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blacksmith work

Reliability and durability of the equipment

Durability and reliability are the most important operational characteristics of the equipment. Reliability is the property of equipment to perform its functions, maintaining performance within specified limits for the required period of time. Reliability is the most important performance indicator of the machine, characterizing its quality.

One of the elements of reliability is non-failure operation, i.e., the ability of a machine to remain operational without forced interruptions. Reliability is determined by the time of continuous operation of the machine without downtime associated with adjustments and repairs. Different machine parts naturally have different service lives. As a characteristic of failure-free operation, a period close to the shortest of the service lives of parts is taken.

However, the concept of reliability does not fully reveal the operational qualities of the equipment. Let, for example, one press have a high reliability, i.e., it works for a long time without adjustments, but then it requires a long repair. And when operating another press, frequent short adjustments are required, but there is no need for long-term repairs. In some cases, the second press, despite the lower reliability, has advantages associated with its greater durability.

The property of a machine to maintain its working capacity to the limit state with the necessary interruptions for maintenance and repair is called durability.

Over time, the properties of materials, including the strength of parts, as well as their geometry, change. Consequently, the reliability indicators do not remain constant. Nevertheless, the machine must remain operational, which is ensured not only by its quality, but also by the correct organization of maintenance and repair.

Durability is determined by the time and money spent on repair and adjustment of the machine for the entire period of its operation. This means that the machine, which, other things being equal, produces more products over a long period of time, also has a greater durability. In other words, the concept of durability is also related to the performance of the equipment.

The wear of a part is the result of a gradual change in its dimensions due to friction under the action of various loads under the conditions in which the machine is operated.

Wear and damage that occurs during operation are divided into normal (permissible) and unacceptable (emergency). Acceptable damages that occur under normal operating conditions include abrasive wear, crushing of surface layers, etc. These damages cannot be completely excluded. However, it is necessary to minimize them so that the negative consequences appear after the longest possible time. Allowable wear and damage is eliminated during scheduled repairs.

With unacceptable wear and damage, either the destruction of the part or its deformation occurs, which completely excludes the normal operation of the machine. Unacceptable (emergency) damage is eliminated during emergency repairs, as they appear suddenly.

The durability of parts depends on the correct selection of materials for the rubbing pair. In this case, the operating conditions of the equipment should be taken into account, since the same pair can be wear-resistant under certain conditions, and wear-resistant under others.

The materials used for guides must have high wear resistance, low coefficient of friction, and be able to withstand significant mechanical loads without changing their properties. Bronze and plastics are used as antifriction materials. Lightly loaded gears are also made of plastics, which makes them not only wear-resistant, but also silent in operation.

Materials for parts of brake devices and controls, such as brake discs and clutches, must, on the contrary, have frictional properties, i.e., have a high coefficient of friction.

Particular attention should be paid to the wear of the following parts of forging machines: bearings, guides of hydraulic presses and cranks, plungers, seals, friction discs and brakes, etc. Since wear affects the accuracy of the equipment, wear rates are determined by accuracy standards.

Need to install windows, but do not know what to give preference to? On the one hand, the well-known wooden ones, and on the other, the now popular plastic ones. In both cases, environmental friendliness, safety and reliability of the design corresponds to the price and honesty of the manufacturer. And yet, when new windows need to be installed, a significant difference can be found between these two types.

You need to install windows - the pros and cons of wooden and plastic structures

If you need to install a wooden window, then you should not believe the companies that promise to bring the structure the day after tomorrow. In principle, this is impossible, because the minimum period for manufacturing a wooden structure is 30 days. The wood needs to be dried, painted or tinted, varnished if you need to install wooden windows. But when it will be necessary to install a plastic window, then his company will be able to produce it in a day. Especially if the manufacturer has its own production.

When to Install Windows, then wooden structures are inferior to the palm for two reasons. This is a painstaking installation and a high price. To really install wooden Euro-structures, you will have to pay about 3-4 times than for a structure with a PVC profile.

When need to install windows but, it should be remembered that even the most expensive plastic structures are made of polyvinyl chloride. And this means that at high temperatures, in extreme heat or during a fire, the greatest amount of harmful substances will be released.

Service life also needs to be considered when windows need to be installed. After all, plastic structures will last an average of about 40 years. They have already proven themselves well in the difficult Russian climate. Wooden structures will last for about 10 years, and then the sun, wind and moisture will do their dirty work and gradually destroy the structure.

