Vibration level in the workplace. Rationing of production vibrations

Noise worsens working conditions, has a harmful effect on the human body. With prolonged exposure to noise on the body, undesirable phenomena occur: visual acuity and hearing decrease, blood pressure rises, and attention decreases. Strong prolonged noise can cause functional changes in the cardiovascular and nervous systems. Noise level requirements are established by GOST 12.1.003-83 Noise. General safety requirements (with amendment No. 1), SN 2.2.4 / 2.1.8.562 - 96. Noise at workplaces, in residential and public buildings and in residential areas.

Sound as a physical process is a wave motion of an elastic medium. A person feels mechanical vibrations with frequencies from 20 to 20,000 Hz.

Noise is a disorderly combination of sounds of varying frequency and intensity.

The main characteristics of sound are:

oscillation frequency (Hz); sound pressure (Pa); sound intensity (W/m2). V sound = 344 m/s.

Sound pressure- the variable component of air pressure, arising due to vibrations of the sound source, superimposed on atmospheric pressure.

Quantification of sound pressure is estimated by RMS value.

where T= 30-100 ms.

During the propagation of sound waves, there is a transfer of sound energy, the magnitude of which is determined by the intensity of the sound.

Sound intensity- sound power per unit area, transmitted in the direction of propagation of the sound wave.

Sound intensity is related to sound pressure by the expression

where P - RMS sound pressure;

V is the root-mean-square value of the vibrational velocity of particles in a sound wave.

In a free sound field, the sound intensity can be expressed by the formula

where r- medium density, with- the speed of sound in the medium;

rwith- acoustic resistance of the environment.

The minimum sound pressure and minimum intensity of sounds barely perceptible by the human hearing aid is called threshold.

The sensitivity of the human hearing aid is greatest in the range of 2000-5000 Hz. For the reference - a sound with a frequency of 1000 Hz. At this frequency, the hearing threshold in terms of intensity I 0 = 10-12 W/m2, and the corresponding sound pressure p0 = 2 10-5 Pa. Threshold of pain I max =10 W/m2. The difference is 1013 times.

It is customary to measure and evaluate the relative levels of sound intensity and sound pressure in relation to threshold values, expressed in logarithmic form.

Intensity level: LI= 10 log I/I0 ;

Sound pressure level: lp= 20 lg P/P0-

The audible range is 0 - 140 dB.

The characteristic of the noise source itself is its sound power R- the total amount of sound energy radiated into the surrounding space per second.

Noise source sound power level

LP = 10 lg P/P0,

where R0 - threshold value = 10-12W.

General safety requirements provide for the classification of noise, permissible noise levels in the workplace, general requirements for the noise characteristics of machines and noise measurement methods.

The total sound pressure level during the simultaneous action of two identical sources with levels L1 and L2 in dB can be determined by the formula

Lcommon = L1 + L,

where L1 is the larger of the two summary equations,

L is the correction for the overall noise equation.

If N sources are the same, then Lcommon = L1 + 10 lgL.

Noise in which sound energy is distributed over the entire spectrum is called broadband. If a sound of a certain frequency is heard, then the noise is called tonal. Noise perceived as separate impulses (shocks) is called impulsive.

Sound power and sound pressure as variables can be represented as a sum of sinusoidal oscillations of different frequencies.

The dependence of the RMS values ​​of these components (or their levels) on the frequency is called noise frequency spectrum.

Typically, the frequency spectrum is determined empirically, finding sound pressures not for each individual frequency, but for octave (or one-third octave) frequency bands.

Geometric mean octave bandwidth f cf is defined as:

moreover, for octave bands f b/ f k = 2,

for one-third octave f b / f k = 1.26.

Noise frequency spectra are obtained using noise analyzers, which are a set of electrical filters that transmit an electrical sound signal in a certain frequency band (bandwidth).

According to temporal characteristics, noise is divided into permanent and fickle.

Fickle there are:

- fluctuating over time, the sound level of which changes continuously with time;

- intermittent, the sound level of which drops sharply to the level of background noise;

- impulse, consisting of signals less than 1s.

Noise regulation

To assess the noise, the frequency spectrum of the measured sound pressure level, expressed in dB, in octave frequency bands, is used, which is compared with the limiting spectrum, normalized in GOST 12.1.003-83 SSBT. Noise. General safety requirements (as amended No. 1).

For an approximate assessment of the noise situation, it is allowed to use a single-number characteristic - the so-called sound level, dBA, measured without frequency analysis on the A scale of the noise meter, which approximately corresponds to the numerical characteristic of human hearing. The human hearing aid is more sensitive to high-frequency sounds, so the normalized sound pressure values ​​decrease with increasing f. For constant noise, the normalized parameters are - permissible sound pressure levels and sound levels at workplaces (according to GOST 12.1.003-83).

For intermittent noise, the normalized parameter is the equivalent sound level LA units in dB on the A scale.

The equivalent sound level is the value of the sound level of constant noise, which, within the regulated time interval T = t2 - t1, has the same root mean square value of the sound level as the noise in question.

Direct noise levels are measured by special integrating sound level dosimeters.

If the noise is tonal or impulse, then the permissible levels should be taken 5 dBA less than the values ​​\u200b\u200bspecified in GOST.

The classification of means and methods of noise protection is given in GOST 12.1.029 - 80. Means and methods of noise protection. Classification.

Noise protection methods are based on:

1. noise reduction at the source;

2. reduction of noise on the way of its propagation from the source;

3. the use of PPE against noise (PPE - personal protective equipment).

Methods to reduce noise in the propagation path:- achieved through construction and acoustic measures. Methods for reducing noise along the path of its propagation - casings, screens, soundproof partitions between rooms, sound-absorbing linings, noise silencers. Acoustic treatment of premises refers to the lining of part of the internal surfaces of the fences with sound-absorbing materials, as well as the placement of piece absorbers in the premises.

The greatest effect is in the zone of reflected sound (60% of the total area). Efficiency - 6-8 dB.

Noise reduction method sound absorption is based on the transition of sound vibrations of air particles into heat due to friction losses in the pores of the sound-absorbing material. The more sound energy is absorbed, the less it reflects. Therefore, to reduce noise in the room, it is acoustically treated by applying sound-absorbing materials to the internal surfaces, as well as placing piece sound absorbers in the room.

The efficiency of a sound-absorbing device is characterized by the sound absorption coefficient a, which is the ratio of the absorbed sound energy E absorption to the falling E fall,

a= E absorption / E pad.

Sound-absorbing devices are porous, porous-fibrous, membrane, layered, volumetric, etc.

Soundproofing is one of the most effective and common methods for reducing industrial noise along its path.

With the help of soundproof barriers, you can reduce the noise level by 30-40 dB.

The method is based on the reflection of a sound wave incident on a fence. However, the sound wave is not only reflected from the fence, but also penetrates through it, which causes the fence to vibrate, which itself becomes a noise source. The higher the surface area of ​​the fence, the more difficult it is to bring it into an oscillatory state, therefore, the higher its soundproofing ability. Therefore, effective soundproofing materials are metals, concrete, wood, dense plastics, etc.

To assess the soundproofing ability of the fence, the concept of sound transmission has been introduced. t, which is understood as the ratio of the sound energy that has passed through the fence to the incident on it.

The reciprocal of sound transmission is called sound insulation (dB), it is related to sound transmission by the following formula

R = 10 lg (1/ t) .

Vibration

1. Vibration can cause functional disorders of the nervous and cardiovascular systems, as well as the musculoskeletal system.

