Vibration level in the workplace. Analysis of the overall vibration level

The reason for the excitation of vibrations is the unbalanced force effects arising 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. The mean square value of the vibration velocity is not more than 2 mm / s.

The vibration safety of a machine is assessed on the basis of monitoring its vibration characteristics. The normalized parameters of the vibration characteristics 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 band, and for general vibration in the octave or one-third octave band.

In order for the effect of vibration not to worsen the well-being of the worker and not to lead to the appearance of vibration sickness, it is necessary to observe the maximum permissible vibration level (MPU). PDU is the level of a factor that, during daily (except weekends) work, but not more than 40 hours per week during the entire working experience, should not cause illness or health abnormalities. Compliance with the remote control vibration does not exclude health problems in hypersensitive people.

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

Dynamic balancing of rotors throughout the entire operating range on a bench with a vacuum chamber;

Application of AMP bearings;

Application of vibration damping.

You can fight vibration both at the source of its origin 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 in accordance with GOST 12.1.012-90 “Vibration safety. General requirements ”, the installation is placed on a block foundation, which should not be connected with the foundation of the room. The mass of the foundation for the compressor is selected in such a way that the vibration amplitude of the base of the foundation does not exceed 0.1-0.2 mm, which corresponds to the permissible norm according to “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. This is the responsibility of the hygienic vibration standards, which are established for a work shift duration of 8 hours.

Standardized parameters:

The root-mean-square value of the vibration velocity or the corresponding logarithmic level - determined by the formula:

where - threshold speed value.

Vibration acceleration level - determined by the formula:

where is the acceleration threshold.

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

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

where - operating rotor speed.

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

The reasons causing the appearance of noise during the operation of the compressor unit:

The gas flow in the compressor flow path causes aerodynamic noise, which arises due to the non-uniformity of the flow and the formation of vortices;

Gas flow in compressor nozzles, pipelines;

Rotating impeller blades and other rotating parts.

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

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

The noise should not exceed its limits. The standards set the remote control for sound pressure in octave bands, as well as sound levels depending on:

1. type of work;

2. duration of exposure to noise 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 per week during the entire working experience, should not cause illness or health abnormalities.

6.1. CHARACTERISTICS OF VIBRATION PARAMETERS

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

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

Vibration is characterized by a spectrum of frequencies (in Hz) and such kinematic parameters as vibration velocity (in m / s) or vibration acceleration (in m / s 2). In addition to the absolute values ​​of these parameters, their logarithmic levels (in dB) are also used.

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

The hygienic assessment of vibration is carried out during the examination of normative and technical documentation for new technological processes, equipment and hand-held machines, when monitoring the serial production of new and modernized hand-held machines, as well as those purchased abroad, when supervising the working conditions of vibration-hazardous professions, when certifying 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:

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. Indicators characterizing vibration when using these measurement and evaluation methods are presented in tab. 6.2.

Table 6.2.Vibration Measurement and Evaluation Methods

Note.

1 Average value over the measurement time in accordance with the time constant of the device.

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

3 Average value according to the “equal energy” rule, taking into account the vibration duration.

The main method characterizing the vibration impact on workers is frequency analysis. Measurements are carried out for local vibration in octaves (geometric mean frequencies of 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 obtaining 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 specificity of the effect of vibration on the human body. Frequency (spectral) analysis method,

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 exposure time.

Rice. 6.1.Variants of the direction of the conditional coordinate axes with local vibration

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

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

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

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

If workers are exposed to vibration (local or general) during a shift (8 hours), and the vibration is constant in time (the vibration velocity changes by no more than 6 dB during the observation time), then for the hygienic assessment, methods of integral estimation in frequency and spectral (more accurate) are used. ... If the workers are exposed to vibration that is not constant in time, namely, for 8 hours they service equipment that generates vibration, the parameters of which change> 6 dB, or equipment that generates constant vibration, but only a part of the shift, then the dose method is used to characterize the vibration effect. assessment or integral assessment taking into account time, since the remote controls are set based on an 8-hour vibration exposure.

For example, if the vibration characteristics of a hand tool are the 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 impact 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 allows measuring both the levels of vibration acceleration (vibration velocity) within the normalized frequencies of one-third octave and / or octave bands, and 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 of measurement and processing of results - GOST 12.1.012-90 “Vibration safety. General requirements ", etc.

When carrying out measurements, one should be guided by the general rules set forth in the "Methodological guidelines for carrying out measurements and hygienic assessment of industrial vibrations" approved by the USSR Ministry of Health? 3911-85.

