Thermal irradiation intensity is a device for measuring. Which thermal radiation meter with verification is better to buy? Total loss ratio
To measure the integral intensity of thermal radiation, devices sensitive to the infrared and visible regions of the spectrum are used - thermoelectric actinometer, radiometer, bolometer, etc.
Operating principle of a thermoelectric actinometer (FIG4) based on the different absorptivity of blackened and shiny silver foil strips. Due to the difference in temperature between the blackened and unblackened areas of the silver foil, an electric current arises in the thermopile located underneath them. The current strength is directly proportional to the intensity of thermal radiation, the values of which are read from the scale of the device. Measuring range E 0-14000 W/m, measurement error ±175 W/m.
Fig.4 Instruments for measuring heated surfaces
To measure the temperature of heated surfaces of equipment, contact thermometers and resistance thermal converters (thermocouples) or remote ones (pyrometers, etc.) are used.
EXPERIMENTAL
Work procedure and report preparation
1. Connect the stand to the alternating current network, and the source of thermal radiation to the socket of the control panel.
2. Turn on the source of thermal radiation (upper part) and the heat flow meter IPP-2m.
3. Install the head of the heat flow meter in the tripod so that it is offset relative to the stand by 100 mm. Manually move the tripod along the ruler, placing the meter head at different distances from the source of thermal radiation, and determine the intensity of thermal radiation at these points (determined as the average value of at least 5 measurements). Enter the measurement data into the table. Construct a graph of the dependence of the average value of thermal radiation intensity on distance.
4. By installing various protective screens, determine the intensity of thermal radiation at given distances. Assess the effectiveness of the protective action of screens using formula (2). Construct a graph of the dependence of the average value of thermal radiation intensity on distance.
5. Install a protective screen (as directed by the teacher). Place the wide brush of the vacuum cleaner over it. Turn on the vacuum cleaner in air extraction mode, simulating an exhaust ventilation device, and after 2-3 minutes (after establishing the thermal mode of the screen), determine the intensity of thermal radiation at the same distances as in point 3. Assess the effectiveness of the combined thermal protection using formula (2) . Construct a graph of the dependence of the intensity of thermal radiation on distance. Based on the measurement results, determine the effectiveness of “exhaust ventilation” (the amount of heat carried away by the vacuum cleaner). The same efficiency can be determined by measuring the temperature of the heat shield using the temperature sensor of the IPP-2m meter in the mode with and without “exhaust ventilation”.
6. Switch the vacuum cleaner to “blower” mode and turn it on. Directing the air flow to the surface of the protective screen ("shower" mode), repeat the measurements in accordance with point 5. Compare the measurement results pp. 5 and 6.
7. Attach the vacuum cleaner hose to one of the racks and turn on the vacuum cleaner in “blower” mode, directing the air flow almost perpendicular to the heat flow (slightly towards) - imitation of an “air curtain”. Using the IPP-2m temperature sensor, measure the air temperature at the location of the heat screens without an air curtain and with a curtain.
Lab report
A) Table
B) Graphs of the dependence of the intensity of thermal radiation on distance
C) Calculation of the effectiveness of the protective action of screens
D) Calculation of the efficiency of exhaust ventilation
D) Conclusions
1. What is radiant heat exchange between bodies?
2. How is the intensity of thermal radiation determined?
3. What determines the amount of radiant heat absorbed by the human body?
4. What is the most in an efficient way heat transfer?
5. List the main measures to protect workers from possible overheating.
6. What is shielding of radiating surfaces? What types of screens are there?
7. How is the effectiveness of thermal radiation protection using screens determined?
8. What is ventilation?
9. What is air exchange and air exchange rate?
10.What instruments are used to measure the intensity of thermal radiation?
Bibliography
1. Kukin P.P., Lapin V.L., Podgornykh E.A. etc. Safety of technological processes and production: Tutorial for universities - M.: Higher School, 2001, 318 p.
2. Belov S.V. Life safety. Textbook for universities - M.: Higher school, 2005, 600 p.
3. Rusak O.N., Malayan Ts.R., Zanko N.G. Life safety. -SPb-M.: Krasnodar, 2005, 445 p.
4. Rusak O.N. Safety and labor protection. Textbook - St. Petersburg: LTA, MANEB, 1999, 320 p.
5. SanPin 2.2.4.548-96. “General sanitary and hygienic requirements for thermal radiation from heated surfaces of technological equipment.”
Laboratory work No. 2
20.03.2014
Measuring the density of heat flows passing through building envelopes. GOST 25380-82
Heat flow is the amount of heat transferred through an isothermal surface per unit time. Heat flow is measured in watts or kcal/h (1 W = 0.86 kcal/h). The heat flux per unit of isothermal surface is called the heat flux density or heat load; usually denoted by q, measured in W/m2 or kcal/(m2 ×h). Heat flux density is a vector, any component of which is numerically equal to the amount of heat transferred per unit time through a unit area perpendicular to the direction of the component taken.
Measurements of the density of heat flows passing through enclosing structures are carried out in accordance with GOST 25380-82 “Buildings and structures. Method for measuring the density of heat flows passing through enclosing structures.”
This GOST establishes a method for measuring the density of heat flow passing through single-layer and multi-layer enclosing structures of buildings and structures - public, residential, agricultural and industrial.
Currently, during the construction, acceptance and operation of buildings, as well as in the housing and communal services industry, much attention is paid to the quality of construction and finishing of premises, thermal insulation of residential buildings, as well as saving energy resources.
An important evaluation parameter in this case is the heat consumption from insulating structures. Testing the quality of thermal protection of building envelopes can be carried out at different stages: during the commissioning of buildings, at completed construction sites, during construction, during overhaul structures, and during the operation of buildings to draw up energy passports of buildings, and based on complaints.
Heat flux density measurements should be carried out at ambient temperatures from -30 to +50°C and relative humidity no more than 85%.
Measuring the heat flux density makes it possible to estimate the heat flow through the enclosing structures and, thereby, determine the thermal technical qualities of the enclosing structures of buildings and structures.
This standard is not applicable to assessing the thermal properties of enclosing structures that transmit light (glass, plastic, etc.).
Let's consider what the method of measuring heat flux density is based on. A plate (the so-called “auxiliary wall”) is installed on the enclosing structure of the building (structure). The temperature difference formed on this “auxiliary wall” is proportional to its density in the direction of the heat flow. The temperature difference is converted into electromotive force of thermocouple banks, which are located on the “auxiliary wall” and are oriented parallel along the heat flow, and connected in series along the generated signal. Together, the “auxiliary wall” and the thermocouple bank constitute a transmitter for measuring heat flux density.
Based on the results of measuring the electromotive force of thermocouple batteries, the heat flux density is calculated on pre-calibrated converters.
The diagram for measuring heat flux density is shown in the drawing.
1 - enclosing structure; 2 - heat flow converter; 3 - emf meter;
t in, t n- temperature of internal and external air;
τ n, τ in, τ’ in- temperature of the outer and inner surfaces of the enclosing structure near and under the converter, respectively;
R 1, R 2 - thermal resistance of the enclosing structure and heat flow converter;
q 1 , q 2- heat flux density before and after fixing the converter
Sources of infrared radiation. Infrared protection in workplaces
The source of infrared radiation (IR) is any heated body, the temperature of which determines the intensity and spectrum of emitted electromagnetic energy. The wavelength with the maximum energy of thermal radiation is determined by the formula:
λ max = 2.9-103 / T [µm] (1)
where T is the absolute temperature of the radiating body, K.
Infrared radiation is divided into three areas:
- short-wave (X = 0.7 - 1.4 µm);
- medium wave (k = 1.4 - 3.0 µm):
- long-wave (k = 3.0 µm - 1.0 mm).
Electric waves in the infrared range have a mainly thermal effect on the human body. When assessing this impact, the following is taken into account:
· wavelength and intensity with maximum energy;
· emitted surface area;
· duration of exposure during the working day;
· duration of continuous exposure;
· intensity physical labor;
· intensity of air movement in the workplace;
· type of fabric from which the workwear is made;
· individual characteristics of the body.
The short-wave range includes rays with a wavelength λ ≤ 1.4 µm. They are characterized by the ability to penetrate into the tissues of the human body to a depth of several centimeters. This impact causes severe damage to various human organs and tissues with aggravating consequences. There is an increase in the temperature of muscle, lung and other tissues. In the circulatory and lymphatic systems specific biologically active substances are formed. The functioning of the central nervous system is disrupted.
The mid-wave range includes rays with a wavelength λ = 1.4 - 3.0 µm. They penetrate only into the superficial layers of the skin, and therefore their effect on the human body is limited to an increase in the temperature of the exposed areas of the skin and an increase in body temperature.
Long-wave range – rays with wavelength λ > 3 µm. Influencing the human body, they cause the strongest increase in the temperature of the affected areas of the skin, which disrupts the functioning of the respiratory and cardiovascular systems and disrupts the thermal balance of orgasm, leading to heat stroke.
According to GOST 12.1.005-88, the intensity of thermal irradiation of technological equipment and lighting devices working from heated surfaces should not exceed: 35 W/m 2 when irradiating more than 50% of the body surface; 70 W/m2 with irradiation from 25 to 50% of the body surface; 100 W/m2 with irradiation of no more than 25% of the body surface. From open sources (heated metal and glass, open flame), the intensity of thermal radiation should not exceed 140 W/m2 with irradiation of no more than 25% of the body surface and the mandatory use of personal protective equipment, including face and eye protection.
The standards also limit the temperature of heated surfaces of equipment in the working area, which should not exceed 45 °C.
The surface temperature of equipment, the inside of which is close to 100 °C, should not exceed 35 °C.