In accordance with GOST 24346-80 (STSEV 1926-79) Vibration. Terms and Definitions. vibration is understood as the movement of a point or a mechanical system, in which there is an alternate increase and decrease in time of the values ​​of at least one coordinate.

It is customary to distinguish between general and local vibration. The general vibration acts on the entire human body through the supporting surfaces - the seat, the floor; local vibration has an effect on individual parts of the body.

Vibration can be measured using both absolute and relative parameters.

The absolute parameters for measuring vibration are vibration displacement, vibration velocity and vibration acceleration.

The main relative vibration parameter is the level of vibration velocity, which is determined by the formula

LV = 10 lg V2 / V02 = 20 lg V / V0,

where V- vibration velocity amplitude, m/s;

V0 = 5*10-8 m/s - threshold value of vibration velocity.

In the frequency (spectral) analysis, kinematic parameters are normalized: root-mean-square values ​​of vibration velocity V(and their logarithmic levels LV) or vibration acceleration a - for local vibrations in octave frequency bands; for general vibration in octave and 1/3 octave frequency bands.

In accordance with GOST 12.1.012-90 SSBT. vibration safety. General safety requirements There are the following types of general vibration - three categories:

1- transport vibration;

2- transport and technological vibration;

3- technological vibration.

Technological vibration, in turn, is divided into four types:

3a - at permanent workplaces in industrial premises, central control posts, etc.;

3b - at workplaces in office premises on ships;

3c - at workplaces in warehouses, household and other industrial premises;

3d - at workplaces in plant management, design bureaus, laboratories, training centers, computer centers, office premises and other premises for mental work.

General vibration is normalized in active bands with geometric mean frequencies of 1, 2, 4, 8, 16, 32, 63 Hz and in 1/3 octave bands with geometric mean frequencies of 0.8; 1.0; 1.25; 1.6;... 40; fifty; 63; 80 Hz.

Local vibration is normalized in active bands with geometric mean frequencies of 8, 16, 32, 63, 120, 250, 500, 1000 Hz.

Vibration is normalized in the direction of three orthogonal coordinate axes X, Y, Z for general vibration, where Z is the vertical axis, and Y, X are horizontal; and XP , YP, ZP - for local vibration, where XP coincides with the axis of the places of coverage of the vibration source, and the ZP axis lies in the plane formed by the XP axis and the direction of supply or application of force.

Permissible values ​​​​of the parameters of transport, transport-technological and technological vibration are given in GOST 12.1.012-90.

At integral assessment vibration by frequency, the normalized parameter is the corrected value of the controlled parameter V (vibration velocity or vibration acceleration), measured using special filters or calculated using the formulas given in GOST 12.1.012-90.

Dose approach allows you to evaluate the cumulation of the impact of the factor at work and outside of working hours.

When assessing vibration dose the normalized parameter is equivalent adjusted valueVECV, determined by the formula

VEKV =,

where is the vibration dose, which is calculated by the expression

where V(t) is the instantaneous corrected value of the vibration parameter at the moment of time t, obtained using a corrective filter with a characteristic in accordance with the table given in the standard, t- exposure time of vibration per shift.

Technical requirements and measuring instruments correspond to the noise and vibration meter VShV - 001; as well as foreign vibroacoustic sets by Brüel & Kjær (Denmark).

General vibration measurement points are selected at workplaces (or in working service areas), and for self-propelled and transport-technological machines - at working areas and seats of drivers and personnel. Measurements are carried out in a typical technological mode of operation of the equipment (machine).

The total time of work in contact with manual machines that cause vibration should not exceed 2/3 of the shift. At the same time, the duration of a one-time exposure to vibration, including micropauses that are included in this operation, should not exceed 15-20 minutes.

The total time of work with a vibratory tool is about 8 hours. working day and 5-day week should not exceed 30% of shift working time for a fitter, 22% for an electrician; for the installer 15%.

When working with a vibrating tool, the mass of equipment held by hands should not exceed 10 kg, and the pressing force should not exceed 196 N.

The main methods of combating vibrations of machines and equipment are:

Reducing vibration by acting on the source of excitation (by reducing or eliminating driving forces);

Detuning from the resonance mode by a rational choice of the mass and rigidity of the oscillating system; (either by changing the mass or stiffness of the system, or at the design stage - a new mode w).

Vibration damping is an increase in the mechanical active impedance of oscillating structural elements by increasing dissipative forces during vibrations with frequencies close to resonant ones.

Dissipative forces are forces that arise in mechanical systems, the total energy of which (the sum of kinetic and potential energy) decreases during movement, turning into other types of energy.

A dissipative system, for example, is a body moving on the surface of another body in the presence of friction (vibration coatings - the viscosity of materials).

Dynamic vibration damping - (additional reactive impedances) - connection to a protected object of systems, the reaction of which reduces the vibration amplitude at the points of connection of the system;

Changing structural elements and building structures (increasing the rigidity of the system - the introduction of stiffeners).

Vibration isolation - this method consists in reducing the transmission of vibrations from the excitation source to the protected object using devices placed between them. (Rubber, spring vibration isolators).

Active vibration protection.

General requirements for PPE against vibrations are defined in GOST 12.4.002-97 SSBT. Personal protective equipment for hands against vibration. General technical requirements and GOST 12.4.024 - 76. Special anti-vibration footwear.

Requirements for lighting industrial premises and workplaces. Characteristics of natural and artificial lighting. Illumination standards. Choice of light sources, fixtures. Organization of operation of lighting installations.

Properly designed and executed lighting ensures the possibility of normal production activities.

Of the total amount of information, a person receives about 80% through the visual channel. The quality of the incoming information largely depends on lighting: unsatisfactory quantitatively or qualitatively, it not only tires the eyesight, but also causes fatigue of the body as a whole. Irrational lighting can also cause injuries: poorly lit hazardous areas, blinding light sources and glare from them, sharp shadows impair visibility to such an extent that it causes a complete loss of orientation for workers.

In case of unsatisfactory lighting, in addition, labor productivity decreases and product defects increase.

Lighting is characterized by quantitative and qualitative indicators.

Quantitative indicators include: luminous flux, luminous intensity, illumination and brightness.

The part of the radiant flux that is perceived by human vision as light is called the luminous flux Ф and is measured in lumens (lm).

Luminous flux Ф - the flux of radiant energy, estimated by visual sensation, characterizes the power of light radiation.

The unit of luminous flux - lumen (lm) - is the luminous flux emitted by a point source with a solid angle of 1 steradian at a light intensity of 1 candela.

The luminous flux is defined as a quantity not only physical, but also physiological, since its measurement is based on visual perception.

All light sources, including lighting devices, radiate a luminous flux into space unevenly, therefore, the value of the spatial density of the luminous flux is introduced - luminous intensity I.

The luminous intensity I is defined as the ratio of the luminous flux dФ, emanating from the source and propagating uniformly within an elementary solid angle, to the value of this angle.

The unit of light intensity is the candela (cd).

One candela is the intensity of light emitted from a surface of 1/6 10 5 m 2 of total radiation (state standard of light) in the perpendicular direction at the solidification temperature of platinum (2046.65 K) at a pressure of 101325 Pa.

Illuminance E - the ratio of the luminous flux dФ incident on the surface element dS, to the area of ​​​​this element

Lux (lx) is the unit of illumination.

The brightness L of a surface element dS at an angle relative to the normal of this element is the ratio of the luminous flux d2Ф to the product of the solid angle dΩ, β of which it propagates, the area dS and the cosine of the angle?

