Modern man does not imagine his existence without various mechanisms that simplify life and make it much safer. Any equipment used is primarily valued for its safety. This quality largely follows from another property - reliability.
And what is it? How is this term deciphered? And what does he really mean? Let's figure it out!
Definition
So, reliability is the ability of an object to maintain specified properties and technical characteristics over a specific time interval. In addition, this property emphasizes the ability to preserve all specified qualities during transportation and / or in severe, extreme conditions.
In fairness, it is worth noting that reliability is a complex concept that cannot be briefly described. In particular, in technology, this definition is decomposed into several concepts that are closely related to each other. Let's look at each of them.
About technical reliability
Only an object that satisfies four requirements at once or, rather, has traits that must be traced in its characteristics and properties, can be recognized as reliable in technology. To make it easier to understand this definition, we list them:
- As we have already said, reliability is the ability to perform for a period of time the functions that are structurally embedded in the device. For example, an electric motor is required to consume a strictly defined amount of energy and provide a set rotation speed. If we continue this topic, then for the power supply system the ability to produce the desired voltage is important, the value of which can fluctuate only within strictly limited limits.
- The performance of work functions should also occur only within those technological limits that were laid down by the device manufacturer. For example, the engine is required to operate under environmental conditions that will not lead to its destruction.
- On the contrary, if stable operation is required in conditions of high dustiness of the room, then the device must provide this for the longest possible time interval. Note that this and all the above reliability characteristics are necessarily fulfilled.
- The object, among other things, is obliged to have the ability to preserve all of its technical characteristics, not only in the working position, but also at rest. So, a car’s engine should (subject to certain conditions) be ready to start, even if the car had stood in the box for several months or even years before.
Intermediate conclusions
Thus, reliability is a very important quality of any object. In no case can it be opposed or confused with other qualitative concepts. For example, a plant for the purification of industrial emissions can be very attractive in price, in its ability to trap particulate matter from the air in the greatest possible amount. That's just without information about how long these characteristics can be stored, its purchase is very dangerous, and often completely useless.
On the contrary, in the specification of the device there can be 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 of these points.
Some additions
Depending on the purpose of the facility, reliability is a synonym for reliability, maintainability, and 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 an unrecoverable sensor in a sealed enclosure, then for it reliability will be the ability to maintain its operability in a given period of time. Simply put, if this device works without failures for 12 months with a one-year warranty, then it should be considered fairly reliable.
However, there are certain exceptions to such strict rules. Remember how we talked about a car that is on conservation? In this case, reliability is not a synonym for the word “failure-free”, which implies the immediate start of the engine, but “durability” and “maintainability”. No one can guarantee that the engine will start immediately and will work without problems.
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 likelihood of trouble-free, uninterrupted operation of equipment, entire systems and production complexes.
In most cases, the ability of the device to reach its maximum service life without serious damage and the need for maintenance is extremely important. This is especially true for those items that must be operated in extremely difficult conditions.
What should be guided when evaluating the reliability of an object?
As a rule, manufacturers are guided by GOST 27.002-89 "Reliability in technology. Basic concepts. Terms and definitions", from which practically all concepts of reliability adopted in the domestic technical and industrial branches are derived. However, this standard does not cover all 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 an element, system object.
- The stability of the whole complex as a whole.
These concepts are not only connected, but also logically flow from each other. Therefore, we will consider this term in a common, uniform sense.
Basic concepts of reliability theory: object, element and system
An object is a certain technical product that should be monitored, starting from the design stage and ending with delivery to the consumer. It should be remembered that this definition includes not only individual elements, but also rather complex systems: cars, buildings, complexes of industrial buildings and systems.
Thus, a system is understood as a set of objects connected by a certain common function that it should carry out. An element, as you might guess, is called a small, component part of an object that has certain functions. The operability and technical reliability of the entire system as a whole depends on each element individually.
All these concepts are quite relative, since they can be considered through each other. Thus, an object in some kind of research can be considered a system (since it is itself a collection of elements), or it can be an independent element if it is considered from the point of view of a large and remote working complex.
Simply put, it all depends on the scale, which must be taken into account when researching. This is precisely what the theory of reliability speaks of, which has now stood out for a long time as an independent and very important scientific branch.
The relationship of man and machine
People who work as machine and production operators are also separate elements of systems. They are connected both among themselves and with mechanisms. Systems interact in real time. A sign of their integrity and reliability is a clear relationship of structural objects and elements with each other.
About possible states of an object
It should be noted that each object in a given time interval can be in a certain state. Specific reliability indicators depend on this. Let's list them:
- Working condition. In this case, the object fully complies with all regulatory parameters that the manufacturer has laid in it.