Machines or equipment must operate in a passport or standard technological mode in terms of speed, load, operation performed, object to be processed, etc. When controlling for general vibration, all sources transmitting vibration to the workplace should be included.

Measurement points, i.e. the places where vibration sensors are installed 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 the places of contact of the operator's hands with handles, control levers, etc.

The vibration sensor must be fixed in the manner specified in the manufacturer's instructions. When measuring general vibration on hard-surfaced sites (asphalt, concrete, metal plates, etc.) or on seats without elastic linings, the vibration sensor must be attached directly to these surfaces using threads, magnets, mastics, etc. In addition, the vibration sensor can be threaded (or magnetically attached) to a rigid steel disc (200 mm in diameter and 4 mm thick), which is placed between the floor and the legs of a standing person or the seat and the body of a seated person. When measuring local vibration, it is preferable to fix the sensor at the test points on the thread, although it is also possible to attach 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 surface in sequence along three mutually perpendicular directions (Z, X, Y axes). Measurements in the direction of maximum vibration (excess compared to measurements in other axes> 12 dB) are allowed if the same permissible levels are set in 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 counts must be at least 3 for local vibration; 6 - for general technological vibration; 30 - for

general transport and transport-technological (while driving) vibration with subsequent processing.

After carrying out the required number of measurements at the point of measurement, average values ​​are taken as the determining value of the vibration level, calculated in the same way as for noise (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 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 show the permissible values ​​of total vibration (workplaces) only in octave frequency bands, the values ​​in one-third octave frequency bands are omitted.

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

For non-constant vibrations, fluctuating in time, intermittent, when contact with vibration takes part of a 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 time studies.

To calculate the equivalent level, the values ​​of the corrections to the corrected level are used for the duration of vibration, 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 per week during the entire working experience, should not cause diseases or deviations in the state of health detected by modern research methods in the process of work or in the remote periods of life of the present and subsequent generations. Compliance with the remote control vibration does not exclude health problems in hypersensitive persons.

table6.3. Maximum permissible values ​​of parameters of local vibration 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 during the machining of cast iron, three readings were taken (along the Z axis). 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, measurements on the other axes are not shown. 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 the weighting factors for the octave frequency bands (table 6.6 or 6.7) it is necessary to determine the corrected octave levels of vibration velocity, and then carry out the energy summation of their levels in pairs, taking into account the corrections (see table 5.2). In our case, the corrected level of vibration velocity is 122.6 and 123 dBA (Table 6.8).

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

The measurement results are recorded in a protocol of the established form. In the conclusion, the analysis of the vibration factor is given, indicating the magnitude of the excess of the MPL, as well as the conditions that determine the increased levels of vibration. In addition, the factors of working conditions that aggravate the unfavorable effect of vibration are noted: large dynamic and static loads (for manual machines, the weight per hand, 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 work organization", 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 tools used when working vertically down and horizontally. Pressing forces should not exceed 100 N for a one-handed machine, 150 N. for a two-handed machine.

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

Continuation of table. 6.5

Table 6.6.The value of the weighting factors (dB) for local vibration

Note.** When assessing 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 hand tool handles should be above 21 ° C, the optimal range is from 25 to 32 ° C. At the same time, the air temperature for any types 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 in the range of 22-24? C, the air speed - no more than 0.2 m / s ...

6.2. STUDY OF THE INFLUENCE OF VIBRATION ON THE BODY

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

Of the physiological methods, the most important are pallesiometry (measurement of vibration sensitivity), algesimetry (measurement of pain sensitivity), stabilography (study of the vestibular analyzer), dynamometry, electromyography, cold test thermometry, capillaroscopy, rheovasography, i.e. methods reflecting the state of the sensory system, neuromuscular apparatus and peripheral circulation, which are most rapidly involved in the pathological process under the action of vibration. For research, it is recommended to select a group of workers with 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, a study of vibration sensitivity and a cold test must be carried out (according to indications: RVG of peripheral vessels, radiography of the musculoskeletal system); for workers exposed to general vibration - vibration sensitivity (according to RVG indications of peripheral vessels, examination of the vestibular apparatus, audiometry, radiography of the musculoskeletal system, ECG).

Since of the listed methods, measurement of vibration sensitivity and cold test 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 assessment of the data obtained.

Vibration Sensitivity Study can be carried out using tuning forks with a vibration rate of 128 or 256 per minute. Determine the duration of the sensation of oscillations of the tuning fork after the installation of the legs of the vibrating tuning fork on any part of the skin of the limb. When the sensitivity changes, weakening or shortening of the vibration sensation (hypesthesia) or the absence of vibration sensation (anesthesia) of the tuning fork is observed. Vibration sensitivity can be determined more accurately using pallestesiometers such as VT-1 or IVCH-02.