L = d2Ф/(dΩ dS cos θ) = dI/(dS cosθ),

where dI is the intensity of the light emitted by the surface dS in the direction θ.

The reflection coefficient characterizes the ability to reflect the light flux incident on it. It is defined as the ratio of the light flux reflected from the surface Fotr. to the flow Fpad falling on it..

The main quality indicators of lighting include the pulsation coefficient, the indicator of blindness and discomfort, the spectral composition of light.

To assess the conditions of visual work, there are such characteristics as the background, the contrast of the object with the background.

When illuminating industrial premises, natural lighting is used, created by the light of the sky, penetrating through the light openings in the external enclosing structures, artificial, carried out by electric lamps and combined, in which natural lighting that is insufficient according to the norms is supplemented by artificial light.

Natural lighting of the room through the light openings in the outer walls is called lateral, and the lighting of the room through the lanterns, light openings in the walls at the places of the height difference of the building is called the top. The combination of overhead and side daylight is called combined daylight.

The quality of natural lighting is characterized by the coefficient of natural illumination (KEO). It represents the ratio of natural illumination, created at some point in a given plane indoors by sky light, to the value of outdoor horizontal illumination, created by the light of a completely open sky; expressed as a percentage.

According to the design, artificial lighting can be of two systems - general and combined. In the general lighting system, luminaires are placed in the upper zone of the room evenly (general uniform lighting) or in relation to the location of the equipment (general localized lighting). In the combined lighting system, local lighting is added to the general lighting, created by lamps that concentrate the luminous flux directly at the workplace.

The use of one local lighting is not allowed.

According to the functional purpose, artificial lighting is divided into the following types: working, security, evacuation, security and duty.

Working lighting - lighting that provides normalized lighting conditions (illuminance, lighting quality) in rooms and in places where work is performed outside buildings.

Safety lighting - lighting arranged to continue working in case of emergency shutdown of working lighting. This type of lighting should create on working surfaces in industrial premises and on the territories of enterprises that require maintenance when working lighting is turned off, the smallest illumination in the amount of 5% of the illumination normalized for working lighting from general lighting, but not less than 2 lux inside the building and not less than 1 lux for territories of enterprises.

Escape lighting should be provided for the evacuation of people from the premises in case of emergency shutdown of working lighting in places dangerous for the passage of people. It should provide the lowest illumination on the floor of the main passages (or on the ground) and on the steps of the stairs: indoors - 0.5 lux, and in open areas - 0.2 lux.

Safety lighting and evacuation lighting are called emergency lighting. Exit doors of public premises for public purposes, in which there may be more than 100 people, as well as exits from industrial premises without natural light, where there may be more than 50 people at the same time or with an area of ​​​​more than 150 m2, must be marked with signs. Exit signs may be illuminated or non-illuminated, provided that the exit designation is illuminated by emergency lighting fixtures.

Emergency lighting fixtures may be provided for burning, switched on simultaneously with the main lighting fixtures of normal lighting and not burning, automatically switched on when the power supply to normal lighting is interrupted.

Security lighting should be provided along the boundaries of territories protected at night. Illumination should be at least 0.5 lux at ground level in a horizontal plane or at 0.5 m from the ground on one side of a vertical plane perpendicular to the boundary line.

Emergency lighting is provided for non-working hours. Its scope, illumination values, uniformity and quality requirements are not standardized.

The main task of lighting in production is to create the best conditions for vision. This problem can only be solved by a lighting system that meets certain requirements.

Illumination in the workplace should correspond to the nature of visual work, which is determined by the following parameters:

The smallest size of the object of distinction (the object under consideration, its separate part or defect);

Characteristics of the background (the surface adjacent directly to the object of distinction on which it is viewed); the background is considered light - when the surface reflectance is more than 0.4, medium - when the surface reflectance is from 0.2 to 0.4, dark - when the surface reflectance is less than 0.2.

The contrast of the object of distinction with the background K, which is equal to the ratio of the absolute value of the difference between the brightness of the object Lo and the background Lf to the brightness of the background K = |Lo - Lf|/ Lf; the contrast is considered large - at K more than 0.5 (the object and background differ sharply in brightness), medium - at K from 0.2 to 0.5 (the object and background differ markedly in brightness), small - at K less than 0, 2 (object and background differ little in brightness).

It is necessary to ensure a sufficiently uniform distribution of brightness on the work surface, as well as in the surrounding space. If there are surfaces in the field of view that differ significantly from each other in brightness, then when looking from a brightly lit to a dimly lit surface, the eye is forced to readjust, which leads to visual fatigue.

There should be no harsh shadows in the workplace. The presence of sharp shadows creates an uneven distribution of surfaces with different brightness in the field of view, distorts the size and shape of objects of distinction, as a result, fatigue increases, and labor productivity decreases. Particularly harmful are moving shadows, which can lead to injury.

There should be no direct and reflected glare in the field of view. Glitter - increased brightness of luminous surfaces, causing a violation of visual functions (blindness), i.e. deterioration in the visibility of objects.

Direct glare is associated with light sources, reflected glare occurs on a surface with a large reflectance or reflection in the direction of the eye.

The criterion for assessing the blinding effect created by the lighting installation is the blinding index Ro, the value of which is determined by the formula

Rho = (S - 1) 1000,

where S is the glare coefficient equal to the ratio of the threshold brightness differences in the presence and absence of glare sources in the field of view.

The criterion for assessing uncomfortable glare, which causes discomfort with an uneven distribution of brightness in the field of view, is an indicator of discomfort.

The amount of illumination must be constant over time so that eye fatigue does not occur due to re-adaptation. A characteristic of the relative depth of fluctuations in illumination as a result of a change in the time of the luminous flux of light sources is the pulsation coefficient of illumination Kp.

Kp (%) \u003d 100 (Emax - Emin) / 2Esr,

where Еmax, Emin and Еср are the maximum, minimum and average values ​​of illumination for the period of its fluctuation.

For correct color reproduction, the required spectral composition of light should be selected. Correct color reproduction is provided by natural light and artificial light sources with a spectral characteristic close to that of the sun.

Requirements for lighting of premises are established by SNiP 23-05-95 Natural and artificial lighting. For the premises of industrial enterprises, standards have been established for KEO, illumination, permissible combinations of glare indicators and pulsation coefficient. The values ​​of these norms are determined by the category and sub-class of visual work. In total, eight digits are provided - from I; where the smallest size of the object of distinction is less than 0.15 mm, up to VI, where it exceeds 5 mm; Category VII is set for work with luminous materials and products in hot shops, VIII - for general monitoring of the production process. When the distance from the object of distinction to the eye of the worker is more than 0.5 m, the category of work is set depending on the angular size of the object of distinction, determined by the ratio of the minimum size of the object of distinction to the distance from this object to the eyes of the worker. The subclass of visual work depends on the characteristics of the background and the contrast of the object of distinction with the background.

For the premises of residential, public administrative and amenity buildings, standards for KEO, illumination, an indicator of discomfort and a pulsation coefficient of illumination have been established. In cases of special architectural and artistic requirements, cylindrical illumination is also regulated. Cylindrical illumination characterizes the saturation of the room with light. It is calculated by engineering method.

The choice of these norms depends on the category and sub-class of visual work. For such premises, 5 categories of visual work are provided - from A to D.

