RU2542683C1 - Method to increase efficiency of item operation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: average duration of item control t_c is determined, as well as average duration of item repair t_r, the cost of Y_r of item repair per unit of time, cost Y_c of item control per unit of time, profit ∋_f per unit of time from operation of the item without failures, the average number of failures B(k) of the item per unit of time at the number of controls k, then they make dependence of efficiency of ∋ item operation on the specified parameters of reliability, control and repair. Optimal number of controls k is determined on the basis of the condition d∋/dk=0.

EFFECT: reliability of items with minimum costs.

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Description

FIELD OF THE INVENTION

The invention relates to methods for ensuring the reliability of products and conducting tests, in particular on the basis of non-destructive testing, in various fields of technology: transport, mechanical engineering, energy and others. More specifically, the invention relates to methods for improving product performance and optimizing product control in various industries.

State of the art

The prior art attempts to optimize non-destructive testing, for example, in publications [1] - [4] of the European Commission and the IAEA. There are also known “Methodological recommendations for optimizing operational non-destructive testing”, Rosenergoatom Concern, 2007. A disadvantage of the known methods is the inability to optimize the frequency of product inspection during its operation on their basis.

As the closest analogue, a well-known method for increasing the efficiency of product operation, disclosed in patent RU 2301992 C2 (published on June 27, 2007), is adopted. The basis of this known method is the method of non-destructive testing of the product, which allows to increase the efficiency of its operation. However, this method does not allow to optimize the frequency of control of the product.

SUMMARY OF THE INVENTION

The objective of the invention is to create a more advanced method of monitoring products during their operation, which allows to increase the efficiency of operation of products in general.

The technical result achieved by the invention is to optimize the frequency of inspection of products, including non-destructive methods, and to ensure the level of reliability of products at minimal cost.

The above set of technical results is achieved by the fact that the method of increasing the efficiency of product operation is to determine the level of reliability of the product, determine the methods and means of non-destructive testing of the product, select the technology of repair of the product, while determining the average duration t _to control the product, the average duration t _p repair of the product, the value of I _p repair of the product per unit of time, the cost _to have control of the product per unit of time, the profits _of ∋ per unit time from the operation of Elihu without failure, the average number of failures in (k) products at a time when the number of the k controls, make ∋ dependence of the efficiency of operation of the mentioned product reliability parameters, control and repair

∋ = ∋ _о [1-t _r B (k) -t _to k] -U _p t _p B (k) -U _to t _to k

the optimal number of controls k is determined from the condition d∋ / dk = 0,

carry out the operation of the product, during which carry out the optimal number of controls.

A distinctive feature of this method is the use of the dependence of the operational efficiency of the product with the characteristics of the operational control of the product, its repair and the reliability level of the product.

Brief Description of the Drawings

Figure 1 shows the dependence of operational efficiency ∋ on the number of controls for the design (or upcoming) life k. It was shown that maximum efficiency is achieved with the optimal number of k _opt controls.

Figure 2 graphically shows the solution of the equation to determine the optimal number k _opt controls. The optimal amount of k _opt controls corresponds to the intersection of the horizontal curve 1 with curve 2.

Figure 3 shows a special case of determining the optimal number k _opt controls. In the shown example, k _opt = 0, since curve 1 and curve 2 did not intersect.

The implementation of the invention

The most critical products of modern technology are subjected to repeated non-destructive testing (ultrasound, radiographic, eddy current and other types). So, in nuclear energy, the regulatory document “Rules for the Construction and Safe Operation of Equipment and Pipelines of Nuclear Power Plants” PNAEG-7-008-89 establishes the following structure of non-destructive tests of vessels and pipelines of a reactor installation: incoming inspection at the NPP site; during the development of capacity, as well as periodic operational control during operation with a frequency of four years, and in case of defects, the frequency may be one year. Thus, the number of product controls can reach seven to ten or more during the design life of the reactor installation.

Carrying out operational periodic non-destructive testing requires material costs, time (which leads to a decrease in operating efficiency) and is usually regulated by top-level documents, for example, in nuclear energy, the federal-level document PNAEG-7-008-89 mentioned above. Non-destructive testing of the product is carried out to increase its reliability and safety.

