How to write justifications for overhaul school buildings, plans, estimates?
Answer
The rationale for the overhaul of the school building is the results of the technical survey. It determines the degree of its physical and moral deterioration, the need for repair and reconstruction work.
To conduct such a survey, it is necessary to involve a specialized organization under a civil law contract for the performance of work.
<…>In accordance with paragraph 5.8 of the Regulations on the organization and implementation of the reconstruction, repair and maintenance of residential buildings, communal and socio-cultural facilities (VSN 58-88 (r)), approved. By order of the State Committee for Architecture dated November 23, 1988, the development of design estimates for the overhaul and reconstruction of buildings (objects) should provide for:
- conducting a technical survey, determining the physical and obsolescence of design objects;
- drawing up design estimates for all design decisions for redevelopment, functional reassignment of premises, replacement of structures, engineering systems or their re-arrangement, landscaping and other similar works;
- feasibility study and;
- development of a project for the organization of major repairs and reconstruction and a project for the production of works, which is being developed by a contractor.<…>
The preparation of the listed documents requires engineering and survey work, and, accordingly, the required level of qualification. Such a survey is carried out by a specialized organization under an agreement with an educational organization.
Consequently, the establishment of the need for a major overhaul of the school building is established based on the results of a technical survey, determining the degree of physical and moral depreciation of the building. The contract for the technical survey may also provide for the preparation of design estimates, a feasibility study and a work project.
A technical examination of the physical condition of a building can be carried out in accordance with GOST 31937-2011 "Buildings and structures. Rules for the inspection and monitoring of the technical condition", put into effect by Order of Rosstandart dated December 27, 2012 No. 1984-st.
- Decree of the AS of the Moscow District dated September 19, 2014 No. A40-116450 / 13. Dismantling and replacement of elements and systems of the premises are aimed at restoring its functional purpose and are not capitalized works (sections III, V, VI, VIII, XI, XII, XIII, XIV appendix 8);- Resolution of the Fifteenth Arbitration Court of Appeal dated July 10, 2014 No. А53-17409/2013. Repair costs for repairing cracks in the foundation, walls, floors and roofs, strengthening the structure, plastering the walls, painting, replacing the roof, new concrete flooring can be taken into account for tax purposes at a time;
- Decree of the Federal Antimonopoly Service of the Central District dated 05.11.13 No. А54-7269/2012. Worn-out structures were replaced with newer and more durable ones, communications were replaced, partial redevelopment was carried out with an increase in the total area of partitions up to 20 percent. The inspection noted that the work performed led to an increase in the area of the premises. But the court, on the basis of floor plans, concluded that the total area of the disputed premises had changed insignificantly due to the use of more modern materials with construction work;
- Decree of the Federal Antimonopoly Service of the Volga-Vyatka District of December 25, 2013 No. A43-32179 / 2012. Malfunctions have been eliminated, the building has been restored to a usable condition, partitions have been installed. The inspection indicated a change in the purpose of the property. The court noted that there was no increase in production capacity, improvement in quality and changes in the range of products, changes in the main technical and economic indicators of the building;
- Decree of the Federal Antimonopoly Service of the East Siberian District dated November 1, 2013 No. A19-3291 / 2013. Dismantling of wall cladding from plywood chipboard, partitions, metal lintels, skirting boards, wooden stands, cabinet shelves, wall cladding and installation of a suspended plasterboard ceiling, patching potholes in existing cement floors; replacement of wooden windows with PVC blocks, installation of door blocks; laying heating pipelines; re-installation of heating radiators; punching holes in brick walls Oh; repair of concrete preparation; installation of finishing screed, insulation with mineral wool, linoleum and carpeting and other works are repair;
- Resolution of the Eighth Arbitration Court of Appeal dated May 17, 2012 No. A81-888 / 2011. The inspectorate indicated that due to installation work in fact, new fixed assets were created, without dismantling the old ones. The court took into account that dismantling before the work was carried out was impossible, since the work was carried out at an existing, operated facility (section XX, appendix 8). The works meet the signs of a major overhaul;
- Decree of the Federal Antimonopoly Service of the Urals District dated September 15, 2011 No. A76-25924 / 10. Replacing cast-iron pipes with polyethylene pipes is a major overhaul, not a reconstruction, functional purpose the pipeline has not changed (Section XVI App. 8);
- Decree of the Federal Antimonopoly Service of the Volga-Vyatka District of August 12, 2011 No. А82-7144/2010. Repair of floors, cable channels and replacement of door blocks are major repairs (Section VI, Appendix 8);
- Decree of the Federal Antimonopoly Service of the North Caucasus District dated April 11, 2011 No. A53-10464 / 2010. Installation of new ventilation systems and the water supply system meets the signs of a major overhaul (sections XII and XIII, annex 8), and not modernization or reconstruction. As a result of the repair, there was no improvement in production and an increase in its technical and economic indicators, the throughput of pipelines was not increased;
- resolutions of the Federal Antimonopoly Service of the North Caucasus District dated February 16, 2011 No. A32-15838 / 2010, dated February 11, 2011 No. A32-16132 / 2010. Insulation, puttying, priming, painting walls, finishing balconies, dismantling and laying paving slabs, dismantling and installing wells are repair works, their cost is not capitalized (Section IV and XVI Annex 8);
- Decree of the Federal Antimonopoly Service of the Central District dated December 30, 2010 No. A68-1971 / 10. Facade repair and strengthening costs structural elements buildings are under renovation. Also, current expenses include expenses for work preceding repairs (preparation of a project plan, conducting geodetic tests), and for redevelopment associated with these works;
- Decree of the Federal Antimonopoly Service of the Moscow District of December 3, 2010 No. A40-13115 / 10-114-80. Dismantling of roofing slabs, lathing from timber, insulation of coatings, leveling screeds, roof fencing, dismantling of roofing from roll materials, sheathing the bottom of the gallery, installation of covering panels, floor installation, installation of girders, installation of decking trusses, replacement of windows. These works relate to repairs (in particular, section IV, annex 8);
- Decree of the Federal Antimonopoly Service of the Volga-Vyatka District dated 02.11.10 No. А82-4702 / 2009. The administrative and production building "turned" into a cultural and entertainment center, there was a change in the quantitative parameters (after the completion of the work, the total area of the leased premises increased). The area, number of storeys and volume of the building have not changed. The court recognized that the work carried out, by its nature, was aimed at restoring the building and was repair;
