To analyze industrial injuries, three main methods are used: statistical, monographic and economic.

Statistical method is based on a study of the causes of injuries according to documents registering accidents (acts on form N-1, certificates of incapacity for work) for a certain period of time. This method makes it possible to determine the comparative dynamics of injury rates in individual industries, enterprises, workshops and sections of one enterprise and to identify patterns of growth or decrease in injury rates.

To assess the level of injury, relative statistical indicators of the frequency and severity of injury are used.

The number of accidents per thousand workers over a certain calendar period is taken as an indicator of the frequency of injuries:

Kch=(T*1000)/R

where T is the number of accidents for a given period; P is the average number of employees for the same period.

The average duration of disability per accident is taken as an indicator of the severity of injury:

where D is the total number of days of incapacity for all accidents for a given period.

In an in-depth statistical analysis of injuries, in addition to identifying the direct causes of injuries, accidents are also analyzed by the nature of the impact on the human body, by type of work, information about the victims (profession, length of service, age, gender) and data on the time of the incident (month of the year, day of the week) are also analyzed. , shift, hour of the working day).

Statistical methods include the following stages of research: observation, accumulation of statistical material and processing (analysis) of the obtained data with subsequent conclusions and recommendations. The analysis of statistical material grouped into tabular summaries becomes more visual when it is graphically depicted in the form of charts and graphs.

Variations of the statistical method are group and topographic.

The group method of studying injuries is based on the repeatability of accidents, regardless of the severity of the injury.

The topographic method consists of studying the causes of accidents at the location of their occurrence.

Statistical research methods make it possible to obtain a general picture of the state of injury, establish its dynamics, and identify certain connections and dependencies. However, the production conditions in which the recorded accidents occurred are not studied in depth.

Monographic method the study of injuries includes a detailed study of the entire complex of conditions in which the accident occurred: labor and technological processes, workplace, main and auxiliary equipment, processed materials, personal protective equipment, general conditions of the production environment, etc.

As a result of such a study, not only the causes of accidents that have occurred are identified, but also, most importantly, potential hazards and hazards that can have a harmful effect on workers.

Monographic analysis makes it possible to most fully establish ways to prevent injuries and occupational diseases.

Economic method consists in determining the economic damage from industrial injuries, as well as in assessing the effectiveness of costs aimed at preventing accidents in order to optimally allocate funds for labor protection measures.

A systematic approach to solving the problem of occupational safety involves studying the full range of factors influencing working conditions at all stages of the production process. In this case, complex research methods are used that combine the methods discussed above.

The objective characteristics of injuries are determined based on the study of multiple quantitative indicators, the magnitude of which is influenced by a large number of factors simultaneously acting in various combinations.

To determine the degree of influence of several factors on the main indicators of injury, to identify the nature and closeness of the relationship between indicators and factors of injury, for example, methods of dispersion and correlation analyzes are used.

In recent years, the method of scientific forecasting of occupational safety has begun to find application. It serves for probabilistic assessment of injury dynamics, prediction of unfavorable factors of new industries, technologies and development of safety requirements for them. The system of occupational safety standards (OSSS) provides for the development of a methodology for a comprehensive assessment of the safety of technological processes and equipment at the stage of their design, manufacture and operation.

What is the topographic method?

The topographic method of analyzing the causes of industrial injuries is that the places where accidents occurred are marked on the site plan. If they recur periodically at certain workplaces, this indicates an imperfect organization of the work regime and the disadvantage of these places.

The concentration of accidents at such workplaces gives grounds for the employer to take the necessary measures to determine the true causes of accidents in order to develop appropriate measures. The advantage of the topographic method of analysis is its simplicity, convenience and clarity.

How is the monographic method of injury analysis carried out?

This method involves a detailed examination of facilities being operated or just being designed or constructed in order to identify obvious or potential hazards. It is used to determine the causes of accidents that occur in difficult working conditions, so that measures can be clearly defined.

The monographic method reveals not only the causes of accidents that occurred earlier, but also potential dangers and harmful factors that can lead to disruption of the normal work process and inadequate reaction of workers.