The main types of protection against infrared radiation include:
1. time protection;
2. protection by distance;
3. shielding, thermal insulation or cooling of hot surfaces;
4. increase in heat transfer from the human body;
5. personal protective equipment;
6. eliminating the source of heat generation.
There are three types of screens:
· opaque;
· transparent;
· translucent.
In opaque screens, when the energy of electromagnetic vibrations interacts with the substance of the screen, it is converted into thermal energy. As a result of this transformation, the screen heats up and it itself becomes a source of thermal radiation. Radiation from the screen surface opposite the source is conventionally considered as transmitted radiation from the source. It becomes possible to calculate the heat flux density passing through a unit area of the screen.
With transparent screens, things are different. Radiation falling on the surface of the screen is distributed inside it according to the laws of geometric optics. This explains its optical transparency.
Translucent screens have the properties of both transparent and opaque.
· heat reflective;
· heat-absorbing;
· heat dissipating.
In fact, all screens, to one degree or another, have the property of absorbing, reflecting or dispersing heat. Therefore, the definition of a screen for a particular group depends on which property is most strongly expressed.
Heat-reflecting screens are distinguished by a low degree of surface blackness. Therefore, they reflect most of the rays falling on them.
Heat-absorbing screens include screens in which the material from which they are made has a low thermal conductivity coefficient (high thermal resistance).
Transparent films or water curtains act as heat-removing screens. Screens located inside glass or metal protective contours can also be used.
E = (q – q 3) / q (3)
E = (t – t 3) / t (4)
q 3 - IR radiation flux density using protection, W/m 2 ;
t - temperature of IR radiation without protection, °C;
t 3 - temperature of IR radiation using protection, °C.
Instruments used
To measure the density of heat flows passing through building envelopes and to check the properties of heat-protective screens, our specialists have developed series devices.
Heat flux density measurement range: from 10 to 250, 500, 2000, 9999 W/m2
Scope of application:
· construction;
· energy facilities;
· scientific research etc.
Measurement of heat flux density, as an indicator of the thermal insulation properties of various materials, is carried out using devices of the series at:
· Thermal testing of enclosing structures;
· determination of heat losses in water heating networks;
carrying out laboratory work in universities (departments of “Life Safety”, “Industrial Ecology”, etc.).
The figure shows a prototype of the stand “Determination of air parameters in the working area and protection from thermal influences” BZZ 3 (manufactured by Intos+ LLC).
The stand contains a source of thermal radiation (household reflector). Screens made of different materials (metal, fabric, etc.) are placed in front of the source. The device is placed behind the screen inside the room model at various distances from the screen. An exhaust hood with a fan is fixed above the room model. The device, in addition to a probe for measuring heat flux density, is equipped with a probe for measuring the air temperature inside the model. In general, the stand is a visual model for evaluating efficiency various types thermal protection and local ventilation system.
Using the stand, the effectiveness of the protective properties of screens is determined depending on the materials from which they are made and on the distance from the screen to the source of thermal radiation.
Operating principle and design of the IPP-2 device
Structurally, the device is made in a plastic case. On the front panel of the device there are a four-digit LED indicator and control buttons; On the side surface there are connectors for connecting the device to a computer and a network adapter. On the top panel there is a connector for connecting the primary converter.
Appearance device
1 - LED battery status indication
2 - LED indication of threshold violation
3 - Measurement value indicator
4 - Connector for connecting a measurement probe
5 , 6 - Control buttons
7 - Connector for connecting to a computer
8 - Connector for connecting a network adapter
Operating principle
The operating principle of the device is based on measuring the temperature difference on the “auxiliary wall”. The magnitude of the temperature difference is proportional to the heat flux density. The temperature difference is measured using a strip thermocouple located inside the probe plate, which acts as an “auxiliary wall”.
Indication of measurements and operating modes of the device
The device polls the measuring probe, calculates the heat flux density and displays its value on the LED indicator. The probe polling interval is about one second.
Registering measurements
The data received from the measuring probe is recorded in the non-volatile memory of the unit with a certain period. Setting the period, reading and viewing data is carried out using software.
Communication interface
Using the digital interface, current temperature measurement values, accumulated measurement data can be read from the device, and device settings can be changed. The measuring unit can work with a computer or other controllers via the RS-232 digital interface. The exchange rate via the RS-232 interface is user adjustable from 1200 to 9600 bps.
Device features:
- the ability to set sound and light alarm thresholds;
- transfer of measured values to a computer via RS-232 interface.
The advantage of the device is the ability to alternately connect up to 8 different heat flow probes to the device. Each probe (sensor) has its own individual calibration coefficient (conversion factor Kq), which shows how much the voltage from the sensor changes relative to the heat flow. This coefficient is used by the device to construct the calibration characteristic of the probe, which is used to determine the current measured value of the heat flux.
Modifications of probes for measuring heat flux density:
Heat flow probes are designed to measure surface heat flow density in accordance with GOST 25380-92.
Appearance of heat flow probes
1. Pressure-type heat flow probe with spring PTP-ХХХП is available in the following modifications (depending on the range of heat flow density measurement):
PTP-2.0P: from 10 to 2000 W/m2;
PTP-9.9P: from 10 to 9999 W/m2.
2. Heat flow probe in the form of a “coin” on a flexible cable PTP-2.0.
Heat flux density measurement range: from 10 to 2000 W/m2.
Modifications of temperature probes:
Appearance of temperature probes
1. Submersible thermal converters TPP-A-D-L based on the Pt1000 thermistor (resistance thermal converters) and thermal converters TXA-A-D-L based on the XA thermocouple (electrical thermal converters) are designed for measuring the temperature of various liquid and gaseous media, as well as bulk materials.
Temperature measurement range:
For TPP-A-D-L: from -50 to +150 °C;
For TXA-A-D-L: from -40 to +450 °C.
Dimensions:
D (diameter): 4, 6 or 8 mm;
L (length): from 200 to 1000 mm.
2. Thermal transducer TXA-A-D1/D2-LP based on the XA thermocouple (electric thermal transducer) is designed to measure the temperature of a flat surface.
Dimensions:
D1 (diameter of “metal pin”): 3 mm;
D2 (base diameter – “patch”): 8 mm;
L (length of the “metal pin”): 150 mm.
3. Thermal transducer TXA-A-D-LC based on the XA thermocouple (electric thermal transducer) is designed for measuring the temperature of cylindrical surfaces.
Temperature measurement range: from -40 to +450 °C.
Dimensions:
D (diameter) – 4 mm;
L (length of the “metal pin”): 180 mm;
Tape width – 6 mm.
The delivery set of the device for measuring the density of the thermal load of the medium includes:
1. Heat flux density meter (measuring unit).
2. Probe for measuring heat flux density.*
3. Temperature measurement probe.*
4. Software**
5. Cable for connecting to a personal computer. **
6. Certificate of calibration.
7. Operating manual and passport for the device.
8. Certificate for thermoelectric converters (temperature probes).
9. Certificate for the heat flux density probe.
10. Network adapter.
* – Measuring ranges and probe design are determined at the ordering stage
** – Items are available upon special order.
Preparing the device for operation and taking measurements
1. Remove the device from the packaging container. If the device is brought into a warm room from a cold one, it is necessary to allow the device to warm up to room temperature for at least 2 hours.
2. Charge the batteries by connecting the AC adapter to the device. Charging time for a completely discharged battery is at least 4 hours. In order to increase the service life of the battery, it is recommended to completely discharge it once a month until the device automatically turns off, followed by a full charge.
3. Connect the measuring unit and the measuring probe with a connecting cable.
4. When the device is equipped with a disk with software, install it on your computer. Connect the device to a free COM port of the computer using appropriate connecting cables.
5. Turn on the device by briefly pressing the "Select" button.
6. When the device is turned on, the device performs a self-test for 5 seconds. If there are internal faults, the device displays the fault number on the indicator, accompanied by a sound signal. After successful testing and completion of loading, the indicator displays the current value of the heat flux density. Explanation of testing faults and other errors in the operation of the device is given in the section 6 of this operating manual.
7. After use, turn off the device by briefly pressing the "Select" button.
8. If you plan to store the device for a long time (more than 3 months), you should remove the batteries from the battery compartment.
Below is a diagram of switching in the “Operation” mode.
Preparation and carrying out measurements during thermal testing of enclosing structures.
1. Measurement of heat flow density is carried out, as a rule, from the inside of the enclosing structures of buildings and structures.
It is allowed to measure the density of heat flows from the outside of enclosing structures if it is impossible to carry them out from the inside (aggressive environment, fluctuations in air parameters), provided that a stable temperature on the surface is maintained. Heat transfer conditions are monitored using a temperature probe and means for measuring heat flux density: when measured for 10 minutes. their readings must be within the measurement error of the instruments.
2. Surface areas are selected that are specific or characteristic of the entire enclosing structure being tested, depending on the need to measure local or average heat flux density.
The areas selected for measurements on the enclosing structure must have a surface layer of the same material, the same treatment and surface condition, have the same conditions for radiant heat transfer and should not be in close proximity to elements that can change the direction and value of heat flows.
3. The areas of the surface of the enclosing structures on which the heat flow converter is installed are cleaned until visible and tactile roughness is eliminated.
4. The transducer is pressed tightly over its entire surface to the enclosing structure and fixed in this position, ensuring constant contact of the heat flow transducer with the surface of the areas under study during all subsequent measurements.
When attaching the converter between it and the enclosing structure, the formation of air gaps is not allowed. To eliminate them, a thin layer of technical petroleum jelly is applied to the surface area at the measurement sites, covering surface irregularities.