- Decree of the Federal Antimonopoly Service of the Urals District dated September 21, 2010 No. A47-6070 / 2008. The reconstruction works specified in the contract are repair works, since they did not cause a change in the intended purpose of the gate building (gatehouse), the technical and economic indicators of the building's functioning did not change. Dismantling of structures on the foundation, dismantling of insulation of coatings, dismantling of brick walls, reinforced concrete floors, reinforcement of masonry walls and concrete foundations, laying of brick partitions, laying of slabs and coatings, change of small coatings of steel and roll coatings, vapor barrier device, insulation, screed, putty and priming, painting, plastering, installation of gate frames, replacement of roofing and heating system; installation of window and door blocks, equipped with a basement;
- Decree of the Federal Antimonopoly Service of the Moscow District dated September 4, 2009 No. A40-94373 / 08-139-447. Works on partial redevelopment, repair of the vestibule, floors, change of air ducts, repair and partial replacement of masonry, replacement of the partition and part concrete base rightfully classified as a major overhaul. As a result of the work carried out, the service or technological purpose of both the building as a whole and the repaired premises of the building has not changed (sections II, III, V, XII appendix 8);
- Decree of the Federal Antimonopoly Service of the Moscow District dated February 15, 2010 No. A40-95760 / 08-116-293. As a result of the work performed, the old fence was dismantled, a new fence was installed and painted, gates were installed and swing gate. Since the technological and service purpose of the fence has not changed, these works are a major overhaul (section XXI appendix 8);
- Resolution of the Ninth Arbitration Court of Appeal dated July 14, 2009 No. A40-16205 / 09-99-33. When replacing, the type of new coating must comply with the requirements of the norms and specifications for new construction. Fireproof doors are installed in the working rooms. For this, auxiliary work was carried out: removal of trim, removal of door panels, dismantling door frames. Also, work was carried out to improve the cosmetic and industrial condition of the office premises. The works are recognized as current repairs, since they do not meet the criteria for a major one (Sections VI and VIII, Appendix 3);
- Decree of the Federal Antimonopoly Service of the Moscow District dated May 26, 2009 No. A40-27155 / 07-98-157. Punching of openings in brick structures and installation of blocks in external and internal doorways, dismantling of masonry and laying of individual sections of brick walls, dismantling and installation of gable rafters, changing lathing with gaps from boards up to 30 mm thick, dismantling of metal structures, installation of perforated flooring, old mineral wool insulation, insulation of coatings with mineral wool boards, installation of ventilation galvanized steel sheet systems, waterproofing with sealant, louvered grilles, door blocks and other construction and installation works related to major repairs;
- Decree of the Federal Antimonopoly Service of the North-Western District dated October 17, 08 No. A56-48759 / 2007. Adjustment of central heating systems, change of individual sections of heating appliances and small sections of pipelines when eliminating leaks and blockages in pipes, repair and replacement of control and shut-off valves in individual rooms, and other maintenance works are related to maintenance works, their cost is not capitalized (Sec. XIII App. 3);
- Decree of the Federal Antimonopoly Service of the West Siberian District dated August 27, 2008 No. A81-461 / 2008. The work carried out by the company on the repair of the pipeline is fully consistent in content with the overhaul (Section XVII Appendix 8);
- Decree of the Federal Antimonopoly Service of the North-Western District dated May 21, 2007 No. A56-27115 / 2006. Laying of partitions, installation of additional bathrooms and hoods, repair and Finishing work(puttying, wall painting, tiling, device suspended ceilings, door repair) are a major overhaul
The correct qualification of various types of work on the restoration of fixed assets: current and major repairs, on the one hand, and reconstruction, modernization, retrofitting, on the other, is a necessary condition for high-quality financial planning in an institution. Ultimately, the acceptance and fulfillment of budget obligations, the reflection of operations in budget accounting and reporting, and the calculation of taxes depend on this.
It is no secret that in cases of all types of repairs, the costs are written off to the current expenses of the institution, and in the case of reconstruction, modernization and additional equipment, they are attributed to an increase in the initial cost of fixed assets. However, it is often very difficult to distinguish between these concepts in practice. Consider the main approaches to the definition listed species works.
Terminology
- modernization -
- retrofitting -
- trouble-shooting;
- Finishing work.
Table 1
Functional purpose of the fixed asset
An object | Main functions |
| Building | |
| Fence, fence | |
| Highway | |
| Automobile | |
| A computer | 2. Store information. |
Repair
traditionally differ different levels average
The term "reconstruction"
The term "modernization"
The term "equipment"
Work planning
Goal definition
APPLICATION FOR REPAIR, RECONSTRUCTION, MODERNIZATION, ADDITIONAL EQUIPMENT
Object name | Inventory number | Cause | Planned events | Planned result |
|
| 333222333 | |||||
| VAZ-21114 car | 555666555 | Do-it-yourself repair | Recovery | ||
| Automated workstation (computer included) | 555666777 | ||||
| House of culture building | 777888999 | The roof is leaking | Replace soft roof | ||
| House of culture building | 777888999 | Performance Improvement | |||
and finishing works
table 2
Reflection in the budget accounting of works on repair, reconstruction, modernization, additional equipment
| No. p / p | Contents of operation | Accounting entry 1 | |
| debit budget account | |||
| 1 | 2 | 3 | 4 |
KRB 0 401 01 225 | KRB 0 302 08 730 |
||
KRB 0 401 01 226 | KRB 0 302 09 730 |
||
KRB 0 105 00 340 | KRB 0 302 22 730 |
||
| KRB 1 401 01 272 KRB 2 401 01 272 KRB 2 106 04 340 | KRB 0 105 00 440 |
|
KRB 0 106 01 310 | KRB 0 302 19 730 |
||
KRB 0 106 01 310 | KRB 0 302 09 730 |
||
KRB 0 105 00 340 | KRB 0 302 22 730 |
||
KRB 0 106 01 310 | KRB 0 105 00 440 |
||
KRB 0 101 00 310 | KRB 0 106 01 410 |
||
The correct qualification of various types of work on the restoration of fixed assets: current and major repairs, on the one hand, and reconstruction, modernization, retrofitting, on the other, is a necessary condition for high-quality financial planning in an institution. Ultimately, the acceptance and fulfillment of budget obligations, the reflection of operations in budget accounting and reporting, and the calculation of taxes depend on this. It is no secret that in cases of all types of repairs, the costs are written off to the current expenses of the institution, and in the case of reconstruction, modernization and additional equipment, they are attributed to an increase in the initial cost of fixed assets. However, it is often very difficult to distinguish between these concepts in practice. Consider the main approaches to the definition of these types of work.
Terminology
Many normative legal acts begin with definitions of concepts and terms used in the document. For example, Art. 6 BC RF, art. 8 and 11 of the Tax Code of the Russian Federation, Art. 15 and 20 of the Labor Code of the Russian Federation. In cases where there is no clear and unambiguous definition for key terms, the application of legislative norms in practice raises a lot of questions and controversial situations.
