Reliability is ... Technical reliability. Coefficient of reliability

Modern man does not think of his existence without various mechanisms that simplify life and make it much safer. Any technique used is primarily valued for its safety. This quality largely follows from another property - reliability.

And what is it? How is this term correctly interpreted? And what does it really mean? Let's understand!

Definition

So, reliability is the ability of an object to retain specified properties and technical characteristics over a certain time interval. In addition, this property emphasizes the ability to retain all specified qualities during transportation and / or in severe, extreme conditions.

For the sake of justice it is worth noting that reliability is a complex concept that can not be briefly described. In particular, in the technique, the definition is decomposed into several concepts, closely related to each other. Let's analyze each of them.

About technical reliability

In technology, only an object that satisfies four requirements at once or, more likely, has features that can be traced in its characteristics and properties can be recognized as reliable. To make it easier to understand this definition, we list their list:

• As we have already said, reliability is the ability to perform functionally built-in functions for a period of time. For example, an electric motor must consume a certain amount of energy and provide a set speed of rotation. If we continue this topic, then it is important for the power supply system to produce the required voltage, the magnitude of which can fluctuate only in strictly limited limits.
• The performance of work functions should also occur only within the technological limits that were laid by the device manufacturer. For example, the engine requires operation under those environmental conditions that will not lead to its destruction.
• On the contrary, if a stable operation is required in conditions of a high dust content of the room, then the device must provide this for as long as possible a time interval. Note that this and all the above reliability characteristics are fulfilled.
• The object, among other things, must be able to maintain all its technical characteristics, not only in working position, but also at rest. So, the engine of the car must (subject to certain conditions) be ready to start, even if the car has stood in the box for several months or even years before that.

Intermediate conclusions

Thus, reliability is a very important quality of any object. In no case can it be contrasted or confused with other qualitative concepts. For example, a plant for the purification of industrial emissions can be very attractive at a price, by its ability to trap solid particles from the air as much as possible. But only without knowing how long these characteristics can last, its purchase is very dangerous, and often completely useless.

On the contrary, the specification of the device can have a lot of information about reliability, but there will not be a single word about exactly what characteristics it has. Thus, the definition of reliability should include all these points.

Some additions

Depending on the purpose of the object, reliability is a synonym for failure-free operation, maintainability, durability. It should be clearly understood that this quality is perceived only taking into account the characteristics of the object itself. For example, if you take a non-recoverable sensor in a sealed enclosure, then for him the reliability will be the ability to maintain its performance in a given period of time. Simply put, if this device works without failures for 12 months with an annual warranty, then it should be recognized as sufficiently reliable.

However, there are certain exceptions to such strict rules. Do you remember how we talked about the car, which is on conservation? In this case, reliability is not synonymous with the word "failure-free", which implies immediate engine start, but "durability" and "maintainability". Nobody can guarantee that the engine will immediately start, and without problems will work.

A reliable power plant is guaranteed to withstand storage (under more or less suitable conditions) and will be able to function after carrying out some maintenance activities. Thus, ensuring reliability is a list of necessary measures that are aimed at increasing the probability of trouble-free, uninterrupted operation of equipment, entire systems and production complexes.

In most cases, the ability of the device to reach its service life without serious breakdowns and the need for maintenance is extremely important. This is especially true for those items that must be used in extremely difficult conditions.

What should be guided, assessing the reliability of the object?

As a rule, manufacturers are guided by GOST 27.002-89 "Reliability in technology: basic concepts, terms and definitions," from which practically all the concepts of reliability adopted in the domestic technical and industrial sectors are derived. However, this standard does not cover all the concepts, and therefore sometimes we will make explanations.

Immediately consider the types of reliability. Modern science suggests that there are only two of them:

• Fault tolerance of the object, system object.
• Stability of the whole complex as a whole.

These concepts are not only connected, but also logically follow from each other. Therefore, we will consider this term in a general, unified understanding.

Basic concepts of reliability theory: an object, an element, and a system

The object is a certain technical product, which must be controlled, from the design stage and ending with the delivery to the consumer. It should be remembered that this definition includes not only individual elements, but also rather complex systems: machines, buildings, complexes of production buildings and systems.

Thus, a system is understood as the totality of objects connected by some common function, which it must implement. An element, as you might guess, is a small, component part of an object that has certain functions. From each element individually depends on the operability and technical reliability of the entire system in general.

All these concepts are relatively relative, since they can be viewed through each other. Thus, an object can be considered as a system at some research (since it is itself a collection of elements), and can be an independent element if viewed from the point of view of a large and remote working complex.

Simply put, everything depends on the scale, which must be taken into account when researching. This is exactly what the reliability theory says, which at the present time has long been isolated as an independent and very important scientific branch.

The relationship of man and machine

People who work as machine operators and production facilities are also separate elements of the systems. They are connected both with each other, and with mechanisms. The systems interact in real time. A sign of their integrity and reliability is a clear interconnection of structural objects and elements with each other.

Possible state of the object

It should be noted that each object in a particular time interval may be in a certain state. It is from this that specific reliability indicators depend. Let's list them:

• Working condition. In this case, the object fully meets all the regulatory parameters that the manufacturer has put into it.
• Defective it is recognized when at least one of these parameters does not meet the specifications.
• In the state of operability, the object can perform all its basic functions, and the value of the established indicators will be within the technical norm. It should be remembered that a faulty device can be started, but it can not be called operational, and its reliability indicators will surely decrease until they become zero.
• Inoperability is a condition in which an object does not conform to the technical standards contained in it and can not perform its functions. On reliability in this case, the conversation does not go in principle.

