Industrial vibration is a danger to human health, as well as to building structures, technological equipment. Under the influence of mechanical vibrations, the wear of machines accelerates, the time period between their repairs decreases, the accuracy of measuring instruments and control equipment decreases. Transmitted through solid foundations, vibration affects other, non-production premises, maintenance staff. Assessment of harmful fluctuations is included in the system of sanitary-hygienic assessment of working conditions.
General concept
Industrial vibration occurs as a result of mechanical vibrations of working machines, the movement of liquids and other unbalanced influences. An increased level of vibration has a negative effect on human health, reducing its performance, and with prolonged exposure causes occupational diseases. Therefore, issues of combating mechanical vibrations in sanitation are given special importance.
Vibration can be transmitted to a person either directly through contact with equipment or tools, or indirectly through elements of industrial premises. The requirements for the control of this unfavorable factor and its maximum permissible values are set forth in a number of regulatory documents (SN 2.2.4-2.1.8.566-96, SP 1102-73, GOST 12.1.012-2004, SanPiN 2.2.4.3359-16 and others).
Kinds
Industrial vibration is classified according to several criteria:
1. By localization:
- The total. Such vibration affects the nervous, musculoskeletal, cardiovascular system, gastrointestinal tract (sensation of pain in the stomach or lower epigastric region). With prolonged exposure, a vibrational disease can occur - an incurable pathology.
- Local (local) transmitted in the limbs of a person when resting on a vibrating surface.
2. By source of appearance:
- For local vibrations: from a manual mechanized or non-mechanized tool.
- For general vibration: category I, II and III (described below).
3. In the direction in space: X, Y, Z-oscillations. The most dangerous are those that are directed along the axis of the body.
4. According to the spectrum:
- Narrow-band (the vibration level of one third of the octave to be controlled is 15 dB more than in neighboring sections of the same width).
- Broadband (their spectrum is continuous for more than 1 octave).
5. By frequency:
- Low-frequency (<4 and <16 Hz for general and local vibrations, respectively).
- Mid frequencies (<16 and <63 Hz); o high-frequency (<63 and <1000 Hz, respectively).
6. By duration:
- Permanent.
- Periodically arising (oscillating, intermittent, impulsive).
Types of general production vibration
General vibrations according to the source are divided into 3 types:
- Transport (machines such as tractors, mine transport, combines, trucks, snow blowers are most susceptible to them);
- Transport and technological (arising when moving along the surface of production facilities - excavators, cranes, floor filling machines for loading the mixture into the furnace, rolling stock for the construction and repair of the railway, pavers and other equipment).
- Technological, arising from stationary equipment (machines, presses, pumps, fans, drilling, chemical and petrochemical plants and others).
Specifications
The main indicators describing various types of industrial vibration are the following:
- Circular frequency (number of oscillations per second). When measuring vibrations, the vibration spectrum is divided into frequency bands, for each of which an intensity assessment is carried out. For this, octave filters are used, the nominal bandwidth of which is equal to one octave.
- Amplitude (maximum deviation) of vibrational movement.
- The highest or rms vibrational velocity and acceleration.
Sources
Industrial vibration sources, in accordance with the type of general vibrations, include:
- narrow-band - construction vehicles, trams, tractors, combines, trams, railway cars and locomotives;
- polyharmonic (changing according to the periodic law) - metal and woodworking machines, internal combustion engines, hydraulic turbines and generators, compressors, textile machines, vibro conveyors;
- random and polyharmonic - drilling machines, hoisting cranes, jack hammers and perforators, earth and carbon machines.
Local vibration is generated by such tools as:
- rotary (grinding and polishing machines, chainsaws);
- rotary percussion (wrenches);
- percussion (chipping hammers, riveting devices);
- rotary shock (mining mechanized tools, rotary hammers);
- pressing (scissors with the number of moves per minute more than 500).
Such vibration is exposed to metal cutters, riveters, wood cutters, grinders and other workers.
Causes
The cause of vibrations are unbalanced force effects - reciprocating or rotational; shock interactions in gears, rolling bearings, valves of engines and compressors, crank mechanisms. Mechanical vibrations can also occur in robotic plants and lines.