The transducer can be fixed along its side surface using a solution of building plaster, technical petroleum jelly, plasticine, a rod with a spring and other means that prevent distortion of the heat flow in the measurement area.
5. For operational measurements of heat flux density, the loose surface of the transducer is glued with a layer of material or painted over with paint with the same or similar degree of blackness with a difference of Δε ≤ 0.1 as that of the material of the surface layer of the enclosing structure.
6. The reading device is located at a distance of 5-8 m from the measurement site or in an adjacent room to eliminate the influence of the observer on the heat flow value.
7. When using devices for measuring emf that have restrictions on ambient temperature, they are placed in a room with an air temperature acceptable for the operation of these devices, and the heat flow converter is connected to them using extension wires.
8. The equipment according to claim 7 is prepared for operation in accordance with the operating instructions for the corresponding device, including taking into account the required holding time of the device to establish a new temperature regime in it.
Preparation and carrying out measurements
(during laboratory work using the example laboratory work“Research on means of protection against infrared radiation”)
Connect the IR radiation source to a power outlet. Turn on the IR radiation source (upper part) and the IPP-2 heat flux density meter.
Place the head of the heat flux density meter at a distance of 100 mm from the IR radiation source and determine the heat flux density (the average value of three to four measurements).
Manually move the tripod along the ruler, placing the measuring head at the distances from the radiation source indicated in the form of Table 1, and repeat the measurements. Enter the measurement data into the form Table 1.
Construct a graph of the dependence of IR radiation flux density on distance.
Repeat measurements according to paragraphs. 1 - 3 with various protective screens (heat-reflecting aluminum, heat-absorbing fabric, metal with a blackened surface, mixed - chain mail). Enter the measurement data in the form of Table 1. Construct graphs of the dependence of the IR radiation flux density on the distance for each screen.
Table form 1
Assess the effectiveness of the protective action of screens using formula (3).
Install a protective screen (as directed by the teacher) and place a wide vacuum cleaner brush on it. Turn on the vacuum cleaner in air extraction mode, simulating an exhaust ventilation device, and after 2-3 minutes (after establishing the thermal mode of the screen), determine the intensity of thermal radiation at the same distances as in point 3. Assess the effectiveness of the combined thermal protection using the formula (3 ).
Plot the dependence of the intensity of thermal radiation on the distance for a given screen in exhaust ventilation mode on a general graph (see paragraph 5).
Determine the effectiveness of protection by measuring the temperature for a given screen with and without exhaust ventilation using formula (4).
Construct graphs of the effectiveness of exhaust ventilation protection and without it.
Set the vacuum cleaner to blower mode and turn it on. Directing the air flow to the surface of the specified protective screen (shower mode), repeat the measurements in accordance with paragraphs. 7 - 10. Compare the measurement results pp. 7-10.
Attach the vacuum cleaner hose to one of the stands and turn on the vacuum cleaner in “blower” mode, directing the air flow almost perpendicular to the heat flow (slightly towards) - imitation of an air curtain. Using a meter, measure the temperature of IR radiation without and with a “blower”.
Construct graphs of the protection efficiency of the “blower” using formula (4).
Measurement results and their interpretation
(using the example of laboratory work on the topic “Research of means of protection against infrared radiation” in one of the technical universities in Moscow).
- Table.
- Electric fireplace EXP-1.0/220.
- Rack for placing replaceable screens.
- Stand for mounting the measuring head.
- Heat flux density meter.
- Ruler.
- Vacuum cleaner Typhoon-1200.
The intensity (flux density) of IR radiation q is determined by the formula:
q = 0.78 x S x (T 4 x 10 -8 - 110) / r 2 [W/m 2 ]
where S is the area of the radiating surface, m2;
T is the temperature of the radiating surface, K;
r - distance from the radiation source, m.
One of the most common types of protection against IR radiation is shielding of emitting surfaces.
There are three types of screens:
·opaque;
·transparent;
· translucent.
Based on their operating principle, screens are divided into:
·heat-reflective;
·heat-absorbing;
·heat dissipating.
The effectiveness of protection against thermal radiation using E screens is determined by the formulas:
E = (q – q 3) / q
where q is the flux density of IR radiation without protection, W/m2;
q3 - IR radiation flux density using protection, W/m 2.
Types of protective screens (opaque):
1. Mixed screen - chain mail.
E chainmail = (1550 – 560) / 1550 = 0.63
2. Metal screen with a blackened surface.
E al+coating = (1550 – 210) / 1550 = 0.86
3. Heat-reflecting aluminum screen.
E al = (1550 – 10) / 1550 = 0.99
Let's plot the dependence of the IR radiation flux density on the distance for each screen.
As we can see, the effectiveness of the protective action of screens varies:
1. The minimum protective effect of a mixed screen - chain mail - 0.63;
2. Aluminum screen with blackened surface – 0.86;
3. The heat-reflecting aluminum screen has the greatest protective effect - 0.99.
Normative references
When assessing the thermal technical qualities of building envelopes and structures and establishing real heat consumption through external building envelopes, the following main regulatory documents are used:
· GOST 25380-82. Method for measuring the density of heat flows passing through building envelopes.
· When assessing the thermal properties of various means of protection against infrared radiation, the following main regulatory documents are used:
· GOST 12.1.005-88. SSBT. Work area air. General sanitary and hygienic requirements.
· GOST 12.4.123-83. SSBT. Means of protection against infrared radiation. Classification. General technical requirements.
· GOST 12.4.123-83 “System of occupational safety standards. Means collective defense from infrared radiation. General technical requirements".
TESTS.
Test 3. Microclimate.
Indoor microclimate- this is the state of the internal environment of a building, which has both positive and negative effects on humans, characterized by indicators of temperature, mobility and humidity
1. The average daily temperature for 2 days turned out to be +12 degrees. What time of year is this?
1) warm, 2) cold, 3) cannot be determined.
Answer:
According to GOST 30494-96 Cold season– a period of the year characterized by an average daily outside air temperature equal to 8ºC and below. Warm period of the year– a period of the year characterized by the average daily outside air temperature above 8º C.
In accordance with established sanitary rules and regulations (SNiP 23-01-99). The microclimate of industrial premises depends quite strongly on the assessment of the nature of clothing, since it helps to achieve thermal insulation and acclimatize the body at different times of the year. A warm season can be called a temperature regime of +10 and above, and a cold season - below +10.
2. Heat loss due to convection is proportional to:
Answer:
Convection(from lat. convectiō- “transfer”) is a type of heat exchange in which internal energy is transferred by jets and flows.
In cases where liquids or gases are involved in heat exchange, phenomena usually occur convection: Simultaneously with the flow of heat, flows of matter arise - the more heated layers float upward, and the less heated ones sink. Such mixing greatly accelerates the heat transfer process. In the case when a solid body is in a flow of liquid or gas flowing around it, heat transfer is also convective in nature and occurs much faster than in a medium at rest. Therefore, even a small wind (draft) leads to an increase in heat loss from the surface of the body.
The release of heat by organisms depends on the thermal conditions of the environment, which are determined by temperature, humidity, air speed and radiant energy.
Proportional two mutually dependent quantities are called if the ratio of their values remains unchanged.
If two quantities are related to each other in such a way that an increase (decrease) in one proportionally (by the same amount) increases (decreases) the other quantity, then such quantities directly proportional.
3. Heat loss due to convection is inversely proportional to:
1) air humidity, 2) body temperature, 3) air temperature.
Answer:
If two quantities are related to each other in such a way that an increase (decrease) in one proportionally (by the same amount) decreases (increases) the other quantity, then such quantities inversely proportional.
4. Heat loss due to convection does not depend on:
1) air humidity, 2) body temperature, 3) air temperature.
Answer:
5. Heat loss due to evaporation is proportional to:
1) air humidity, 2) body temperature, 3) air density.
Answer:
Evaporation- the process of phase transition of a substance from a liquid state to a vapor or gaseous state, occurring on the surface of the substance. The process of evaporation is the reverse of the process of condensation
6. Heat loss due to evaporation does not depend on:
1) air humidity, 2) body surface area, 3) air temperature.
Answer:
7. When normalizing microclimate parameters, the following are taken into account:
1) time of year; 2) body temperature; 3) surface area.
Answer:
Microclimate parameters in accordance with GOST 12.1.005-88 And SanPiN 2.2.4. 548-96 must ensure the preservation of the thermal balance of a person with the surrounding production environment and the maintenance of an optimal or acceptable thermal state of the body.
The parameters characterizing the microclimate in production premises are:
Air temperature, t˚C
Temperature of surfaces (walls, ceiling, floor, equipment enclosures, etc.), t p ˚C
Relative air humidity, W%
Air velocity, V m/s
Thermal irradiation intensity, P W/m 2
8. What air flow speed is allowed when performing work associated with nervous and emotional stress:
1) up to 1m/s; 2) up to 0.5 m/s; 3) up to 0.3 m/s; 4) up to 0.1 m/s.
Answer:
Nervous-emotional tension may be caused by responsibility for the work being performed, high requirements for the quality of welded joints, complexity or unusualness of the work, especially under time pressure.
according to GOST 30494-96– change in air speed – no more 0.07 m/s for optimal performance and 0.1 m/s– for acceptable;
9. What temperature (in degrees Celsius) is allowed when performing work associated with nervous and emotional stress:
1) 18-20; 2) 20-22; 3) 22-24 ; 4) 24-26.
Answer:
Optimal and permissible temperatures, relative humidity and air velocity in the working area of production premises must correspond to the values given in the relevant documents. In cabins, on consoles and control stations for technological processes, in computer rooms, as well as in other rooms when performing operator-type work related with nervous-emotional stress, optimal air temperatures must be observed (22-24°C), its relative humidity (40–60%,) and speed (no more than 0.1 m/s).