Visual work belongs to one of the first three categories (depending on the smallest size of the object of distinction), if it consists in distinguishing objects with a fixed and non-fixed line of sight. The subclass of visual work in this case is determined by the relative duration of visual work when the vision is directed to the working surface (%).

Visual work belongs to the category of guides if it consists in reviewing the surrounding space with a very short, episodic distinction between objects. Category G is set at high saturation of the room with light, and category D - at normal saturation.

The norms of natural lighting depend on the light climate in which the administrative region is located. The required value of KEO is determined by the formula

KEO = en mN,

Where N is the number of the natural light supply group, which depends on the implementation of the light openings and their orientation along the horizon;

en - KEO value indicated in the tables of SNiP 23-05-95;

mN - coefficient of light climate.

For lighting production facilities and storage buildings, as a rule, the most economical discharge lamps should be used. The use of incandescent lamps for general lighting is allowed only if it is impossible or technically and economically inexpedient to use discharge lamps.

For local lighting, in addition to discharge light sources, incandescent lamps, including halogen ones, should be used. The use of xenon lamps indoors is not allowed.

For local lighting of workplaces, luminaires with non-translucent reflectors should be used. Local lighting of workplaces, as a rule, should be equipped with dimmers.

In rooms where the occurrence of a stroboscopic effect is possible, it is necessary to turn on neighboring lamps in 3 phases of the supply voltage or connect them to a network with electronic ballasts.

In the premises of public, residential and auxiliary buildings, if it is impossible or technical and economic inexpediency to use discharge lamps, as well as to ensure architectural and artistic requirements, it is allowed to provide incandescent lamps.

The lighting of staircases in residential buildings with a height of more than 3 floors must have automatic or remote control, which ensures that some of the lamps or lamps are turned off at night so that the illumination of the stairs is not lower than the norms of evacuation lighting.

In large enterprises, there should be a specially designated person in charge of lighting operation (engineer or technician).

It is necessary to check the level of illumination at the control points of the production room after the next cleaning of the lamps and replacement of burned-out lamps.

Glasses of light openings should be cleaned at least 4 times a year for rooms with significant dust emissions; for lamps - 4-12 times a year, depending on the nature of the dustiness of the production premises.

Burnt out lamps must be replaced in a timely manner. In installations with fluorescent lamps and DRL lamps, it is necessary to monitor the serviceability of the switching circuits, as well as ballasts.

Vibration regulation is carried out in two directions:

I direction - sanitary and hygienic;

II direction - technical (equipment protection).

When hygienic regulation of vibration is guided by the following regulatory documents:

GOST 12.1.012-90 SSBT. Vibration safety;

CH 2.2.4/2.1.8.566-96. Industrial vibration, vibration in the premises of residential and public buildings. Sanitary standards: approved. Decree of the State Committee for Sanitary and Epidemiological Supervision of Russia dated October 31, 1996 N 40.

The following criteria for assessing the adverse effects of vibration are introduced in accordance with the above classification:

· the “safety” criterion, which ensures the non-violation of the health of the operator, assessed by objective indicators, taking into account the risk of the occurrence of an occupational disease and pathologies provided for by the medical classification, and also excludes the possibility of traumatic or emergency situations due to the impact of vibration. This criterion is met by the sanitary and hygienic standards established for category 1;

· the criterion “limit of decrease in labor productivity”, which ensures the maintenance of the normative labor productivity of the operator, 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;

· the “comfort” criterion, which provides the operator with a feeling of comfortable working conditions in the complete absence of the disturbing effect of vibration. This criterion is met by the standards established for categories 3b and 3c.

Vibration load indicators for the operator are formed from the following parameters:

For sanitary standardization and control, the mean square values ​​of vibration acceleration a or vibration velocity V, as well as their logarithmic levels in decibels, are used;

When evaluating the vibration load on the operator, vibration acceleration is the preferred parameter.

The normalized frequency range is set:

For local vibration in the form of octave bands with average geometric frequencies 1; 2; 4; eight; sixteen; 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; sixteen; 20; 25; 31.5; 40; fifty; 63; 80 Hz.

Along with the vibration spectrum, a one-number parameter can be used as a normalized 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 a person of vibration of different frequencies is taken into account by weighting factors, the values ​​of which are given in the above regulatory documents.

In case of non-constant vibration, the norm of the vibration load on the operator is single-digit standard values ​​of the vibration dose or the equivalent time-corrected value of the controlled parameter.

The main methods of combating vibrations of machines and equipment.

1. Reducing vibrations by acting on 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 regime by a rational choice of the mass or rigidity of the oscillating system.

3. Vibration damping. This is the process of reducing the vibration level of the 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 their docking 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. Changing the structural elements of machines and building structures.

6. When working with a manual mechanized electric and pneumatic tool, personal protective equipment for hands from the effects of vibrations is used. These include mittens, gloves, as well as anti-vibration pads or plates, which are equipped with mounts in the hand.

On fig. 27 shows the classification of methods and means of collective protection against vibration.

Rice. 27. Classification of methods and means of protection against vibration

Question number 57.

Industrial microclimate (meteorological conditions)- the climate of the internal environment of industrial premises, is determined by the combination of temperature, humidity and air velocity acting on the human body, as well as the temperature of the surrounding surfaces, thermal radiation and atmospheric pressure. Rationing of the microclimate 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 of the working area.

There are two types of standards: 1. Optimal microclimatic conditions are established according to the criteria for the optimal thermal and functional state of a person; they provide a sense of thermal comfort and create the prerequisites for a high level of performance. 2. In cases where, due to technological requirements, technical and economically justified reasons, optimal microclimatic conditions cannot be provided, the norms establish admissible values ​​of microclimate indicators. They are established according to the criteria of the permissible thermal and functional state of a person for the period of an 8-hour work shift. Permissible microclimate parameters do not cause damage or health problems, but can lead to general and local sensations of thermal discomfort, tension in thermoregulation mechanisms, deterioration in well-being and decreased performance. According to GOST 12.1.005-88, permissible indicators are set differently for permanent and non-permanent jobs.

The optimal parameters of the microclimate in industrial premises are provided by air conditioning systems, and the permissible parameters are provided by conventional ventilation and heating systems.

thermoregulation- a set of physiological and chemical processes in the human body aimed at maintaining a constant body temperature. Thermoregulation provides a balance between the amount of heat that is continuously generated in the body and the excess heat that is continuously given off to the environment, i.e. maintains the thermal balance of the body: Q ex =Q dep .

Heat exchange between a person and his environment is carried out using the following mechanisms due to: infrared radiation, which radiates or receives the surface of the body ( R ); convection (With ), i.e. through heating or cooling of the body by air washing the surface of the body; heat transfer ( E ) due to evaporation of moisture from the surface of the skin, mucous membranes of the upper respiratory tract, lungs. Q dep = ± R ± C - E.

Under normal conditions, with a weak movement of air, a person at rest loses about 45% of all thermal energy produced 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 heat is given off through the skin, approximately 13% – through the respiratory organs, about 7% of the heat is spent on warming the food, water and inhaled air. At a resting state of the body and at an air temperature of 15 0 C, sweating is insignificant and amounts to approximately 30 ml per 1 hour. At high temperatures (30 o C and above), especially when performing hard physical work, sweating can increase tenfold. So, in hot shops with increased muscular work, the amount of sweat released is 1 ... 1.5 l / h, the evaporation of which takes 2500 ... 3800 kJ.