So it was until recently with regard to the issue of delimitation by a budgetary institution of work on repair, reconstruction, modernization, and additional equipment. Until 2009, neither the Instruction on Budget Accounting, nor the legislation on accounting in general, nor the legislation on budget classification contained these concepts.
In 2009, the Ministry of Finance of Russia for budget institutions Methodological recommendations for the use of KOSGU were developed (system letter of the Ministry of Finance of Russia dated July 21, 2009 No. 02-05-10 / 2931), which contained, in particular, clear definitions of the terms "reconstruction", "modernization", expenses for articles (sub-articles) of KOSGU. In the same letter, distinctive characteristics were given repair work.
In the system letter on the procedure for applying KOSGU in 2010 (letter of the Ministry of Finance of Russia dated February 05, 2010 No. 02-05-10 / 383), similar definitions are given for operations that increase the value of an item of fixed assets:
- reconstruction is a change in the parameters of capital construction objects, their parts (height, number of floors, area, indicators of production capacity, volume) and the quality of engineering and technical support. This definition completely coincides with the one given in paragraph 14 of Art. 1 of the Town Planning Code of the Russian Federation;
- modernization - a set of works to improve the object of fixed assets, leading to an increase in the technical level and economic characteristics of the object, carried out by replacing its structural elements and systems with more efficient ones;
- retrofitting - addition of fixed assets with new parts, parts and other mechanisms that will form a single whole with this equipment, give it new additional functions or change performance indicators, and their separate use will be impossible.
- trouble-shooting;
- maintenance of technical, economic and operational indicators at the initially envisaged level;
- carrying out non-capital redevelopment of premises;
- Finishing work.
Further, when considering the principles that make it possible to draw a line between different types of work, the concept of “functional purpose of a fixed asset” will be repeatedly used. Before qualifying the type of work, it is necessary to clearly articulate what the fixed asset is intended for, and then determine how the performance of these functions will change as a result of the work. At first glance, it seems that it is not difficult to give such a definition (see Table 1).
Table 1
Functional purpose of the fixed asset
An object | Main functions |
| Building | 1. Provide weather protection. 2. Ensure the safety of property. 3. Provide conditions for the activities of people. 4. Provide conditions for the operation of equipment. |
| Fence, fence | 1. Mark the boundaries of the site. 2. Restrict access to the site. |
| Highway | 1. Ensure the movement of cars. 2. Ensure safety when moving cars. 3. Provide comfort when moving cars. |
| Automobile | 1. Ensure the movement of people and goods. 2. Ensure safety when moving people and goods. 3. Ensure the protection of people and goods from atmospheric phenomena. 4. Ensure the safety of the property in the car. |
| A computer | 1. Process information - transform information of one type into another. 2. Store information. |
The following sections will show how the definition of the functionality of a fixed asset becomes the key to distinguish between different types of work.
Repair
The concept of "repair" includes not only troubleshooting, but also maintaining the performance of the facility. In other words, repair work is aimed at restoring the full performance of the object of its functions.
Even if as a result of the repair there was an improvement in the characteristics of the object, its value does not increase. This provision is especially relevant in relation to computer technology, the generations of which are changing very quickly.
traditionally differ different levels repairs: current, average and capital. At the same time, there is no unambiguous distinction between these concepts in the legislation. For example, in the Town Planning Code of the Russian Federation, the term "overhaul" occurs repeatedly, but its definition is not given. Since there are no differences between current and major repairs in terms of the application of budget classification and the procedure for maintaining budget accounting, the accountant does not need to distinguish between such expenses.
At the same time, it is necessary to take into account the fact that in the practice of construction organizations, major repairs often mean a set of works to improve capital construction projects, which does not correspond to the terminology defined by budget legislation.
Finishing work can be distinguished as a separate type of repair. There is no definition of this term in the system letters of the Ministry of Finance of Russia, but its meaning can be understood from the above list of works. Finishing works are understood as works that are not due to the restoration of the object, but also do not lead to an improvement in its main characteristics, for example, painting in a different color.
Basically, the term “finishing work” is applied to capital construction projects, but by analogy it can also be attributed to vehicles (a car can also be painted in a different color without the purpose of restoration) and to any other property when the work concerns only changes appearance object.
It is precisely the definition of the functional purpose of the fixed asset that will help to distinguish between finishing work and work leading to the improvement of the fixed asset. If the work does not affect the quality of the performance of the main functions and does not add new functions, then such work can be classified as finishing.
Reconstruction, modernization, additional equipment
The term "reconstruction" applies exclusively to capital construction projects. Therefore, it is not possible to reconstruct a car or a personal computer. Only a building or structure can be reconstructed. Reconstruction involves changing the parameters of an object. Reconstruction also includes improving the quality of engineering and technical support, however, the content of these works in normative documents is not explained.
The term "modernization" involves the replacement of nodes, and these nodes must be in good condition. If a faulty unit is replaced, then such work is not an upgrade, but a repair. If no nodes are replaced, then such work is retrofitting.
Thus, for the correct application of the term "modernization", it should be clearly understood what it means to replace a good part: the part must be good before replacement, but does not have to remain so after dismantling.
The term "equipment" involves an inherent improvement in an item of property, plant and equipment. It follows from this that new parts added to the object must be, firstly, difficult to separate, and secondly, give the object new properties.
Work planning
An important task at the stage of work planning is setting goals and determining the scope of work.
Goal definition
In order to correctly determine which category of work, repair or reconstruction (modernization, retrofitting), the operation that the institution plans to carry out belongs to, first of all, it is necessary to determine the goal.
If the original purpose of the work is to restore working capacity or specifications, or external changes that do not affect the quality of the object's performance of its functions, which means that repairs are being carried out.
If the purpose of the work is to improve the main characteristics of a serviceable object or adding new features, this means that they can be classified as reconstruction, modernization or retrofitting. In this case, further it is necessary to decide on the choice of one of the three types of operations. If the operation involves the replacement of components or parts, then this is a modernization (or reconstruction). If the operation involves the addition of nodes and parts, then this is additional equipment (or completion).
Justification of the need for expenses for the work
In order to exclude unnecessary questions about the feasibility of carrying out repair and other work during control and auditing activities, as well as to streamline all operations with property, including the restoration of fixed assets, it is recommended that the institution establish the following procedure at the accounting policy level:
- To appoint by a separate order (instruction), without including in the text of the accounting policy itself, persons responsible for the operation of various types of property under operational management, use, lease, etc. However, such persons do not have to be financially responsible. For example, the person who owns the computer may be the person responsible for the computer, and a specially designated qualified person may be responsible for the operation of all computers in the institution.
