Degrees of electric shock effect on body of a person:

Vibrations and acoustic vibrations

Mechanical vibrations, produced by working machines, moving liquids and other sources and transmitted by constructions of production buildings, equipment, person, are identified as vibration.

In construction the main sources of vibration are machines for preparation, distribution and vibration compaction of concrete mixture: concrete mixers, batching plants, vibroplatform, also building machines, compressors, bulldozers and others.

Total vibration damages the nervous and cardiovascular systems, gastrointestinal tract, musculoskeletal system. At continuous work without effective protection measures the vibrating disease can develop - fatal disease, which is accompanied by the change in blood vessels of upper or lower extremities, arterial pressure reduction, blood supply disturbance of internals, reduction of cardiac beat frequency.

The reduction of fingers sensitivity, arthropathy and hands neurosis is observed at the continuous influence of local vibration.

By the direction of effect the vibration is considered more harmful if it effects lengthways of body axis, than perpendicular to it.

For description of vibrations the following characteristics are used:

- amplitude of vibration displacement, i.e. maximum deviation of oscillating point from equilibrium position;

- the oscillatory velocity;

- the vibration acceleration;

- the oscillation period;

- the oscillation frequency

Classification of vibration.

a. by the method of transmission on a person it is found out the general vibration, transmitted through the supporting surface of a person in the sitting or standing position;

b. by the sources of origin it is classified only general vibration, dividing it on the following categories:

- transport vibration, influencing on the operators of the moving machines and vehicles at their movement on the territory and roads, and also at their construction (agricultural and industrial tractors, self-moving agricultural machines (including combines); the trucks (including tractors, road scraper, graders, paving compactor and etc.); the snowplows);

- transport and technological vibration, influencing on the operators of machines with limited displacement only on specially prepared surfaces of the working areas, industrial areas or mine workings (excavators, industrial and building cranes, mine loading machine, tow-to-yarn machines, concrete pavers);

- technological vibration, influencing on the operators of the stationary machines or are dispatched on working places, not having the sources of vibration (metal-working and woodworking machine, equipment for bore-hole drilling, equipment of building materials industry (except concrete pavers).

c. By frequency composition the vibrations can be:

- low-frequency vibrations (with prevalence of maximum levels in octave-frequency band 1-4 Hz – for general vibrations, 8-16 Hz – for local vibrations);

-middle-frequency vibrations (8-16 Hz – for the general vibrations, 31,5-63 Hz – for local vibrations);

-high-frequency vibrations (31,5-63 Hz – for general vibrations, 125-1000 Hz – for local vibrations)

 

2.6 Noise is a disorderly combination of sounds of different frequency and intensity (power), appearing at mechanical oscillations in solid, fluid and gaseous mediums.

Classification of noise, influencing on a person.

1. By the character of the spectrum:

- broadband noise - with continuous spectrum by the width of more than one octave;

- tone noise - there are showed tones in the spectrum. Tone character of noise for practical goals is determined by the measure in 1/3 octave-frequency band on level excess in one band on nearby ones not less than on 10 db.

2. By temporary characteristics:

- constant noise, which sound level for 8-hours workday or for the time of measure changes not more than on 5 dBA at measures on time characteristics of sound level meter "slowly";

- inconstant noise, sound level for 8-hours workday or for the time of measure changes more than on 5 dBA at measures on time characteristics of sound level meter "slowly".

3. Inconstant noises are divided on:

-oscillating noise in the time, sound level continuously changes in the time;

- discontinuous noise, which sound level changes stepply (on 5 dBА and more) moreover the interval duration, during of which the level stays the constant, is 1s and more;

- pulsed noise, consisting of one or several sound signals, each of duration less 1s differ not less than on 7 db.

The sound wave is characterized by sound pressure (P, Pa), intensity (I, W/m²), frequency (f, Hz).

The sound pressure shows the difference between instantaneous value of pressure and average pressure in quiet ambience. Our acoustic organ reacts exactly on changing of air pressure. Than more the pressure, that stronger the irritation of acoustic organ and the feeling of sound volume.

At spreading of the sound wave in space the energy transport occurs; the amount of transported energy is defined by the intensity of the sound.

The intensity of the sound is an amount of sound energy, passing at one second through the unit of area, perpendicular to the direction of the sound wave spreading.

