Resource vs. Lifetime

Often, the consumer has to deal with such concepts as warranty period, service life and shelf life, each of which has its own special meaning. Many buyers are often confused and do not see the difference between these categories, and the time period allocated for each of the terms can be completely different.

Life time

This is the time period during which the product (or service) must be suitable for use, otherwise the manufacturer of the product is obliged to eliminate the defects. The Law “On the Protection of Consumer Rights” clearly regulates the rights and obligations of the product manufacturer, and the buyer has every right to refer to the law in such a situation.

The service life is necessarily established for certain long-term use products, especially for functional parts and assemblies that can cause serious damage if broken. This often happens when consumers use durable goods that have long been due for write-off. For example, planes of Russian airlines purchased at auctions of decommissioned equipment in Europe, or touring amusement parks that have almost fallen into disrepair. The manufacturer is obliged to establish service life for the following groups of goods:

goods for children (strollers, bicycles, etc.),
equipment and devices for heating and hot water supply, plumbing,
home furnishings,
household goods, cultural goods,
sporting goods, pleasure craft and watercraft,
technical means for keeping animals at home and caring for plants

However, the manufacturer is not required to assign a service life for all durable goods; there is a category of goods that do not require a specified service life. In this case, the manufacturer of goods or services may refuse this procedure or assign a service life voluntarily. As practice shows, very few manufacturers are willing to take responsibility and refuse to set a service life for their product, because this entails a huge risk. The fact is that according to the Law “On the Protection of Consumer Rights”, in the event of a breakdown of a product that does not have a service life, the manufacturer will be held liable for ten years. Not every entrepreneur will agree to this, which is why almost all durable goods have a service life.

The service life begins to count from the moment the act of purchase and sale is completed. The sales consultant must notify the buyer of the product about the service life established by the manufacturer. The seller's lack of awareness indicates his incompetence, since providing such information is part of his duties. It’s another matter when the manufacturer is located in another country and obtaining information about the service life is impossible. Then the store is forced to take on greater responsibility, since the buyer has the right to compensation for damage resulting from defects in the product, and the effect of this law is not limited by time. Simply put, damage caused by imperfections or manufacturing defects of a product without a service life is compensated by the store, regardless of the time of occurrence of this damage.

This is extremely unprofitable for stores, so they try not to deal with goods whose manufacturers, due to territorial remoteness, cannot provide information about their service life. Although some sellers rely on the legal ignorance of buyers who are simply not informed about the specifics of selling such goods. It is regulated by clause 2 of Article 1097 of the Civil Code of the Russian Federation and clause 3 of Article 14 of the Law “On the Protection of Consumer Rights”.

Best before date

The concept of expiration date applies mainly to food products. This is the time interval after which the product loses its consumer properties and becomes unfit for consumption or use. Unlike durable goods, the service life of which begins from the moment the product is transferred to the buyer, for food products the shelf life begins to count from the time of production. Thus, the shelf life does not depend on the fact of sale of the goods - unsold goods are subject to write-off and disposal. Any food product sold in a store must have an expiration date on it. If you come across a food product that does not have such information, you should not buy it, as it was manufactured with obvious violations. After all, if the product is already expired, its use can cause serious poisoning or even worse.

Expired products pose a serious threat to human life and health, which means that every consumer should carefully study the product label during the purchasing process. The same applies to other categories of products, for example, household chemicals, medicines, etc. By law, such products must contain information about the expiration date, because they not only lose their characteristics, but are also dangerous to human life.