- To oblige persons responsible for the operation of property objects to monitor their technical condition, as well as to draw up applications for repairs, reconstruction, modernization, and additional equipment. Determine what said works are not performed without a corresponding request approved by the head.
- Set up an application form. A sample of filling out the tabular part of the application is given below (the header must contain the details of the institution, date and number, the signature of the head, and the basement - the signature of the person responsible for the operation of the property).
Object name | Inventory number | Cause | Planned events | Planned result |
|
| Automated workstation (computer included) | 333222333 | The image on the monitor is fuzzy, “floats”, cannot be eliminated by adjustments | Diagnostics and repair, if necessary, by means of a third-party organization | Recovery | |
| VAZ-21114 car | 555666555 | Knocking in the front suspension - silent blocks collapsed | Do-it-yourself repair | Recovery | |
| Automated workstation (computer included) | 555666777 | System resources - the amount of RAM - are not sufficient to use the "AAA" program | Retrofitting additional RAM | Ability to use the AAA program | |
| House of culture building | 777888999 | The roof is leaking | Replace soft roof | Recovery performance characteristics | |
| House of culture building | 777888999 | Rain dripping from the roof melt water the porch is flooded, the steps are covered with ice and collapse, injuries are possible | Build a canopy over the porch | Performance Improvement | |
The person responsible for the operation of the property must draw up applications, whether or not funds are available to carry out the proposed activities. The introduction into practice of the establishment of such a procedure for planning repair and other work will solve not only the problems of substantiating costs during control and auditing activities, but also systematizes all the activities of the institution for the maintenance and maintenance of property. Also, when developing an accounting policy, it is advisable to make a decision regarding replacement requests Supplies(toner, cartridges) and routine maintenance.
At the stage of planning work on reconstruction, modernization, additional equipment, it is necessary to take into account the requirements of Art. 34 of the RF BC, which establishes the principle of effectiveness and efficiency in the use of budgetary funds. And local governments receiving interbudgetary transfers (with the exception of subventions) should also take into account the requirements of Art. 136 BK RF. In other words, it is necessary to be ready to justify the feasibility of the improvements made to the property and finishing works as well as the fact that the ongoing improvements are aimed specifically at better implementation of the main activities of the institution. For example, what institution could indicate the reason when drawing up an application for work on installing a car radio in a car (if it was not in the factory delivery)?
Features of concluding contracts for the performance of work
When planning repair and other work, making cash expenses, as well as during control and auditing activities, various conflict situations. Many of these situations can be avoided if we follow a simple principle: the KOSGU item, to which the costs of the contract will be charged, is determined by what is the result of the execution of the contract.
This principle implies that the KOSGU article is determined depending on what has changed in the institution itself as a result of the implementation of the contract. This principle is very simple, but, unfortunately, in practice there are situations of its deep misunderstanding. Common Mistakes are:
- mistake number 1 - the definition of the article of KOSGU, depending on what happened to the performer;
- mistake number 2 - determining the article of KOSGU, depending on what happens in the institution later.
If it is necessary to single out different types of work within the framework of one contract, then this should be done in the “Subject of the contract” section, clearly indicating two (or more) types of work, as well as in the “Amount of the contract” section, indicating the cost of the relevant types of work. Consequently, the performer will report for the work performed with different documents: one act for repair work and another for improvement work.
The same situations may arise during large-scale reconstruction of buildings or restoration of monuments. When analyzing specific cases, some of the entire complex of reconstruction works can be qualified as repair and restoration work, will be partially paid for by sub-article 225 of KOSGU and will not lead to an increase in the cost of the building for the entire amount of work performed under the contract. And during the restoration of the monument, a significant improvement can also be made, requiring the application of Article 310 of KOSGU in some part of the contract amount and leading to an increase in the cost of the monument.
Reflection in the budget accounting of works on repair, reconstruction, modernization, additional equipment
table 2
Reflection in the budget accounting of works on repair, reconstruction, modernization, additional equipment
| No. p / p | Contents of operation | Accounting entry 3 | |
| debit budget account | budget accounting credit | ||
| 1 | 2 | 3 | 4 |
| Acceptance of the cost of services (works) of the contractor for the repair or restoration of working capacity or finishing works (including the cost of the contractor's own materials). | KRB 0 401 01 225 | KRB 0 302 08 730 |
|
| Acceptance of the cost of services (works) for the development of project documentation for repair work. | KRB 0 401 01 226 | KRB 0 302 09 730 |
|
| Acquisition under a separate transaction of materials for the production of repair work. | KRB 0 105 00 340 | KRB 0 302 22 730 |
|
Write-off of own materials used for repair work.
| KRB 1 401 01 272 KRB 2 401 01 272 KRB 2 106 04 340 | KRB 0 105 00 440 |
|
| Acceptance of the cost of services (works) of the contractor for reconstruction, modernization, additional equipment (including the cost of the contractor's own materials). | KRB 0 106 01 310 | KRB 0 302 19 730 |
|
| Acceptance of the cost of services (works) for the development of project documentation for reconstruction, modernization, retrofitting. | KRB 0 106 01 310 | KRB 0 302 09 730 |
|
| Acquisition under a separate transaction of materials for the performance of works on reconstruction, modernization, additional equipment. | KRB 0 105 00 340 | KRB 0 302 22 730 |
|
| Write-off of own materials used for work on reconstruction, modernization, additional equipment. | KRB 0 106 01 310 | KRB 0 105 00 440 |
|
| Increase in the value of fixed assets as a result of reconstruction, modernization, additional equipment. | KRB 0 101 00 310 | KRB 0 106 01 410 |
|
2 In digits 18, 22, 23 of the budget accounting account number, the corresponding codes for the type of activity and analytical account are indicated.
3 The application is made separately for each item of fixed assets. The table shows examples of filling out an application for different types of work.
4 In digits 18, 22, 23 of the budget accounting account number, the corresponding codes for the type of activity and analytical account are indicated.
During the operation of the car, its reliability and other properties gradually decrease due to wear of parts, as well as corrosion and fatigue of the material from which they are made. Various faults appear in the car, which are eliminated during maintenance and repair. The need and expediency of car repair are primarily due to the uneven strength of their parts and assemblies. Consequently, repairing a car, even just by replacing some of its parts and assemblies that have a small resource, is always more expedient and justified from an economic point of view. Therefore, during operation, cars undergo periodic maintenance at motor transport enterprises (ATP) and, if necessary, current repairs (TR), which is carried out by replacing individual parts and assemblies that have failed. This allows you to keep cars in technically sound condition.