10. What air humidity (in%) is allowed when performing work associated with nervous and emotional stress:
1) 30-40; 2) 40-60; 3) 45-55; 4) 50-60.
Answer:
11. What kind of work is associated with neuro-emotional stress:
1) in the office; 2) at the table; 3) in the cockpit.
Answer:
Nervous-emotional tension- connected with the presence emergency situations, tension of attention and auditory analyzer in noise conditions.
12. What is the intensity of thermal radiation from heated parts of equipment at 15% of irradiated heat (W/m2):
1) 30; 2) 40; 3) 50; 4) 60.
Answer:
The intensity of thermal irradiation of the human body- thermal energy of the source per unit surface of the human body, W/m2.
Thermal radiation from heated surfaces plays an important role in creating unfavorable microclimatic conditions in production premises.
The greatest danger of radiant heat is from molten or heated metal. Heat transfer can occur by convection, conduction and radiation. Heat transfer is carried out: during convection - by a moving medium (flows of air, steam or liquid); with thermal conductivity - heat transfer in solids; during radiation - intense infrared rays, which do not directly heat the air, but when absorbed by solid bodies, the radiant energy turns into thermal energy. Heated solids become sources of heat and heat the air in the room by convection.
Permissible values of the intensity of thermal irradiation of the body surface of workers from industrial sources
Irradiated body surface, % Thermal irradiation intensity, W/m2, no more
50 and more 35
no more than 25,100
13. What is the intensity of thermal radiation from heated parts of equipment at 40% of irradiated heat (W/m2):
1) 50; 2) 70; 3) 90; 4) 100.
Answer:
The intensity of thermal irradiation of workers from heated surfaces of technological equipment, lighting devices, insolation at permanent and non-permanent workplaces should not exceed 35 W/m2 at 50% irradiation human surface and more, 70 W/m2 – with irradiation 25.50% surfaces and 100 W/m2 – with irradiation no more than 25% body surface.
14. What is the intensity of thermal radiation from heated parts of equipment at 60% of irradiated heat (W/m2):
1) 80; 2) 90; 3) 100; 4) 110.
Answer:
15. What is the intensity of thermal radiation from open sources (W/m2):
1) 120; 2) 130; 3) 140; 4) 150.
Answer:
The intensity of thermal irradiation of workers from open sources (heated metal, glass, open flame, etc.) should not exceed 140 W/m2, in this case, no more than one person should be exposed to radiation 25% body surfaces and the use of personal protective equipment is mandatory.
16. Which source does the incandescent lamp belong to:
1) open; 2) closed; 3) to none.
Answer:
Incandescent lamp- an artificial light source in which light is emitted filament body, heated electric shock to high temperature. A coil of refractory metal (most often tungsten) or a carbon filament is most often used as a filament body. To prevent oxidation of the filament upon contact with air, it is placed in an evacuated flask or a flask filled with inert gases or halogen vapors.
Open or closed type. In the first case, the lamp and socket are not separated from the external environment, in the second case they are limited by the shell. An additional special seal makes it possible to use the lamps in rooms with wet conditions.
17. What is the most optimal temperature in degrees Celsius of heated surfaces with which the worker must come into contact:
1) 30; 2) 35; 3) 40; 4) 45.
Answer:
Thermal protective equipment must ensure irradiation at workplaces of no more than 350 W/m2 and equipment surface temperature of no higher than 308 K (35 °C) at a temperature inside the source up to 373 K (100 °C) and not higher than 318 K (45 °C) at temperatures inside the source above 373 K (100 °C).
18. What is the maximum permissible temperature in degrees Celsius of heated surfaces with which the worker must come into contact:
1) 35; 2) 40; 3) 45; 4) 50.
Answer:
In all cases, the temperature of heated surfaces of technological equipment or its enclosing devices in order to prevent typical injuries should not exceed 45°C.
19. How far should you remove it? workplace from structures whose temperature is 4 degrees higher than permissible:
1) 1m; 2) 2m; 3) 3m; 4) 4m.
Answer:
When the temperature of the internal surfaces of enclosing structures is lower or higher than the optimal air temperature, workplaces must be removed from them at a distance of at least 1 m.
20. Which of the protective equipment does not apply to individual:
1) glasses; 2) costumes; 3) screens; 4) overalls.
Answer:
Personal protective equipment(PPE) - means used by an employee to prevent or reduce exposure to harmful and dangerous production factors, as well as to protect against pollution. They are used in cases where work safety cannot be ensured by the design of equipment, organization of production processes, architectural and planning solutions and collective protective equipment
Article 212 of the Labor Code of the Russian Federation establishes a number of conditions aimed at ensuring safe conditions labor. One of them is the acquisition and issuance by the employer of certified special clothing, shoes and other personal protective equipment. When providing workers with personal protective equipment (hereinafter referred to as PPE), means for flushing and neutralization, the employer complies with the standards labor legislation and protects workers from exposure to harmful and hazardous factors production.
4.1. PRODUCTION MICROCLIMATE PARAMETERS
Meteorological conditions in hygienic terms represent a complex of physical environmental factors that affect the heat exchange of the body and its thermal state.
The meteorological conditions of the internal environment of industrial premises (microclimate) are determined by combinations of temperature, humidity, air speed and surface temperature. The formation of the production microclimate is significantly influenced by the technological process and the climate of the area.
The microclimate parameters are assessed by a doctor in accordance with the sanitary rules and regulations “Hygienic requirements for the microclimate of industrial premises” (SanPiN 2.2.4.548-96). This document outlines the optimal and acceptable parameters of the microclimate of industrial workplaces, taking into account the severity of the work, periods of the year, as well as methods for measuring them.
In order to monitor compliance with standards when conducting instrumental studies, it is necessary to measure the temperature of the air and surfaces of enclosing structures and technological equipment, relative humidity and air speed. If there are sources of infrared radiation at workplaces, the intensity of thermal radiation should be determined.
Measuring temperature, humidity, air speed of the working area. Aspiration psychrometers are traditionally used to measure air temperature and humidity. Dry bulb readings characterize the ambient air temperature. According to the ratio of the temperature of a dry and wet thermometer, the reservoir of which is wrapped in a thin cloth moistened with water, using
The corresponding table determines the relative air humidity (the ratio of absolute humidity to maximum), expressed as a percentage.
There are modifications of psychrometers: MV-4M with a mechanical drive and M-34 with an electric drive. Temperature measurement range - from -30 to +50? C, relative humidity - within 10-100%. This device can measure the temperature and humidity of the air in the working area even near a source of infrared radiation without additional screens, since the thermometer reservoirs are protected by double polished metal screens.
To study temperature dynamics, when it is necessary to determine the limits of fluctuations, self-recording thermographs (daily or weekly) of the M-16 type are used. For the same purpose, hygrographs of the M-21 type are used to estimate relative humidity. It should be remembered that hygrographs and thermographs cannot be used without shields if work areas are exposed to radiant heat.
To measure air speed, vane anemometers ASO-3 (within 0.3-5 m/s) and cup anemometer MS-13 (from 1 to 30 m/s) are traditionally used. Air velocity less than 0.5 m/s is measured using electric anemometers, as well as catathermometers.
Modern devices are more advanced, multifunctional, portable, easy to operate, and can be equipped with an additional kit for automatically recording measurement results and data analysis on a computer. These are thermohygrometers, thermal anemometers, as well as devices that simultaneously or sequentially determine all meteorological parameters of the air. IN table 4.1 The ranges for determining temperature, relative humidity and air velocity by some of the domestic instruments currently produced are given.
Thanks to additional devices, some devices can record air parameters over time during the working day.
For example, IVA-6AR is an autonomous recording device with an external probe. The display constantly shows the current temperature and relative humidity values. A miniature memory module can be connected to the device, turning it into a thermohygrograph - a device that allows you to record the results
Table 4.1.Instruments for measuring temperature, relative humidity and air velocity, detection range
data over 20 thousand measurements at a specified interval. The processing program allows you to view accumulated data in text or graphical form on the computer screen, highlight values that exceed established thresholds, and print a report for any time interval.
The microprocessor thermoanemometer TTM-2 with a retractable telescopic probe also allows for continuous measurement with data accumulation for transmission to a computer.
Many devices are additionally equipped with a “black ball”, since the THC index is an important indicator for assessing the degree of harmfulness of the heating microclimate (see below).
Measuring the intensity of thermal radiation. Actinometers and radiometers are used to measure the intensity of thermal radiation from industrial sources.
The currently produced radiometers "Argus-03" (non-selective radiometer) allow you to measure thermal radiation in the spectral range of 0.5-20 microns and intensity from 1 to 2000 W/m 2, and "RAT 2P-Kvarts 41" (energy illumination radiometer ) is designed to measure thermal radiation from 10 to 20,000 W/m 2 in the spectral range of 0.2-25 microns (with an infrared filter from 1 to 15 microns).
In accordance with current sanitary standards The maximum values of infrared irradiation of a worker’s body are usually measured and assessed. In some cases, with intense irradiation of an intermittent nature, the average intensity value (q) for a given period of irradiation is calculated (for example, when choosing the parameters of air showering) using the formula:
For example, a worker, performing a certain operation, was in the irradiation zone for 20 minutes twice within an hour. The radiation intensity during this period varied from 400 to 3000 W/m2 (5 min - 400 W/m2,
7 min - 1500 W/m2 and 8 min - 3000 W/m2). In this case, the average radiation intensity was 1825 W/m2.
In a similar way, the weighted average value of infrared (thermal) exposure (IR) is calculated to determine the class of working conditions according to microclimatic parameters, taking into account the period of time when there was no radiation in the workplace.