- It is recognized as defective when at least one of these parameters does not meet the specified technical characteristics.
- In a state of operability, an 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 start, but it cannot be called operational, and its reliability indicators will confidently decline until they become zero.
- Inoperability is a condition in which an object does not comply with the technical standards laid down in it and cannot fulfill its functions. In this case, there is no talk of reliability in principle.
Limit state of reliability
When discussing the reliability of technical systems, the concept of limit state is of great importance. In short, this is the name of the situation in which further operation of the machine or device becomes unacceptable and / or impossible. A similar condition occurs as a result of a breakdown or the occurrence of some serious defects, material tension. Moreover, any attempt to operate can end in disrepair, since the device is likely to fail and collapse.
Signs of the limit 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 greater manufacturability of production processes, but the manufacturer must provide all these data at the request of the consumer.
What are the common signs of a terminal state?
As we already said, there are two types of objects:
- Restored is the element whose operability can be fully restored, and under standard conditions.
- Accordingly, an object that cannot be restored cannot be restored as an unrecoverable object. In any case, in standard conditions.
For each category, there are certain common signs by which it is possible to diagnose the onset of the limit state with full confidence. Of course, the reliability of technical systems in this case will also be different: if it (the system) consists of only one object that is not amenable to restoration measures, then its reliability indicators will be zero. If the object can be repaired (or replaced by one that cannot be repaired), the indicators can be brought back to normal.
As for objects that cannot be repaired, the limit state for them comes at the very moment when the
warranty period or other resource that was laid down by the manufacturer is exhausted. The same can be said about the maximum permissible output, in which the further operation of the device becomes unreasonably dangerous. In some cases, the reliability coefficient is calculated. Its 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 an indicator of failure rate.
We 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) is the number of failures for a certain period of time.
- Dt is the time interval taken as an axiom in which you fix the total number of problems with the system.
Important! The absolute value of failures is taken from specialized reference books. In each industry, it is completely different, so we are not physically able to provide a gigantic list on the pages of this material.
By calculating the reliability coefficient, you can easily find out what to expect from the object. The lower the indicator, the more reliable it should be recognized as a device, car or home.
About restored objects
As in the previous situation, the limit comes in the event that further operation becomes simply impossible or extremely impractical. In the latter option, a combination of several factors should be taken into account:
- Maintaining an object at a minimum safe and / or operational level becomes impossible or too costly.
- As a result of wear, the device or machine has come to such a state that it is easier and cheaper to buy a similar object.
In some cases, the manufacturer believes that the limit state occurs at a time when the entire set of accumulated problems can be corrected only by major repairs. In principle, this is a fairly reasonable approach, as it helps to prevent many serious troubles. Thus, a synonym for the word "reliability" is serviceability, maintainability.
It should be remembered that in the process of operation, the subject may have other states, which we will talk about now.
Transition of objects to various states during its operation
- Damage - an event consisting in the violation of the health of the object while maintaining its operability.
- Failure - an event consisting in the violation of the health of the object.
- Failure criterion - a distinctive feature or set of those according to which the fact of failure is established.
- Recovery is the process of detecting and eliminating a failure (damage) in order to restore its operability (serviceability).
Practical Reliability Analysis
When specialists are engaged in the analysis of 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 failure. If we assume that the item is theoretically recoverable, but under certain conditions it will not be feasible and / or impossible to repair, it would be more reasonable to transfer it to the category of which cannot be repaired.
Take, for example, a meteorological satellite. During its ground-based design, construction and testing, it relates to refurbished items. When it is put into low Earth orbit, the probability of repair tends to zero, and therefore the success of the entire program depends on reliability.
The reliability of intangible concepts
Above, we told you about what the theory of reliability studies when it comes to material objects: things, devices, mechanisms, ships, airplanes, etc. But can at least some of these concepts be used in a more mundane representation? How, for example, do you know the reliability of banks? After all, they do not have a producer who would recommend taking their contribution after a certain deadline !?
In principle, there is a solution in this case as well, although the reliability is determined using slightly different indicators. Let's list what criteria you should pay attention to first of all:
- The structure of a financial institution, a summary of its founders.
- The composition of the commission of founders.
- Reviews, customer opinions, more than two or three years old. It is better not to pay attention to more recent information in principle.
- The main percentage of 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 it’s definitely not worth contacting this bank. Always try to get to the truth: if there is no such information on the site or in the constituent documents that are publicly available, look at the list of organizations that are somehow related to this institution. If they (even if 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 list above makes you wary and insecure, we strongly advise against using the services of this particular financial institution.