Limit state of reliability

When the reliability of technical systems is discussed, the concept of the limiting state becomes of great importance. In short, this is the situation in which further operation of the machine or appliance becomes unacceptable and / or impossible. A similar condition occurs as a result of breakage or the occurrence of some serious defects, the strength of the material. In this case, any attempt to exploit can end badly, since the device is likely to fail and crash.

Signs of the limiting state are established by the manufacturer, and the information should be reflected in the technical specification attached to the object. Every year there is a general increase in reliability due to more technological processes of production, but all these data the manufacturer must represent at the request of the consumer.

What are the common signs of the onset of the limiting state?

As we have already said, there are two types of objects:

• Recoverable is the element whose operability can be resumed completely, and under standard conditions.
• Accordingly, an unrecoverable object is one whose performance can not be renewed. In any case, in standard conditions.

For each category, there are certain common signs, by which it is possible to diagnose, with complete certainty, the onset of the limiting state. Of course, the reliability of technical systems in this case will also be different: if it (the system) consists of only one object that can not be restored, its reliability indicators will be zero. If the object can be repaired (or replaced with one that does not lend itself to repair), the figures can actually be adjusted to the norm.

As for objects that can not be repaired, the limit state for them comes at the very moment when the warranty period or other resource that was laid by the manufacturer is exhausted. The same can be said about the maximum permissible production, in which further operation of the device becomes unreasonably dangerous. In some cases, the reliability factor is calculated. The formula is quite simple:

Ki = li / lb

Let's find out what the variables mean:

• Li is the absolute value of the failure rate;
• Lb is the failure rate index.

Calculate the failure rate

To do this, use the following equation:

L (i) = n (t) / (Nt * Dt)

• L (t) is the total number of failures.
• Nt is the average number of elements in the system.
• N (t) - the number of failures for a certain period of time.
• Dt - the time taken for the axiom, in which you fix the total number of problems with the system.

Important! The absolute value of refusals is taken from specialized reference literature. In every industry, it is completely different, so we can not bring the giant list on the pages of this material physically.

Calculating the reliability factor, you can easily find out about what to expect from the object. The lower the indicator, the more reliable it is to recognize the appliance, the car or the house.

About the restored objects

As in the previous situation, the limit comes in the event that further exploitation becomes simply impossible or extremely inexpedient. In the latter variant, several factors should be taken into account:

• Maintaining an object at a minimally safe and / or efficient level becomes impossible or too costly.
• As a result of wear and tear, the device or machine came to such a state that it is easier and cheaper to buy a similar object.

In some cases, the manufacturer believes that the limiting state comes at a time when the entire set of accumulated problems can be corrected only by making major repairs. In principle, this is a fairly reasonable approach, since it helps to prevent many serious troubles. Thus, the synonym for the word "reliability" is serviceability, maintainability.

It should be remembered that in the process of exploitation the object can have other states, which we will now talk about.

Transition of objects to different states during its operation

• Damage is an event consisting in a violation of the integrity of the object while maintaining its operability.
• Failure is an event involving a violation of the operability of the object.
• The rejection criterion is a distinctive feature or a set of such, according to which the fact of refusal is established.
• Recovery - the process of detecting and eliminating a failure (damage) in order to restore its operability (serviceability).

Practical reliability analysis

When specialists analyze the reliability of an object, machine or building, it becomes extremely important for them to make the right decision about what to do in case of refusal. If we assume that, theoretically, the object is recoverable, but under certain conditions its repair will not be appropriate or / and impossible, it is more reasonable to transfer it to the category not subject to repair.

Take, for example, a meteorological satellite. During its surface design, creation and testing, it refers to the objects to be reconstructed. When it is taken out to near-earth orbit, the probability of repair tends to zero, and therefore the success of the entire program depends on reliability.

Reliability of non-material concepts

Above we have told you that it studies the theory of reliability when it comes to material objects: things, instruments, mechanisms, ships, planes, etc. But can any of these concepts be used in a more mundane view? How, for example, to find out the reliability of banks? After all, they do not have a producer, who would recommend to withdraw their contribution after the onset of a certain deadline !?

In principle, there is a solution in this case, although the definition of reliability is made by slightly different indicators. Let's list which criteria you should pay attention first:

• The structure of the financial institution, a summary of its founders.
• Composition of the commission of founders.
• Reviews, opinions of clients, and not less than two or three years old. On more recent information, it is better not to pay attention in principle.
• The main percentage for both deposits and loans.
• Providing bank guarantees.

First of all, you should pay attention to the composition of the founders. Some names and surnames will immediately tell knowledgeable people that you do not need to communicate with this bank. Always try to get to the bottom of the truth: if there is no such information on the website or in the constituent documents that are available in the public domain, look at the list of organizations that are related to this institution in one way or another. If they (even in the distant past) were involved in financial scandals, it is better to look for a more secure place for your money.

This is how the reliability of banks is determined. If at least one item from the above list causes you to be wary and insecure, we strongly advise you not to use the services of this particular financial institution.