Sanitary standards for vibration of workplaces. Bearing Condition Determination
Vibration
What is vibration?
Vibration is the vibration of solids or particles with a frequency of less than 20 Hz, which is perceived by a person through touch.
Why is prolonged exposure to vibration harmful to humans?
Vibrations in excess of permissible sanitary standards have a harmful effect on the nervous and cardiovascular systems. Working, long time those exposed to the harmful effects of vibration become ill with vibration disease, the main symptoms of which are neurovascular disorders of the fingers, which manifests itself in increased sensitivity to cooling of the hands (numbness, blueness or paleness), the appearance of pain in the joints of the hands and fingers, as well as headaches, increased fatigue and irritability.
What can be a source of harmful vibrations in agriculture?
A machine operator working on a tractor or other agricultural machine may be exposed to the harmful effects of vibrations. Hand-held electric or pneumatic tools used to repair agricultural machinery can also create vibrations that are harmful to the worker. These are the most common sources of vibration.
What are the maximum permissible sanitary standards for vibration?
The standards limiting vibrations when working with machinery and equipment and in the workplace are given in Table 8.
Table 8. Limiting vibration standards
|
frequency Hz |
Vibrotool |
Workplace |
||
|---|---|---|---|---|
|
vibrational speed, cm/s |
vibration speed level, dB |
vibrational speed, cm/s |
||
| — | — | |||
At frequencies up to 11 Hz, the following oscillatory displacements are normalized for workplaces:
| frequency Hz | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 |
| Displacements, mm | 0,6 | 0,5 | 0,4 | 0,2 | 0,1 | 0,08 | 0,07 | 0,05 | 0,045 | 0,04 | 0,035 |
Who gives permission to work with a tool whose vibration exceeds sanitary standards?
The enterprise administration must obtain such permission from the local sanitary and epidemiological service authorities.
It is prohibited to work with machines whose vibration levels are more than 4 times (more than 12 dB) higher than sanitary standards.
How is vibration measured?
Vibration meters and vibrographs are used to measure vibrations in workplaces. various models. The most common noise and vibration meter is ISHV-1. Instrument vibration is also measured using sound level meters.
How are machine vibration parameters determined?
The vibration parameters of machines are determined according to technical documentation for new machines, and for operating machines - according to actual measurements carried out at least once a year, as well as after repairs for all types of machines, and for manual ones - at least twice a year.
What is the permissible contact time for a worker with a vibrating tool or in the workplace with a machine that does not meet the requirements of sanitary standards?
The contact time of workers in this case depends on the amount of excess of permissible levels of sanitary standards and corresponds to the following values (Table 9).
Table 9. Allowable contact time for workers with vibrating tools that do not meet sanitary standards
|
Excess of permissible vibration velocity levels in octave frequency bands relative to sanitary standards, dB |
Allowable total vibration activity per work shift, min |
|
|---|---|---|
|
manual machines | ||
|
Up to 3 (1.41 times) | ||
|
Up to 6 (2 times) | ||
|
Up to 9 (2.8 times) | ||
|
Up to 12 (4 times) | ||
To eliminate the influence of harmful vibrations on a worker, it is necessary to maintain the ratio of the duration of exposure to vibration and the performance of other operations not related to it, at least 1:2. For example, if the sanitary standards for vibration of a manual machine exceed 9 dB, it is advisable to establish a procedure for operating the machine for 10 minutes with periods of other types of work for 20 minutes each, that is, 10 + 20 + 10 + 20 + 10 + 20 + 10 = 100 minutes. The rest work time(480-100 = 380 min) work not related to vibration should be carried out.
What are the requirements for vibrating equipment?
Vibrating equipment includes powered tools, mechanisms, manual controls, devices or workpieces, during operation of which vibrations occur that exceed 20% of the maximum permissible sapitary standards.
Only equipment, tools, mechanisms or devices that are in good working order, within the limits of permissible wear and tear, should be allowed for operation.
After repair, equipment and machines that generate vibrations are checked for vibration compliance with sanitary standards before being put into operation.
It is prohibited to use vibrating equipment in modes other than those specified in the nameplate if the resulting vibrations transmitted to the workers’ hands and pressing forces exceed sanitary standards. acceptable standards.
What are the requirements for operating personnel of vibrating equipment?