Example.At the steelworker's workplace with the furnace damper open, the radiation was 1500 W/m2, and the operating time was 2 hours; with the damper closed - 350 W/m2 for 4 hours. Work outside the influence of infrared radiation - 1 hour (including regulated breaks). The shift average maintenance value is calculated as a time-weighted average:
Measuring the temperature of the surfaces of enclosing structures and technological equipment. Electric thermometers, thermocouples, and infrared thermometers are used to measure surface temperatures.
Surface thermometer TCM 1510 is a portable electronic device designed for measuring the temperature of surfaces in the range 0-300 °C by contact method, produced with a replaceable set of probes. The sensor is connected to the device using an extended cable.
Pyrometers S-110 and S-210 (infrared thermometers) are designed for non-contact measurement of surface temperature various objects in the range from -20 to +200?C (grade S-110) and from -20 to +600?C (grade
S-210).
When carrying out measurements in cabins, control panels, control rooms and other small rooms, when the distance from a person to the fences does not exceed 2 m, the temperatures of the internal surfaces of the fences are directly measured with the subsequent calculation of their weighted average temperatures (tSVP) according to the formula:
Measurement and calculation of indicators for a comprehensive assessment of microclimate parameters. For an integral assessment of the microclimate, the environmental thermal load index (THI) is used, which characterizes the combined effect on the human body of temperature, humidity, air speed and thermal radiation from surrounding surfaces.
The THC index is an indicator expressed in °C, calculated on the basis of the temperature of the psychrometer wet bulb (twl) and the temperature inside the “black ball” (tsh) according to the equation:
TNS = 0.7 tvl + 0.3 tm.
As follows from the formula, to determine this indicator, a ball thermometer and an aspiration psychrometer are needed.
A traditional ball thermometer is a hollow blackened ball, in the center of which a thermometer reservoir is placed (with a measurement range of 0-50? C). The temperature measured at the center of the ball (t w) is the equilibrium temperature from radiative and convective heat exchange between the ball and the environment. It must be remembered that devices cannot be placed in close proximity to open fire or large surfaces with a temperature above 100? C.
Currently produced multifunctional devices for assessing microclimate parameters are additionally equipped with a probe with a “black ball”. Here are some of them.
A ball thermometer is an electronic digital thermohygrometer, which is equipped with a thin-walled metal sphere with a black matte surface with a diameter of 90 mm and a stand. You can measure temperature (from -20 to 90? C), relative humidity (from 0.5 to 99%), wet bulb temperature (t w) and temperature in the “black ball” (t w). The TNS index is determined by calculation.
Meteoscope (Fig. 4.1)- By additional agreement The kit may include a ball thermometer for measuring the THC index in the range from 10 to 50? C and the intensity of thermal radiation from 10 to 1000 W/m2.
A black sphere is produced for TKA-PKM thermohygrometers (models 20, 23, 24, 41, 42, 43) for measuring (calculating) the THC index.
Rice. 4.1.Air climatic parameter meter "Meteoscope"
The digital universal device is designed for measuring temperature, humidity, pressure and air flow speed in residential and industrial premises.
Technical characteristics: air flow speed measurement range: from 0.1 to 20 m/s; limits of permissible basic relative error of the air flow velocity measurement channel: in the range from 0.1 to 1 m/s: ?(0.05+0.05V), in the range from 1 to 20m/s: ?(0.1+0 .05V); ambient temperature measurement range: from -10 to +50 ? C; limit of permissible basic absolute error of the temperature measurement channel: ? 0.2?C; relative humidity measurement range: from 30 to 98%; limit of permissible basic absolute error of the relative humidity measurement channel: ?3%; absolute atmospheric pressure measurement range: from 80 to 110 kPa, from 600 to 825 mm Eg; limit of permissible basic absolute error of the channel for measuring absolute atmospheric pressure: ?0.13 kPa, ? 1 mm Eg; operating mode establishment time: 1 min; continuous operation time of the meter without recharging the battery: 10 hours (Manufacturer: instrument-making company “ETM-Zashchita.”)
TKA-PKM (mod. 24) is an electronic thermo-hygrometer equipped with a “black ball” for simultaneous measurement of temperature, relative air humidity, temperature inside the “black ball”, wet bulb temperature, as well as the THC index.
IVTM-7KZ with a “black ball” is a portable microprocessor meter for temperature and relative air humidity, wet-bulb temperature, and ball temperature. The TNS index is determined by calculation.
Procedure for conducting assessment studies industrial microclimate. The study begins with identifying the hygienic features of technological processes (determining the sources of formation and release of heat, moisture, infrared radiation), architectural and planning solutions, and room ventilation systems. It is necessary to have floor plans indicating technological equipment, workplaces and ventilation systems.
Points for measuring microclimate parameters are outlined. The selection of points is carried out depending on the purpose of the survey. When compiling general characteristics working conditions measurements are carried out at workplaces. If the workplace consists of several sections of the production facility, then measurements are carried out on each of them at points that are minimally and maximally distant from sources of local heat generation, cooling or moisture release (heated units, windows, doorways, gates, open bathtubs, etc.) .
In rooms with a high density of workplaces in the absence of sources of local heat release, cooling or moisture release, measurement points are marked evenly throughout the room: for an area of up to 100 m 2 - 4 measurement points, for an area of 101-400 m 2 - 8 points; with an area of more than 400 m2 every 10 m.
During sanitary and hygienic control of ventilation systems, in addition to measurements at the named points, measurements are also taken in open openings of shelters, aeration openings, supply jets from air supply devices, air showers and curtains.
Next, timing observations are carried out to determine the duration of workers’ stay in specific meteorological conditions. This is especially important during uneven technological processes, when, when performing individual operations, sometimes short-term, significant changes in microclimate parameters occur.
Microclimate studies are carried out at maximum load of technological equipment and operation of all ventilation
systems When measuring temperature, humidity, air speed, the following general rules must be observed:
1) measurements should be carried out in the cold period of the year - on days with the outside air temperature close to the average temperature of the coldest month of winter, in the warm period of the year - on days with the outside air temperature close to the average temperature of the hottest month;
2) measurements must be carried out at the beginning, middle and end of the shift with a uniform progress of the technological process and a monotonous microclimate. If the technological process is associated with a significant change in heat release during individual operations, then, in addition to the above, measurements should be taken at this time;
3) measurements of temperature, humidity, air velocity must be carried out at a height of 1 m from the surface of the floor or working platform when working while sitting, and at a height of 1.5 m when working while standing;
4) to determine the difference in air temperature and the speed of its movement along the vertical working area, additional measurements should be taken at a height of 0.1 m from the surface of the floor or working platform.
Measurement of the temperature of the internal surfaces of enclosing structures (walls, floors, ceilings), external surfaces of technological equipment or its enclosing devices (screens, etc.) should be carried out in cases where workplaces are located at a distance of no more than 2 m from them. The temperature of each surface is measured at two levels: at a height from the floor of the workplace of 0.1 and 1 m (sitting position) and 0.1 and 1.5 m (standing position).
Measurement of the intensity of infrared radiation is carried out directly at the level of the irradiated areas of the surface of the human body. The receiver of the device should be turned in the direction of maximum thermal radiation, perpendicular to the incident flow at a height of 0.5; 1.0 and 1.5 m from the floor or working platform. In this case, it is necessary to determine approximately the surface of the body exposed to irradiation (less than 25%, from 25 to 50%, more than 50% of the body surface) taking into account the proportion of each area of the body: head and neck - 9%; chest and abdomen - 16%; back - 18%; hands - 18%; legs - 39%.
For example, if a worker is facing the radiation source, then when the entire surface facing the source is irradiated, it amounts to more than 50% of the body surface, if the surface is exposed to irradiation.
Only the face, chest, arms, and abdomen are irradiated - from 25 to 50%, if the face and chest are irradiated - less than 25% of the body surface.
The method for measuring the THC index is similar to the method for measuring air temperature.
It is necessary to compile a description of production premises, taking into account the category of work performed in them in terms of energy consumption in accordance with departmental regulatory documents(based on the category of work performed by 50% or more of those working in a given premises), and if they are absent, then conduct a study and assess the work according to the degree of severity and intensity.
You can also rely on the following data.
In accordance with SanPiN 2.2.4.548-96 " Hygienic requirements to the microclimate of industrial premises" are divided into light, moderate and heavy physical work.
Light physical work (I category): 1a (energy consumption up to 139 W) - work carried out while sitting and accompanied by minor physical stress (a number of professions in precision instrument and mechanical engineering enterprises, watchmaking, clothing production; in the field of management, etc.; 1b (140 -174 W) - work carried out sitting, standing or associated with walking and accompanied by some physical stress (a number of professions in the printing industry, at communications enterprises; controllers, foremen in various types of production, etc.).
Medium heavy work (II category): 11a (175-232 W) - work associated with constant walking, moving small (up to 1 kg) objects in a standing or sitting position and requiring a certain physical exertion (a number of professions in mechanical assembly shops of machine-building enterprises, in spinning weaving production); 11b (233-290 W) - work associated with walking, moving heavy objects (up to 10 kg) and accompanied by moderate physical stress (a number of professions in mechanized foundries, rolling, forging, thermal, welding shops of machine-building and metallurgical enterprises, etc. ).
Heavy physical work (III category): energy consumption is more than 290 W. These are jobs associated with the constant movement and carrying of heavy objects (more than 10 kg), requiring great physical effort (a number of professions in forge shops with hand forging, foundries with manual filling and pouring of supports of machine-building, metallurgical enterprises, etc.).