This method studies in detail production circumstances, working conditions, features of the technological process, the condition of machines, equipment, etc. To determine the causes of accidents, victims are grouped by profession, gender, age and work experience, and injuries are divided by type of work and the nature of the traumatic actions factors, the time of their occurrence and the nature of the damage.

The results of the monographic method of analysis in homogeneous industries are used in the reconstruction or design of industries or technological processes of the same type.

How is the statistical method of injury analysis carried out?

The statistical method of analyzing industrial injuries is used to determine quantitative indicators characterizing the overall level of injuries. The statistical method is based on the study of accidents according to acts in the N-1 form. For this purpose, relative values ​​are used - indicators (coefficients) of frequency, severity and total disability losses.

The frequency indicator (# ") characterizes the number of accidents that occur for every 1000 workers over a certain period of time and is determined by the formula:

where T is the total number of injuries for the reporting period (six months, year), determined based on closed sick leave;

P is the average number of employees for the same period.

The injury severity indicator (ISI) characterizes the overall severity of injuries during the analyzed period. This value shows how many days of disability per injury, and is determined by the formula:

where D is the total number of days of temporary disability for all accidents recorded during the reporting period.

The overall level of occupational injuries (I.) is calculated using the formula:

This indicator takes into account the number of days of incapacity per 1000 employees during the reporting period.

Comparison of calculated indicators makes it possible to identify the most unfavorable conditions and take appropriate measures to prevent occupational injuries and create healthy and safe working conditions.

Is material damage from accidents determined in reporting?

Static reporting indicates:

sick leave payments;

cost of damaged equipment, tools and materials;

the cost of destroyed buildings, structures and other costs.

What are the types of material losses from work-related injuries?

The main elements that make up the material damage of industrial injuries for the reporting period include:

payment to victims under certificates of incapacity for work P1

pension assigned to the victim in connection with injury P2

pension assigned to close relatives of the victim in connection with the loss of a breadwinner (P3);

assistance with temporary transfer of an employee to another job due to injury (P4)

compensation for damage to an employee in case of partial loss of working capacity P5

employer's costs for professional training of an employee who is hired to replace someone who quit due to injury (B6)

other losses (B7).

By summing up certain component indicators, you can calculate the total material costs (in rubles):

Statistics show that the largest percentage of material costs from industrial injuries are payments for sick leave (more than 50%).

The approximate material damage of industrial injuries can be determined by the formula:

where PII is total material losses;

Day - the total number of days of incapacity for work during the reporting period;

Zsr - average salary of victims;

1.5 - coefficient taking into account material costs.

The obtained indicators are used to determine the economic efficiency of measures to prevent industrial injuries.

The purpose of the analysis of industrial injuries is to exclude the manifestation of the causes leading to industrial injuries. Various methods are used in the analysis.

Statistical research method includes the collection of information about accidents, accumulation and processing of statistical materials with subsequent conclusions and recommendations. With this method, a predetermined number of accidents are analyzed. This method requires the collection of a large statistical array of data on all indicators being studied. With the help of statistical analysis, it is possible to detect patterns inherent in these indicators, to study the peculiarities of the occurrence of accidents in certain professions, at certain production sites, among certain categories of workers.

The main sources of statistical information are accident investigation reports in form N-1 (occupational accident report). The results of the analysis of statistical material are presented in the form of tables, diagrams, and graphs.

The statistical approach is aimed at identifying general patterns in the manifestation of injuries. Injury rates are considered as a function of various variables. Identifying the most significant of these variables and the nature of their influence on injuries is the main goal of the method. With its help, it is impossible to develop any specific recommendations for the prevention of individual accidents - it is aimed at identifying general ways to combat certain types of injuries.

It must be taken into account that the use of a statistical method can be effective if cases of injury are repeated repeatedly when performing the same operations. If during the reporting period (for example, a year) few injuries occur while performing the same work, then for their analysis it is recommended to take the number of injuries that occurred over a longer period of time (from three to five years).

Group method- one of the varieties of statistical method. According to this method, data is processed after preliminary grouping of accidents according to characteristic (homogeneous) characteristics: types of work, uniformity of equipment, climatic conditions, time of injury, age, qualifications and specialty of victims, etc. The method allows for the grouping of characteristics measured both quantitatively and qualitatively.