With long-term operation, cars reach a state where the costs of funds and labor associated with maintaining them in working condition in the conditions of ATP become greater than the profit they bring in operation. This technical condition of vehicles is considered to be the limit, and they are sent for overhaul (CR) at the ARP. The task of the CD is to restore the lost performance and resource of the car to the level of a new year close to it with optimal costs.
All parts from cars arriving in the Kyrgyz Republic can be divided into three groups:
The first group includes parts that have completely exhausted their resources and must be replaced with new ones when repairing a car. The number of such parts is relatively small and amounts to 25 ... 30%. The details of this group include pistons, piston rings, bearing shells, various bushings, rolling bearings, rubber products, etc.
The second group of parts, the number of which reaches 30 ... 35%, are parts whose resource allows them to be used without repair. This group includes all parts, the wear of the working surface of which is within acceptable limits.
The third group includes other parts of the car (40 ... 45%). These parts can only be reused after they have been restored. This group includes most of the most complex and expensive basic car parts, in particular the cylinder block, crankshaft, block head, gearbox and rear axle housings, camshaft, etc. The cost of restoring these parts does not exceed 10 ... 15% of the cost their manufacture. Thus, the main source of economic efficiency of CR cars is the use of the residual resource of parts of the second and third groups. The cost of CR cars and their units, even in relatively small modern enterprises, usually does not exceed 60 ... 70% of the cost of new cars. At the same time, great savings in materials and labor resources are achieved. KR cars also allows you to support not high level the number of car parks in the country. The organization of car repair in our country is constantly given great attention.
In this course project, the technological process of repairing the ZIL-1Z0 drive axle will be considered in the future. Defective:
- 1. Cracks in the crankcase
- 2. Wear of the hole for the roller bearing of the bevel gear drive bearings;
- 3. Wear of the holes for the pinion bearing;
- 4. Wear of the holes for the differential bearing;
V.A. Sidorov, Donetsk National Technical University(Donetsk, Ukraine)
In the history of operation of the mechanical equipment of metallurgical enterprises, three main approaches to the repair of equipment should be distinguished.
1. Forced repairs, or repairs after a failure- This approach is typical for the 30s of the last century. The reason is a small number of metallurgical machines, a low level of qualification of maintenance and repair personnel, and the absence of a repair base. The main task is to stop the operating machine at the first sign of damage and prevent significant damage due to the destruction of the elements. The consequence of such a sudden stop is a violation of the technological mode of the unit or installation.
The technical condition of the mechanisms was assessed using organoleptic methods. Main methods of control: analysis of the noise of mechanisms; vibration perception, including imaging techniques mechanical vibrations; determination of the degree of heating of parts; visual inspection of the mechanism; touch methods. The accumulation of experience was slow, as the consequences of accidents were eliminated, and was not always fully transferred to subsequent generations. Methodological justification - the rules for the technical operation of mechanical equipment for the redistribution of metallurgical production and individual units, were developed until the 90s of the last century.
The consequences of this approach are known - unscheduled shutdowns due to sudden failures, loss of productivity of the metallurgical unit, unpreparedness of repairs. This largely determines the low quality of unprepared, emergency repairs. The mechanization of metallurgical processes, the improvement of metallurgical machines required the development of more efficient, planned methods for restoring a working state.
2. Scheduled preventive maintenance and scheduled maintenance.
The increase in the fleet of metallurgical machines, the number of metallurgical enterprises, the use of the same technologies and equipment required an increase in the failure-free operation of mechanical equipment. The conducted studies of the durability of parts of metallurgical machines made it possible to obtain statistical data and issue recommendations on the time of forced replacements. It was assumed that carrying out a certain amount of repair work at regular intervals would ensure the failure-free operation of the mechanisms.
Methodological support - regulation on preventive maintenance (PPR) of mechanical equipment of ferrous metallurgy enterprises. The development and implementation of the main provisions of these documents made it possible to form a system of maintenance and repair (MRO). Issues related to the maintenance of the maintenance and repair system were resolved; frequency, duration and complexity of repairs; organization, planning and execution of repairs; reporting on repairs; provision of spare parts, etc. Repair terms are systematized, the forms of technical documentation, the content of typical and specific works performed during scheduled repairs of metallurgical equipment are defined.
The main event in the MRO system is a failure - a violation of the operable state of a mechanism or machine. Methods of statistical and probabilistic analysis of events were used. These studies were actively carried out in the 70-80s of the last century, and continue now. This allows you to effectively solve the problems of modeling reliability parameters in the design, operation, and provision of spare parts.
The systematic approach used in the accounting and analysis of failures, the use of the obtained data by repair services made it possible to increase the reliability of the operation of metallurgical machines. In practice, the PPR system is currently used at metallurgical enterprises during repairs. The conducted studies indicated a significant spread in the resource of the same type of parts due to differences in the quality of manufacture and operation. Clarification of the actual state of mechanical equipment required the use of in-place technical diagnostics.
It is impossible to establish the service life of individual and small-scale equipment elements operating under conditions of unstable loads. Therefore, within the framework of the PPR system, it was possible to adjust the timing of replacements by conducting revisions - inspections of parts and assemblies in case of incomplete disassembly of the mechanism, carried out during the current repairs of mechanisms. It is known that unnecessary dismantling of even serviceable equipment leads to a deterioration in the general technical condition of the mechanism. The solution of this issue is also possible using the methods of technical diagnostics.
3. Repairs according to condition– the decision to repair is made on the basis of information about the technical condition of the mechanism. Organizationally, it was supposed to be sufficient to form departments or diagnostic bureaus in the structure of the enterprise's repair services. The main method of control is the measurement of vibration parameters and comparison with standard values. The method was tested on rotary-type power machines, where it showed high efficiency. Therefore, the “Regulations on the maintenance of equipment of enterprises of the mining and metallurgical complex” declares only the principles that equipment diagnostics must meet: “carrying out diagnostics and documenting changes in the technical condition, determining the reasons that caused them; carrying out diagnostics of the technical condition by non-destructive testing methods, mainly without dismantling and stopping the equipment; determination of the scope of repair work and maintenance based on the results of diagnostic control”. Many diagnostic issues have not yet been resolved for power machines, and the diagnosis of metallurgical machines has individual characteristics. The solution of this problem requires the development of the concept of technological safety.