Based on the results of the study, it is necessary to draw up a protocol, which should reflect general information about the production facility, the placement of technological and sanitary equipment, sources of heat generation, cooling and moisture release, a diagram of the location of areas, points for measuring microclimate parameters and other data are given. At the conclusion of the protocol, the results of the measurements performed should be assessed for compliance with regulatory requirements.
Evaluation of research results for compliance with hygienic standards. When assessing the data obtained, a dynamic characterization of meteorological conditions should be provided whenever possible. The measured temperature, humidity, air velocity at various points in the room at workplaces during various operations are compared with the optimal or permissible standard values given in SanPiN 2.2.4.548-96 “Hygienic requirements for the microclimate of industrial premises” (Table 4.2 and 4.3).
Optimal microclimate parameters provide a feeling of thermal comfort during an 8-hour work shift with minimal stress on the thermoregulation mechanisms, maintaining health and a high level of performance.
Acceptable microclimatic conditions ensure the preservation of health, but can lead to a feeling of thermal discomfort, strain on the thermoregulatory mechanisms and decreased performance.
When choosing a standard for comparison with measurement results, it is necessary to proceed from the fact that optimal microclimate parameters are created during air conditioning, for example in the radio-electronic industry, instrument making, in cabins, on consoles and control stations during operator-type work, in rooms where there are no significant technological heat and moisture releases.
When using table 4.2 or 4.3 it is necessary to take into account that the cold period refers to the period of the year characterized by the average daily temperature of the outside air equal to +10? C and below, the warm period refers to the period of the year characterized by the average daily temperature above +10? C.
It is necessary to evaluate the differences in air temperatures in height and horizontally, as well as changes in air temperature during
Table 4.2.Optimal values of microclimate indicators in industrial workplaces
Table 4.3.Acceptable values of microclimate indicators at workplaces of industrial premises
Note.*At an air temperature of 25? C and above, the maximum values of relative air humidity should not exceed the following limits: 70% (at t = 25? C); 65% (at t = 26? C); 60% (at t = 27? C); 55% (at t = 28? C).
shifts. When ensuring optimal microclimate values at workplaces, these differences should not exceed 2? C. If the permissible values are ensured, changes in height are possible up to 3? C (for all categories of work), and horizontally and during a shift - up to 4? C for light work, up to 5? C for moderate work and up to 6? C - during heavy work, if the absolute values of air temperature at different heights and in different areas of the premises do not exceed the limits permissible values.
The temperature assessment of internal surfaces, enclosing structures, devices, as well as technological equipment is carried out in accordance with table 4.2 when ensuring optimal microclimate indicators or with table 4.3 while ensuring acceptable microclimate parameters. As can be seen from these tables, the range of regulated surface temperatures differs from the optimal or permissible air temperature values by no more than 2? C.
If any of the surrounding surfaces differs significantly in temperature from the rest, then it is taken into account and assessed separately by the amount of infrared radiation.
Permissible values for the intensity of thermal radiation in the workplace have been established:
1) from industrial sources heated to a dark glow (materials, products, etc.), at a level of 35 W/m2 when irradiating 50% or more of the body surface, 70 W/m2 - when the irradiated surface is from 25 to 50% , and 100 W/m 2 - when irradiating no more than 25% of the body surface;
2) from radiation sources heated to a white and red glow (molten metal, glass, flame, etc.) at a level of 140 W/m2, while more than 25% of the body surface should not be exposed to irradiation and the use of personal protective equipment is mandatory, including face and eye protection.
Taking into account the unidirectional effect of high temperature and infrared radiation, the standard provides for a lower permissible temperature limit in the presence of infrared radiation in the workplace (even if it complies with the standards), namely, the air temperature should not exceed the optimal values for the warm period: 25? C (work category Ia) , 24?C (Ib), 22?C (11a), 21?C (11b), 20?C (III). Likewise, to reduce the heat load on the body, lower
relative humidity parameters at air temperature 25? C and above (see note to Table 4.3).
Considering that a combined effect of microclimate parameters is possible, i.e. when one indicator can compensate or enhance the effect of another, it is also recommended to focus on the integral indicator - THC index - when assessing the industrial microclimate. Acceptable values of the THC index for preventing overheating of the body are given in table 4.8.
When equipping workplaces with air showers, which is a necessary measure to prevent overheating when the intensity of thermal radiation exceeds 140 W/m 2, do they evaluate the temperature and speed of the air flow blowing the worker in accordance with the MR? 5172-90 “Prevention of overheating of workers in a heating microclimate” (Table 4.4). The same values are accepted when designing ventilation as design standards for air ventilation in accordance with SNiP 41-01-2003 “Heating, ventilation and air conditioning”.
SanPiN 2.2.4.548-96 presents hygienic requirements for industrial premises equipped with traditional - convective - heating and air conditioning systems. If production premises are equipped with radiant heating systems, microclimate parameters must be assessed in accordance with acceptable values in accordance with document R 2.2.2006-05 “Guide to the hygienic assessment of working environment factors and the labor process. Criteria and classification of working conditions" (Table 4.5). The regulations provide for moderate work during an 8-hour work shift.
4.2. STUDY OF THE INFLUENCE OF MICROCLIMATE
ON THE BODY
Microclimatic conditions in production premises are regulated by relevant documents, but it is not possible to provide for absolutely all situations that arise. In addition, the main hygienic assessment of the microclimate is carried out according to individual meteorological indicators, which does not always give a complete picture of the possible impact of the environment, since the combination of these indicators can be very diverse. In this regard, the doctor may need clarification and
Dusting depending on the intensity of infrared radiation (average over the irradiation time)
Table 4.5.Acceptable microclimate parameters of industrial premises equipped with radiant heating systems
physiological justifications for the nature of the microclimate and the degree of its impact on the human body, for example, when determining the class and degree of harmfulness of working conditions according to microclimatic parameters.
Representatives of certain professions (sailors, miners, etc.) are forced to stay in rooms with unfavorable meteorological conditions, especially when performing work in the Far North or southern regions, and the doctor must be able to assess the functional state of the body and propose measures to prevent pathological conditions.
The impact of the industrial microclimate on well-being and health can be determined using physiological research methods based on indicators characterizing the thermal state.
Thermal state is the result of thermoregulation processes. Thermoregulation is a set of physiological processes that ensure correspondence between heat production and heat transfer from the body, depending on microclimate fluctuations and aimed at maintaining body temperature within certain narrow limits.
Human biological capabilities in maintaining temperature homeostasis are limited. Muscular work causes a restructuring of thermoregulation in a working person due to increased metabolism and energy expenditure. The stress of thermoregulation processes also occurs when exposed to an unfavorable microclimate, leading under certain conditions to the development of pathological conditions (overheating or hypothermia).
Thermal state can be assessed by subjective (thermal sensation) and objective indicators. The latter include indicators of the activity of the cardiovascular, respiratory systems, and gas exchange. More often than others in hygienic practice, indicators are used that, reflecting the state of thermoregulation processes, most closely correlate with heat sensations. This is body temperature, skin temperature and “heat content” calculated on the basis of these data and its change. During in-depth studies, the heat balance is determined taking into account specific heat losses: heat transfer by convection, radiation, evaporation.
Assessment of human thermal sensations. In the practice of hygienic research, a person’s thermal sensations are assessed using a 7-point scale.
no scale. In response to the doctor’s questions about his sensations of heat, the examinee gives one of the following ratings: 1 - cold; 2 - cool; 3 - slightly cool; 4 - comfort; 5 - slightly warm; 6 - warm; 7 - hot. Data from a survey of workers about their thermal sensations are taken into account in conjunction with the results of an objective study of the thermal state of the body.
Measuring skin temperature. For this purpose, an electric thermometer, an infrared thermometer, and a heat meter are used.
Measuring skin temperature to assess its dynamics must be carried out at strictly defined points. IN production conditions use the following five points: on the forehead - a point located between the brow ridges, 0.5 cm above their upper edge; on the chest - at the upper edge of the sternum; on the hands - on the back side between the bases of the first phalanges of the thumb and index fingers; in the middle of the outer surface of the thigh and lower leg. The skin temperature of a dressed man (room and work clothes) with a comfortable feeling is: on the forehead - 33.8-34.5? C; on the hand - 33.1-33.6? C; on the thigh - 33.0-33.4? C; on the lower leg - 32.2-32.8? C.
Currently, in the practice of hygienic research, it is customary to evaluate the weighted average skin temperature, calculated in accordance with its value in individual areas and the significance of the area of these areas in relation to the entire surface of the body.
The weighted average skin temperature (t. wc) is calculated using the formula:
In comfortable conditions, in a state of relative rest, the weighted average skin temperature is 32.8-34.2? C. During physical activity, comfortable sensations are observed at lower values of weighted average temperatures: during moderate work - 31.0-32.5 °C, heavy work - 30.0-31.4 °C.
Under conditions of exposure to an unfavorable microclimate (in a state of relative physical rest), the feeling of “hot” occurs when the average weighted skin temperature increases to 36? C and above, and the feeling of “cold” - at 28-29? C.
Measuring body temperature. Typically, body temperature is measured in the armpit or rectum (experimental conditions). Use a medical electrothermometer or special equipment with sensors. The duration of one-time body temperature measurement is at least 5 minutes.
The human body temperature at rest with a comfortable feeling of heat averages 36.7 °C (axillary) and 37.2 °C (rectal).
Intense physical work, even in optimal microclimatic conditions, can lead to an increase in body temperature (rectal) to 37.5-37.7? C. A change in body temperature under the influence of an unfavorable microclimate indicates a strain in thermoregulation processes and an imbalance in heat balance. Thus, the maximum permissible physiological value (at rest) is body temperature (rectal) equal to 37.5? C, and during cooling - 36.9? C.