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

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

It should be remembered that as physiological zero levels of vibration sensitivity in this device, 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, are taken. The research results are entered on the vibrogram form. Evaluation of the results obtained can be carried out in accordance with tab. 6.9.

Especially informative when assessing vibration sensitivity is the determination of the value of the temporary shift of the thresholds (VSP). This is the difference in vibration sensitivity measured after operating 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 the vibrational speed in the octave frequency bands of 63, 125, 250 Hz, the vibration sensitivity indicator shifts upward: by 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 initial level. When exposed to vibration with a maximum value of the vibrational speed 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 vibrational sensitivity shifts of more than the indicated values, as well as the recovery time, is a sign of analyzer fatigue and the possibility of developing persistent disorders.

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

When assessing the PSP of vibration sensitivity, one should take into account age-related changes in this function, especially pronounced in men: at the age of 40-49, there is an increase in the threshold at frequencies of 63, 125, 250 Hz, respectively, by 1, 2 and 3 dB; 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 in symmetrical areas of the skin of the trunk and extremities. Normally, a person feels every injection. With a change in sensitivity, it is possible that there is no reaction to the 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 algesimeter. The sensitivity threshold is determined by the barely noticeable sensation of a needle prick protruding from the swivel head of the device, the palmar and dorsum of the hand. Normally, the boundaries of the physiological fluctuation range of the pain sensitivity indicator on the dorsum of the hand are 0.26–0.38 mm; on the grooves of the fingers of the dorsum of the hand - 0.76-0.86 mm, on the palmar surface of the fingers -

0.2-0.55 mm.

Investigation of temperature sensitivity. Take one test tube with hot (about 40 ° C), another with cold (18-22 ° C) water and alternately apply it to the symmetrical parts of the trunk and limbs. Normally, a person can distinguish well between the touch of cold and hot water. Sensory disturbances are possible by types of anesthesia, thermohypesthesia, less often thermohyperesthesia. A more accurate study can be carried out using thermoesthesiometers.

Study of peripheral circulation. The severity of the 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 II and III fingers is measured, followed by cooling the hands for 5 minutes in cold water (8-10 ° C). After cessation of cooling, the temperature of the skin is measured again 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 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 of the skin temperature exceeds 20 minutes.

The data of physiological studies carried out upon admission to work make it possible to identify persons with individual characteristics of the body that contribute to an earlier

the 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 arms, persons with high initial thresholds of vibration sensitivity, more than 8-10 dB higher than physiological zero for a frequency of perception 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 octave bands of 32-250 Hz, causing angiospastic reactions.

6.3. CLASSIFICATION OF WORKING CONDITIONS BY PRODUCTION INDICATORS

VIBRATION

An assessment of working conditions when exposed to vibrations at work, depending on the excess of the current standards, is presented in the document R 2.2.2006-05 “Guidelines for the hygienic assessment of the factors of the working environment and the labor process. Criteria and classification of working conditions ".

The degree of harmfulness and hazard 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 remote control characterizes the degree of harm or danger of working conditions (table 5.7).

When workers come into contact with sources of both constant (part of a shift) and non-constant vibration (general, local), to assess the 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 corrected levels of vibration velocity or vibration acceleration in dB are compared with the values ​​of the current standards СН 2.2.4 / 2.1.8.566-96 "Industrial vibration, vibration in premises of residential and public buildings". And then, by exceeding the MPL (by ... dB), determine the degree of harmfulness and hazard of working conditions (see table 5.7).

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

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

Development of recreational activities. Based on the results of the sanitary examination, 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 medical and preventive measures. The 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 corrected vibration level does not exceed the MPL established by sanitary legislation. So, in accordance with SanPiN 2.2.2.540-96 "Hygienic requirements for hand tools and work organization", it is prohibited to use hand tools that generate vibration levels that are more than 12 dB higher than the remote control. The same document provides for protection by the time of those working in conditions of exceeding the remote control of vibration with the obligatory 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 working modes should indicate: the permissible 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 busy with at this time.

Regulated breaks: the first one 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 the hands, etc. Lunch break should be at least 40 minutes.

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

Table 6.10.Permissible total time of action of local vibration per shift, depending on the value of exceeding the remote control

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 working regimes: 1: 1; 1: 2; 1: 3, etc.