Persons at least 18 years of age who have completed training are allowed to work with vibrating equipment. medical checkup who have the appropriate qualifications and have passed the technical minimum according to the rules safe execution works
It is prohibited to allow persons suffering from cardiovascular diseases, an active form of tuberculosis, peptic ulcer disease, vegetative-endocrine disorders, functional disorders of the peripheral and central nervous system, mental illness, diseases of the musculoskeletal system, diseases of the middle and inner ear, chronic liver diseases.
When working with vibrating equipment that meets the requirements of sanitary standards, the total time of contact with vibrating surfaces should not exceed 2/3 of the working day. Under this working regime, if other factors of working conditions comply with sanitary standards, the lunch break should be at least 40 minutes and two regulated breaks are established for active rest, industrial gymnastics and physical prophylactic procedures: 20 minutes 1...2 hours after the start of the shift and 20...30 minutes 2 hours after the lunch break.
Overtime work with vibrating equipment is prohibited.
Work with vibrating equipment is carried out, as a rule, in heated rooms with an air temperature of at least 16°, with a humidity of 40...60% and a movement speed of no more than 0.3 m/s.
When working in the cold season in unheated rooms or in the open air, for periodic heating, workers must create heated rooms with an air temperature of 22 ° C at a speed of no more than 0.3 m/s and a humidity of 40...60%.
Local heating is provided at workplaces. Those working with power tools are provided with individual vibration protection equipment.
All workers involved in work with vibrating equipment undergo periodic examinations once a year with the participation of doctors: a therapist, a neurologist, an otolaryngologist, and, if indicated, other specialists.
Workers who show even initial signs of vibration disease are transferred to work that is not associated with exposure to vibration and noise.
To prevent vibration disease, it is recommended to periodically use workers in other operations that do not involve exposure to vibration. For this purpose, complex teams are being introduced at repair enterprises, where its members alternate jobs when performing production processes.
Vibration of a general and local nature has a certain effect on human body. This has been proven through multiple studies and experimental tests. Therefore, there are certain acceptable vibration levels for industrial or domestic levels. It is very important to take them into account.
The maximum permissible vibration standards in the workplace are considered to be those that take into account vibrations and the amplitude of movement of household or industrial equipment for certain period work, taking into account the transfer of vibrations to other objects, surfaces and physical bodies located in the room. Sanitary standards introduce regulated sanitary standards for noise and vibration levels. This takes into account the specific operation of the equipment and its scope of application. Sanitary standards do not regulate vibration changes in self-propelled vehicles or transport, since these objects are in motion and do not have a stationary position during operation.
Vibration regulation and control of vibration changes
Hygienic standards for noise and vibration establish permissible vibration standards, which are calculated based on the design features of the element under study, as well as the nature of its application. Notes and uncertainties in vibration measurements should be addressed to the manufacturer and designer of the machine whose vibration testing has not been validated and accepted by the regulatory community. GOST indicators for vibration standards of smoke exhausters establish the efficiency, reliability and safety of equipment.Sanitary standards for vibration of plunger pumps are needed primarily in order to calculate the maximum safe indicators for the human body, since most of the objects under study are in direct contact with a person and can harm his health if not functioning properly.
the main task all instruments and sensors for measuring vibration vibrations - measure the permissible levels of noise and vibration of equipment that is located near workplaces and has direct contact with individuals. Vibration testing should take into account the fact that human contact with a machine in production is systematic and should not contribute to the development in the body of specific occupational diseases or deformations during work, which may subsequently affect the productivity and performance of a person.
Among the most noticeable benefits of checking the permissible vibration levels of equipment, it is worth highlighting the following:
- Regular monitoring and systematic measurements of changes in vibration indicators significantly improve the work process and optimize the labor system. Since any changes in vibration indicators can affect the productivity, performance and physical health of employees.
- Hygienic standards for vibration of pipelines in production allow us to draw up a correct picture of working conditions and take measures to improve or optimize them.
- Checking indicators and establishing vibration standards in residential buildings is carried out not only at the production level, but also in the domestic sphere. Knowing the level of vibrations allows you to take a more competent approach to arranging your home life, as well as protect yourself from the possible influence of vibrations on the body.
- Local and global inspections of vibration standards at enterprises allow us to get an overall picture of the sanitary working conditions in a certain area, and take measures to improve equipment or modernize work facilities.
What do regulatory documents reflect?