The essence of the group method is to determine differences in occupational injury rates based on data grouped according to characteristic characteristics. If the differences turn out to be significant, then the grouping feature allows us to establish the reason for the higher injury rate in one group or another.

Topographic method consists of studying the causes of industrial injuries at the scene of the incident and serves to identify work areas in which dangerous situations occur with increased frequency. To do this, draw up a plan (scheme) of the enterprise (workshop, site) indicating production facilities on it. Conventional signs mark places of industrial injuries, including those where microtraumas were received. After summarizing the data obtained, work areas are identified that require the use of special measures to protect workers from occupational injuries, for example, protective fences, blocking, and in some cases, changes in work technology, changes in equipment design, improvement of work technology and special preventive measures.

Monographic method is an analysis OPF, characteristic of a particular production area, equipment, or technological process. The purpose of the method is to identify the main circumstances, subjective and objective causes of a particular dangerous situation, a specific accident, or to determine OPF, that may arise when performing a particular technological operation. The method is based on a comprehensive detailed study of the conditions for the occurrence of a situation in which there could or may be industrial hazards.

The monographic method takes into account a number of factors of a technical, organizational-sociological, psychophysiological and sanitary-hygienic nature that can become causes of industrial injuries. Such factors, for example, include unfavorable environmental factors: noise, vibration, lighting conditions, size and condition of the work area, etc.

Using the monographic method (unlike the previous ones), not only industrial accidents can be studied, but also dangerous situations that resulted in the threat of injury, i.e. in the absence of accidents at the site under study.

Expert method is based on the involvement of qualified specialists in a particular field: a group of experts assesses the significance of a particular cause in the total set of causes of accidents.

Basically, the expert method is used in cases where, when analyzing industrial injuries, it is impossible or difficult to identify certain causes or factors that arise in complex multifactor systems or objects.

Method of graphical construction of cause-and-effect relationships used in the analysis of injury cases resulting from the action of several factors.

It is obvious that there is a cause-and-effect relationship between the realized danger (i.e. the accident) and the causes (factors that caused the accident). Every accident has a cause, which may be a consequence of another cause, etc. The graphical display of such dependencies resembles a branching tree, which is why such graphs are called “cause trees.” With the help of graphical construction of cause-and-effect relationships, the interaction of unfavorable factors that caused a dangerous production situation is clearly displayed and they are assessed.

Methodological identification of causes falls into two stages: building a model of the situation and analyzing this model. At the same time, to identify the causes of industrial injuries as an event that has already happened, the model of the situation is built in the reverse order: from the moment of injury to the events that preceded it.

When analyzing this model, sequential, parallel, circular and concentric forms of causal relationships are used (Fig. 2.1).

Rice. 2.1. The main types of forms of cause-and-effect relationship: A- consistent; b- parallel; V- circular; g - concentric

Sequential form of causation(see Fig. 2.1, A) looks like this: there is an initial cause that causes the second, the second causes the third, etc. As a result, the latter cause leads to injury. Parallel form of causation(see Fig. 2.1 , b) implies the existence of two or more parallel connections that result in injury.

Circular form of causality(see Fig. 2.1, V) presupposes the existence of a primary cause that causes the second, the second - the third and further. The next reason aggravates the first, the first the second and further, until one of the reasons leads to injury.

Concentric form of causation(see Fig. 2.1, G) suggests that one of the factors is the source of several causes, which, developing in parallel, cause a common cause leading to injury.

In real conditions of analysis of industrial injuries, the given forms of causal relationships in various combinations can serve as components of complex network models. This method, despite its complexity and labor intensity, allows us to identify the true causes of industrial injuries.

When analyzing injuries using the cause-and-effect relationship method, you can use the construction of an Ishikawa cause-and-effect diagram (Fig. 2.2), which allows you to present the relationships between the consequence, the result and all possible causes influencing them.

The construction of an Ishikawa diagram (variant names: “problem tree”, “fishbone”) can be carried out in the following order:

• 1) collection of factors (causes) associated with an industrial injury;
• 2) grouping factors (reasons) according to semantic and cause-effect relationships;
• 3) ranking of factors (reasons) within each block;

Rice. 2.2.