The following can be distinguished as design and technological factors causing vibration of industrial premises:
- improper arrangement of the bases and foundations of equipment;
- excessive rigidity of structures (fastening of working platforms, seats, controls and other elements);
- design features of the equipment;
- technological errors in the manufacture of components (imbalance of rotating flywheels, shafts, errors in the manufacture of parts);
- poor-quality installation of equipment at the place of operation;
- increased load or speed during operation;
- untimely carrying out preventive maintenance of equipment.
Effects on the human body
The impact of industrial vibration on human health is complex:
- bone-articular disorders - dystrophic lesions of the spine (osteochondrosis, spondylosis), decreased bone density (osteoporosis);
- deterioration of cellular and humoral immunity;
- cardiovascular diseases (angiospasm - narrowing of blood vessels, impaired blood circulation and tissue nutrition, development of venous stasis);
- microtraumatization of tissues;
- decreased activity of antioxidant defense enzymes;
- neuropathy.
With prolonged local vibration, numbness of the fingers is felt, joint diseases and limb neurosis develop. General vibration also affects the vestibular apparatus, gastrointestinal tract, sensory organs (decrease in visual acuity and hearing) and other systems. The most harmful vibrations are those whose frequency is in the range of 3-30 Hz, since their values are close to the natural vibrations of human organs (a resonance phenomenon occurs). Vibrations with a frequency of 6-9 Hz can cause rupture of internal organs.
The severity of the influence of mechanical vibrations depends on the following factors:
- spectral composition;
- direction;
- place of exposure;
- duration.
Vibratory disease
The systematic effect of industrial vibration contributes to the occurrence of vibrational illness. It is curable only in the early stages. Subsequently, in the event of irreversible changes in the internal organs, it is impossible to get rid of it.
As subjective signs, this pathology manifests itself in the form of the following symptoms:
- dizziness, headaches, flickering of "flies" in the eyes;
- breaking pains in the hands, worse at night;
- numbness, chilliness, whitening, swelling of the fingers; burning, tingling in them;
- bad sleep;
- worsened well-being;
- decreased performance.
Other signs are also characteristic:
- hypotension;
- multiple organ failure caused by insufficient blood supply (at the stage of decompensation);
- decreased heart rate;
- metabolic disorders (hypothyroidism and other pathologies);
- decreased sensitivity;
- angioedema;
- pathology of the musculoskeletal system (myofibrosis, arthrosis) and others.
Rationing
Rationing of industrial vibration is carried out in order to exclude the possibility of vibration disease in workers and employees. Controlled parameters are regulated by GOST 12.1.012-90, which lists tables with restrictive values of the main indicators.
The sanitary norms for industrial vibration of general and local type are normalized depending on the geometric mean values of the vibration frequency. There are several hazard classes in which the occurrence of vibro-illness is possible. The first corresponds to the lowest level (optimal working conditions), under which there is no contact with general and local vibration.
Sanitary and hygienic measures to prevent negative consequences from mechanical vibrations include certification of workplaces, preliminary and current sanitary supervision, control over the use of personal protective equipment (vibration damping gloves, shoes).
Methods
There are several methods for evaluating production vibration:
- frequency - the spectrum of vibrations is measured (the rms values of vibration velocity and acceleration in full frequency bands or 1/3 of the range are calculated);
- total (integral) frequency estimate (adjusted value of vibration velocity and acceleration or their logarithmic indicators);
- integral, taking into account the duration of the effect of vibration at an equivalent value.
Weighting factors are selected according to the recommendations of CH 2.2.4 / 2.1.8.566-96.
Devices
Measurement of mechanical vibrations under operating conditions is performed using the following instruments:
- vibrometers (IShV-1, Assistant, VShV-003, models of the Bruhl & Kj r company and others);
- weight and band filters;
- vibration sensors (DN series produced by Vibropribor, Bruhl and Kjr production and others);
- sound level meters (for detecting equivalent levels in generally accepted frequency bands);
- level recorders;
- magnetographs for recording oscillations in order to conduct frequency analysis, calculate the equivalent level.
Measurement points are selected on surfaces in contact with the human body. If the workplace is unstable, then control is performed at least 3 points with maximum vibration. To measure the overall vibration, instruments with a higher sensitivity are selected. Vibration sensors are installed in three mutually perpendicular planes.