Based on the results of vibration checks and calculations, the sanitary group provides regulatory documentation and a complete schedule of measurements and vibration indicators of equipment in production or in the domestic sphere. The regulatory package of documents contains the following information:1) Full information on the frequency analysis of vibrations of equipment, taking into account the features of their design, operation and placement in a certain area in the area being inspected. All measurements and indicators must be based on the regulatory framework and not exceed permissible level vibrations.
2) Integral assessment of the vibration frequency of the object being tested, taking into account the characteristics of the test, the equipment used, as well as the nature of the surfaces of the equipment being tested and the characteristics of its use.
3) Maximum permissible doses of vibrations in the tested area, taking into account the permissible limits and standards of the sanitary group.
Standard indicators provide data on the maximum permissible limits of vibration velocity and vibration acceleration of the equipment or machinery being tested. This takes into account the specifics of its functioning and interaction with individuals.
Based on the results of measurements of vibration indicators, an equivalent indicator of the vibration produced in a specific place is calculated and its relationship with the regulated framework of permissible vibrations for the human body at a certain place of work.
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Why and how is the permissible dose of vibration measured in production?
The dose of vibration is determined by calculating the square of the impact of vibration on the body over a certain period of operation of the element under study. This method calculation allows you to most effectively calculate the permissible limits of vibrations in the workplace. A qualified vibration test of a modern type is capable of analyzing equipment remotely at workplaces where the work schedule is not standardized, and a stationary test of the old type is not able to give adequate results and identify errors.Technical documentation and regulated frameworks that establish the basis for inspection and standards for the use of this or that equipment in production must take into account the length of the working day, as well as the peculiarities of the functioning of the objects being inspected. Upon completion of the inspection, the customer is provided with complete documentation of the studies performed and data on the vibration field of the equipment in the area being tested.
The standards for vibration indicators of hand-held equipment are regulated by GOST 17770-72. The main verified indicators of this type of equipment are:
- indicators of vibration and vibration frequencies in areas of machines that are in direct contact with human hands;
- the force that an employee applies when pressing a certain area of the object being tested during work;
- total weight of the machine and its individual parts, taking into account the specifics self made person with this equipment.
In the process of checking manual machines, attention is paid to the ratio of the mass of the machine and the force of a person pressing on the corresponding area during operation. When checking pneumatic drives, they check the amount of effort that a person applies while working with the equipment.
The force that a person applies when pressing individual parts of a manual machine during work is also a regulated and standardized indicator that determines the quality and efficiency of work. This force should not exceed 200N. In this case, the total weight of the machine being tested, taking into account the efforts made by a person when working with it, should not exceed 100 N.
It is also important to note that when checking vibration indicators, the heating temperature of the equipment being tested is taken into account during operation. The contact surface that comes into contact with human hands should not have a thermal conductivity higher than 0.5 W.
Why is equipment testing necessary?
Exceeding the regulated limits of thermal conductivity and vibration can be detrimental not only to the machine itself (with strong vibrations, parts break, contacts overheat, and individual machine parts fail), but also to the person who is in constant contact with the equipment during working hours. Vibrations can have a destructive effect on the human body and contribute to the development of occupational diseases.The EcoTestExpress laboratory offers a comprehensive vibration test of equipment or household appliances, which will allow you to extend the life of your equipment and maintain your health. We use only modern and high-precision equipment, which allows us to check all tested elements to the maximum extent possible. short time. Based on the results of the inspection, the customer is provided with a complete picture production process and the functioning of its individual elements. All calculations and data are entered into a regulatory journal. It is also subsequently handed over to the customer for further analysis and changes to the work or household process.
You can submit a request for a vibration level assessment using the form below.
Vibration standards are very important when diagnosing rotary equipment. Dynamic (rotary) equipment occupies large percentage in the total volume of equipment of an industrial enterprise: electric motors, pumps, compressors, fans, gearboxes, turbines, etc. The task of the chief mechanic and chief power engineer service is to determine with sufficient accuracy the moment when carrying out maintenance work is technically, and most importantly, economically justified. One of the best methods for determining the technical condition of rotating components is vibration monitoring with BALTECH VP-3410 vibration meters or vibration diagnostics using BALTECH CSI 2130 vibration analyzers, which allow reducing unreasonable costs of material resources for operation and Maintenance equipment, as well as assess the likelihood and prevent the possibility of unscheduled failure. However, this is only possible if vibration monitoring is carried out systematically, then it is possible to detect in time: wear of bearings (rolling, sliding), shaft misalignment, rotor imbalance, problems with machine lubrication and many other deviations and malfunctions.