The changes that have taken place over the past 20 years in the technology of metallurgical production are changing approaches to ensuring the reliability of mechanical equipment. The appearance of the "furnace-ladle" unit combines the technological characteristics of electric arc furnaces and continuous casting machines into one metallurgical complex. Casting of continuous series of 30...70 melts is possible only with the full restoration of the working condition of the mechanical equipment on repair days based on information about the technical condition. Only the complete absence of failures in the process of operation makes it possible to ensure the technological safety of a metallurgical enterprise under the prevailing conditions. Mechanical equipment in this metallurgical complex performs the task of ensuring continuity technological process within the given parameters. It seems necessary to develop the next level of methodological support - justifying the need for repairs based on information about the technical condition. The development of this document is possible only taking into account the implementation of previously accumulated experience in the maintenance and repair of mechanical equipment.
The main stages of the solution are:
1. Clarification of terminology
First of all, it is necessary to clarify the term "technical condition". The modern definition (GOST 20911-89) is a state that is characterized at a certain point in time under certain environmental conditions by the values of the parameters established by the technical documentation for the object. The proposed interpretation does not satisfy the requirements of information support for strategies that use data on the actual state of the equipment. For restored mechanical systems, the task of ensuring operability is reduced to determining the methods and timing of repair actions within the framework of the accepted system of maintenance and repair. Therefore, from a practical point of view, knowledge of the technical condition is necessary to make a decision on the need and timing of measures to restore or maintain the performance of a technical system (object) at the proper level.
The following definition of technical condition is proposed. The technical condition of a mechanical system is a set of features that determine the degree of need for maintenance operations or repair actions.
The term "technical maintenance and repair system" currently has the following definition: a set of interrelated tools, documentation, maintenance and repair, performers necessary to maintain and restore the quality of products included in this system. The defined functions of the system do not include fail-safe mechanical equipment management.
From the standpoint of cybernetics, management is the receipt, storage and processing of information for the organization of purposeful actions. Therefore, to manage the reliability of mechanical equipment, the maintenance and repair system must contain functions for obtaining and processing information about the technical condition of the equipment. The presence of information transforms a technical system with unpredictable implementations, usually represented as a "black box" into a control object with feedback based on the analysis of information about the results of functioning.
The lack of information about the technical condition of mechanical equipment creates a passive attitude of repair services, which leads to unscheduled downtime, which is becoming a traditional phenomenon. At the same time, the task of the repair services is to adapt the mechanism to changing operating conditions - the parameters of the technological process, the changing properties of parts and components of the mechanism, the quality of maintenance and repair.
It is necessary to determine the content of the term "information" in a specific application to the technical condition of mechanical equipment that satisfies the solution of problems of managing the reliability of mechanical equipment. It is proposed to consider the information as a result of the transformation of the initial data to reduce the degree of uncertainty of the technical state of the system. The received information message should allow a reasonable decision to be made on the need to take measures to maintain or restore the working state of the mechanism.
Information should be understood not just as any information and data about the system, but as information that would simultaneously characterize the degree of uncertainty of the system (syntactic level), would have a certain content, meaning (semantic level), would be useful to the consumer of information (pragmatic level). It is this information that must be obtained for management. This information must be processed according to certain rules and used to develop control decisions that must be implemented in a specific action.
2. Formation of the main provisions
Health axioms for mechanical equipment it is proposed to formulate as follows: low noise and vibration levels; minimization of dynamic, in particular, shock processes; non-exceeding of the permissible temperature values of the mechanism parts; no unacceptable external loads, no cracks or oil leaks. Of course, this provision is an addition to the definition of a healthy state - the performance of all functions by the mechanism within the specified parameters.
Classification of types of repair impacts and maintenance used during the operation phases of mechanical equipment. Maintenance work: inspection of the mechanism, cleaning of the mechanism, protection against corrosion, lubrication of the mechanism and tightening threaded connections. Repair actions for mechanical equipment: adjustment (adjustment of gaps and relative position of parts, balancing), replacement of wear parts and restoration of body parts, assemblies and parts. The need for each impact can be determined by several decision rules, comparing them with a limited number of diagnostic features.
Definition health factors: status of fixed connections; state of contact surfaces; mutual arrangement of parts; even distribution of forces; accumulation of fatigue damage. For each of the factors, based on the need for repairs, four levels are defined: good condition, small deviations, the need for repair actions and pre-failure. The levels of factors are established by changes in the physical and chemical wear processes, qualitative parameters of the interaction of elements. The boundaries of the levels correspond to the change in the wear rate, separating the boundaries of natural and pathological aging.
Status of fixed connections can be assessed as meeting the design requirements if the mating parts are stationary relative to each other when the load is applied. This applies to threaded, keyed, splined connections, landings of bearings and gears on the shaft and in the housing. With a fixed fit of the outer ring of the bearing, the surface mating with the shaft is matte (Fig. 1).
The movement of mating parts with the appearance of small gaps, under the influence of variable forces or vibrations, in the presence of an oxidizing agent, leads to the appearance of a mechano-chemical wear process - fretting corrosion. This activates the conditions for the development of damage to the mating parts, leads to the appearance of knocks. Visually manifests itself in the form of intense oxidation of surfaces, the appearance of corrosion products on the surface of parts in the form of dark spots on the seating surfaces of the bearing rings (Fig. 2).
Increase in diametrical dimensions seats, for example, a loose fit of rolling bearings leads to rotation of the bearing rings on the shaft and in the housing (Fig. 3). This increases the rate of development of wear processes. Rotation of the bearing in the housing or along the shaft is accompanied by an increase in the temperature of the housing parts of the bearing assembly, a change in the nature of noise and vibration, and leads to unacceptable wear of the housing parts.
The appearance of a gap in a fixed connection leads to the occurrence of shocks, while changing the nature and values of the acting forces. The emerging dynamic phenomena in the nodes of the mechanism increase the contact stresses and stresses in the details. Cracks across the treadmills are the result of dynamic loads, impacts (Fig. 4a). Chips of the sides of the rings are the result of the dynamic effects of the axial force (Fig. 4b).
Health factors and levels are shown in Table 1.
Based on the analysis of the considered factors of the mechanism's performance, a hypothesis is proposed that the transition from one level of technical condition to another should be carried out stepwise. Determination of a stepwise change in the values of diagnostic parameters with a change in the level of health factors and, accordingly, the technical condition will make it possible to determine the cause of the malfunction, and the consequence in the form of a malfunction of the nodes.
3. Formation of criteria for the need to repair mechanical equipment in the form of absolute values of diagnostic parameters, typical spectrograms and dependencies.
Absolute values vibration parameters are the most commonly used in the technical diagnostics of mechanical equipment.