In order to ensure efficient heat exchange between man 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 - heat 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 on the parts of the body most distant from its axis. A characteristic feature of the 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 cm2 of skin. The feeling of pain arises as a result of irritation not only of the skin, but also of a number of internal organs. Often the only signal that warns of trouble in the state of one or another internal organ is pain. Unlike other sensory systems, pain provides little information about the world around us, but rather informs us of the internal dangers that threaten our body. If the pain did not warn, then even with the most ordinary actions, we would often inflict damage on ourselves. The biological meaning of pain is that, being a signal of danger, it mobilizes the body to fight for self-preservation. Under the influence of a pain signal, the work of all body systems is rebuilt and its reactivity increases.

6.1. CHARACTERISTICS OF VIBRATION PARAMETERS

Vibration is one of the most common harmful production factors in industry, agriculture, and transport; it can have a negative impact on human health and performance, and under certain conditions lead to the development of a vibration disease.

Vibration- these are complex mechanical oscillatory movements of the instrument, floor, seat, etc., transmitted to the human body or its individual parts by direct contact.

Vibration is characterized by the frequency spectrum (in Hz) and its kinematic parameters such as vibration velocity (in m/s) or vibration acceleration (in m/s2). In addition to the absolute values ​​of these parameters, their logarithmic levels (in dB) are also used.

Vibrations occurring in production conditions are distinguished by the method of transmission and direction of impact on a person, as well as by physical properties (frequency composition, distribution of energy over time). Presented in tab. 6.1 vibration classification is conditional, but, being to a certain extent related to the degree and nature of changes developing in the body, it has hygienic significance and is taken into account when regulating and assessing vibration.

Hygienic assessment of vibration is carried out during the examination of regulatory and technical documentation for new technological processes, equipment and manual machines, when controlling the serial production of new and modernized manual machines, as well as those purchased abroad, while supervising the working conditions of vibration-hazardous professions, during certification of workers places, investigation of cases of vibration disease.

Vibration assessment methods. In accordance with the sanitary standards "Industrial vibration, vibration in the premises of residential and public buildings" (SN 2.2.4 / 2.1.8.566-96), the hygienic assessment of vibrations should be carried out by the following methods: frequency analysis of the normalized parameter (vibration velocity or vibration

Table 6.1.Vibration classification

The end of the table. 6.1

rhenium), an integral estimate of the frequency of the normalized parameter, an integral estimate taking into account the time of vibration exposure. Vibration metrics using these measurement and evaluation methods are presented in tab. 6.2.

Table 6.2.Methods for measuring and evaluating vibration

Note.

1 The average value over the measurement time according to the time constant of the instrument.

2 Frequency-weighted value (using corrective filters or special calculations).

3 The average value according to the "equal energy" rule, taking into account the duration of the vibration.

The main method characterizing the vibration impact on workers is frequency analysis. Measurements are carried out for local vibration in octaves (geometric mean frequencies 8, 16, 31.5, 63, 125, 250, 500 and 1000 Hz) and for general vibration in one-third octave bands and octaves (geometric mean frequencies 1, 2, 4, 8, 16 , 31.5 and 63 Hz). This method allows you to get the most complete hygienic characteristics of vibration, i.e. not only the intensity of vibration, but also the nature of the vibration spectrum (low, medium and high frequency), which determines the specifics of the effect of vibration on the human body. Method of frequency (spectral) analysis,

in addition, it allows, when carrying out the corresponding calculations, to go to the integral and then to the dose assessment of vibration, taking into account the time of exposure.

Rice. 6.1.Options for the direction of conditional coordinate axes in case of local vibration

Rice. 6.2.The direction of the conditional coordinate axes with general vibration: a - in a standing position; b - in a sitting position

The method of integral estimation by the frequency of normalized parameters involves the measurement of a one-digit indicator - the corrected vibration level, determined as the result of the energy summation of vibration levels in octave frequency bands, taking into account octave corrections. This method of measurement is less time-consuming than the frequency vibration analysis method, however, it is also less informative.

The dose assessment method is used for intermittent vibrations, taking into account the time of exposure to vibration during a shift. This method is related to the method of integrated frequency estimation and allows one to obtain a one-number characteristic in the following ways:

1) calculation of the equivalent corrected level from the measured (or calculated) corrected value and timing data;

2) instrumental measurement of the equivalent corrected value.

The equivalent corrected level of time-varying vibration corresponds to the corrected level of vibration constant in time and equal in energy, acting for 8 hours.

If the workers are exposed to vibration (local or general) during the shift (8 hours), and the vibration is constant in time (vibration rate changes by no more than 6 dB during the observation time), then for hygienic assessment methods of integral frequency assessment and spectral (more accurate) . If workers are exposed to non-constant vibration in time, namely, for 8 hours they serve equipment that generates vibration, the parameters of which change > 6 dB, or equipment that generates constant vibration, but only part of the shift, then the dose-rate method is used to characterize the vibration impact. evaluation or integrated evaluation over time, since the remote controls are set for an 8-hour vibration exposure.

For example, if the vibration characteristics of a hand tool are corrected vibration levels (vibration velocity and vibration acceleration in dB) and the levels of the same normalized parameters in octave frequency bands, then the characteristic of the vibration effect on the operator will be the equivalent corrected vibration level (vibration velocity, vibration acceleration in dB), as the operating time with this tool may vary depending on the technology. Since workers are most often exposed to intermittent vibrations, it is almost always necessary to measure (or calculate) equivalent corrected vibration levels when evaluating working conditions.

Vibration measurement technique. The currently produced vibration measuring equipment makes it possible to measure both the levels of vibration acceleration (vibration velocity) within the limits of the normalized frequencies of one-third octave and/or octave bands, and the corrected and equivalent corrected levels of vibration acceleration (vibration velocity). The main characteristics of some devices are indicated in tab. 5.1.

To unify vibration measurements, state standards have been introduced that establish requirements for instruments, methods for measuring and processing results - GOST 12.1.012-90 “Vibration safety. General requirements”, etc.

When taking measurements, one should be guided by the general rules set forth in the “Methodological guidelines for measuring and hygienic assessment of industrial vibrations” approved by the USSR Ministry of Health. 3911-85.

Machines or equipment must operate in the passport or typical technological mode in terms of speed, load, operation performed, object being processed, etc. When controlling general vibration, all sources that transmit vibration to the workplace should be turned on.

Measuring points, i.e. Vibration sensors installation sites should be located on a vibrating surface in places intended for contact with the operator's body:

1) on the seat, working platform, floor of the working area of ​​the operator and maintenance personnel;

2) in places of contact of the hands of the worker with handles, control levers, etc.

The vibration sensor must be attached in the manner specified in the manufacturer's instructions. When measuring general vibration on sites with a hard surface (asphalt, concrete, metal plates, etc.) or seats without elastic facings, the vibration sensor must be attached directly to these surfaces on a thread, magnet, mastics, etc. In addition, the vibration sensor can be threaded (or magnetically) attached to a hard steel disk (200 mm in diameter and 4 mm thick), which is placed between the floor and legs of a standing person or the seat and body of a seated person. When measuring local vibration, it is preferable to fix the sensor at the control points on the thread, although it is also possible to fasten it with a metal element in the form of a clamp, clamp, etc.

At each control point, the vibration sensor is installed on a flat, smooth area in succession in three mutually perpendicular directions (Z, X, Y axes). Measurements are allowed in the direction of maximum vibration (exceeding measurements in other axes >12 dB) if the same allowable levels are set for all axes.

After installing the vibration sensor at the selected control point, turn on the vibrometer and carry out the necessary measurements, sequentially performing manipulations according to the instructions.