GOST ISO 10816-1-97 establishes two main criteria for the general assessment of the vibration state of machines and mechanisms of various classes, depending on the power of the unit. According to one criterion, I compare the absolute values of the vibration parameter in a wide frequency band, and according to another, changes in this parameter.
Resistance to mechanical deformation (for example, falling).
| vrms, mm/s | Class 1 | Class 2 | Class 3 | Class 4 |
| 0.28 | A | A | A | A |
| 0.45 | ||||
| 0.71 | ||||
| 1.12 | B | |||
| 1.8 | B | |||
| 2.8 | WITH | B | ||
| 4.5 | C | B | ||
| 7.1 | D | C | ||
| 11.2 | D | C | ||
| 18 | D | |||
| 28 | D | |||
| 45 |
The first criterion is the absolute vibration values. It is associated with defining boundaries for absolute value vibration parameters established from the conditions of permissible dynamic loads on bearings and permissible vibration, transmitted outward to the supports and foundation. The maximum parameter value measured at each bearing or support is compared with the zone boundaries for that machine. In the devices and programs of the BALTECH company, you can specify (select) your vibration standards or accept the international one included in the Proton-Expert program from the list of standards.
Class 1 - Separate parts of engines and machines connected to the unit and operating in their normal mode (serial electric motors with a power of up to 15 kW are typical machines in this category).
Class 2 - Medium-sized machines (typical electric motors with power from 15 to 875 kW) without special foundations, rigidly mounted engines or machines (up to 300 kW) on special foundations.
Class 3 - Powerful prime movers and other powerful machines with rotating masses mounted on massive foundations that are relatively rigid in the direction of vibration measurement.
Class 4 - Powerful prime movers and other powerful machines with rotating masses mounted on foundations that are relatively compliant in the direction of vibration measurement (for example, turbogenerators and gas turbines with power output greater than 10 MW).
To qualitatively assess machine vibration and make decisions on necessary actions in a specific situation, the following status zones have been established.
- Zone A- As a rule, new machines that have just been put into operation fall into this zone (the vibration of these machines is normalized, as a rule, by the manufacturer).
- Zone B- Machines falling into this zone are usually considered suitable for further operation without any time limit.
- Zone C- Machines falling into this zone are generally considered unsuitable for long-term continuous operation. Typically, these machines can operate for a limited period of time until a suitable opportunity for carrying out repair work.
- Zone D- Vibration levels in this area are generally considered to be severe enough to cause damage to the machine.
The second criterion is the change in vibration values. This criterion is based on comparing the measured vibration value during steady state operation of the machine with a preset value. Such changes may be rapid or gradually increasing over time and indicate early damage to the machine or other problems. A vibration change of 25% is usually considered significant.
If significant changes in vibration are detected, it is necessary to investigate the possible causes of such changes in order to identify the causes of such changes and determine what measures need to be taken in order to prevent the occurrence of dangerous situations. And first of all, it is necessary to find out whether this is a consequence of incorrect measurement of the vibration value.
Users of vibration measuring equipment and devices themselves often find themselves in a sticky situation when they try to compare readings between similar devices. Initial surprise often gives way to indignation when a discrepancy in readings is discovered that exceeds the permissible measurement error of the instruments. There are several reasons for this:
It is incorrect to compare the readings of devices whose vibration sensors are installed in different places, even close enough;
It is incorrect to compare the readings of devices whose vibration sensors have various ways fastening to an object (magnet, pin, probe, glue, etc.);
It must be taken into account that piezoelectric vibration sensors are sensitive to temperature, magnetic and electric fields and are capable of changing their electrical resistance in case of mechanical deformation (for example, a fall).
At first glance, comparing specifications two devices, we can say that the second device is significantly better than the first. Let's take a closer look:
For example, consider a mechanism whose rotor speed is 12.5 Hz (750 rpm), and the vibration level is 4 mm/s, the following instrument readings are possible:
a) for the first device, the error at a frequency of 12.5 Hz and a level of 4 mm/s, in accordance with technical requirements, is no more than ±10%, i.e. the device reading will be in the range from 3.6 to 4.4 mm/s;
b) for the second, the error at a frequency of 12.5 Hz will be ±15%, the error at a vibration level of 4 mm/s will be 20/4*5=25%. In most cases, both errors are systematic, so they are arithmetically summed. We obtain a measurement error of ±40%, i.e. the device reading is probably from 2.4 to 5.6 mm/s;
At the same time, if vibration is assessed in the vibration frequency spectrum of the mechanism components with a frequency below 10 Hz and above 1 kHz, the readings of the second device will be better compared to the first.