These are the following groups of food products:

bakery industry products,
sugar and flour confectionery products,
vegetable oils and products of their processing,
products of the canning and vegetable drying industry,
beer and non-alcoholic industry products,
products of the tea and salt industry,
food concentrates,
meat and meat products,
products of the dairy and butter-cheese industry,
baby food products,
biologically active food supplements,
In addition, the following groups of non-food products must have an expiration date:
products for the prevention and treatment of diseases at home,
perfumery and cosmetic products,
household chemical goods,
cultural goods, goods for leisure and entertainment,
products for keeping fish, birds and animals at home

According to the laws in force in the Russian Federation, stores do not have the right to sell expired products, but in practice such cases can be observed everywhere. The buyer should get into the habit of checking the expiration date of the product, especially if it is displayed at the edge of the display case. As a rule, the freshest products are placed in the far corner of the shelves, but products with expired or about to expire are located in close proximity to the buyer. However, sometimes even vigilance does not save you from purchasing low-quality food products; the fact is that large stores often cheat with labels and change the expiration date on the labels. Buyers demonstrate surprising negligence in this matter - having come home from the store and finding an expired product, few go back and begin to demand justice. But the buyer has the right not only to exchange an expired product, but also to compensation for moral damage.

Of course, the seller can also be understood: what to do with a mountain of expired products that cost a tidy sum? The Law of the Russian Federation “On the Quality and Safety of Food Products” obliges the seller to immediately get rid of products whose shelf life has come to an end, and, of course, not to sell them under any circumstances. Unscrupulous supermarkets solve the “problem” in another way - by processing expired products. It is very easy to prepare cold cuts or goulash from a rotten piece of meat, which can then be sold as fresh. And in the smokehouse of the same supermarket you can quite easily smoke fish that has begun to rot, which can also then be put into circulation. In general, there are plenty of similar tricks in the arsenal of any large store, but the seller does not have the right to such processing. The buyer can only count on the help of government supervision and control authorities, which must conduct an inspection of the trading enterprise in the event of complaints. Representatives of the service organize sanitary-epidemiological and other types of examination, during which the compliance or non-compliance of the product with consumer characteristics is revealed.

Guarantee period

This is a period of time during which the buyer has the opportunity to identify significant defects in the product that were not identified during the purchase process and make demands on the manufacturer of the product. Information about the warranty period can be seen directly in the documentation relating to the sales deed. This can be either a separate warranty card or notes in the contract. Moreover, very often the warranty period in the technical data sheet of the product differs from the period on the warranty card, which is a hidden fraud of the store, which wants to save itself from unnecessary worries by shortening the warranty period. This trick only works on uninformed buyers, but legally literate people know that the only correct one is the warranty period from the manufacturer, and not from the seller.

There are cases when the warranty period is not specified in the technical documentation. You can find out by contacting the manufacturer; fortunately, nowadays there are many ways to communicate. If the manufacturer does not provide a warranty period for this type of product, then usually the seller sets a warranty period of six months, and for real estate objects two years. There are precedents when the warranty period assigned by the seller was less than six months, but the law is merciful to consumers in this situation. If the buyer can prove that the goods sold were already defective, then within six months he has the right to count on compensation for damages. The same time frame (six months) is established for goods that do not have a warranty period (neither the manufacturer nor the seller has assigned one).

The warranty period begins to count from the moment the purchase and sale is completed, and not at all when the product leaves the assembly line. If defects in the product are discovered before it is transferred to the buyer, the latter has the right to free repair or exchange of the product. If the buyer has chosen free repairs, then he should be aware that the time required for repairs is not included in the warranty period. Even more than that: the warranty “does not tick” from the very moment the buyer contacts the service center and writes a statement of claim. If the buyer chooses to exchange the product, then the warranty for the new product is counted again.

The buyer should be aware that when transporting defective goods to a service center or store for repair, delivery costs are paid by the seller or service center. However, this only applies to those goods whose weight exceeds five kilograms. But refusal to reimburse transportation costs in territories where there is no representative office of a store or service center is unlawful, since the seller is obliged to pay the costs to the buyer after delivery of the goods.