The total number of readings must be at least 3 for local vibration; 6 - for general process vibration; 30 - for

general transport and transport-technological (during movement) vibration with subsequent processing.

After carrying out the required number of measurements at the measurement point, the average values ​​calculated in the same way as for noise are taken as the determining value of the vibration level (see tables 5.2 and 5.3).

Hygienic regulation. The results of studies of constant vibrations obtained by one of the indicated methods (spectral or integral) are compared with the maximum permissible values ​​of the sanitary standards "Industrial vibration, vibration in the premises of residential and public buildings" CH 2.2.4 / 2.1.8.566-96 (Table 6.3; 6.4 and 6.5). The last two tables present the permissible values ​​of the total vibration (jobs) only in octave frequency bands, the values ​​in one-third octave frequency bands are omitted.

The maximum permissible vibration levels are set for a duration of vibration exposure of 8 hours.

For non-permanent vibrations, fluctuating in time, intermittent, when contact with vibration takes part of the shift, the assessment, according to CH 2.2.4 / 2.1.8.566-96, is carried out according to the equivalent corrected level of vibration velocity or vibration acceleration, which is calculated on the basis of the following values:

1) measured, as shown earlier, vibration levels within octave bands or corrected levels;

2) the duration of the vibration, determined by chronometric studies.

To calculate the equivalent level, the values ​​of corrections to the corrected level for the duration of the vibration are used, similar to noise (Table 5.4).

The maximum permissible level (MPL) of vibration is the level of a factor that, during daily (except weekends) work, but not more than 40 hours a week during the entire working experience, should not cause diseases or deviations in the state of health detected by modern research methods in in the process of work or in the remote periods of life of the present and subsequent generations. Compliance with the remote control of vibration does not exclude health problems in hypersensitive individuals.

Table6.3. Maximum permissible values ​​of local vibration parameters along the axes Ζ, Χ, Υ

Table6.4. Maximum permissible values ​​of transport vibration in octave frequency bands

Calculation example.When measuring the vibration velocity by the spectral method on the handle of a chipping hammer, three readings were taken (along the Z axis) during the processing of cast iron. Next, the average levels of vibration velocity in octave frequency bands are calculated, which are given in tab. 6.8. Since the Z-axis is the direction of maximum vibration, measurement results for other axes are not given. Working time with a hammer during a shift is 5 hours.

To proceed to the calculation of the vibration dose, you must first determine the corrected level of vibration velocity (integral indicator). To do this, using weighting factors for octave frequency bands (Table 6.6 or 6.7) you need to determine the corrected octave levels of vibration velocity, and then carry out pairwise energy summation of their levels, taking into account the corrections (see table 5.2). In our case, the corrected vibration velocity level is 122.6 and 123 dB (Table 6.8).

Since working with a hammer takes 5 hours per shift, taking into account the correction for time (see. tab. 5.4), equal to -2, the equivalent adjusted value of the vibration velocity level will be 121 dB. This value is compared with the admissible equivalent corrected level of vibration velocity (see. tab. 6.3), equal to 112 dB.

The measurement results are documented in a protocol of the established form. In conclusion, an analysis of the vibration factor is given, indicating the magnitude of exceeding the maximum permissible limit, as well as the conditions that determine increased levels of vibration. In addition, there are factors of working conditions that exacerbate the adverse effect of vibration: large dynamic and static loads (for manual machines, the mass attributable to the hands, pressing force is estimated), prolonged work in a forced position, general or local cooling, etc.

So, in accordance with SanPiN 2.2.2.540-96 "Hygienic requirements for hand tools and organization of work", the mass of the hand tool assembly (including the mass of the plug-in tool, attached handles, hoses, etc.) should not exceed 5 kg for the tool, used to work with different orientations in space, and 10 kg for a tool used when performing work vertically down and horizontally. The pressing force should not exceed 100 N for a one-handed machine, and 150 N for a two-handed machine.

Table 6.5.Maximum permissible values ​​of workplace vibration along the Ζ, Χ, Υ axes in octave frequency bands

Continuation of the table. 6.5

Table 6.6.Weighting value (dB) for local vibration

Note.** When evaluating the transport-technological and technological vibration, the values ​​of the weight coefficients for the directions Χ, Υ are taken equal to the values ​​for the directions Ζ.

Table 6.8.Stages of calculating the corrected level of vibration velocity

The surface temperature of the handles of a hand tool should be above 21 ° C, the range from 25 to 32 ° C is optimal. At the same time, the air temperature for any type of work according to the severity and seasons of the year (for closed heated rooms) should not be less than 16 ° C, humidity - no more than 40-60%, air speed - no more than 0.3 m / s.

When working outdoors in the cold season, it is necessary to organize a special heated room for periodic heating and rest of the worker, the temperature in which during the cold season should be within 22-24 ° C, the air speed should not exceed 0.2 m / s .

6.2. STUDY OF THE INFLUENCE OF VIBRATION ON THE ORGANISM

Assessment of the health status of workers exposed to vibration is carried out during examination using physiological and clinical research methods, as well as in the analysis of occupational and non-occupational morbidity.

Of the physiological methods, pallesthesiometry (measurement of vibration sensitivity), algesimetry (measurement of pain sensitivity), stabilography (study of the vestibular analyzer), dynamometry, electromyography, thermometry with a cold test, capillaroscopy, rheovasography, i.e. methods reflecting the state of the sensory system, neuromuscular apparatus and peripheral circulation, most quickly involved in the pathological process under the action of vibration. For research, it is recommended to select a group of workers in vibration-hazardous professions with an experience of no more than 10 years under the age of 30 years.

When conducting preliminary and periodic medical examinations in accordance with the order? 90 (1996) of the Ministry of Health of the Russian Federation for workers exposed to local vibration, it is mandatory to conduct a study of vibration sensitivity and a cold test (according to indications: RVG of peripheral vessels, radiography of the musculoskeletal system); for workers exposed to general vibration - vibration sensitivity (according to the indications of RVG of peripheral vessels, examination of the vestibular apparatus, audiometry, radiography of the musculoskeletal system, ECG).

Since vibration sensitivity measurement and a cold test are among the listed methods, they are mandatory studies during preliminary and periodic medical examinations of workers exposed to vibration, it is necessary to dwell in more detail on their application and evaluation of the data obtained.

Vibration Sensitivity Study can be carried out using tuning forks with a number of oscillations of 128 or 256 in 1 min. The duration of the sensation of vibrations of the tuning fork is determined after the installation of the stem of the vibrating tuning fork on any part of the skin of the limb. With a change in sensitivity, a weakening or reduction in the time of sensation of vibration (hypesthesia) or the absence of a sensation of vibration (anesthesia) of the tuning fork are observed. Vibration sensitivity can be determined more accurately using BT-1 or IVCh-02 type pallesthesiometers.

When using the VT-1 device, the vibration sensitivity threshold is measured for frequencies of 63, 125, 250 Hz by successively pressing the corresponding button of the horizontal row.

The patient puts the III or IV finger of the right or left hand, lightly touching, on the vibrator rod. The tester, by successively pressing the buttons of the vertical row (-10; -5; 0; 5; 10 dB, etc.), determines the vibration level that is first felt by the patient, i.e. sets the vibration sensitivity threshold.

The average value obtained after 6 measurements (3 in ascending, ie from imperceptible vibration to clearly perceptible, and 3 in descending) is taken as the value of the vibrational sensitivity threshold.