It is necessary to pay attention to the presence of an RMS detector in the device. Replacing the RMS detector with an average or amplitude value can lead to an additional error of up to 30% when measuring a polyharmonic signal.
Thus, if we look at the readings of two instruments when measuring the vibration of a real mechanism, we can find that the real error in measuring the vibration of real mechanisms under real conditions is no less than ± (15-25)%. It is for this reason that it is necessary to be careful when choosing a manufacturer of vibration measuring equipment and even more attentive to the constant improvement of qualifications of a vibration diagnostics specialist. Since, first of all, how exactly these measurements are carried out, we can talk about the result of the diagnosis. One of the most effective and universal devices for vibration control and dynamic balancing of rotors in their own supports is the Proton-Balance-II kit, produced by BALTECH in standard and maximum modifications. Vibration standards can be measured by vibration displacement or vibration velocity, and the error in assessing the vibration state of equipment has a minimum value in accordance with the international standards IORS and ISO.
24.10.2017, 17:42
One of the unpleasant factors that can affect both the well-being of employees and, ultimately, their professional capabilities is vibration in the workplace. We tell you how the law regulates this issue.
Where are the workplace vibration standards established?
One of the most important aspects of labor protection is the vibration that employees experience while performing their work functions.
In practice, industrial vibration of workplaces can be associated with:
- with vehicles (driving and/or escort);
- with the operating features of production equipment, mechanisms, etc.
Since 2017, the level of vibration in the workplace has been established by Section IV of SanPiN 2.2.4.3359-16, which is called “Sanitary and epidemiological requirements for physical factors in the workplace.” It was approved by Decree of the Chief State Sanitary Doctor of the Russian Federation dated June 21, 2016 No. 81.
Types of vibration
From the point of view of occupational hygiene, the specified SanPiN divides vibration into several types, which are disclosed below in the table.
Types and types of vibration
| Criterion | Types and description |
| By method of transfer to employee | 1. General Affects the body through various supporting surfaces. For someone standing - through the feet, for someone sitting - through the buttocks, and for someone lying down - through the back and head. 2. Local (local) vibration in the workplace In case of sedentary work, it passes through the hands, feet and forearms, which are in contact with vibrating work surfaces. |
| By source | 1. Local from hand mechanized tools (with engines), manual control devices for machines and equipment. 2. Local from hand-held non-mechanized tools (for example, straightening hammers), fixtures and workpieces. 3. General vibration of the 1st category - from railway transport, the crew of aircraft, self-propelled and trailed vehicles, Vehicle when driving (including during road construction). Sources:
4. General vibration of the 2nd category is transport and technological vibration, when the machine moves along specially prepared surfaces of production premises, industrial sites, and mine workings. Sources:
5. General vibration of the 3rd category is technological vibration from stationary machines or goes to workplaces where there are no sources of vibration. Sources:
|
In this case, the general vibration of the 3rd category at the site of action is:
- in a permanent work area;
- in warehouses, canteens, service rooms, duty rooms and other industrial premises where there are no machines with vibration;
- in plant management premises, design bureaus, laboratories, training centers, computer centers, health centers, office premises, workrooms, etc. for mental work personnel.
Vibration indicators
From a scientific point of view, sanitary standards for workplace vibration are based on the following indicators:
- corrected vibration acceleration (aw, m s-2);
- adjusted vibration acceleration level (Law, dB);
- equivalent vibration acceleration.
As a result, vibration assessment in the workplace is carried out on the basis of complex formulas and corresponding calculations:
Vibration measurement
To make a correct measurement of vibration in the workplace, special techniques are used that have been certified. In this case, the main device - a vibrometer - must meet 2 conditions:
1. Meets the requirements of GOST ISO 8041-2006 “Vibration. Impact of vibration on humans. Measuring instruments".
2. Equipped with octave and one-third octave filters of class 1 according to the national standard of the Russian Federation (GOST R 8.714-2010 (IEC 61260:1995) “Octave and sub-octave bandpass filters. Technical requirements and test methods.”