 , (1)

where: I - intensity of the sound, W/m²;

W - sound energy, W;

S - area, m².

Between intensity of the sound and its sound pressure exists the definite dependency:

 , (2)

where: I - intensity of the sound, W/m²;

R - sound pressure, Pa;

ρ - density of the ambience, kg/m³;

c - speed of the sound in the same ambience, m/s.

For characteristics of the noise level it is used not direct values of the sound intensity and sound pressure, by those it is uncomfortably operate, but their logarithmic values, defined as the level of sound intensity or level of sound pressure.

The level of sound intensity is defined by the formula:

 , (3)

where L_I - level of intensity in decibel (db);

I - sound intensity, W/m²;

I₀ - sound intensity, corresponding to the edge of audibility of human ear (I₀ - constant value; I₀ =10-12 Vt/m2 on frequency 1000 Hz).

The human ear, and also some acoustic instruments react not on sound intensity, but on sound pressure, which level is defined by the formula:

 , (4)

where R - sound pressure, Pa;

R0 – edge of sound pressure (R₀ - constant value; R₀ =2·10^-5 Pa on frequency 1000 Hz).

The acoustic organs of the person perceive the sound waves with frequency 20-20000 Hz. The oscillations with frequency below of 20 Hz (infrasound) and above of 20000 Hz (ultrasound) do not cause the auditory feelings, but biologically influence on organism.

The perception of the sound by a person depends on its frequencies, intensity and sound pressure. The least intensity (I₀) and the least sound pressure (R₀), perceived by the person on given frequency, is identified as the edge of audibility. At f=1000 Hz R₀=2·10^-5 Pa and I₀=10-12 W/m².

If R=20 Pa and I=10 W/m² then person feels the pain - an ear-ache edge.

Between these edges is the area of audibility.

Electric current

Types of electric current effects:

– Thermal. The result of effect is burns, skin heating.

– Electrolytic. The result of effect is the decomposition of organics inside the person (blood).

 – Biological. The result of effect is a spasm (contraction) of muscles.

 – Electrodynamic (mechanical), results in myorrhexis (muscles rupture). The presence of the voltage source and closed circuit results in current rush.

Electrical injury is an injury got because of the effect of electric current or electric arc. Types of electrical injuries:

- Local electrical injury (probability 20%);

- Electric shock (25%);       

- Mixed (55%).

Types of local electrical injuries:

Burn. It is got because of the effect of electric arc. The symptoms are the redness, vesication, skin necrosis, carbonization.

Electric signs. The skin and internal organs resistance results in the skin rupture as the circlet in the place of passing of electric current through the skin.

The skin metallization. At the becoming of the short circuit occurs the melting of electric parts, and flying in different sides parts of metal are hit on skin.

Mechanical damages.

Electrical autonomous. At the becoming of the electric arc occurs the bright flash and effects on retina (bright electric sparks at welding).

Mixed.

Degrees of electric shock effect on body of a person:

1 degree – convulsive, perceptible a little the contraction of muscles;

2 degree - convulsive contractions of muscles without loss of consciousness;

3 degree - loss of consciousness with the retention of breathing and heart work;

4 degree - loss of the consciousness with breathlessness and heart work;

5 degree - apparent death.

Factors effecting on the result of electric injury:

1.Electric resistance of the body of a person. The person is stroked by current, which depends on voltage and resistance of the body: ,

where I – current, A

U – voltage, V

R – electrical resistance, Ohm·m.

2. Parts of body of the person, damaged at electric injury of the person:

skin in place of the current entering;

internal organs;

skin in place of the current leaving.

3. The resistance of internal organs is insignificant. The resistance of the skin depends on its conditions (clean and dry or humid (sweated)).

Types of current:

- perceptible current (1 mA for variable voltage);

- continuous current 10-15 mA;

- mortal current 0,1 A.

Duration of the current is defined: heart in weakened condition 1 sec. (where in 0,5 sec. occurs the heart fibrillation).

The mortal way of the current passing: head - left hand (left leg).

The ways of current passing: (Fig. 1.)

 

Fig. 1. The ways of current passing

Anthropogenic dangers

Activity of a person is important, necessary section, providing the interaction of technical systems. At this the person, operating by energy and information flows, solves the problems, consisting from the row of stages: perception of information; its estimation, analysis and generalization on the base of beforehand given and stated criteria, taking a decision about the further actions, realization of taken decision. However, on all stages of activity it is possible the wrong actions of a person.