At the same time, it must be remembered that the physiological zero levels of vibration sensitivity in this device are taken to be the average statistical values ​​of the vibration speed established for young, practically healthy people at frequencies of 63, 125, 250 Hz and equal to 81, 70, 73 dB, respectively. The results of the study are recorded on the vibrogram form. The evaluation of the results obtained can be carried out in accordance with tab. 6.9.

Particularly informative in assessing vibration sensitivity is the determination of the value of the temporary threshold shift (TTS). This is the difference in vibration sensitivity measured after working with vibration equipment

Table 6.9.Evaluation of vibration sensitivity measurement results

compared to baseline (before work). VSP depends on the frequency and level of vibration. Normally, when exposed to vibration with maximum values ​​of vibrational velocity in the octave frequency bands of 63, 125, 250 Hz, the vibration sensitivity indicator shifts upward: at 63 Hz - up to 5 dB; at 125 Hz - up to 7 dB; at 250 Hz - up to 10 dB with recovery within 15 minutes or less to the original level. When exposed to vibration with the maximum value of the vibrational velocity in the frequency bands of 8 and 16 Hz, the VSP of vibration sensitivity at 125 Hz is normally up to 3 dB, at 250 - up to 5 dB. An increase in shifts in vibration sensitivity over the indicated values, as well as in recovery time, is a sign of analyzer fatigue and the possibility of developing permanent disorders.

To assess the long-term effects of vibration exposure, the value of the constant threshold shift (PST), associated with irreversible changes in vibration sensitivity, is used. PSP is determined from workers in the morning before work and is evaluated in comparison with the baseline vibration sensitivity curve taken at work. The value of the PSP depends on the frequency, intensity of vibration and the length of service in contact with it.

When evaluating the PSP of vibration sensitivity, age-related changes in this function, especially pronounced in men, should be taken into account: at 40-49 years old, an increase in the threshold at frequencies of 63, 125, 250 Hz by 1, 2 and 3 dB, respectively, is observed; in 50 years and more - by 6, 8 and 8 dB, respectively.

PSP (minus age corrections) at frequencies of 63, 125 and 250 Hz more than 5, 7 and 10 dB indicates a pronounced decrease in sensitivity and the appearance of signs of vibration damage.

Study of pain sensitivity. With the tip of a pin, injections are made into symmetrical areas of the skin of the trunk and limbs. Normally, a person feels every injection. With a change in sensitivity, there may be no reaction to an injection (anesthesia), a decrease (hypesthesia) or an increase (hyperesthesia) of the reaction.

More accurate information about pain sensitivity can be obtained using a BM-60 type algesimeter. The threshold of sensitivity is determined by a barely noticeable sensation of a needle prick protruding from the rotary head of the device, the palmar and back surfaces of the hand. Normally, the boundaries of the range of physiological fluctuations in the index of pain sensitivity on the back surface of the hand are 0.26-0.38 mm; on the grooves of the fingers of the back surface of the hand - 0.76-0.86 mm, on the palmar surface of the fingers -

0.2-0.55 mm.

Temperature sensitivity study. Take one test tube with hot (about 40 ? C), another with cold (18-22 ? C) water and alternately apply to the symmetrical parts of the trunk and extremities. Normally, a person distinguishes well between the touch of cold and hot water. Sensitivity disturbances are possible according to the types of anesthesia, thermohypesthesia, less often thermohyperesthesia. A more accurate study can be carried out using thermoesthesiometers.

Research of peripheral circulation. The severity of changes can be judged by the indicators of skin thermometry with a cold test. The temperature of the skin of the dorsum of the nail phalanges of the II and III fingers is measured, followed by cooling of the hands for 5 minutes in cold water (8-10 °C). After cooling is stopped, the skin temperature is again measured at the same points every minute until the initial values ​​are restored. Normally, the skin temperature before cooling is 27-31 ° C, after cooling there is no whitening, the temperature recovery time is up to 20 minutes. A decrease in temperature to 18-20 ° C, the appearance of individual white spots or a continuous whitening of the terminal phalanges or two or three phalanges of at least one finger indicate, respectively, a weakly positive, moderately positive and sharply positive reaction. In this case, the recovery time for skin temperature exceeds 20 minutes.

The data of physiological studies conducted upon admission to work make it possible to identify individuals who have individual characteristics of the body that contribute to an earlier

development of vibration disease (risk group). It is not recommended to hire a job associated with exposure to vibration, especially in combination with pronounced local loads on the muscles of the hands, persons with high initial thresholds of vibration sensitivity, more than 8-10 dB higher than the physiological zero for a perception frequency of 125 Hz, as well as low temperature skin. It should be borne in mind that the latter indicator can be used as one of the criteria for professional suitability when selecting to work with equipment that creates vibration with maximum intensities in the octave bands of 32-250 Hz, causing angiospastic reactions.

6.3. CLASSIFICATION OF WORKING CONDITIONS BY INDICATORS OF PRODUCTION

VIBRATIONS

Evaluation of working conditions when workers are exposed to vibrations, depending on the magnitude of the excess of existing standards, is presented in the document R 2.2.2006-05 “Guidelines for the hygienic assessment of factors in the working environment and the labor process. Criteria and classification of working conditions.

The degree of harmfulness and danger of working conditions is established taking into account the temporal characteristics of vibration.

For constant vibrations (general or local) acting on workers for 8 hours, the assessment of working conditions is carried out according to the corrected value of vibration acceleration (vibration velocity). Its excess over the MPC characterizes the degree of harmfulness or danger of working conditions (Table 5.7).

When workers come into contact with sources of both constant (part of a shift) and non-permanent vibration (general, local), to assess working conditions, measure (or calculate taking into account the duration of this contact) the equivalent corrected level of vibration velocity or vibration acceleration in dB.

Certain equivalent adjusted levels of vibration velocity or vibration acceleration in dB are compared with the values ​​of the current standards SN 2.2.4 / 2.1.8.566-96 "Industrial vibration, vibration in residential and public buildings." And then, by exceeding the MPD (by ... dB), determine the degree of harmfulness and danger of working conditions (see table 5.7).

With equivalent corrected values ​​of vibration velocity and acceleration in absolute terms, the multiplicity of the excess in comparison with the maximum control is determined.

With the combined action of local vibration and a cooling microclimate (working in a cooling microclimate), the hazard class of working conditions according to the vibration factor increases by one step.

Development of recreational activities. Based on the results of the sanitary inspection, an order is given on the need to take measures to reduce the adverse effects of vibration. They may include organizational and technical measures, optimization of work and rest regimes, the use of personal protective equipment, as well as therapeutic and preventive measures. Radical measures include the prohibition of the use of vibration hazardous equipment or the limitation of the time of its use during the shift so that the equivalent adjusted vibration level does not exceed the MPS established by sanitary legislation. So, in accordance with SanPiN 2.2.2.540-96 "Hygienic requirements for hand tools and organization of work", it is prohibited to use hand tools that generate vibration levels that are more than 12 dB higher than the maximum permissible level. The same document provides for the protection of time working in conditions of exceeding the maximum vibration control with the mandatory use of personal protective equipment (Table 6.10).

Labor regimes for working vibration-hazardous professions should be developed by the labor protection services of enterprises. The work modes should indicate: the allowable total time of contact with vibrating hand tools, the duration and organization of breaks, both regulated and constituent pauses while working with a vibrating tool, a list of works that operators with a hand tool can be engaged in at this time.