Should those exposed to local vibration at standard levels and exceeding the MPU undergo a medical examination in accordance with the orders of the Ministry of Health? 90 (1996) and? 83 (2004) as a neurologist, otolaryngologist, therapist, and those exposed to general vibration undergo a medical examination, in addition, if indicated, by a surgeon and an ophthalmologist. The physiological methods of research that are mandatory in this case were discussed earlier in section 6.2. of this chapter.

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

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 normative documents:

GOST 12.1.012-90 SSBT. Vibration safety;

CH 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 31.10.96 N 40.

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

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

· The criterion “limit of labor productivity decrease”, which ensures the maintenance of the standard 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 criterion "comfort", providing 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 root-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 geometric mean frequencies of 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; twenty; 25; 31.5; 40; 50; 63; 80 Hz.

Along with the vibration spectrum, a single-digit 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 effect of vibration of various frequencies on a person is taken into account by weight coefficients, the values ​​of which are given in the above regulatory documents.

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

Basic methods of vibration control of machinery and equipment.

1. Reducing vibrations by acting on the excitation source by reducing or eliminating forcing 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 rational choice of mass or stiffness 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. For this, the vibrating surface is covered with a material with high internal friction (rubber, cork, bitumen, felt, etc.). Vibrations propagating along communications (pipelines, channels) are weakened by their joining through sound-absorbing materials (rubber and plastic gaskets). Anti-noise mastics are widely used, applied to the metal surface.

4. Dynamic vibration damping is most often carried out by installing the units on the foundations. For small objects, a massive base plate is installed between the base and the unit.

5. Modification of structural elements of machines and building structures.

6. When working with manual mechanized electric and pneumatic tools, use personal protective equipment for hands from vibration. These include mittens, gloves, as well as vibration-proof pads or plates, which are equipped with fasteners in the hand.

In 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, as well as the temperature of the surrounding surfaces, thermal radiation and atmospheric pressure acting on the human body. 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.

There are two types of standards: 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 a high level of performance. 2. In cases where, due to technological requirements, technical and economically justified reasons, optimal microclimatic conditions cannot be ensured, 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 shift. Allowable microclimate parameters do not cause damage or health disorders, but can lead to general and local sensations of thermal discomfort, tension in thermoregulatory mechanisms, deterioration of well-being and decreased performance. According to GOST 12.1.005-88, permissible indicators are set differentially 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 ensures a balance between the amount of heat continuously generated in the body and the excess heat that is continuously released into the environment, i.e. maintains the thermal balance of the body: Q out =Q dep .

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 ) 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 weak air movement, a person at rest as a result of thermal radiation loses about 45% of all thermal energy produced by the body, convection – up to 30% and evaporation – up to 25%. In this case, over 80% of the heat is given off through the skin, about 13% – through the respiratory organs, about 7% of the heat is spent on warming up the food, water and inhaled air. At rest and at an air temperature of 15 ° C, perspiration is insignificant and amounts to about 30 ml per hour. At high temperatures (30 ° C and above), especially when performing heavy physical work, sweating can increase tenfold. So, in hot shops with enhanced 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 humans 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 define convective heat transfer; 1 and 3 – evaporation of sweat; 4 - heat radiation. The standards for these parameters are set differentially depending on the severity of the work performed.

Under tactile sensitivity is the sensation of touch and pressure. On average, there are about 25 receptors per 1 cm 2. 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 developed on the parts of the body farthest 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 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 that warns of a problem 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 about the internal dangers that threaten our body. If pain did not warn us, 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.

Vibration measurement points for assessing the state of machines and mechanisms are selected on bearing housings or other structural elements that respond to dynamic forces to the maximum extent and characterize the general vibration state of the machines.

GOST R ISO 10816-1-97 regulates vibration measurements of bearing housings in three mutually perpendicular directions passing through the axis of rotation: vertical, horizontal and axial (a). The measurement of the overall vibration level in the vertical direction is carried out at the highest point of the housing (b). The horizontal and axial components are measured at the level of the bearing cap connector or the horizontal plane of the axis of rotation (c, d). Measurements carried out on protective casings and metal structures do not allow determining the technical condition of the mechanism due to the nonlinearity of the properties of these elements.

(a)	(b)
(v)	(G)

a) on electric machines; b) in the vertical direction; c, d) on the bearing housing

The distance from the sensor installation site to the bearing should be as short as possible, without contact surfaces of various parts in the path of vibration propagation. The place of installation of the sensors must be sufficiently rigid (do not install the sensors on a thin-walled case or casing). Use the same measurement points and directions when performing condition monitoring. The increase in the reliability of the measurement results is facilitated by the use at characteristic points of devices for quick fixation of the sensors in certain directions.

