What is reliability? Reliability indicators: definition and characteristics

The property of the object to perform certain functions assigned to it, while maintaining performance characteristics within certain limits, corresponding to specified modes and conditions of use, is reliability. Reliability indicators can be very different, but the quality of the performance of a particular product largely depends on them.

Components

There are three main components of this definition:

• Performance of established functions;
• Time required for this;
• Certain operating conditions.

If we talk about the performance of given functions, then it is worth noting two concepts that relate to the theoretical and practical understanding of what constitutes reliability. Reliability indicators from this point of view are as follows: serviceability and operability of the specified product.

Serviceability and serviceability

Performance is a certain state of the object, in which it retains the ability to perform specified functions with parameters determined by technical documentation. At the same time, it is worth noting the fact that performance and serviceability are not properly identified, since the second is a state in which it fully meets the established requirements in the technical documentation.

Time is another important element that implies reliability. Reliability indicators in this case include this concept is far from accidental, since the physical essence of reliability lies in the fact that any product must necessarily retain its technical parameters within a certain time.

Other components

In addition, the definition of reliability also includes operating conditions. For technical systems that operate under different conditions, it can be characteristic of a different time before the first failure occurs.

It is necessary to understand correctly, what a broad meaning is the term "reliability" in itself. Reliability indicators include a large range of quality without any specific definition of their quantification and certain properties. However, in the process of establishing the reliability of a certain object or a common technical system, there is a need to uncover those concepts and properties that are included in the complex indicator. For example, for specialized equipment of various power plants, among such concepts are the following:

• durability;
• Maintainability;
• Failure-free operation.

And they themselves also depend on a number of other parameters.

Secondary indicators

If we talk about what the main parameters of reliability depend on, we can distinguish three main factors. It:

• Quality. Indicators of quality (reliability) include a set of properties by which the degree of suitability of a particular technical device is determined for its use for its intended purpose.

Quality directly depends on the way in which this or that product is used. For example, if a specialized steam turbine unit, which was originally designed to carry basic loads, will be used in a special maneuvering mode, then such operation will ultimately begin to negatively affect its condition and, accordingly, its quality, and also low results , When reliability indicators are calculated.

• Vitality. It is the ability of a certain technical device to prevent any serious violations, as well as to exclude the process of development of all kinds of accidents and physical malfunction of the equipment.

• Security. A certain property of technical devices, which provides for the absence of possibility of occurrence of any situations that are dangerous for people and their environment. Thus, in the process of calculating reliability indicators, these features are also taken into account.

In the course of considering the reliability of various complex systems, the notion of stability in connection with the failure of the work of individual elements is also considered. In some cases, the notion of "safety" can also be applied.

What is it?

Preservation is the property of any equipment to remain in good order during its storage. Like other reliability indicators of systems, it provides the ability of the product to maintain its main technical characteristics within the established limits. If we mean that storage is an integral part of the operation, then safety is reliability in storage conditions.

We can say that this parameter is rather complicated, and it will be rather difficult to evaluate it with some specific characteristic, since any reliability indicators of the products can be the criteria of safety.

The main feature of this concept is that there is a prevailing permanent failure due to a reduction in the installed characteristics of the components, which is due to their aging. Preservation is a rather important technical concept, and in combination with reliability it makes it possible to determine the reliability of one or another equipment in different states. This is all the more important for the reason that a large amount of equipment has some specific storage periods that are equal to or even exceed the established working time. The definition of reliability indicators of technical systems includes a very large number of other factors that differ in nature.

Example

As an example, we can consider the reliability of a steam turbine power unit, which includes:

• Quality of materials used in the production process;
• Perfection of the developed design;
• Used manufacturing technology;
• Applied technology of transportation and installation of equipment;
• Quality of used fuel;
• Conditions of operation and maintenance of devices.

And this is only a short list of what includes the characteristics of reliability indicators. The creation and application of new, increasingly complicated installations requires the constant provision of their increasingly high degree of reliability. That is why a specialized "reliability theory" was developed, which has recently become quite widespread.