Scheduled breaks: the first lasting 20 minutes (1-2 hours after the start of the shift) and the second 30 minutes (2 hours after the lunch break) are provided for outdoor activities, a special complex of industrial gymnastics, physiotherapy thermal procedures for hands, etc. The lunch break must be at least 40 minutes.

When working with a vibration hazardous hand tool, the duration of a one-time continuous exposure to vibration is not

Table 6.10.Permissible total time of action of local vibration per shift, depending on the magnitude of exceeding the MPD

should exceed 10-15 minutes. It is advisable to provide for the following ratio of durations of one-time continuous exposure to vibration and subsequent pauses in labor modes: 1:1; 1:2; 1:3 etc.

Are those exposed to local vibration at standard levels and exceeding the MPS required to undergo a medical examination in accordance with the orders of the Ministry of Health? 90 (1996) and? 83 (2004) by a neurologist, otolaryngologist, therapist, and those exposed to general vibration undergo a medical examination, in addition, according to indications, by a surgeon and an ophthalmologist. The obligatory physiological research methods are discussed earlier in Section 6.2. of this chapter.

Persons working in vibration-hazardous professions are advised to take vitamin prophylaxis (vitamins C, B 1, nicotinic acid, multivitamins) as prescribed by a doctor in order to increase the body's resistance.

24.10.2017, 17:42

One of the unpleasant factors that can affect the well-being of employees and, as a result, their professional capabilities, is vibration in the workplace. Let's talk about how the law regulates this issue.

Where are workplace vibration standards set?

One of the most important aspects of labor protection is the vibration experienced by employees during the performance of their work functions.

In practice, industrial vibration of workplaces can be associated with:

• with vehicles (driving and/or escorting);
• with the features of the operation of production equipment, mechanisms, etc.

Since 2017, the level of vibration at 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 the 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 health, the specified SanPiN divides vibration into several types, which are disclosed in the table below.

Types and types of vibration

In this case, the general vibration of the 3rd category at the place of action is:

• in a permanent working area;
• in warehouses, in canteens, household, duty and other industrial premises where there are no machines with vibration;
• in the premises of the plant management, design bureaus, laboratories, training centers, computer centers, health centers, office premises, work rooms, etc. for mental labor personnel.

Vibration indicators

From a scientific point of view, the sanitary norms of workplace vibration are based on the following indicators:

• corrected vibration acceleration (aw, m s-2);
• corrected level of vibration acceleration (Law, dB);
• equivalent vibration acceleration.

As a result, vibration assessment in the workplace is carried out on the basis of complex formulas and related calculations:

Vibration measurement

To make the correct measurement of vibration in the workplace, special methods are used that have been certified. In this case, the main device - the vibrometer - must meet the 2 conditions:

1. Complies with the requirements of GOST ISO 8041-2006 “Vibration. The effect of vibration on a person. Measuring instruments".

2. Equipped with class 1 octave and one-third-octave filters according to the national standard of the Russian Federation (GOST R 8.714-2010 (IEC 61260:1995) "Octave bandpass and fractional octave filters. Technical requirements and test methods."

Permissible vibration standards

The table below shows the limits for acceptable vibration in the workplace.

Vibration limits in the working area

As you can see, the vibration that affects the employee is checked by the method of integral assessment according to the equivalent adjusted level of vibration acceleration, taking into account the time of exposure to vibration.

Please note that these workplace vibration requirements apply to both the 40-hour workweek and the shortened workday.

It is impossible to work with local vibration with current rms levels that exceed the norms by more than 12 dB (4 times) according to the integral estimate.

In addition, it is impossible to work with general vibration with current rms levels above the norms by 24 dB (8 times) according to the integral estimate.

The reason for the excitation of vibrations is the unbalanced force effects that occur during the operation of the machine. Their sources in the compressor unit are: poor-quality balancing of rotors, wear of bearings, uneven gas flow.

The range of human vibration sensitivity is from 1 to 12000 Hz with the highest sensitivity from 200 to 250 Hz.

Vibration standards are defined in SNiP 2.2.4/2.1.8.566-96 “Vibration. General safety requirement”. The permissible vibration level at the operator's workplace is 0.2 dB. RMS value of vibration velocity is not more than 2 mm/s.

The vibration safety of the machine is assessed on the basis of monitoring its vibration characteristics. The normalized parameters of the vibration characteristic are the root mean square value of the vibration velocity or the corresponding logarithmic level (dB) and the level of vibration acceleration (dB) - for local vibration in the octave frequency band, and for general vibration in the octave or one-third octave band.

To ensure that the impact of vibration does not worsen the well-being of the worker and does not lead to the appearance of vibration sickness, it is necessary to observe the maximum permissible vibration level (MPL). MPL is the level of a factor that, during daily (except weekends) work, but not more than 40 hours a week during the entire working experience, should not cause diseases or deviations in the state of health. Compliance with the remote control of vibration does not exclude health problems in hypersensitive people.

To reduce vibration in the design of the compressor unit, the following parts and works are provided:

Dynamic balancing of rotors in the entire operating range on a stand with a vacuum chamber;

Application of AMP bearings;

Application of vibration damping.

Vibration can be controlled both at the source of its occurrence and along the path of propagation. To reduce vibrations in the machine itself, it is necessary to use materials with high internal resistance. To combat vibration according to GOST 12.1.012-90 “Vibration safety. General requirements”, the installation is placed on a block foundation, which should not be connected to the foundation of the room. The mass of the foundation for the compressor is selected in such a way that the amplitude of vibrations of the base of the foundation does not exceed 0.1-0.2 mm, which corresponds to the permissible standard according to the “Vibration Standards. General requirements".

To protect a person from vibration, it is necessary to limit the vibration parameters of workplaces and the surface of contact with the hands of workers, based on physiological requirements that exclude the possibility of vibration disease. Hygienic vibration standards are responsible for this, which are set for a working shift of 8 hours.

Normalized parameters:

RMS value of vibration velocity or the corresponding logarithmic level - , determined by the formula:

where - speed threshold.

Vibration acceleration level - determined by the formula:

where - acceleration threshold value.

The values ​​of speed and acceleration are determined by the formulas:

where a is displacement, m, f is vibration frequency:

where - operating frequency of rotation of the rotor.

Established hygienic standards (vibration velocity level) of technological vibration that occurs when working in a production room with vibration sources (category - 3, technical type - a) (when stationary machines are operating) in the octave range with a geometric mean frequency value of 1000 Hz should not exceed 109 db. Such a high permissible value of the vibration velocity level was chosen, since the installation is located in an underground bunker, where personnel enter several times a year for maintenance. installation maintenance.

Causes of noise during the operation of the compressor unit:

The flow of gas in the flow part of the compressor causes aerodynamic noise, which occurs due to the inhomogeneity of the flow and the formation of vortices;

Gas flow in compressor nozzles, pipelines;

Rotating impeller blades and other rotating parts.

By nature, the noise is broadband with a continuous spectrum with a width of more than one octave.

According to time characteristics, a constant sound level, which changes by no more than 5 dB per shift when measured on the “slow” time characteristic of a sound level meter according to GOST 17187-81 "Sound level meters. General technical requirements and test methods."

Noise must not exceed its limits. The standards establish the sound pressure control panel in octave bands, as well as sound levels depending on:

1. type of work;

2. duration of noise exposure per shift;

3. the nature of the noise spectrum.

The maximum permissible noise level (MPL) is the level of a factor that, during daily (except weekends) work, but not more than 40 hours a week during the entire working experience, should not cause illness or deviations in health.