• 4) analysis of factors (reasons);
• 5) establishing the main factors (causes) that led to the industrial injury, and indirect ones accompanying the industrial injury.

Ergonomic method is based on a comprehensive study of the “man - machine - production environment” system.

Each type of work activity must correspond to certain physiological, psychophysiological and anthropometric characteristics of the employee. Only with a comprehensive correspondence of the indicated human properties and the rational organization of the workplace to the characteristics of a specific work activity is it possible to effectively ensure labor safety. Violation of such compliance can cause occupational injuries (Fig. 2.3).

Hypothetically, every 10-30 thousand cases of unsafe actions or working conditions at work under certain circumstances can lead to death, therefore, in order to assess the real risk in the presence of hazardous factors, they should be identified. For this purpose, it is necessary to use the results of certification of workplaces for working conditions, which will make it possible to detect, first of all, production factors that pose a real danger.

Rice. 2.3.

Analysis of statistical data on first aid, as well as unsafe actions and working conditions, allows us to identify the most significant and most common factors and causes contributing to the occurrence of industrial injuries. To do this, you can use the method of constructing a Pareto chart.

The essence of the method is that Pareto charts can be used as a tool that allows you to identify and display problems, establish the main factors and causes of industrial injuries that are most often found in the production sector.

When analyzing using the Pareto method, diagrams can be constructed both for possible factors and for possible causes (for example, unsafe actions of workers) of industrial injuries.

Let's list the common rules for constructing a Pareto chart(Fig. 2.4):

• 1) it is necessary to decide what problems (causes of problems) should be investigated, what data should be collected and how to classify them;
• 2) develop forms for recording initial data (for example, a check sheet);
• 3) collect data by filling out forms and calculate the results for each factor under study (indicator, characteristic);

Rice. 2.4.

• 1-7 - studied factors of interest; 8 - other factors
• 4) prepare a table form for constructing a diagram, providing in it columns for the totals for each factor being checked separately, the accumulated sum of manifestations of the corresponding factor, percent of the total (accumulated interest);
• 5) fill out the table, arranging the data obtained for the factor being tested in descending order of importance;
• 6) prepare axes (one horizontal and two vertical lines) for constructing a diagram. Apply a scale with intervals from 0 to a number indicating the total amount of identified factors on the left ordinate axis, and a scale with intervals from 0 to 100 on the right ordinate axis, reflecting the percentage measure of the factor. Divide the x-axis into intervals in accordance with the number of factors being studied or the relative frequency of their manifestation;
• 7) build a bar chart. The height of the column (laid down on the left scale) is equal to the number of manifestations of the corresponding factor or as a percentage of the total number. The columns are arranged in descending order (decreasing repeatability of the factor). The last column characterizes “others”, i.e. insignificant factors, and may be higher than neighboring ones;
• 8) draw a cumulative curve (Pareto curve) - a broken line connecting the points of accumulated amounts (quantitative measures of factors or percentages). Each point is placed above the corresponding column of the bar chart, focusing on its right side;
• 9) put all symbols and inscriptions on the diagram;
• 10) analyze the resulting diagram.

The advantage of this method lies in its simplicity and clarity, as well as the ability to assess the quantitative significance of each factor or cause that can lead to or accompany an industrial injury, which allows the data obtained to be used when planning measures to prevent industrial injuries.

The disadvantage of this method when analyzing industrial injuries is the difficulty of taking into account the possible consequences of specific factors and causes, which can lead to incorrect conclusions.

For example, some frequently repeated unsafe acts may result in minor health consequences, while others may cause severe consequences even if they occur only once.

The concept of “analysis of industrial injuries” is widely used in organizing and planning the work of industrial enterprises. Let's consider the methods used and their tasks.

A competent and scientifically based approach is necessary to establish the causes of accidents leading to injuries in the workplace and temporary loss of ability for workers to work. Methods for analyzing industrial injuries are specially developed methods, during the use of which the causes of this phenomenon at a particular enterprise are established and measures are developed to eliminate and prevent industrial injuries.

An accident has occurred: what should the employer do?

When accidents occur, it indicates poor performance in preventing and preventing workplace injuries. The manager must appoint a special commission to investigate the causes and circumstances of the incident, establish them and take the necessary measures. These materials, along with reporting data, are stored in the organization’s archives.