Analysis of data on technogenic accidents and catastrophes shows that significant part of dangers appears because of wrong, incorrect taken decisions, when he himself becomes the source of dangers. According to statistics about 45 % of emergencies on nuclear power plants, over 60 % of accidents on objects with raised risk, 80 % of air disasters and catastrophes on the sea, and also 90% of car accidents occurs because of wrong action of people.

The error is defined as nonfulfillment of the given problem (or carrying out by the person of forbidden action) that can be the reason of heavy consequence - traumas, death of people, damage of equipment or property or irregularity of the normal current planned operations. The errors due to the fault of person can occur in different spheres and conditions of its vital activity:

- on rest, during the journey, at going in for sport: at vehicles driving; careless treatment with fire, sharp subjects, weapons; at bathing in water reservoirs; during the trips in mountains; on training and competition on different types of sport;

- at home, at the usage of appliances, domestic gas, open fire, pesticides, instrument and devices; at treatment with the home wastes, the boiling liquids, with subject containing mercury; the consumption of the bad products, alcohol, medicine and etc;

- in the field of production activity: at irregularity of stated working regimen and inaction at the moment, when its participation in process of activity is necessary;

- in emergency situations natural and technogenic kinds, related, as a rule, to unpreparedness of the people to actions in emergency situations; to their inability to foresee, for instance at treatment with combustible and explosive agents or control of complex technical systems; at avalanching, descent of torrents and so on;

- at contact of the people between themselves: the sources of errors can be dishonourableness, negligence, revenge, jealousy, insults, religious and national conflicts and so on;

- at control of economy and state activity – errors is often are caused by tendency of people to break laws of the nature: for instance, construction pulp and paper mill on Baikal, projects of turning of the North rivers to the South and others.

 The feature of the person to mistake is a function his psychological condition and intensity of mistakes in mostly depends on conditions of surrounding ambience and effecting loads on the person. It is determined that dependence of the mistakes occurrence frequency from effecting loads is nonlinear. So, at very low level of loads the majority of operators work inefficient (the task seems boring and does not cause the interest), and quality of work does not correspond to necessary. At moderate loads the quality of the operator’s work turns out to be optimum so the moderate load can be considered as conditions sufficient for ensuring of the attentive work of the person-operator. But at further increase of the loads the quality of work of the person becomes worse that is explained, mainly, by such demonstrations of the physical stress, as fear, nervousness, rapidness of pulse and frequency of breathing, increasing of temperature, ejection of adrenaline in blood and so on.

In the system "person - environment" person is the most changeable component. His behaviour is defined by lots of individual factors. Often, the different operators the similar tasks execute in the different actions.

The main particularities of personality and conditions of the organism of the person, inciting him to carrying out of mistakes, can be divided on innate particularities and temporary conditions.

The physiological features of the person and his heredity, including sense organs (ear, vision, smell, touch, taste), support-locomotion (muscular power, velocity of the motion, co-ordination etc.) and psychomotor systems (reflexes, reactions and etc.), intellect (level of knowledges, ability to orientate) are concerned to innate particularities.

The temporary conditions such as physical and psychological tiredness, resulting in the reduction of attention and muscular power, worsening of health and capacity to work, contribute to occurrence of mistakes. As factors, detracting attention, can be temporary functional disturbance of the organism (for instance, unexpectedly appeared headache, dizziness, spasm of muscle and so on), temporary switching over of attention to some event or subject, not connected with work; the fatigue, sudden external effect (noise or bright flash of the light).

The reasons of mistakes are divided on direct, main and contributory.

The direct reasons of mistakes depend on psychological structure of operator’s action (the mistakes of the perception - has not recognized, has not found; the mistakes of memories - has forgotten, has not remembered, wasn’t able to restore; the mistakes of thinking - has not understood, has not provided, has not generalized; the mistakes of decision taking, return reaction ,etc.) and type of these actions i.e. from psychological regularities, defining the optimum activity - the discrepancy to psychic possibilities of information organization (size or speed of the information reception, attitude to the edge of the distinguishing, small duration of the signal and etc.) from lack of the skill (the standard actions in non-standard situation) and structures of attention (didn’t concentrated, didn’t not switch over, quickly tired).