Mounting of vibration sensors is regulated by GOST R ISO 5348-99 and the recommendations of the sensor manufacturers. To mount the transducers, the surface on which it is attached must be free of paint and dirt, and when measuring vibration in the high-frequency range - from paint and varnish coatings. The test points at which vibration measurements are taken are designed to ensure repeatability during sensor installation. The place of measurement is marked with paint, punching, installation of intermediate elements.

The mass of the transducer should be less than the mass of the object by more than 10 times. In a magnetic holder, for fixing the sensor, magnets with a holding force of 50 ... 70 N are used; to shift 15 ... 20 N. Not fixed transducer is detached from the surface at acceleration over 1g.

Shock impulses are measured directly at the bearing housing. With free access to the bearing housing, measurements are taken with a sensor (indicator probe) at the test points indicated on. The arrows indicate the direction of the sensor location when measuring shock pulses.

1 - indicator probe of the device; 2 - bearing housing; 3 - propagation of stress waves; 4 - rolling bearing; 5 - area of ​​measurement of shock impulses

Before measuring shock impulses, it is necessary to study the design drawing of the mechanism and make sure that the measurement points are selected correctly, based on the conditions for the propagation of shock impulses. The surface at the measurement site must be flat. Thick layers of paint, dirt, scale must be removed. The sensor is installed in the area of ​​the emission window at an angle of 90 0 to the bearing housing, the permissible deflection angle is not more than 5 0. The force of pressing the stylus to the surface of the control point must be constant.

Selecting a frequency range and vibration measurement parameters

In mechanical systems, the frequency of the disturbing force coincides with the frequency of the response of the system to this force. This allows the source of the vibration to be identified. The search for possible damage is carried out at predetermined frequencies of mechanical vibrations. Most of the damages are rigidly related to the rotor speed of the mechanism. In addition, informative frequencies can be associated with the frequencies of the working process, the frequencies of the elements of the mechanism and the resonant frequencies of the parts.

• the lower frequency range should include 1/3… 1/4 of the turnover frequency;
• the upper frequency range should include the 3rd harmonic of the informative frequency of the controlled element, for example, a gearing;
• the resonant frequencies of the parts must be within the selected frequency range.

Analysis of the overall vibration level

The first step in diagnosing mechanical equipment usually involves measuring the overall vibration level. To assess the technical condition, the rms value (RMS) of the vibration velocity is measured in the frequency range of 10 ... 1000 Hz (for a speed of less than 600 rpm, the range of 2 ... 400 Hz is used). To assess the condition of rolling bearings, vibration acceleration parameters (peak and RMS) are measured in the frequency range of 10 ... 5000 Hz. Low-frequency vibrations freely spread over the metal structures of the mechanism. High-frequency vibrations quickly attenuate with distance from the source of vibrations, which makes it possible to localize the site of damage. Measurement at an infinite number of points of the mechanism is limited to measurements at control points (bearing units) in three mutually perpendicular directions: vertical, horizontal and axial ().

The measurement results are presented in tabular form () for subsequent analysis, which includes several levels.

Table 7 - Values ​​of vibration parameters for control points of a turbocharger

Measuring point	RMS value of vibration velocity (mm / s), for measurement directions, frequency range 10 ... 1000 Hz			Vibration acceleration asks / apik, m / s 2, frequency range 10 ... 5000 Hz
	vertical	horizontal	axial
1	1,8	1,7	0,4	4,9/18,9
2	2,5	2,5	0,5	5,0/19,2
3	3,3	4,0	1,8	39,9/190,2
4	2,4	3,4	1,5	62,8/238,5

First level of analysis- the assessment of the technical condition is carried out according to the maximum value of the vibration velocity recorded at the control points. The permissible level is determined from the standard range of values ​​according to GOST ISO 10816-1-97 (0.28; 0.45; 0.71; 1.12; 1.8; 2.8; 4.5; 7.1; 11, 2; 18.0; 28.0; 45.0). The increase in values ​​in this sequence is 1.6 on average. This series is based on the statement that a 2-fold increase in vibration does not lead to a change in the technical condition. The standard assumes that an increase in values ​​by two levels leads to a change in technical condition (1.6 2 = 2.56). The next statement is that a 10-fold increase in vibration leads to a change in the technical condition from good to emergency. The vibration ratio at idle and under load should not exceed 10 times.