Each new accident leads to a revision of the effectiveness of the labor protection system, and this requires analytical work: identifying the number of injuries received over a selected period of time, the number of victims, and the degree of injuries received.

How are incidents analyzed?

The first way to analyze overall injury rates is to simply examine written documents. However, when developing a general company policy on occupational safety and injury elimination, others are also used.

There are the following methods for analyzing injuries in an enterprise:

• monographic. It is partially described above, but it is not limited to the study of materials from accident investigations. Using it, labor protection specialists study in detail the circumstances at specific workplaces, the condition of inventory and equipment, working conditions, protective equipment and the progress of production processes;
• topographic. With its help, the most hazardous areas are identified: all the designations of workplaces, sections and workshops are put on the diagram and the number of accidents for a certain period is noted. Where injuries most often occur, a set of research activities is carried out to identify their causes and a set of necessary preventive measures is carried out;
• statistical, more about it below.

Analysis of injuries at an enterprise is a complex and multifaceted task. Listed above are only the main ways to determine the causes of this phenomenon. Modern developers offer to use the latest developments, including:

• scientific forecasting of labor safety for new industries or technologies and the development of special safety precautions for them at the design or manufacturing stage. That is, an analysis of the risk of injury is carried out before the occurrence of an accident. This is an effective and efficient approach to prevent damage and eliminate health hazards;
• use of automated systems for operational accounting and accident prevention;
• deterministic methods, when the study of information is carried out according to a certain criterion, which allows identifying the relationship of injuries with specific operating conditions (observation, questioning of workers, studying the phenomenon in homogeneous groups that unite workers by age, gender, qualifications, profession) and others.

Statistical method of analysis

An analysis of industrial injuries at an enterprise without studying specific figures will always be insufficiently accurate and complete. The statistical method precisely involves the study of quantitative reporting indicators using certain formulas and coefficients that allow us to identify the overall picture and the dynamics of the state of labor safety.

The main coefficients calculated when studying written documents (sick leave certificates and investigation reports): severity coefficient and frequency coefficient.

They are determined by formulas.

Severity coefficient is a quotient of the total number of days of disability and the number of cases of injury for a certain period;

Frequency coefficient is the quotient of the number of accidents for a certain period when the number of days of incapacity for work exceeded three, multiplied by 1000, and the average number of employees.

It is worth noting that many of the above methods are used in practice quite often in combination. Occupational safety and health professionals can use all available options to help reduce the risk of injury.

1. ANALYSIS OF OCCUPATIONAL INJURIES

1.1. Causes of industrial injuries

and methods of its analysis

To improve working conditions in production, the task is always to establish the causes and patterns of accidents and occupational diseases. This is preceded by a deviation of the production process from the normal course.

Causes of industrial injuries

Currently, the analysis identifies the following causes of industrial injuries.

1. Organizational – absence or unsatisfactory provision of instructions and training in safe work methods; lack of work design, management and supervision of work; unsatisfactory work and rest regime; improper organization of the workplace, pedestrian and vehicle traffic; absence, malfunction or non-compliance with working conditions of work clothes, personal protective equipment, etc.

2. Technical reasons are divided into three types:

a) design - non-compliance of building structures, technological equipment, transport and energy devices with safety requirements; imperfect design of mounting equipment, hand and portable power tools; absence or imperfection of protective fuses and other technical safety measures;

b) technological – incorrect choice of equipment, equipment for lifting mechanisms and mechanization; disruption of the technological process;

c) unsatisfactory technical maintenance - lack of scheduled preventive inspections, technical maintenance and repair of equipment, equipment and vehicles; malfunction of hand and portable power tools.

3. The reasons for the unsatisfactory state of the production environment are unfavorable meteorological conditions; poor lighting; increased noise and vibration levels; increased concentration of harmful substances in the air of the work area; presence of harmful radiation, etc.

4. Psychophysiological – discrepancy between the anatomorphological and psychological characteristics of the human body and working conditions; unsatisfactory psychological climate in the team; alcohol intoxication, etc.