Method for calculating the change in heat content. “Change in heat content” is an integral indicator that allows one to indirectly judge the state of the heat balance, including heat deficiency (heat transfer exceeds heat generation) or heat accumulation (heat generation exceeds heat transfer). Obtaining this indicator is less labor-intensive than directly determining heat accumulation (or heat deficit) using the indicators of the heat balance equation. The indicator “change in heat content” is calculated based on body temperature (the “core” temperature) and the weighted average skin temperature (the “shell” temperature), the methods for determining which are quite simple and accessible.
To calculate the “change in heat content” indicator, it is necessary to determine the average body temperature using the formula:
Θ = k? tT + (1 - k) ? t-svk,
where: Θ - average body temperature, ? C; tj. - body temperature (rectal or axillary), ? C; ^ vk - weighted average skin temperature, ? C; k - mixing coefficients, reflecting the proportion of tissues with a temperature close to the “core”; (1 - k) - mixing coefficients, reflecting the proportion of tissues with a temperature close to the “shell”. The value of k can be determined using table 4.6.
Table 4.6.Body temperature mixing coefficients (k)
with different heat sensations and energy consumption of a person, W
Then the heat content in the body is calculated (Q) in kilojoules or kilocalories (1 kcal = 4.186 kJ) per 1 kg according to the formula:
Q = C? Θ,
where: C is the specific heat capacity of body tissues, equal to 3.47 kJ/(?C? kg).
The change in heat content (deficiency or accumulation of heat) in the body under given microclimatic conditions is determined in comparison with the heat content under conditions of thermal comfort in a state of relative rest with calculated body temperatures of 37.2 °C (rectal), 36.7 °C (axillary) and weighted average skin temperature 33.2? C.
The optimal thermal state of the body (defined as comfortable) when performing moderate work corresponds to an average body temperature of 35.3-35.8 °C, a change in heat content of 0.87 kJ/kg (? 0.2 kcal/kg).
Methodology for calculating the direct indicator of heat load on the body using the basic heat balance equation. This is one of the most adequate, although relatively complex, methods for hygienic assessment of the microclimate.
The basic heat balance equation takes into account the main factors that influence changes in heat content in the human body:
Q = M? C? R - E,
where: Q - heat load on the body (accumulation or heat deficiency); M - heat production (metabolic heat, accounting for 67-75% of energy expenditure); C - convection exchange between the body and the surrounding air; R - radiation heat exchange between the body and the environment; E - heat transfer from the body by evaporation.
In this formula, the quantities R And WITH can be negative if heat transfer occurs by radiation and convection, or positive if, as a result of heat exchange, the body receives heat in the indicated ways, which is determined by the difference between the temperature of the skin and the temperature of surrounding surfaces (for R) or skin temperature and air temperature (for WITH). At a temperature of air and surrounding surfaces of 32-35? C, heat transfer by convection and radiation is sharply reduced, while evaporation (mainly sweat) takes the leading place in heat transfer. If the temperature of the air and surrounding surfaces further increases, the body begins to receive additional heat due to convection and radiation, and sweating increases even more.
In comfortable conditions, heat transfer by convection and radiation accounts for 70-80% of the body's total heat transfer. At low temperatures, heat transfer by convection and radiation increases significantly. The heat balance can be close to zero when the amount of heat production corresponds to the total heat transfer. With a value Q within?2 W the thermal state of a person corresponds to optimal. A positive or negative heat load (accumulation or deficit of heat) greater than these values is a consequence of the stress of thermoregulation processes, and values exceeding permissible values are an indicator of the development of overheating or hypothermia.
The heat balance can be assessed by instrumental and calculation methods. By measuring convection, radiation and evaporation heat transfer (methods are given in this chapter) and heat production using the gasometric method, it is possible to determine the amount of heat accumulation or deficit.
When determining the heat balance, you can also use calculation method. It consists in finding the components of the heat balance equation using tables and formulas according to the
data obtained during examination of the subject (body weight, height, weighted average skin temperature, moisture loss) and study of the microclimate of the room (temperature, relative humidity and air speed, temperature of surrounding surfaces).
The measurement and assessment of specific heat losses are also important, since even in conditions when the thermal balance is not disturbed, a discomforting state can be associated with a redistribution of heat transfer pathways and tension in the thermoregulatory mechanisms.
Heat meters are used to determine the total convection and radiation heat transfer.
It is recommended to measure heat flow in the absence of visible sweating on the same areas of the body surface on which skin temperature is measured. This technique is used mainly to assess a cooling or thermoneutral environment, when these heat transfer paths are the main ones and the stress of thermoregulation processes can be judged from them. Heat meter sensors are applied to various points of the body (face, chest, hand, thigh, lower leg), after which readings are taken in kilocalories per 1 m 2 per 1 hour [kcal / (m 2 ? h)]. The heat flux density at each individual part of the body is determined as the average value of at least 5 measurements taken sequentially at equal intervals of time. The weighted average heat flux is calculated similarly to the weighted average skin temperature using the weighting factors given in the same formula:
With a comfortable feeling of heat, the weighted average heat flux is 44-67 (38-59) for light work, 68-111 (60-96) for moderate work, 112-134 (97-115) W/m2 for heavy work [ kcal/(m2 ? h)].
The heat flux density from the body surface, equal to 163 W/m 2, corresponds to the subjective limit of cold tolerance (“very cold”).
In some cases, it becomes necessary to determine radiation heat transfer, since the ratio of heat transfer by radiation and convection has a certain significance for creating thermal comfort for the worker. To determine the radiation heat balance between the surface of the human body and surrounding objects in the room, a differential radiometer is used.
When determining evaporative heat transfer, the evaporation of water from the surface of the skin and lungs is taken into account. The ratio of heat loss due to evaporation from the surface of the lungs and skin varies depending on the air temperature: at 10 °C it is 1:2, at 20 °C - 1:3, and at 30 °C and above - 1:5 or more . Therefore, under conditions of a heating microclimate, when evaporative heat transfer is the only possible way of heat transfer from the surface of the skin, it is the intensity of sweating that reflects the degree of tension in thermoregulation processes under these conditions.
The amount of sweating (in grams) can be determined by weighing the subject (naked) on an accurate scale. Moisture loss is determined by the decrease in body weight over 2 or 4 hours, recalculated for 1 hour. The “filter notebook” method is also used, which allows you to determine local sweating from individual areas of the skin, and when carrying out the necessary calculations, general sweating. The “filter notebook” consists of two filter papers measuring 4X2 cm, on top of which is laid tracing paper of the same size, attached to the underlying layers (stitched on a sewing machine). The filter notebook, pre-weighed on an electroanalytical balance, is glued to a certain area of the skin with thin strips of adhesive plaster or tape (the increase in the weight of the notebook due to the adhesive plaster does not exceed 0.2 mg). After 5 minutes, remove the notebook and immediately weigh it.
The weighted average value of sweating is determined by recalculating local moisture losses measured on 6 areas of the skin (forehead, chest, hand, thigh, lower leg, back) per 1 m2 of skin surface according to the formula:
To determine total sweating, the amount of sweat accumulated per 1 m2 is multiplied by the body surface area (1.6-1.8 m2), which is clarified using tables.
Evaporative heat transfer can be calculated by entering a factor of 2.4 kJ/g (0.6 kcal/g). The body's moisture loss in comfortable conditions with relative rest is approximately 50 g/h. In a heating microclimate, moisture loss increases 5-10 times. In comfortable conditions, when performing light work, moisture loss reaches 100, during moderate work - up to 150 and during heavy work - up to 180 g/h.
4.3. CLASSIFICATION OF WORKING CONDITIONS ACCORDING TO MICROCLIMATE INDICATORS
Classification of working conditions as optimal or acceptable (class 1 and 2) based on microclimate indicators (temperature, humidity, air speed, infrared radiation) is carried out in accordance with SanPiN 2.2.4.548-96 for each individual parameter (see table 4.2 And 4.3) or according to the integral indicator - TNS index (Table 4.8).
If the microclimate parameters deviate from the permissible ones, it is necessary to establish the degree of harmfulness or danger of working conditions, focusing on R 2.2.2006-05 “Guide to the hygienic assessment of factors in the working environment and the labor process. Criteria and classification of working conditions."
First, it is necessary to determine the nature of the microclimate (cooling or heating) according to its parameters (or more precisely according to physiological indicators characterizing the human condition), and then carry out an assessment according to table 4.7.
Assessment of the heating microclimate. Heating microclimate - a combination of microclimate parameters in which there is a violation of heat exchange with the environment, expressed in the accumulation of heat in the body above the upper limit of the optimal value (>0.87 kJ/kg) and/or an increase in the proportion of heat loss due to the evaporation of sweat (>30%) in the general structure of thermal balance, the appearance of general or local uncomfortable thermal sensations (slightly warm, warm, hot).
In a heating microclimate, the permissible limits of air temperature or thermal radiation are exceeded.
The degree of harmfulness of working conditions is determined mainly by the thermal load of the environment (THC index, an integral indicator reflecting the combined effect of temperature, humidity, air speed and thermal radiation with an intensity of up to 1000 W/m2).
For assessment, the average shift value of the TNS index is taken. In a monotonous microclimate, it is calculated as the arithmetic mean of three measurements; in a dynamic microclimate or in the case where work is performed at different workplaces with different heat loads, it is calculated as a time-weighted average. The class of working conditions according to the TNS index is established in accordance with table 4.8.