Free delivery also applies if the buyer is provided with a similar product during the warranty repair of the purchased product. Buyers often forget or do not know about this right to provide goods free of charge during the repair period, and cunning sellers often take advantage of this. If you back up your demand for the provision of goods for the period of repair with a written statement, then the effect will simply surprise you. The store will provide you with the goods within three days, and will do its best to “adjust” the repair process at the service center, because the seller will be interested in returning the goods to you as soon as possible. However, this rule does not apply to the following groups of goods:

1. Cars, motorcycles and other types of motor vehicles, trailers and numbered units for them, except for goods intended for use by disabled people, pleasure craft and watercraft
2. Furniture
3. Electrical household appliances used as toiletries and for medical purposes (electric shavers, electric hair dryers, electric curling irons, medical electric reflectors, electric heating pads, electric bandages, electric blankets, electric blankets)
4. Electrical household appliances used for heat treatment of products and cooking (household microwave ovens, electric ovens, toasters, electric boilers, electric kettles, electric heaters and other goods)
5. Civilian weapons, main parts of civilian and service firearms.

Article 5.
Rights and obligations of the manufacturer (performer, seller) in the field of establishing the service life, shelf life of the product (work), as well as the warranty period for the product (work)

1. For a product (work) intended for long-term use, the manufacturer (performer) has the right to set a service life - the period during which the manufacturer (performer) undertakes to provide the consumer with the opportunity to use the product (work) for its intended purpose and bear responsibility for significant deficiencies that arise through his fault.

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RELIABILITY IN TECHNOLOGY - BASIC CONCEPTS - TERMS AND DEFINITIONS - GOST 27-002-89 (approved by the Decree of the USSR State Standard dated... Relevant in 2018

To the terms “Assigned service life”, “Assigned resource”, “Assigned storage period” (clauses 4.10; 4.9; 4.11)

The purpose of establishing the assigned service life and assigned resource is to ensure the forced early termination of the use of the object for its intended purpose, based on safety requirements or technical and economic considerations. For objects subject to long-term storage, a designated storage period can be established, after which further storage is unacceptable, for example, due to safety requirements.

When an object reaches its assigned resource (designated service life, designated storage period), depending on the purpose of the object, operating features, technical condition and other factors, the object can be written off, sent for medium or major repairs, transferred for use other than its intended purpose, or re-mothballed ( during storage) or a decision may be made to continue operation.

The assigned service life and assigned resource are technical and operational characteristics and do not relate to reliability indicators (durability indicators). However, when establishing the assigned service life and assigned resource, the predicted (or achieved) values of reliability indicators are taken into account. If a safety requirement is established, then the assigned service life (resource) must correspond to the values of the probability of failure-free operation in relation to critical failures, close to unity. For safety reasons, a safety factor may also be introduced.

Durability indicators characterize the ability of a technical product to maintain operability over time until the onset of a limiting state, when it loses its operability with an established system of maintenance and repairs.

The list of durability indicators used is as follows:

T r – average resource, i.e. average technical life before major overhaul;

T pγ - gamma percentage resource;

T rn - assigned resource;

T r.u- installed resource;

T sl - average service life;

T slγ- gamma-percentage service life;

T sl.n- assigned service life;

T sl.u- established service life;

T sp- service life before decommissioning of the product or maximum service life.

The concept of “resource” characterizes durability, based on the operating time of the product, and “service life” – based on calendar time.

The initial data for calculating the resource, the procedure for its calculation and statistical evaluation, as well as the procedure for adopting the required resource of products are regulated by the methodological instructions MU10-71 “Industrial Products. Definition of a resource." M.: Standards Publishing House, 1972.

Since the resource is understood as the total operating time to the limit state, its indicators are determined using formulas similar to the MTBF formulas.

Average product life - this is the mathematical expectation of its resource. The statistical estimate of the average resource is:

Where T r- resource i-th object;

Ν - number of products delivered for testing or commissioning.

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

Probability of resource provision T pγ, corresponding to the value γ /100, is determined by the formula

Where T r- operating time to the limiting state (resource);

γ is the number of products (%) that do not reach the limit state with a given probability.

The value of the gamma percentage resource is determined using resource distribution curves (Fig. 23).

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

Figure 9 – Determination of the gamma percentage resource value:

A And b– curves of resource loss and distribution, respectively

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

Average service life - mathematical expectation of service life. A statistical estimate of the average service life is determined by the formula: , (5.22)

Where T sl- life time i-th product.