Regarding the values of vibration velocity, the boundaries of the categories of technical condition for metallurgical machines coincide with the recommendations of the GOST 10816-1-97 standard for class 1 machines. In this case, individual characteristics, massiveness of metallurgical machines should be taken into account. The ratio of vibration at idle and under load should not exceed a 10-fold increase. The change in state occurs when the vibration increases by more than 2.6 times. It has been established that the upper limit of the poor condition of metallurgical gearboxes is the general level of vibration velocity: 4.5 mm/s for rigid foundations and 7.1 mm/s for flexible foundations. Higher values are typical for an emergency condition, considered as a loss of control over the technical condition of the mechanism. It should be noted that the margin of safety of the mechanism makes it possible to withstand even higher values of vibration velocity, but this leads to a sharp decrease in the durability of the elements. It is necessary to correct the frequency range of measurement recommended by the standard 10 ... 1000 Hz. The frequency range should be set to 2…400 Hz when diagnosing mechanisms with a rotation speed of less than 600 rpm.
Studies carried out on combined gearboxes of small and medium section rolling mills have shown the need to regulate the values of vibration acceleration. It is recommended to use ratios of peak and RMS values of vibration acceleration in the frequency range of 10…4000 Hz.
The spectral pattern of the vibration signal changes dramatically when the technical condition changes. For effective monitoring of the technical condition, it is necessary to monthly conduct a spectral analysis of the vibration velocity components. There are several stages in the history of damage development:
Good condition is characterized by a low level of the turnover frequency component and the presence of a large number low-amplitude harmonics (Fig. 5a);
Initial imbalance - the appearance of harmonics of the reverse frequency with the predominance of the first harmonic (Fig. 5b) is the most auspicious time for balancing, adjusting, tightening threaded connections;
Medium level of damage - numerous harmonics appear with a predominance of one and a half harmonics (1½, 2½, 3½ ... of the rotational frequency), indicating the presence of gaps between the mating parts, in this case, restoration of the bearing seating surfaces is required (Fig. 5c);
Significant damage leads to a significant predominance of the first harmonic, in this case, the restoration of the foundation is also necessary (Fig. 5d).
For rolling bearings, it is also possible to distinguish characteristic vibration acceleration spectrograms associated with various degrees of damage (Fig. 6). The serviceable state is characterized by the presence of insignificant amplitude components in the low-frequency region of the studied spectrum 10…4000 Hz (Fig. 6a). The initial stage of damage has several components with an amplitude of 3.0...6.0 m/s2 in the middle part of the spectrum (Fig. 6b). The average level of damage is associated with the formation of an "energy hump" in the range of 2...4 kHz with peak values of 5.0...7.0 m/s2 (Fig. 6c). Significant damage leads to an increase in the amplitude values of the components of the "energy hump" over 10 m/s2 (Fig. 6d).
Bearing replacement should be carried out after the beginning of the decrease in the values of the peak components. At the same time, the nature of friction changes - sliding friction appears in the rolling bearing, the rolling elements begin to slip relative to the treadmill.
A practically serviceable mechanism will have a minimum level of vibration with minimal random deviations of individual parameters. Deterioration of the state leads to an increase in the probabilistic characteristics of random deviations - there is an accumulation of small damage and a choice of further damage development. With the further development of a specific damage, the values of deterministic processes increase and the changes in random deviations decrease. The patterns of damage development, having a common manifestation, are individual for each mechanism, which complicates the task of recognizing the technical condition.
The dependencies between the parameters can serve as the most generalized characteristic of the technical condition, taking into account changes in the speed of rotation, load. Some examples of dependencies are shown in Figures 7-10.
The invariance of the vibrational behavior of the mechanism when changing the external parameters for metallurgical machines are the most reliable "diagnostic portraits". A change in the control dependencies indicates a change in the technical condition. This should be considered as a justification for the first indicator method of technical monitoring, which precedes the diagnostic method.
4. Formation of standard solutions
Despite the difference in designs, technical characteristics and operating modes, the elements of a metallurgical machine basically have the same functional purpose. The design of a metallurgical machine usually includes a motor, a gearbox and executive agency(Fig. 11). These elements have differences in their functions and loading modes.
Engine
The main type of damage to the mechanical part of the engine is the gradual damage to the bearings as a result of smallpox chipping or lubrication failure. The development time of damage, 1...2 months, allows you to use trend changes to recognize the occurrence of faults. Alignment violations, timely replacement of damaged rotors, detection of damage to the electrical part of the engines should be carried out by the repair service of the shop during routine repairs.
The gradual accumulation of damage during the operation of the electric motor makes it possible to use the values of the general level of vibration to control the current state: the root mean square value of the vibration velocity in the frequency range of 2…400 Hz; RMS and peak values of vibration acceleration in the frequency range 10…5000 Hz. Frequency ranges must be specified after vibration studies of motor bearing assemblies.
Decisions made: additional lubrication, tightening of threaded connections, replacement of bearings. The basis for the decision is an increase in the current vibration values above the permissible value, a stable increase in vibration values, and the absence of vibration reduction after the repair actions.
It is possible to use the decision rules given in GOST 25364-97: permissible value after repair - 2.8 mm / s; operation without restrictions - 4.5 mm / s; operation in a limited time interval (up to seven days) - 7.1 mm / s; operation is not allowed at vibration velocities exceeding 7.1 mm/s.
With a simultaneous increase in the vibration of the two supports by 1.0 mm / s with stabilization of the rotational speed, prompt measures must be taken to find out the reasons for the change. An increase in the vibration of the engine bearing support by 2.0 mm/s for a period of up to 3 days or an increase by 3.0 mm/s, regardless of the duration of the increase, should serve as the basis for taking prompt measures to identify the reasons for which the engine can be stopped.
Control points are located in the vertical direction, at the lowest point of the motor bearing assemblies.
Additional diagnostic parameters for making a decision to stop the engine: an increase in the temperature of the bearings over 60 0С; increase in no-load current up to 10% of the nominal values; rotation frequency instability over 3.0 rpm.
The polling frequency is 1 time in 15 minutes, the polling duration is 1 minute, the period between measurements is 100 µs. To build trends, an hourly value is used, for the archive, a shift value, a weekly value is selected. The choice of values is made by the operator of the stationary system.
Reducer
Causes of gearbox damage:
- gradual damage to bearings, gears as a result of smallpox chipping, loosening of bearings and loosening of threaded connections;
Sudden damage associated with a violation of the lubrication regime, the destruction of threaded connections, gears or rolling bearings. The development time of these lesions ranges from 5 minutes to several hours.
For the timely detection of gradual and sudden damage, it is proposed to use the values of the general vibration level and changes in the spectral pattern of vibration to monitor the current state. Controlled parameters when measuring the overall level of vibration: RMS value of vibration velocity in the frequency range of 2…400 Hz; RMS and peak values of vibration acceleration in the frequency range 10…5000 Hz.