Methods for analyzing industrial injuries

When analyzing industrial injuries in order to identify and eliminate the causes that cause them, various methods are used:

– topographic: consists of studying the causes of accidents at the place of their occurrence. All accidents are systematically marked with symbols on work plans, as a result of which the places and production areas where injuries occurred are clearly visible;

– statistical: is based on the study of the causes of injuries according to documents recording the facts of accidents that have occurred (acts in form N-1) for a certain period of time. This method allows you to obtain comparative dynamics of injury rates for individual production facilities. In-depth statistical analysis is carried out by type of work, where information about the victims (profession, work experience, gender, age, etc.) and data on the time of the incident (year, month, day of the week, shift, hour of the working day, etc.) are analyzed. . P.);

– group: based on the study of repeated accidents, regardless of the severity of the injury. The available investigation material is divided into groups in order to identify accidents that are identical in circumstances, occurred under the same conditions, and also repeat in the nature of the damage. This allows us to determine the most traumatic professions and types of work;

– monographic: includes a detailed study of the entire complex of production conditions under which the accident occurred: labor and technological processes, workplace, main and auxiliary equipment, personal protective equipment, general conditions of the production environment, etc.

Quantitative assessment of occupational injuries

A number of indicators are used to assess the level of occupational injuries.

Injury frequency rate, which is the number of accidents per 1000 workers over a certain period

Where N– the number of accidents that occurred in the organization during the period under review;

R– the average composition of employees in the organization for the period under review.

The injury severity coefficient represents the average duration of temporary disability per one accident that occurred at work

where is the total number of days of incapacity for work due to injuries for the period under review.

The fatal accident frequency rate is the number of fatal accidents per 1000 workers and is assumed to be

, (1.3)

where is the number of fatal accidents during the period under review.

Example: Calculate the frequency rate and severity rate of injuries for a construction organization with 800 people, if it is known that over five years of its work there were 6 accidents with loss of temporary working capacity with a total duration of 72 days.

Solution: To determine the coefficients of frequency and severity of injuries in an organization, we use formulas (1.1) and (1.2):

;

1.2. Risk analysis methods

Risk is a quantitative assessment of danger, which is expressed as the ratio of the number of certain adverse consequences to their possible number for the period under consideration.

In relation to production activities, the concept of occupational injury risk is used as a quantitative indicator of safety. It determines the actual measure of the probability of damage to the health or death of a worker due to exposure to hazardous production factors during the performance of his work duties. The risk of occupational injuries is largely determined by the qualifications and training of workers to act in a dangerous situation and their protection. During the analysis, the risk value is not determined for each employee. This value can be determined for a group of people characterized by the same time spent in hazardous conditions, for example, for a team of finishing workers, etc.

Risk value R can be defined as the expected value of damage n caused over a period of time Dt, attributed to a group of people of P Human:

The concept of risk always includes two elements: the frequency with which a hazardous event occurs and the consequences of the hazardous event.

Risk assessment includes frequency analysis, consequence analysis and a combination of both. Therefore, it is advisable to consider risk analysis as part of a systematic approach to decision-making and practical measures in solving problems of preventing or reducing danger to human life, diseases or injuries, damage to property and the environment.

Planning and organization of work;

Hazard identification;

When planning and organizing work, the reasons and problems that necessitated the risk analysis are described.

When identifying hazards, the main task is to identify (based on information about the safety of a given facility, the results of examinations and experience in operating similar systems) and clearly describe all the hazards inherent in the system.

In principle, the risk analysis process can end at the hazard identification stage. Only if necessary, after identifying the hazards, can you proceed to the other steps described above.

1.3. Hazard identification methods

Hazard identification can be done using the following basic methods:

- “failure tree”;

- “event tree”;

Equivalent.

The methods can be used individually or in addition to each other. Qualitative methods may include quantitative risk measures. A complete quantitative risk analysis may include all of these methods.

Methods “what will happen if ...?” and checklist belong to the group of qualitative hazard assessment methods. The result of these methods is a list of questions and answers about the facility’s compliance with safety requirements and recommendations for ensuring safety.