If you need to install a plastic window, then at least because it is easier and faster to do it. When you need to install windows, you can mount plastic structures with your own hands, with minimal experience. Such a trick with a wooden structure will no longer work. Installing a wooden structure is quite a process that requires both experience and special tools.
Another reason to install plastic windows is easy maintenance. It will only be necessary to wipe the profile with a cloth, adjust and lubricate the fittings, change the seal. A wooden profile that cracks or absorbs moisture requires more attention. But on the other hand, the tree is subject to restoration, and the plastic will have to be completely changed.

A double-glazed window in a plastic construction is easier to replace. You can do this in a few days. But in a wooden structure, this is much more difficult to do. In it, the double-glazed window is firmly glued into the sash with silicone sealant, and the glazing bead is securely attached. Therefore, it is very difficult to remove a double-glazed window without damaging the glazing bead. This is also taken into account when windows need to be installed. If it is a domestic design, then it will take a week or two to replace the double-glazed window. And if the manufacturer turns out to be foreign, then you will have to wait at least a month for a replacement.

Lecture . RELIABILITY INDICATORS

The most important technical characteristic of quality is reliability. Reliability is estimated by probabilistic characteristics based on statistical processing of experimental data.

The basic concepts, terms and their definitions that characterize the reliability of technology and, in particular, engineering products, are given in GOST 27.002-89.

Reliability- the property of the product to maintain, within the established time limits, the values ​​of all parameters that characterize the ability to perform the required functions in the specified modes and conditions of use, maintenance, repairs, storage, transportation and other actions.

Product reliability is a complex property that may include: failure-free operation, durability, maintainability, storability, etc.

Reliability- the property of the product to continuously maintain operability for a given time or operating time under certain operating conditions.

Working condition- the state of the product, in which it is able to perform the specified functions, while maintaining the acceptable values ​​of all the main parameters established by the regulatory and technical documentation (NTD) and (or) design documentation.

Durability- the property of the product to maintain operability over time, with the necessary interruptions for maintenance and repair, up to its limiting state, specified in the technical documentation.

Durability is determined by the occurrence of events such as damage or failure.

Damage- an event consisting in a violation of the serviceability of the product.

Refusal- an event resulting in a complete or partial loss of product performance.

Working condition- the state in which the product meets all the requirements of regulatory and technical and (or) design documentation.

Faulty state- a condition in which the product does not meet at least one of the requirements of the regulatory and technical and (or) design documentation.

A defective product may be functional. For example, a decrease in the density of the electrolyte in batteries, damage to the lining of a car means a faulty condition, but such a car is operational. An inoperable product is also defective.

Operating time- duration (measured, for example, in hours or cycles) or the amount of work of the product (measured, for example, in tons, kilometers, cubic meters, etc. units).

Resource- the total operating time of the product from the beginning of its operation or its renewal after repair until the transition to the limit state.

limit state- the state of the product, in which its further operation (application) is unacceptable due to safety requirements or is impractical for economic reasons. The limit state occurs as a result of exhaustion of the resource or in an emergency.

Life time- calendar duration of operation of products or its renewal after repair from the beginning of its use to the onset of the limit state

Unhealthy state- the state of the product, in which it is not able to normally perform at least one of the specified functions.

The transfer of a product from a faulty or inoperable state to a serviceable or operable one occurs as a result of restoration.

Recovery- the process of detecting and eliminating the failure (damage) of the product in order to restore its performance (troubleshooting).

The main way to restore performance is repair.

maintainability- property of the product, which consists in its adaptability to maintaining and restoring a working state by detecting and eliminating a defect and malfunction by technical diagnostics, maintenance and repair.

Persistence- the property of products to continuously maintain the values ​​of the established indicators of its quality within the specified limits during long-term storage and transportation

Shelf life- calendar duration of storage and (or) transportation of the product under specified conditions, during and after which serviceability is maintained, as well as the values ​​of reliability, durability and maintainability indicators within the limits established by the regulatory and technical documentation for this object.

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Rice. 1. Product state diagram

Reliability is constantly changing during the operation of a technical product and at the same time characterizes its condition. The scheme of changing the states of the operated product is shown below (Fig. 1).

To quantitatively characterize each of the properties of product reliability, such single indicators as time to failure and failure, time between failures, resource, service life, shelf life, recovery time are used. The values ​​of these quantities are obtained from test or operation data.

Comprehensive reliability indicators, as well as the availability factor, the technical utilization factor and the operational availability factor, are calculated from the input of single indicators. The nomenclature of reliability indicators is given in Table. 1.