If a person’s thermal exposure exceeds 140 W/m2 and the radiation dose exceeds 500 W? h*, then the working conditions are assessed as harmful, while the class of working conditions is established according to the most pronounced indicator: TNS index (Table 4.8) or thermal radiation (Table 4.7). When radiation is more than 1000 W/m 2, the degree of harmfulness of the heating microclimate is determined by the intensity of infrared radiation (time-weighted average value per shift, taking into account periods when there is no radiation).
Workplaces in open areas during the warm period are assessed by the THC index measured at noon in the absence of clouds, in accordance with table 4.8.
If an employee is employed both indoors and outdoors during the warm season, the assessment is carried out based on the average shift value of the TNS index, calculated as a weighted average taking into account the time spent at different workplaces.
Assessment of the cooling microclimate. Cooling microclimate - a combination of microclimate parameters in which the total heat transfer exceeds environment above the amount of heat production of the body, leading to the formation of a general and/or local heat deficit in the human body (>0.87 kJ/kg). If the indoor air temperature of the workplace is below permissible limits, then such a microclimate is considered
The exposure dose of radiation (Wh) is defined as the product of the intensity of thermal radiation (W/m2) by the irradiated surface of the body (m2) and the duration of irradiation for work shift(h).
Table 4.7.Classes of working conditions according to microclimate indicators for working premises
End of table. 4.7
Table 4.8.Classes of working conditions according to the THC index in?С (upper limit) for
industrial premises with a heating microclimate, regardless of the period of the year and open areas during the warm period of the year
to the cooling one. High air speed enhances the cooling effect. The degree of harmfulness of working conditions when working in industrial premises with a cooling microclimate is determined by the air temperature (average shift) according to table 4.9. The table shows the air temperature in relation to the optimal values of the speed of its movement (according to SanPiN 2.2.4.548-96). Therefore, at higher speeds of its movement in the workplace, the air temperature given in table 4.9, should be increased as per note.
For those working in rooms with a cooling microclimate and in the presence of sources of thermal radiation, the class of working conditions is established according to the indicator “thermal exposure” (Table 4.7), if its intensity is above 140 W/m2.
The class of working conditions when working in open areas during the cold season or in unheated rooms can be determined according to Table. 8-11, presented in Guide R 2.2.2006-05. They show average winter temperatures at the most likely wind speed in each climatic region. The latter unites territories that have similar meteorological conditions, according to which workers are provided with a free set of PPE (clothing, shoes, etc.) that meets the necessary requirements for thermal insulation. At air temperatures of -40°C and below, respiratory and face protection is required.
IN table 4.10 given as an example are classes of working conditions based on air temperature for open areas in the winter season in relation to work categories 11a - 11b. The numerator shows the air temperature in the absence of regulated heating breaks, the denominator shows the regulated heating breaks (after no more than 2 hours of exposure to the open air).
Assessment of working conditions when working during a shift in different (cooling and heating) microclimates. If, during a shift, an employee’s production activities are carried out in different microclimates (heating and cooling), it should be assessed separately, establishing a class of working conditions, and then calculate the time-weighted average value.
Example.The transporter periodically performs work in the workshop and in the warehouse. In terms of energy consumption, the work falls into category 11a.
Chronological studies establish that the time it spends in the workshop is 6 hours, in the warehouse - 2 hours. The studies were carried out during the cold period of the year.
When measuring the microclimate parameters in the workshop, the temperature of the air and surrounding surfaces exceeds the permissible ones (relative humidity and air velocity are within permissible values), i.e. heating microclimate. To determine the degree of harmfulness of working conditions, the average shift value of the THC index is calculated, which in this case is equal to 26.0? C, and compared with the data table 4.8. Class of working conditions - harmful 2nd degree (3.2).
When measuring microclimate parameters in a heated warehouse room, it was established that the air temperature, equal to 9? C (average shift), is less than the lower limits of permissible values (cooling microclimate), and table 4.9 working conditions are assessed as harmful 4th degree (3.4).
Calculate the weighted average value of the degree of harmfulness of working conditions per shift, multiplying the employment time in the considered conditions by a conventionally accepted coefficient: for class 1 working conditions - 1, for class 2 working conditions - 2, for class 3.1 working conditions - 3; for class 3.2 working conditions - 4; for class 3.3. working conditions - 5; for class 3.4 working conditions - 6; for class 4 working conditions - 7.
In our example: (6 hours? 4 + 2 hours? 6): 8 hours = 4.5, i.e. degree of harm - between classes 3.2 and 3.3. Since the worker’s body is exposed to temperature changes, the degree of harm is rounded up. Thus, the working conditions of the transporter in terms of microclimate indicators are classified as class 3.3.
4.4. EVENTS TO IMPROVE WORKING CONDITIONS
If, during an inspection of the enterprise, it is found that meteorological conditions do not meet the standards, then the sanitary doctor must develop and propose to the administration measures to improve working conditions in the following areas: improving technological processes taking into account hygienic requirements, reducing the intensity of thermal
Table 4.9.Classes of working conditions based on air temperature (? C, lower limit) during work
in industrial premises with a cooling microclimate
Note.When the air speed increases by 0.1 m/s from the optimal (according to SanPiN “Hygienic requirements for the microclimate of industrial premises”), the air temperature should be increased by 0.2? C.
Table 4.10.Classes of working conditions according to air temperature, ? C, (lower limit)
for open areas in the winter season in relation to the category of work Pa - Pb.
Table 4.11.Time spent at workplaces at air temperatures above permissible values
Table 4.12.Time spent at workplaces at air temperatures below acceptable values
Table 4.13.Recommended duration of infrared exposure
radiation, heat release, moisture release from equipment by means of its sealing, thermal and moisture insulation, shielding, installation of local suction, etc.; improvement of heating, ventilation and air conditioning systems, organization of physiologically based work and rest regimes, drinking regime, provision of workers with personal protective equipment. In this case, “Prevention of overheating of workers in a heating microclimate” MR can serve as a guide for a doctor? 5172-90, “Sanitary rules for ferrous metallurgy enterprises”? 2527-82, etc.
In accordance with SanPiN 2.2.4.548-96, in order to protect against possible overheating or hypothermia of workers, the time spent at workplaces (continuously or cumulatively for a work shift) that do not meet the permissible values for air temperature indicators should be limited (Table 4.11 And 4.12), at the same time, the average air temperature over an 8-hour shift, when people are at work and in rest areas, should not go beyond the regulated permissible values for the corresponding categories of work (see table 4.3).
In order to avoid excessive (dangerous) general overheating and local damage (burn), even when using standard PPE, the duration of continuous infrared irradiation of a person should be limited (irradiated surface area to 25%) according to the MR? 5172-90 (Table 4.13).
The intensity of thermal radiation (W/m2) is determined using a heat flux density meter IPP-2.
The IPP-2 meter is designed for measuring, in accordance with GOST 25380-82, the intensity of heat flow passing through the lining and thermal insulation of power facilities. The set with the device includes a heat flux density converter with a sensor on a spring PTP-Kh-P (Fig. 3a) and a probe for measuring surface temperature (Fig. 3b).
Rice. 3.3a. Heat flux density probe
with spring (PTP-H-P)
Rice. 3.3b. Surface temperature probe
Structurally, the IPP-2 device (Figure 4) is made in a plastic case. On the front panel of the unit there are buttons B and ", and on the side surface there are connectors for connecting the device to a computer and a network adapter. On the top panel there is a connector for connecting a primary heat flux density or temperature transducer.
Rice. 3.4. Appearance of the IPP-2 device:
1 – indication of battery operating modes; 2 – indication of threshold violation; 3 – button » ; 4 – button B; 5 – connector for connecting the primary converter; 6 – LED four-digit seven-segment indicator; 7 – connector for connecting to a computer; 8 – connector for connecting a network adapter
The device operates in one of the modes: OPERATION and SETUP.
OPERATION mode. Is the main operating mode. In this mode, cyclic measurement of the selected parameter is performed. By briefly pressing the » button, you can switch between the modes of measuring heat flux density and temperature, as well as indicating the battery charge in percentage 0...100%. By pressing the " button for two seconds, the device switches to the "SLEEP" mode; in this mode, the device turns off the LED indication, but continues to measure temperature and record statistics. Exit from the “SLEEP” mode is done by pressing any button. By pressing button B for two seconds, the device switches to SETUP mode. Briefly pressing button B turns the device off/on. When turned off, the device stops measuring and recording automatic statistics, while all settings for the device and the real-time clock are saved. In OPERATION mode, the device can periodically automatically record measured values into non-volatile memory with a time reference. The OPERATION mode diagram is shown in Figure 5.
Rice. 3.5. OPERATION mode diagram
LED indication in OPERATION mode. LED 1 (Fig. 3.4) characterizes the condition of the battery. In charging mode, with the AC adapter connected, the LED lights up continuously until the charge is 100%, then goes off. In operating mode with the network adapter disabled, the LED is off, and if the battery is charged less than 10%. LED 2 (Fig. 3.4) blinks to indicate that thresholds have been violated. In the “SLEEP” mode, the dot in the fourth digit of the seven-segment indicator blinks.
SETUP mode. Designed to set and record into the non-volatile memory of the device the operating measurement parameters required during operation. The set parameter values are saved in the device’s memory in the absence of power (with the exception of date/time). The general diagram of the SETUP mode is shown in Fig. 3.6.
Rice. 3.6. General scheme of operation of the SETTINGS mode
This mode allows you to configure two thresholds available in the device, one for each parameter. Thresholds are the upper or lower limits of the permissible change in the corresponding value. When the measured temperature exceeds the upper threshold value or decreases below the lower threshold value, the device detects this event and LED 2 lights up on the indicator (Fig. 3.4). Violation of thresholds is also accompanied by an audible signal.