An analysis of the causes of industrial accidents shows that their occurrence, as a rule, is characterized by a combination of random local events (equipment malfunctions, human errors, etc.). To identify cause-and-effect relationships between these events, logical-graphical methods “fault tree” and “event tree” are used. When analyzing the “fault tree” method, combinations of equipment malfunctions and personnel errors leading to an industrial accident are identified. The method is used to analyze the occurrence of dangerous situations and calculate its probability (based on knowledge of the probabilities of the initial events).

To analyze the development of a dangerous situation, the “event tree” method is used. According to this method, the frequency of each accident scenario is calculated by multiplying the frequency of the main event by the probability of the final event.

Tree analysis methods are the most labor-intensive and are used to analyze projects or modernize complex technical systems and production facilities, and require highly qualified performers. Therefore, we will consider in more detail the application of the “fault tree” method, which is used in production to determine the causes of equipment failures.

The method consists in constructing and analyzing a model, which is a logical-probabilistic model of the cause-and-effect relationships of product failures with failures of its elements and other events. The basic principle of constructing a “failure tree” is to consistently pose questions and give answers for what reasons a product failure may occur. To visually represent a causal relationship using a “fault tree,” logical symbols and event symbols are used. Logical symbols connect events in accordance with their causal relationships. Symbol designations are given in table. 1.1, and event symbols in table. 1.2.

Table 1.1

Notation of logical symbols

logical	Name logical	Causal relationship
		Exit event happens if everything input events happen simultaneously
		Exit event occurs if any of the input events occurs
	"BAN"	The presence of an input causes the appearance of an output then when a conditional event occurs
	Priority "AND"	An output event occurs if all inputs events take place in the right order from left to right
	Exclusive OR	Exit event occurs if one (but not both) of the input events occurs
	"m" from "n"	Exit event occurs if "m" of "n" inputs occur

Table 1.2

Event Symbol Designations

Event symbol
	Initial event secured sufficient initial data
	Event is not enough detailed
	Event entered logical element
	Conditional event used with the logical sign “prohibition”
	Event that can happen or not happen
	Transition symbol

Schemes for the use of logical symbols and event symbols depending on the initial events 1,2,…, n in the “fault tree” diagrams are shown in Fig. 1.1. and 1.2.

Rice. 1.2. Using the logical symbol "OR"

Example 1: Identify risk R death of a person in the construction industry in our country in 1 year, if it is known that 600 people die annually, and the number of workers is 700,000 people.

Rice. 1.3. “Failure tree” for a metal-cutting machine

Solution: To determine the risk of human death, we use formula (1.4):

.

Example 2. Using the “failure tree” method, estimate the probability of failure of the drilling and boring group machine. The main movements of the machine are: the main cutting movement, i.e. rotation of the tool and the feed movement of the cutter.

Solution. Machine failure can occur due to a functional failure resulting from sudden failures of blocks, assemblies, parts of the machine, or due to a parametric failure, which will occur when technological reliability is exhausted, as shown in Fig. 1.3.

Functional failure may occur if the following foreseeable cause-and-effect hazard chains are realized and cause the machine to stop:

Motor failure;

Fuse failure;

Short circuit of the electrical wire to the housing;

Pump failure;

Safety valve spring failure;

Throttle failure;

Check valve failure;

Loss of tightness in the oil pipeline;

Failure of the limiter of the movable gear wheels of the gearbox - machine stop;

Feed box gear failure;

Based on our reasoning, we will build a “failure tree” of a metal-cutting machine, as shown in Fig. 1.3.

In Fig. 1.3 is indicated: 1 - electric motor failure; 2 - limit switch failure; 3 - short circuit of the cable to ground; 4 - fuse failure; 5 - short circuit to the housing; 6 - pump failure; 7 - valve spring failure; 8 - throttle failure; 9 - check valve failure; 10 - failure of the safety valve; 11 - oil line leaks; 12 - main engine clutch failure; 13 - failure of the clutch of the first gearbox shaft; 14 - failure of gearbox gears; 15 - failure of the limiter of the movable gear wheels of the gearbox; 16 - failure of the gearbox gears; 17 - failure of the clutch clutch of the gearbox gears.

1.4. Basic hazard and risk indicators

in production

Accidents at work (occupational diseases are not considered), depending on the consequences, are usually classified as follows:

– fatal accidents;