To determine the permissible value, the minimum value of the vibration velocity recorded in the idle mode is used. Let us assume that during the preliminary examination at idle speed the minimum value of vibration velocity of 0.8 mm / s was obtained. Of course, in this case, the axioms of a working state must be observed. It is desirable to define boundaries of states for equipment being put into operation. Taking the nearest higher value from the standard range of 1.12 mm / s as the border of good condition, we have the following estimated values ​​when working under load: 1.12 ... 2.8 mm / s - operation without time limits; 2.8 ... 7.1 mm / s - operation in a limited period of time; over 7.1 mm / s - damage to the mechanism is possible when operating under load.

Long-term operation of the mechanism is possible when the vibration velocity is less than 4.5 mm / s, recorded during the operation of the mechanism under load at the rated speed of the drive motor.

To assess the condition of rolling bearings at a rotation speed of up to 3000 rpm, it is recommended to use the following ratios of the peak and root-mean-square (RMS) values ​​of vibration acceleration in the frequency range of 10 ... 5000 Hz: 1) good condition - the peak value does not exceed 10.0 m / s 2; 2) satisfactory condition - RMS does not exceed 10.0 m / s 2; 3) a bad condition occurs when 10.0 m / s 2 RMS is exceeded; 4) if the peak value exceeds 100.0 m / s 2 - the state becomes emergency.

Second level of analysis- localization of points with maximum vibration. In vibrometry, the thesis is accepted that the lower the values ​​of the vibration parameters, the better the technical condition of the mechanism. No more than 5% of possible damage is due to damage at low vibration levels. In general, large values ​​of the parameters indicate a greater impact of destructive forces and allow localizing the place of damage. There are the following options for increasing (more than 20%) vibration:

1) an increase in vibration throughout the mechanism is most often associated with damage to the base - frame or foundation;
2) a simultaneous increase in vibration at points 1 and 2 or 3 and 4 () indicates damage associated with the rotor of this mechanism - unbalance, bending;
3) increased vibration at points 2 and 3 () is a sign of damage, loss of compensating capabilities of the connecting element - coupling;
4) an increase in vibration at local points indicates damage to the bearing assembly.

Third level of analysis- preliminary diagnosis of possible damage. The direction of the higher vibration value at the control point with higher values ​​most accurately determines the nature of the damage. In this case, the following rules and axioms are used:

1) the values ​​of vibration velocity in the axial direction should be minimal for rotor mechanisms, a possible reason for the increase in vibration velocity in the axial direction is rotor bending, shaft misalignment;
2) the values ​​of vibration velocity in the horizontal direction should be maximum and usually exceed by 20% the value in the vertical direction;
3) an increase in vibration velocity in the vertical direction is a sign of increased compliance of the mechanism base, weakening of threaded connections;
4) a simultaneous increase in vibration velocity in the vertical and horizontal directions indicates an imbalance in the rotor;
5) an increase in vibration velocity in one of the directions - weakening of threaded connections, cracks in the elements of the body or the foundation of the mechanism.

When measuring vibration acceleration, measurements in the radial direction - vertical and horizontal are sufficient. It is desirable to carry out measurements in the area of ​​the emission window - the zone of propagation of mechanical vibrations from the source of damage. The emission window is stationary under local load and rotates if the load is of a circulating nature. An increased value of vibration acceleration most often occurs when rolling bearings are damaged.

Vibration measurements are carried out for each bearing assembly, therefore the graph of cause-effect relationships () shows the relationship between the increase in vibration in a certain direction and possible damage to the bearings.

When measuring the general level of vibration, it is recommended to measure the vibration velocity along the contour of the frame, bearing support in the longitudinal or cross section (). The values ​​of the vibration ratio of the support and the foundation that determine the state of the threaded connections and the foundation:

• about 2.0 is good;
• 1.4 ... 1.7 - unstable foundation;
• 2.5 ... 3.0 - loosening of threaded fasteners.

Vibration velocity in the vertical direction on the foundation should not exceed 1.0 mm / s.

Shock Pulse Analysis

The purpose of the shock pulse method is to determine the condition of rolling bearings and the quality of the lubricant. In some cases, shock pulse meters can be used to locate air or gas leaks in pipeline fittings.

The shock pulse method was first developed by SPM Instrument and is based on the measurement and registration of mechanical shock waves caused by the collision of two bodies. Acceleration of material particles at the point of impact causes a compression wave in the form of ultrasonic vibrations propagating in all directions. The acceleration of material particles in the initial phase of impact depends only on the collision velocity and does not depend on the ratio of the body sizes.

To measure shock pulses, a piezoelectric sensor is used, which is not affected by vibration in the low and medium frequency range. The sensor is mechanically and electrically tuned to a frequency of 28 ... 32 kHz. The frontal wave caused by mechanical shock excites damped oscillations in the piezoelectric sensor.