Permissible vibration standards
The table below shows the limits of permissible vibration in the workplace.
Vibration limits in the working area
As you can see, vibration that affects an employee is checked using the integral assessment method based on the equivalent corrected level of vibration acceleration, taking into account the time of exposure to vibration.
Please note that these requirements for vibration in workplaces are relevant both for a 40-hour work week and for a shortened working day.
You cannot work with local vibration with current root-mean-square levels that exceed the norm by more than 12 dB (4 times) according to the integral assessment.
In addition, it is impossible to work with general vibration with current root-mean-square levels above the norm by 24 dB (8 times) according to the integral assessment.
Vibration regulation is carried out in two directions:
I direction – sanitary and hygienic;
II direction – technical (equipment protection).
When hygienic standardization of vibrations is guided by the following regulatory documents:
GOST 12.1.012-90 SSBT. Vibration safety;
SN 2.2.4/2.1.8.566-96. Industrial vibration, vibration in residential and public buildings. Sanitary standards: approved. Resolution of the State Committee for Sanitary and Epidemiological Supervision of Russia dated October 31, 1996 N 40.
The following criteria are introduced for assessing the adverse effects of vibration in accordance with the above classification:
· the “safety” criterion, ensuring the non-impairment of the operator’s health, assessed by objective indicators, taking into account the risk of occurrence of occupational diseases and pathologies provided for by the medical classification, and also excluding the possibility of traumatic or emergency situations arising due to exposure to vibration. This criterion is met by the sanitary and hygienic standards established for category 1;
· the criterion “limit of reduction in labor productivity”, which ensures the maintenance of the operator’s standard labor productivity, which does not decrease due to the development of fatigue under the influence of vibration. This criterion is ensured by compliance with the standards established for categories 2 and 3a;
· “comfort” criterion, providing the operator with a feeling of comfortable working conditions during complete absence interfering effects of vibration. This criterion meets the standards established for categories 3b and 3c.
Indicators of vibration load on the operator are formed from following parameters:
For sanitary standardization and control, the root mean square values of vibration acceleration a or vibration velocity V are used, as well as their logarithmic levels in decibels;
When assessing the vibration load on the operator, the preferred parameter is vibration acceleration.
The normalized frequency range is set:
For local vibration in the form of octave bands with geometric mean frequencies 1; 2; 4; 8; 16; 31, 5; 63; 125; 250; 500; 1000 Hz;
For general vibration - octave and 1/3 octave bands with geometric mean frequencies of 0.8; 1.0; 1.25; 1.6; 2.0; 2.5; 3.15; 4.0; 5.0; 6.3; 8.0; 10.0; 12.5; 16; 20; 25; 31.5; 40; 50; 63; 80 Hz.
Along with the vibration spectrum, a single-numeric parameter can be used as a standardized indicator of the vibration load on the operator at workplaces: the frequency-corrected value of the controlled parameter (vibration velocity, vibration acceleration or their logarithmic levels). In this case, the unequal physiological impact on humans of vibration of different frequencies is taken into account by weighting coefficients, the values of which are given in the above-mentioned regulatory documents.
In case of non-constant vibration, the standard vibration load on the operator is the single-digit standard values of the vibration dose or the equivalent time-corrected exposure value of the controlled parameter.
Basic methods of combating vibrations of machines and equipment.
1. Reducing vibrations by influencing the source of excitation by reducing or eliminating driving forces, for example, replacing cam and crank mechanisms with uniformly rotating ones, as well as mechanisms with hydraulic drives, etc.
2. Detuning from the resonance mode by rationally choosing the mass or rigidity of the oscillating system.
3. Vibration damping. This is the process of reducing the level of vibration of a protected object by converting the energy of mechanical vibrations into thermal energy. To do this, the vibrating surface is covered with a material with high internal friction (rubber, cork, bitumen, felt, etc.). Vibrations propagating through communications (pipelines, channels) are weakened by connecting them through sound-absorbing materials (rubber and plastic gaskets). Anti-noise mastics applied to the metal surface are widely used.
4. Dynamic vibration damping is most often carried out by installing units on foundations. For small objects, a massive base plate is installed between the base and the unit.
5. Changes in the structural elements of machines and building structures.
6. When working with hand-held mechanized electric and pneumatic tools, personal protective equipment is used to protect hands from vibration. These include mittens, gloves, as well as vibration-proof pads or plates that are equipped with fastenings in the hand.