Table 1. Approximate nomenclature of reliability indicators

Reliability property		Name of indicator		Designation
Single indicators
Reliability		Probability of failure-free operation Mean time to failure MTBF Mean time between failures Failure rate Remanufactured Product Failure Flow Average failure rate Failure Probability
Durability		Average resource Gamma percentage resource Assigned resource Installed resource Average service life Gamma Percent Life Assigned Life Assigned Life
maintainability		Mean recovery time Probability of recovery Factor of repair complexity
Persistence		Average shelf life Gamma Percent Shelf Life Assigned shelf life Assigned shelf life
Generalized indicators
Set of properties	Availability factor Technical utilization factor Operational Readiness Ratio

Indicators characterizing the reliability

Probability of uptime individual product is evaluated as:

Where T - time from start to failure;

t - time for which the probability of failure-free operation is determined.

Value T can be greater than, less than or equal to t. Therefore,

The probability of failure-free operation is a statistical and relative indicator of the preservation of the operability of the same type of mass-produced products, expressing the probability that, within a given operating time, failure of products does not occur. To establish the value of the probability of failure-free operation of serial products, the formula for the average value is used:

Where N- number of observed products (or elements);

N o- the number of failed products over time t;

N R- the number of workable products at the end of time t testing or operation.

The probability of failure-free operation is one of the most significant characteristics of product reliability, as it covers all factors that affect reliability. To calculate the probability of failure-free operation, data are used that are accumulated through observations of operation during operation or during special tests. The more products are observed or tested for reliability, the more accurately the probability of failure-free operation of other similar products is determined.

Since uptime and failure are mutually opposite events, the estimate failure probabilities(Q(t)) determined by the formula:

Calculation average time to failure (or mean uptime) based on the results of observations is determined by the formula:

Where N o - the number of elements or products subjected to observations or tests;

T i - uptime i-th element (product).

Statistical evaluation of the mean time between failures is calculated as the ratio of the total operating time for the considered period of testing or operation of products to the total number of failures of these products for the same period of time:

Statistical evaluation of the mean time between failures is calculated as the ratio of the total operating time of the product between failures for the considered period of testing or operation to the number of failures of this (their) object (s) for the same period:

Where T - number of failures per time t.

Durability indicators

The statistical estimate of the average resource is as follows:

Where T R i - resource i-th object;

N- the number of products delivered for testing or commissioning.

Gamma percent resource expresses the operating time during which the product with a given probability γ percent does not reach the limit state. Gamma percentage life is the main design indicator, for example, for bearings and other products. The essential advantage of this indicator is the possibility of its determination before the completion of testing of all samples. In most cases, a 90% resource criterion is used for various products.

Assigned resource - the total operating time, upon reaching which the use of the product for its intended purpose must be terminated, regardless of its technical condition.

P oneestablished resource is understood as a technically justified or predetermined value of the resource provided by the design, technology and operating conditions, within which the product should not reach the limit state.

Statistical evaluation average service life determined by the formula:

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Where T sl i - life time i-th product.

Gamma Percent Life represents the calendar duration of operation, during which the product does not reach the limit state with a probability  , expressed as a percentage. To calculate it, use the ratio

Appointed term services- the total calendar duration of operation, upon reaching which the use of the product for its intended purpose must be terminated, regardless of its technical condition.

Underestablished service life understand the feasibility study provided by the design, technology and operation, within which the product should not reach the limit state.

The main reason for the decrease in the durability of the product is the wear of its parts.

Depending on the nature of the evaluation tasks to be solved, indicators can be classified according to various criteria (Fig. 1.2).

The most widely used in assessing the quality of products for industrial purposes are indicators grouped by characteristic properties.

Purpose indicators characterize the properties of the product, which determine the main functions for which it is intended, and determine the scope of its application.

They fall into the following categories:

• indicators of functional and technical efficiency- machine performance, fabric strength, etc.;
• constructive indicators - overall dimensions, coefficients of assembly and interchangeability, etc.;
• indicators of composition and structure - percentage, concentration, etc.

Rice. 1.2. Classification of product quality indicators

Product quality indicators for characterized properties

Indicators characterize the following properties:

• Reliability - the property of a product to continuously maintain operability for some time or some operating time, expressed in the probability of no-failure operation, mean time to failure, failure rate.
• maintainability- property of the product, which consists in its adaptability to the prevention and detection of the causes of failures, damages and elimination of their consequences by carrying out repairs and maintenance. The single indicators of maintainability are the probability of recovery to a healthy state, the average recovery time.
• Recoverability products are characterized by the average recovery time to a given value of the quality index and the level of recovery.
• Persistence - the property of products to maintain a serviceable and operable condition suitable for consumption during and after storage and transportation. Single indicators of shelf life can be the average shelf life and the assigned shelf life.
• Durability - the property of the product to remain operational until the limit state occurs with the established system of maintenance and repairs. Single indicators of durability are the average resource, the average service life.