The peak value of the amplitude of this damped oscillation is directly proportional to the impact velocity. A damped transient has a constant damping value for a given state. Changing and analyzing the damped transient process allows assessing the degree of damage and condition of the rolling bearing ().

Causes of increased shock impulses

1. Contamination of the bearing grease during installation, during storage, during operation.
2. Deterioration of the performance properties of the lubricant during operation leading to the inappropriateness of the applied lubricant to the operating conditions of the bearing.
3. Vibration of the mechanism, which creates an increased load on the bearing. Shock pulses are unresponsive to vibration, reflecting deteriorating bearing conditions.
4. Deviation of the geometry of the bearing parts from the specified one, as a result of unsatisfactory mounting of the bearing.
5. Poor shaft alignment.
6. Increased bearing clearance.
7. Loose bearing seating.
8. Shock impacts on the bearing resulting from the operation of the gearing, collisions of parts.
9. Malfunctions of the electromagnetic nature of electrical machines.
10. Cavitation of the pumped medium in the pump, in which shock waves are directly generated in the pumped medium as a result of the collapse of gas caverns.
11. Vibration of connected pipelines or fittings due to unstable flow of the pumped medium.
12. Bearing damage.

Monitoring the condition of rolling bearings using the shock pulse method

There are always irregularities on the surface of the bearing raceways. During the operation of the bearing, mechanical shocks and shock impulses occur. The value of the shock impulses depends on the condition, the rolling surfaces and the peripheral speed. The shock impulses generated by the rolling bearing increase 1000 times from the start of operation to the moment before the replacement. Tests have shown that even a new and lubricated bearing generates shock impulses.

A logarithmic scale is used to measure such large quantities. An increase in the vibration level by 6 dB corresponds to an increase of 2.0 times; by 8.7 dB - an increase of 2.72 times; by 10 dB - an increase of 3.16 times; by 20 dB - an increase of 10 times; by 40 dB - an increase of 100 times; by 60 dB - an increase of 1000 times.

Tests have shown that even a new and lubricated bearing generates shock impulses. The value of this kickoff is expressed as dBi (dBi- initial level). As the bearing wears out, the value increases dBa(the value of the total shock impulse).

Normalized value dBn for a bearing can be expressed as

dBn = dBa - dBi.

The relationship between dBn and bearing life.

Scale dBn divided into three zones (bearing condition categories): dBn< 20 дБ ‑ хорошее состояние; dBn= 20 ... 40 dB - satisfactory condition; dBn> 40 dB - unsatisfactory condition.

Determination of bearing condition

The technical condition of the bearing is determined by the level and ratio of the measured values dBn and dBi. dBn – the maximum value of the normalized signal. dBi- Threshold value of the normalized signal - Bearing background. The value of the normalized signal is determined by the diameter and speed of the controlled bearing. These data are entered into the device before measurements are taken.

During bearing operation, peak shocks differ not only in amplitude but also in frequency. Examples of assessing the condition of a bearing and operating conditions (mounting, seating, alignment, lubrication) based on the ratio of the shock amplitude and frequency (the number of blows per minute) are given.

1. In a good bearing, shocks occur mainly from the rolling of the balls over the unevenness of the bearing treadmill and create a normal background level with a low value of the shock amplitude ( dBi< 10), на котором имеются случайные удары с амплитудой dBn< 20 дБ.
2. When damage occurs on the treadmill or rolling elements against the general background, peak values ​​of shocks with a large amplitude appear dBn> 40 dB. The blows occur randomly. Background values ​​lie within dBi< 20 дБ. При сильном повреждении подшипника возможно увеличение фона. Как правило, наблюдается большая разница dBn and dBi.
3. In the absence of lubrication, too tight or weak bearing fit, the background of the bearing increases ( dBi> 10), even if the bearing is not damaged on the treadmills. The amplitude of the peak shocks and the background are relatively close ( dBn= 30 dB, dBi= 20 dB).
4. During pump cavitation, background levels are high in amplitude. The measurement is carried out at the pump casing. It should be borne in mind that curved surfaces dampen shock impulses from cavitation. The difference between the peak values ​​and the background is very small (for example, dBn= 38dB, dBi= 30 dB).
5. Mechanical contact near the bearing between the rotating and stationary parts of the mechanism causes rhythmic (repetitive) shock peaks.
6. If a bearing is subjected to shock loading, for example from a piston stroke in a compressor, the shock impulses will be repetitive in relation to the operating cycle of the machine, so the overall background ( dBi) and peak amplitudes ( dBn) of the bearing itself can be easily identified.