The purpose of operational control: 1) identification and fixing of metal defects; 2) identification and fixation of changes in physical and mechanical properties and metal structure; 3) assessment of the condition of the metal; 4) timely repair of identified defects according to the results of monitoring to prevent the occurrence of dangerous conditions of the product associated with its partial or complete destruction.

At the same time, control is carried out for reactor vessels, vessels, pump housings, valves and pipelines and other products.

On the example of nuclear power plants (NPPs) it can be seen that the frequency of non-destructive testing is as follows:

- with removal of thermal insulation - at least 1 time in 4 years for the main equipment and pipelines;

- for other equipment - once every 8 years.

At western production NPPs, a control period of 10 years was established with the possibility of increasing to 11 years.

Both in domestic and foreign literature, there are no indications on the justification of the frequency of operational control adopted in practice, and therefore changes in the existing frequency standards (both downward and upward) require the development of a special justification. The question of the frequency of non-destructive testing is relevant both from an economic point of view (monitoring takes a lot of time, during which commercial use of the object is impossible and the company incurs corresponding losses), and from the point of view of safety and reliability of operation (monitoring leads to increased reliability of the product and reduces the likelihood of its destruction during operation).

The task was solved based on the results of a risk analysis for each specific product. The basic principles of a non-destructive testing program based on risk information are as follows:

- the ability to determine the consequences, likelihood and risk associated with failures;

- development of a non-destructive testing program, the implementation of which will reduce the risk of failures in high-risk areas, taking into account economic considerations (cost).

The main elements that make up the process of planning an operational control based on risk information are:

- assessment of the probability of failures for all considered components;

- assessment of the consequences of failures for all components under consideration;

- ranking of risks associated with all components;

- selection of components to be controlled in accordance with the selected criteria.

Optimization of operational control based on risk information can be performed by comparing two independent events: the consequences of a failure and the likelihood of this failure. In addition, each of these events is evaluated in terms of risk:

- very tall;

- tall;

- average;

- low;

- very low.

Depending on the combination of these estimates, a control decision is made. For example, if the consequences of failure are high and the probability of failure is high, then control should often be done. If the probability of failure and the consequences are very high, then you need to monitor very often. The disadvantage of this approach is that it is not exhaustively determined what is often, what is very often.

The essence of the invention is that it determines the dependence of the product’s operating efficiency on the product’s control characteristics, product reliability level, depending on the control method and product repair characteristics in case of damage (partial or complete destruction). The maximum operational efficiency of the product is determined as the extremum (curve 1 in FIG. 1) on the curve of the dependence of the product's operating efficiency ∋ on the number of controls k for the entire design life (the frequency of control is the quotient of dividing the design life by k).

In other words, since the implementation of operational control is associated with material costs, its optimal organization should provide for the maintenance of a certain ratio between the total costs of control and the benefits derived from the control.

As a specific goal of optimization, it is accepted to obtain maximum efficiency, which, in particular, can be measured as profit or income from the operation of the product. The relation between efficiency ∋ (profit) per unit time, the number of k controls, mean duration t _to control the average duration t _p repair, repair of value _p per unit of time and cost have _to control in the unit of time, is as follows:

where ∋ _about - profit per unit time from the operation of the product, if equipment failure does not occur; In (k), the average number of breakdowns per unit time (probability of destruction) with the number of controls equal to k.

The value of B (k) is, in essence, the strength characteristic of the controlled structural element, more precisely the probabilistic characteristic of failure according to the criterion of the occurrence of a defect in the structure, or according to other criteria, for example, complete destruction of the structure. It can vary in the interval from a certain maximum value B _max corresponding to the case when control is not performed, i.e. k = 0, to the minimum value tending to 0. In the latter case, k takes the maximum value k _max .

A change in the function ∋ (k) in the range 0 <k <k _max can correspond to three cases:

The meaning of expressions (2) - (4) is as follows. The product for which condition (2) is valid must be operated with the highest achievable reliability, i.e. In (k) should tend to 0; this case is not considered by us.

For a product with condition (3), a certain number of breakdowns can be allowed. For a product with condition (4), control is disadvantageous, that is, the optimal number of controls for the entire service life is k = 0.

By differentiating expression (1) and using condition (3), we obtain the condition for achieving maximum product operation efficiency (∋ _max in FIG. 1):

The maximum operational efficiency of the product is achieved with the optimal number of controls (see FIG. 1).

