle) less than 3 C; Relative air humidity between 30-70%; Average air flow rate between m / s; Differences less than 10 C between the radiation temperature of the windows or other vertical surfaces and the radiation temperature of the objects in the room. The operative temperature (T0) is calculated with a 3: T0= A *Ta + (1 - A)* Tr 3 where: Ta is the dry air temperature, C; Tr is the average radiation temperature, C, and A is a coefficient whose values are: 0.5 if the air current is <0.2 m / s; 0.6 if the velocity of the air flows is between m / s and 0.7 if the velocity of the air flows is between m / s. 212

8 Concluzion The quality of work is closely related to the characteristics of professional microclimate. Therefore, a number of prophylactic measures are required, depending on the type of microclimate. Prophylactic measures in the case of professional exposure of workers to warm microclimate (temperature at work constantly above 30 C) are: At workplaces where the air temperature exceeds constantly 300C, salt water (1g NaCl / l), 2-4 l / person / exchange, distributed at 16-18oC, will be provided; Appropriate working arrangements (hot microclimate staff will have breaks to restore the thermoregulation capability, the duration and frequency of which are set according to the intensity of the effort and the values of the microclimate components; Wide-cut clothing made of absorbent fabrics (cotton, cotton) to allow air exchange by replacing the warm air around the human body and to absorb the sweat; Comfort rooms with microclimate comfort. Prophylactic measures for workers exposed to cold microclimate (constant temperature below 5 C): At low temperatures (below 5oC), hot tea will be provided in the amount of liter / person / change; Adequate working arrangements so that part-time work capacity can be recovered during breaks; Thick clothing; Comfort rooms with microclimate comfort. References: [1] Benjamin Morille, Marjorie Musy, Comparison of the Impact of Three Climate Adaptation Strategies on Summer Thermal Comfort Cases Study in Lyon, France, Procedia Environmental Sciences, Volume 38, 2017, pages ; [2]Xiaoshan Yang, Lihua Zhao, Michael Bruse, Qinglin Meng, Evaluation of a microclimate model for predicting the thermal behavior of different ground surfaces, Building and Environment, volume 60, 2013, pages ; [3] Marjorie Musy, Laurent Malys, Christian Inard, Assessment of Direct and Indirect Impacts of Vegetation on Building Comfort: A Comparative Study of Lawns, Green Walls and Green Roof, Procedia Environmental Sciences, volume 38, pages , [4] Tae Cheol Lee, Takashi Asawa, Hidenori Kawai, Yukari Hirayama, Isamu Ohta, Multipoint measurement method for air temperature in outdoor spaces and application to microclimate and passive cooling studies for a house, Building and Environment, volume 114, 2017, pages ; 213