Questions for self-control

1. Where should the vibration test points be located?
2. What is the standard governing vibration measurements?
3. Where should vibration test points not be located?
4. What are the requirements for measuring shock pulses?
5. What are the requirements for choosing a frequency range and vibration measurement parameters?

Vibration standards are very important when diagnosing rotary equipment. Dynamic (rotary) equipment occupies a large percentage of the total volume of equipment of an industrial enterprise: electric motors, pumps, compressors, fans, gearboxes, turbines, etc. The task of the service of the chief mechanic and the chief power engineer is to determine with sufficient accuracy the moment when the PPR is technically, and most importantly, economically justified. One of the best methods for determining the technical condition of rotating assemblies is vibration monitoring with BALTECH VP-3410 vibrometers or vibration diagnostics using BALTECH CSI 2130 vibration analyzers, which can reduce unreasonable costs of material resources for the operation and maintenance of equipment, as well as assess the likelihood and prevent the possibility of unplanned failure ... However, this is possible only 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 overall assessment of the vibration state of machines and mechanisms of various classes, depending on the power of the unit. On one criterion I compare the absolute values ​​of the vibration parameter in a wide frequency band, on the other - the changes in this parameter.

Resistance to mechanical deformation (for example, when 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 values ​​of vibration. It is associated with the determination of the limits for the absolute value of the vibration parameter, established from the condition of permissible dynamic loads on bearings and permissible vibration transmitted to the outside of the supports and the foundation. The maximum parameter value measured at each bearing or support is compared with the zone boundaries for the given machine. Devices and programs of the BALTECH company, you can specify (select) your vibration standards or accept from the list of standards entered international in the "Proton-Expert" program.

Class 1 - Individual parts of motors and machines connected to the unit and operating in their normal mode (serial electric motors up to 15 kW are typical machines in this category).

Class 2 - Medium-sized machines (typical electric motors from 15 to 875 kW) without special foundations, rigidly mounted motors or machines (up to 300 kW) on special foundations.

Class 3 - Powerful prime movers and other powerful machines with rotating masses, mounted on solid foundations, relatively rigid in the direction of vibration measurement.

Class 4 - Powerful prime movers and other powerful machines with rotating masses installed on foundations that are relatively flexible in the direction of vibration measurement (eg turbine generators and gas turbines with an output of more than 10 MW).

For a qualitative assessment of the vibration of the machine and making decisions about the necessary actions in a specific situation, the following state 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 entering this zone are usually considered suitable for further operation without time limits.
• Zone C- Machines entering this area are usually considered unsuitable for long-term continuous operation. Typically these machines can operate for a limited period of time until a suitable repair opportunity arises.
• 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 value of vibration in the steady state operation of the machine with a preset value. Such changes can be rapid or gradually increasing over time and indicate early damage to the machine or other malfunctions. A 25% change in vibration is generally 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 must 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 an incorrect measurement of the vibration value.

The users of vibration measuring equipment and instruments themselves often find themselves in a delicate situation when they try to compare readings between similar instruments. Initial surprise is often replaced by indignation when a discrepancy is found in the readings exceeding 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 if close enough;

It is incorrect to compare the readings of devices whose vibration sensors have different methods of attachment to an object (magnet, hairpin, probe, glue, etc.);

It should be borne in mind that piezoelectric vibration sensors are sensitive to temperature, magnetic and electric fields and are capable of changing their electrical resistance during mechanical deformations (for example, when falling).

At first glance, comparing the technical characteristics of the two devices, we can say that the second device is much 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 the technical requirements, is not more than ± 10%, i.e. the reading of the device 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 add up arithmetically. We get a measurement error of ± 40%, i.e. the reading of the device is likely from 2.4 to 5.6 mm / s;

At the same time, if we evaluate vibration in the frequency spectrum of vibration of the mechanism of 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 a mean or amplitude detector can lead to additional errors in the measurement of the polyharmonic signal up to 30%.

Thus, if we look at the readings of two devices, when measuring the vibration of a real mechanism, we can get that the real error in measuring the vibration of real mechanisms in real conditions is not less than ± (15-25)%. It is for this reason that it is necessary to carefully consider the choice of the manufacturer of vibration measuring equipment and even more carefully to the continuous improvement of the qualifications of a vibration diagnostic specialist. Since, first of all, on how exactly these measurements are carried out, we can talk about the result of the diagnosis. One of the most effective and versatile devices for vibration control and dynamic balancing of rotors in their own supports is the “Proton-Balance-II” set produced by BALTECH in standard and maximum modifications. Vibration standards can be measured in terms of 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.