Economy indicators determine the perfection of the product in terms of the cost of material, fuel and energy and labor resources for its production and operation. This is first of all:

• cost price;
• purchase price;
• consumption price;
• profitability, etc.

indicators characterize the system "man - product - environment of use" and take into account a complex of such human properties as:

• hygienic;
• anthropometric;
• physiological;
• psychological.

indicators characterize:

• information and artistic expressiveness of the product;
• rationality of form;
• the integrity of the composition.

Indicators are related to such properties of the design of the product, which determine its suitability for achieving optimal costs in the production, operation and restoration of the specified values ​​of quality indicators. They are decisive for the efficiency indicators. The individual indicators of manufacturability include:

• specific labor intensity;
• material consumption;
• energy intensity of manufacturing and operation of the product;
• the duration of the maintenance and repair cycle, etc.

Indicators of standardization and unification characterize the saturation of the product with standard, unified and original components, which are the parts, assemblies, assemblies, sets and complexes included in it. This group of indicators includes the coefficients:

• applicability;
• repeatability;
• unification of a product or group of products.

Patent Law Indicators characterize the degree of patent purity of the technical solutions used in the product, which determines its competitiveness in the domestic and foreign markets.

indicators determine the level of harmful effects on the environment during the operation or consumption of the product. These include:

• the content of harmful impurities released into the environment;
• the probability of emission of harmful particles, gases and radiation, the level of which should not exceed the maximum permissible concentration.

Indicators characterize the features of the product that determine the safety of humans and other objects during its use. They should reflect the requirements for measures and means of protecting a person in an emergency situation that is not authorized and not provided for by the rules of operation in a zone of possible danger.

Product quality indicators by the number of characterized properties

The indicator by which the decision is made to evaluate the quality of products is called decisive. The properties taken into account by the defining indicator can be characterized by single, complex (generalizing) and (or) integral indicators that relate to the classification feature of product quality indicators by the number of characterized properties.

Single indicators characterize one property of the product, which is its quality in relation to certain conditions of creation, operation and consumption.

Complex (generalizing) indicators are an average value that takes into account quantitative estimates of the main properties of products and their weight coefficients.

Integral indicators reflect the ratio of the beneficial effect of operation and the cost of acquiring and operating products.

The optimal value of the product quality indicator is the one at which the greatest beneficial effect is achieved from the operation (consumption) of the product at a given cost for its creation and operation (consumption).

Similar quality indicators are determined for consumer goods, but they must take into account the specifics of the purpose and use of these items.

In world practice, in order to assess the degree of superiority of products, it is used gradation (class, grade)— a category or category assigned to products having the same functional application but different quality requirements.

With a numerical designation, the highest class is usually assigned the number 1, and when designating with a number of any characters, such as asterisks, usually the lower class has a smaller number of such characters.

According to the Federal Law of the Russian Federation "On Protection of Consumer Rights":

• for durable goods, the manufacturer is required to establish life time;
• for food, medicines, household chemicals - best before date.

These two indicators establish the terms after which the product poses a danger to the life, health and property of the consumer or becomes unsuitable for its intended use.

Features of assessing the quality of products for industrial purposes and consumer goods are reflected in the industry normative and technical documentation, which regulates the choice, methods for their calculation and scope.

If the child began to get up and move more actively, then it's time to restrict access to some cabinets and drawers for his safety.

In principle, we were not going to choose, because locks from IKEA inspired the greatest confidence. But the presence of 2 large chests of drawers (and this is already 11 drawers) and, in addition to them, 12 other important and dangerous doors, forced us to take a closer look and evaluate other cheaper analogues. They took samples from different manufacturers and almost all of them had to be replaced with IKEA ones.

About the advantages (and there were no disadvantages except for the cost)

They've been running for a year now with no problems. Stick to any surface. The main thing is to degrease it before sticking it.

There is an adjustment for different doors in terms of the width of the lock - we also installed it on a cabinet in the bathroom,

where the distance is short, and on the box under the crib, where the maximum length of the lock was required. Adjustable by cutting the tape. The truth is already irreversible))

The lock is hard enough to open. With long nails I think it's more difficult, with small opening-closing takes seconds. The main thing is to adapt. Well, the child certainly can not do it at all. Unlike other castles we have tried.

The color is only white. We were more than satisfied with this, because. everything in the room is mostly bright, but where it didn’t match, it’s not scary for us, safety comes first.