Production ambience

Production ambience is a part of technosphere that has the raised collection of negative factors. Main bearers of injury and harmful factors in production ambience are machines and other technical devices, chemical and biologically active subjects of the labour, the sources of energy, unregulated actions of workers, breaches of regimens and organization of activity, and also departure from possible parameters of microclimate of working zone.

Injury and harmful factors are divided on physical, chemical, biological and psychophysiological. 

The physical factors - moving machines and mechanisms, raised levels of noise and vibration, electromagnetic and ionizing radiations, insufficient luminosity, increased level of the static electricity, raised value of the voltage in electric circuit and others; chemical - materials and compounds those different on the aggregate condition and have toxic, irritating, sensitizing, carcinogenic and mutagenic influence on organism of the person and influencing on his reproductive function; biological - pathogenic microorganisms (bacteria, viruses and others) and products of their vital activity, and also animals and plants; psychophysiological - a physical overloading (static and dynamic) and nervously-psychic ( mental overstrain, overstrain of analyzers, monotonicity of the labour, emotional overloading).

Injury and harmful factors of the production ambience those are typical for majority of modern productions, are showed in tabl. 2.

The concrete working conditions are characterized by collection of negative factors, and also are differed on level of harmful factors and risk of the demonstration of injury factors.

    Table 2.

Injuring and harmful production factors

The sources of harmful factors	The coverage of factor
Physical factors
Dust level in working zone	Zones of discrete material processing, zones of shake-out and molding treatment, welding and plasma treatment, plastic, glass fiber plastics and others fragile materials treatment, zones of materials crushing and so on
Vibrations: Total Local	Vibroplatforms, vehicles, building machines
	Vibroinstrument, horns of transport machines control
Acoustic vibrations:
Infrasound	Zones next to the vibroplatforms, powerful explosion engines and other high energy systems
Noise	Zones next to the technological equipment of the shock action, devices for gas testing, vehicles, energy machine
Ultrasound	Zones next to the ultrasound generators, crack detectors: bathes for ultrasound treatment
Static electricity	Zones next to the electrical equipment on the constant current, zones of coloring by spray, synthetic materials
Electromagnetic fields and radiation	Zones next to the power lines, electrolamp generators, screens, displays, antennae, magnets
Infrared radiation	Heated surfaces, melted materials, emission of the flame
Laser emission	Lasers, reflected laser emission
Ultraviolet radiation	Zones of welding, plasma treatment
Ionizing radiations	Atomic fuel, sources of radiations used in instruments, crack detectors and at the researches
Current	Electric mains, electric installations, distributors, transformers, equipment with electric drive and etc.
Movable machines, mechanisms, materials, products, parts of destroying constructions	Zones of land transport moving, conveyors, underground mechanisms, moving parts of machines, instrument, zones near the systems of the raised pressure, reservoirs with compressed gas, line tubes, pneumohydroelectric power plants
Height, felling objects	Building and erecting works, machines and plants support
Sharp edges	Cutting and pricking tool, rough edges, roughened surfaces, metallic cutting waste, pieces of brittle materials
Increased or decreased temperature of equipment and materials surface	Steam pipes, gas pipelines, cryogenic systems, chilling equipment, melts
Chemical factors
Gas pollution of working zone	Loss of toxic gas and steams from unpressurized equipment, evaporations from opened reservoirs and at sheddings, outbreak of materials at the seal failure of equipment, coloring by spay, drying of colored surfaces
Dust level of working zone	Welding and plasma treatment of materials contained the Cr2O3, MnO, sprinkling and transportation of disperse materials, coloring by spay, bonding by plumbous welding alloys, bonding of beryllium and by welding alloys containing beryllium
Poison ingress on skin and mucous tunics	Galvanic production, reservoirs filling, liquids spraying (douching, surfaces coloring)
Poison ingress in gastrointestinal tract	Errors at the liquids usage, deliberate actions
Biological factors
Liquid coolants	Materials treatment with the emulsols usage
Psychophysiological factors
Physical overloads:
Static	Continuous work with displays, the work in uncomfortable position
Dynamic	Lifting of the loads, manual labour
Neuropsychic overloads:
Mental stress	Labour of scientific workers, professors, students
Analyser stress	Technical systems operators, airline operators, the work with displays

 

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