Gamma percentage life time represents the calendar duration of operation during which the product does not reach the limit state with probability γ, expressed as a percentage. To calculate it, use the relation

. (5.23)

Designated service life- the total calendar duration of operation, upon reaching which the use of the product for its intended purpose must be stopped, regardless of its technical condition.

Under specified service life understand the technically and economically justified service life provided by the design

Figure 10 - Typical product surface wear curve

ruktion, technology and operation, within which the product should not reach its limit state.

Limit service life T cn represents the calendar duration of operation or use of the product until its decommissioning and decommissioning (use). It is determined in the same way as, for example, the average service life is determined.

It is known that The main reason for the decrease in the durability of a product is the wear of its parts.

By wear and tear is the process of gradual surface destruction of the material of machine parts as a result of friction of other parts, solids or particles against them. It is known that the wear resistance of a material depends not only on the properties of this material, but also on many conditions under which friction occurs. These conditions (factors) include: properties of the conjugate body, properties of the intermediate medium, temperature on the surface, etc.

Figure 10 shows a typical curve of wear characteristics depending on the duration of testing or operation of products

Wear is characterized by three periods:

1. Period primary wear or the running-in period, when a transition occurs from the initial state of the friction surface to a relatively stable state. During the running-in period, the wear rate decreases over time, approaching a certain constant value characteristic of the period of steady wear.

2. Period steady wear, under constant operating conditions of the rubbing surface, is characterized by a constant wear rate.

3. Period accelerated wear and tear .

The results of wear tests and observations of pluses during the operation of equipment are usually expressed in relative values.

Relative wear resistance:

dimensional

where Δ l e - linear wear of the standard,

Δ l m - linear wear of the material of the tested product (sample or part);

weight

E = Δ G e/Δ G m,

where Δ G e - weight wear of the standard,

Δ G m - weight wear of the material of the tested product (sample or part).

Wear can be assessed not only by the relative characteristics of linear wear, but also by the relative change in the volumes of the standard and the test object.

In practice, wear resistance (wear) is often assessed in absolute values such as mm/km, mm 2 /hour, etc.

Three groups of factors have been established that influence the type and intensity of wear on the surface of machine parts: 1 - factors that determine externally mechanical effects on the friction surface; 2 - characteristics of the external environment; 3 - factors associated with the properties of rubbing bodies.

Specific factors of the dimensional group are: a) type of friction (rolling, sliding); b) the speed of relative movement of the rubbing surfaces; c) the magnitude and nature of pressure during friction.

The main factors of the second group associated with the external environment are: a) lubrication; b) gas environment (air, aggressive or protective atmosphere); c) the presence of abrasive (solid) particles on the friction surface.

In reliability theory, the following temporary concepts of reliability are used, which in turn are its indicators.

Operating time– duration or volume of system operation.

Run-to-failure– operating time of the system from the start of operation until the first failure occurs.

Time between failures– operating time of the system from the end of restoration of its operational state after a failure until the next failure occurs.

Recovery time– duration of restoration of the system’s operational state.

Resource– the total operating time of the system from the start of its operation or its resumption after repair until the transition to the limit state.

Life time– calendar duration of operation from the start of operation of the system or its resumption after repair until the transition to the limit state.

Shelf life– calendar duration of storage and (or) transportation of an object, during which the values of parameters characterizing the ability of the object to perform specified functions are maintained within specified limits.

After the expiration of the shelf life, the object must meet the requirements of reliability, durability and maintainability established by the regulatory and technical documentation for the object

Residual resource– the total operating time of the system from the moment of monitoring its technical condition until the transition to the limit state.

Similarly, the concepts of residual time to failure, residual service life and residual shelf life are introduced.

Assigned resource– the total operating time, upon reaching which the operation of the system must be stopped, regardless of its technical condition.

Designated service life– calendar duration of operation, upon reaching which the operation of the facility must be terminated, regardless of its technical condition.