Theory

Today, the mathematical apparatus of the theory of reliability is provided, which is often used in the practice of solving the vast number of the most diverse problems that arise in the production and operation of various equipment. Thus, the basic concepts that determine the reliability indicators (durability) of equipment, include:

• System;
• an object;
• element.

The formulation of these concepts fully corresponds to the basic philosophical concept of the whole and the element. Various technical objects that are considered in this theory of reliability are represented in the form of all possible systems that are a set of functionally interrelated and interacting elements. This system is designed to perform the specified integrity of the program. As elements, separate parts of the system are considered that can perform independent tasks on their own.

The choice of the system, as well as the various parts forming it, is very arbitrary. If an advanced statement of the problem is used, then any system eventually becomes part of a larger system, and any elements are broken up into parts, in turn, turning into its elements. Thus, the division of different equipment into elements and systems directly depends on the hierarchical level at which the tasks are accomplished.

GOST, the concept of a system and an element is combined into one term - "object".

What is he like?

An object is called a certain device of a system or a separate element of it, which is taken for the purpose of studying some of its specific properties outside all possible connections with other parts.

In the process of operation of the whole system as a whole, as well as of its individual element, there can appear such cases in which there is a complete or partial loss of their functional properties. Such a loss of efficiency in the theory of reliability is usually called a failure, and it is one of the basic concepts.

Failure and its features

A failure is any event that involves a violation or a complete cessation of the operability of the object in question. In this case, it happens:

• Sudden or gradual;
• Dependent or independent;
• Partial or final.

If the failure of a certain element does not provide for the rejection of other parts, it is customary to call it independent, while the failure of the device due to the breakdown of other elements is called dependent.

Sudden failures, starting from the name, arise absolutely unexpectedly without any noticeable signs of their appearance, while gradual ones provide for wear or aging of the material, too long exposure to excessive loads, which leads to a gradual decrease in characteristics with full or partial preservation of the operability of the equipment used .

Final or complete failures are a form of equipment failure in which the system loses its operability or the parameters override the permissible limits until the cause of the failure is eliminated. Partial only leads to activation of the warning signal, as well as to the need to reduce the operating parameters to a certain level.

Among other things, it is worth noting the fact that a special place is given to failures or their aggregates, which are the reason for the transition of an object to the limit state, at which achievement its subsequent application for its intended purpose is inexpedient or unacceptable.

How to ensure the reliability of equipment in the production process?

To ensure high reliability and longevity of various products, you must properly comply with the manufacturing and installation of any system. Analysis of statistical information indicates that in the majority of cases emergency stopping of specialized equipment is the cause of the corresponding technological defects, therefore modern manufacturers try to use a number of specialized measures that allow to minimize the risks of failures in various systems even at the stage of manufacturing and installation.

Regardless of which key reliability indicators the manufacturer is trying to provide, they must work in the following areas:

• Increase the degree of factory availability through the release of equipment in a reliable performance. For example, pipelines, turbines, boilers and specialized equipment for water treatment can be supplied with enlarged blocks, while the majority of assembly and welding works are transferred from the original installation site to the factory shop, because under such conditions it is much easier to achieve extremely high quality of work.
• Extensive use of the latest quality control technology at each individual stage of production, from input control of various semi-finished products and raw materials to ensuring control of finishing procedures, full-scale or bench testing. The expediency of carrying out the entrance control was repeatedly confirmed by the statistics of defects that were detected during the specialized control of various products.
• Use of progressive technological production devices with programmatic control, which allow the most detailed processing of components and produce the product with maximum accuracy.
• Mechanization and automation of complex procedures, expansion of the use of advanced technologies.

Practice has repeatedly been proven that the use of modern equipment in the production process, as well as the full compliance with established operating modes allows you to determine the reliability of the final product to a large extent. At the same time, it is necessary to correctly understand the features of the production of a particular equipment or any products, as well as the main risk factors, in order to use all the necessary measures to eliminate or minimize them. Thanks to this, the evaluation of reliability indicators will always be high, regardless of the sphere in which the work is being done.