In Fig. 27 provides a classification of methods and means of collective protection against vibration.
Rice. 27. Classification of methods and means of vibration protection
Question No. 57.
Industrial microclimate (meteorological conditions)– the climate of the internal environment of industrial premises is determined by the combination of temperature, humidity and air speed acting on the human body, as well as the temperature of surrounding surfaces, thermal radiation and atmospheric pressure. Microclimate regulation is carried out in accordance with the following regulatory documents: SanPin 2.2.4.548-96. Hygienic requirements for the microclimate of industrial premises; GOST 12.1.005-88. SSBT. General sanitary and hygienic requirements for the air in the working area.
Two types of standards have been established: 1. Optimal microclimatic conditions are established according to the criteria of the optimal thermal and functional state of a person; they provide a feeling of thermal comfort and create the preconditions for high level performance. 2. In cases where, due to technological requirements, technical and economically justified reasons, optimal microclimatic conditions cannot be ensured, standards are established acceptable values of microclimate indicators. They are established according to the criteria of the permissible thermal and functional state of a person for an 8-hour period work shift. Acceptable microclimate parameters do not cause damage or health problems, but can lead to general and local sensations of thermal discomfort, strain on thermoregulation mechanisms, deterioration of well-being and decreased performance. According to GOST 12.1.005-88, acceptable indicators are established differentially for permanent and non-permanent workplaces.
Optimal microclimate parameters in production premises are provided by air conditioning systems, and valid parameters – conventional systems ventilation and heating.
Thermoregulation– a set of physiological and chemical processes in the human body aimed at maintaining a constant body temperature. Thermoregulation ensures a balance between the amount of heat continuously generated in the body and excess heat continuously released into the environment, i.e. maintains the body's thermal balance: Q ext =Q department .
Heat exchange between a person and his environment is carried out using the following mechanisms due to: infrared radiation, which emits or receives the surface of the body ( R ); convection (WITH ), i.e. through heating or cooling the body with air washing the surface of the body; heat transfer ( E ), conditioned evaporation of moisture from the surface of the skin, mucous membranes of the upper respiratory tract, lungs. Q department = ± R ± C–E.
Under normal conditions, with weak air movement, a person at rest loses about 45% of all thermal energy generated by the body, convection, as a result of thermal radiation – up to 30% and evaporation – up to 25%. At the same time, over 80% of the heat is transferred through the skin, approximately 13% – through the respiratory organs, about 7% of the heat is spent on warming the food, water and inhaled air. When the body is at rest and at an air temperature of 15 0 C, sweating is insignificant and amounts to approximately 30 ml per 1 hour. high temperature(30 o C and above), especially when performing heavy physical work, sweating can increase tenfold. Thus, in hot shops with intense muscle work, the amount of sweat released is 1...1.5 l/h, the evaporation of which requires 2500...3800 kJ.
In order to ensure effective heat exchange between a person and the environment sanitary and hygienic standards for microclimate parameters are established at the workplace, namely: air temperature; air speed; relative humidity; surface temperature. Conditions 1 and 2 determine convective heat transfer; 1 and 3 – sweat evaporation; 4 – thermal radiation. The standards for these parameters are set differentially depending on the severity of the work performed.
Under tactile Sensitivity refers to the sensation of touch and pressure. On average, there are about 25 receptors per 1 cm2. The absolute threshold of tactile sensitivity is determined by the minimum pressure of an object on the skin surface at which a barely noticeable sensation of touch is observed. Sensitivity is most strongly developed in the parts of the body furthest from its axis. Characteristic feature tactile analyzer is the rapid development of adaptation, that is, the disappearance of the feeling of touch or pressure. Thanks to adaptation, a person does not feel the touch of clothing on the body. Feeling pain perceived by special receptors. They are scattered throughout our body; there are about 100 such receptors per 1 cm 2 of skin. The feeling of pain occurs as a result of irritation not only of the skin, but also of a number of internal organs. Often the only signal warning of trouble in the condition of one or another internal organ is pain. Unlike other sensory systems, pain provides little information about the world around us, but rather communicates internal dangers threatening our body. If pain were not a warning, then even with the most ordinary actions we would often cause harm to ourselves. The biological meaning of pain is that, being a danger signal, it mobilizes the body to fight for self-preservation. Under the influence of a pain signal, the work of all body systems is restructured and its reactivity increases.