Upon expiration of the assigned resource (service life, storage period), the object must be removed from service and a decision must be made as provided for in the relevant regulatory and technical documentation - sending it for repair, decommissioning, destruction, checking and establishing a new assigned period, etc.

The listed concepts refer to a specific individual object. There is an important difference between the quantities defined by these concepts and most quantities characterizing the mechanical, physical and other properties of an individual object. For example, geometric dimensions, mass, temperature, speed, etc. can be measured directly (in principle, at any time during the existence of an object). The operating time of an individual object until the first failure, its operating time between failures, service life, etc. can only be determined after failure has occurred or a limit state has been reached. Until these events occur, we can only talk about predicting these values with greater or lesser certainty.

The situation is complicated due to the fact that operating time, service life, service life and shelf life depend on a large number of factors, some of which cannot be controlled, and the rest are specified with varying degrees of uncertainty.

The purpose of establishing the assigned service life and assigned resource is to ensure the forced advance termination of the use of the object for its intended purpose, based on safety requirements or technical and economic considerations. For objects subject to long-term storage, a designated storage period can be established, after which further storage is unacceptable, for example, due to safety requirements.

When the volume of the assigned resource (designated service life, designated storage period) is reached, and depending on the purpose of the object, operating features, technical condition and other factors, the object can be written off, sent for medium or major repairs, transferred for use other than its intended purpose, or re-mothballed ( during storage) or a decision may be made to continue operation.

Before considering the durability indicators of objects, it is necessary to familiarize yourself with the temporary concepts of reliability theory.

Operating time– duration or volume of work of the object. The operating time can be either a continuous value (duration of operation in hours, mileage, etc.) or an integer value (number of work cycles, starts, etc.).

Run-to-failure- operating time of the object from the start of operation until the first failure occurs. This indicator characterizes the system being restored.

Resource– the total operating time of an object from the beginning of its operation or its resumption after repair until the transition to the limit state.

Life time– calendar duration of operation from the start of operation of the facility or its resumption after repair until the transition to the limit state.

Residual resource– the total operating time of the object from the moment of monitoring its technical condition until the transition to the limit state. Similarly, the concepts of residual time to failure, residual service life and residual shelf life are introduced.

Assigned resource– the total operating time, upon reaching which the operation of the object must be stopped, regardless of its technical condition.

According to the current practice of assessing the reliability of consumers' ESN, the following interruptions in ESN are distinguished.

Short break limited in duration by the time interval necessary to restore the ESN automatically using remote control or manual activation where the operator can do this immediately. Such operations usually do not exceed several minutes.

Medium-length break limited by the time interval required to manually restore power in areas where there is no operator on duty. Such operations take 1–2 hours.

Long break, which cannot be qualified as a break of short or medium duration.

In reliability theory, the following durability indicators are used.

Average resource is the mathematical expectation of the resource.

Gamma percentage resource– this is the operating time during which the object will not reach the limit state with a given probability γ, expressed as a percentage.

Assigned resource

Average service life– mathematical expectation of service life.

Gamma percentage life– calendar duration from the start of operation of the object, during which it will not reach the limit state with a given probability, expressed as a percentage.

Designated service life– calendar duration of operation of the object, upon reaching which the intended use must be discontinued.

The main characteristics of durability are average service life and average resource.

For a restored object, the average service life is the average calendar duration of operation of the object from its beginning or resumption after preventative repairs until the onset of the limit state.

The average resource represents the average operating time of an object from the start of operation or its resumption after preventative repairs until the onset of the limit state.

For a non-repairable object, these characteristics coincide and represent the average duration of operation until failure or the onset of a limiting state. In practice, this value will coincide with the average time to failure Tav.

A statistical estimate of the average service life can be obtained from the results of monitoring n similar power grid facilities operated under approximately the same conditions. The formula for statistically assessing the average service life of similar objects based on observation results has the form:

where τj is the service life of the jth object;

n – number of similar objects.

The service life of each specific observation object depends on many random factors, while the limiting state of the object is practically determined by its characteristics, indicating that its further operation becomes unsafe for humans and the environment, or becomes economically unprofitable.