The disadvantage of control takes the form:

The equations obtained above are the conditions for achieving maximum product operation efficiency in conjunction with the optimal number of controls and the time interval between controls (or frequency of control).

The sequence of steps during the implementation of the invention is as follows:

- determine the level of reliability of the product, determine the methods and means of non-destructive testing of the product and choose the technology of repair of the product;

- determine the average duration t _to control the product and the average duration t _p repair of the product;

- determine the cost U _{r of} repair of the product per unit time, the cost of Y _to control the product per unit of time, the profit ∋ _о per unit time from the operation of the product without failures, the average number of failures B (k) (destruction, leakage or detection of a dangerous defect) of the product in unit of time with the number of controls k.

Further, the efficiency ∋ operation of the product depends on the mentioned reliability, control and repair parameters ∋ = ∋ _о [1-t _r B (k) -t _to k] -U _p t _p B (k) -Y _to t _to k.

After that, the optimal number of controls k _opt is determined from the condition d∋ / dk = 0, i.e. by the formula (5).

After that, the product is operated, during which the optimal number of controls is carried out with a frequency of T / k _opt , where T is the design life of the product and the product is repaired according to the control results. At the same time, maximum operational efficiency of the product is achieved.

An example embodiment of the invention

Determine the conditions for achieving the maximum operating efficiency of the pressure vessel body for the design life of 30 years, which corresponds to the optimal number of controls k _opt for the specified life. The probability of destruction of the casing was evaluated by the criterion of resistance to brittle fracture, taking into account the embrittlement of the metal from radiation exposure. The income from the operation of the housing for 30 years was taken equal to ∋ _o = 4 · 10 ⁸ rubles. The cost of control for 30 years was defined as the salary of control operators, taking into account the cost of equipment for control (U _k = 0.8 · 10 ⁶ rubles). The repair cost was taken equal to U _d = 8 · 10 ⁸ rubles. (it was assumed that the concept of “flowing before destruction” is valid for the vessel and complete destruction will not occur, however, with partial destruction, death can occur with the need to pay compensation). The ratio of time for inspection and repair was taken t _p / t _k = 100. The solution of equation (5) by a graphical method is shown in FIG. 2. In this figure, curves 1 and 2 correspond to the values, respectively:

и

.

and

.

The intersection point of curves 1 and 2 corresponds to the optimal frequency of flaw detection inspection of the pressure vessel k _opt = 1.2 or, rounding to the side of the reserve, 2 times in 30 years of operation. At the same time, the maximum operational efficiency of the product for 30 years of operation is achieved, provided that the detected defects are repaired according to the results of the inspection. The second case, when the control is disadvantageous, is considered for the auxiliary pipeline in FIG. 3. In this case, the intersection of curves 1 and 2 is absent, which indicates the fulfillment of condition (6). The maximum operational efficiency is achieved if non-destructive testing is not carried out, i.e. k _opt = 0.

Bibliography

[1] ENIQ report No. 23 “European Framework Document for Risk-informed In-service Inspection” EUR 21581 EN, Luxembourg: Office for Official Publications of the European Communities, 2005.

[2] IAEA-TECDOC-1400 Improvement of in-service inspection in nuclear power plants ", July 2004.

[3] IAEA Regional Workshop, on Qualification of In-Service Inspection Systems and Risk-Informed In-Service Inspection. Zagreb, Croatia, October 18-22, 2004.

[4] About J Victor Chapman, Structural Reliability Models (SRM). Link between RI-ISI & Inspection Qualification, Inspection Interval. "

Claims (1)

A way to increase the efficiency of operation of products, which consists in determining the level of reliability of the product, determining methods and means of non-destructive testing of the product, choosing the technology for repairing the product, characterized in that they determine the average duration t _to control the product, the average duration t _{p of} repairing the product, the cost _r repair of the product per unit time, cost Y _to control the product per unit time, profit прибыль _о per unit time from operation of the product without failures, average number of failures B (k) of the product per unit time, with the number of controls k, is the dependence of the efficiency эффективности operation of the product on the mentioned parameters of reliability, control and repair
∋ = ∋ _о [1-t _r B (k) -t _to k] -U _p t _p B (k) -U _to t _to k,
the optimal number of controls k is determined from the condition d∋ / dk = 0,
carry out the operation of the product, during which carry out the optimal number of controls.

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