The control of the spectral pattern of vibration is carried out by three maximum values of the components of vibration velocity and vibration acceleration when operating at a given speed. A sign of a change in the spectral pattern is a change in the amplitudes of the vibration components by more than 2.6 times, a change in the frequency characteristics of the maximum values.
Changing the rotational speed may lead to a change in the spectral pattern, but this is not a sign of damage. The change in the spectral pattern of the bearings of the input shaft of the rolling stand drive gearbox with a change in rotational speed is shown in Figure 12. A change in the load on the gearbox also changes the form of the spectrogram. In mechanical equipment, along with deterministic processes, there are also stochastic ones. The stability of the probabilistic characteristics of the latter is determined by the technical condition of the system. The amplitude of the vibration velocity components and the stability of the vibration acceleration values can be associated with a change in the speed mode or the technical condition of the combined gearbox. However, these values should remain practically unchanged under stable external influences and have the same type of change when changing the speed.
The frequency of possible damage to the elements of the mechanism must be associated with the actual speed of the motor shaft.
Decisions made: stopping the mechanism, inspecting the mechanism, tightening threaded connections, replacing elements. The basis for the decision is the excess of vibration values of the permissible value, a stable increase in vibration values, the absence of a decrease in vibration after carrying out repair actions, a sharp change in the spectral pattern compared to previous implementations with the same nature of loading. A change in the spectral pattern of vibration acceleration is the basis for an additional inspection of the mechanism. A change in the spectral pattern of vibration velocity requires an urgent decision on repair actions to restore the working state of the mechanism - tightening threaded connections, replacing elements. Clarification of the content of the repair must be carried out after a visual inspection of the mechanism.
To assess the technical condition, the method of relative comparison of the measured values over the operating time is preferable. Additional diagnostic parameters for making a decision to stop the gearbox: an increase in the temperature difference at the inlet and outlet of the lubrication system over 10 0С; increase in no-load current up to 10% of the nominal values; rotation frequency instability over 3.0 rpm.
Executive element
The state of the actuating element is largely determined by external influences on the drive mechanisms. The most informative in the case of a rolling stand is the control of the temporal shape of the vibration signal at the moment of gripping the ingot. This will make it possible to control the wear of the seating surfaces of the pillows and bearings, the presence of gaps between the stand body and the foundation slab, and the weakening of the stand fastening during rolling.
The time form is the most informative parameter in assessing the technical condition of the mechanisms of short-term and re-short-term modes of operation. Fast processes with variable accelerations are difficult to diagnose, because the measurement process requires a certain period of time during which the measured parameter does not remain constant. In this case, it is advisable to carry out joint registration of not average, but instantaneous vibration values and obtain their time base for analysis (Fig. 13).
5. Formation of a list of decision rules
In relation to the technical condition of mechanical equipment, the following definition of information is proposed: a message obtained based on the analysis of data characterizing the change in the parameters of a technical system using decision rules, used to determine the need for a repair action. Decision rules need to be developed regarding the measurement of the overall vibration level, spectral analysis and analysis of the temporal manifestation of the vibration signal.
General vibration measurement
The first step in diagnosing mechanical equipment is usually associated with measuring the overall level of vibration parameters. To assess the technical condition, the root-mean-square value (RMS) of vibration velocity is measured in the frequency range of 10 ... 1000 Hz (for a rotation speed of less than 600 rpm, the range of 2 ... 400 Hz is used). To assess the state of rolling bearings, vibration acceleration parameters (peak and RMS) are measured in the frequency range of 10…5000 Hz, shock pulse parameters at the resonant frequency of the sensor of 30 kHz, or vibration acceleration envelope in the frequency range of 10…30 kHz. Low-frequency vibrations freely propagate through the metal structures of the mechanism. High-frequency vibrations quickly decay as they move away from the vibration source, which makes it possible to localize the damage site. Measurement at an infinite number of points of the mechanism is limited to measurements at control points (bearing units) in three mutually perpendicular directions: vertical, horizontal and axial (Fig. 14).
The measurement results are presented in tabular form (Table 2) for further analysis.
First level of analysis– assessment of the technical condition – is carried out according to the maximum value of the vibration velocity, recorded at the control points. The allowable level is determined from standard range values according to GOST 10816-1-97 (0.28; 0.45; 0.71; 1.12; 1.8; 2.8; 4.5; 7.1; 11.2; 18.0; 28 .0; 45.0). The increase in values in this sequence averages 1.6. This series is based on the assertion that a two-fold increase in vibration does not lead to a change in the technical condition obtained experimentally by the specialists of the Canadian Navy. The standard assumes that an increase in values by two levels leads to a change in the technical condition (1.62 = 2.56). The following statement - an increase in vibration by 10 times leads to a change in technical condition from good to emergency. Therefore, the vibration ratio at idle and under load should not exceed a 10-fold increase.
To determine the allowable value, it is proposed to use the minimum vibration velocity value recorded in the idle mode. Standard 10816-1-97 regulates the permissible values depending on the power of the mechanism, which leads to errors in the assessment of the technical condition. The permissible value of the vibration of the metal-cutting machine must ensure the quality of the products (accuracy and surface roughness) regardless of the drive power and rotational speed.
Assume that during a preliminary survey at idle, a minimum vibration velocity of 0.25 mm/s was obtained. Then, taking the nearest higher value from the standard series 0.28 mm/s as the boundary of a good state, we have the following estimated values when working under load: 0.28 ... 0.71 mm / s - operation without time limits; 0.71 ... 1.8 mm / s - functioning in a limited period of time; over 1.8 mm / s - damage to the mechanism is possible.
To assess the state of rolling bearings at rotation speeds up to 3000 rpm, the following ratios of peak and RMS values of vibration acceleration in the frequency range of 10 ... 5000 Hz can be used: 1) good condition - the peak value does not exceed 10.0 m/s2; 2) satisfactory condition - RMS does not exceed 10.0 m/s2; 3) poor condition occurs when 10.0 m/s2 RMS is exceeded; 4) if the peak value exceeds 100.0 m/s2, the condition becomes alarm.
Second level of analysis– localization of points with maximum vibration. Vibrometry assumes that less value vibration parameters, the better the technical condition of the mechanism. No more than 5% of possible damage is due to damage at low vibration levels. In general, large values of the parameters indicate a greater impact of destructive forces and allow localizing the damage site. There are the following options for increasing (more than 20%) vibration:
1) an increase in vibration throughout the mechanism or machine is most often associated with damage to the base - frame or foundation;
2) a simultaneous increase in vibration at points 1 and 2 or 3 and 4 (Fig. 14) indicates damage associated with the rotor of this mechanism - imbalance, bending;
3) an increase in vibration at points 2 and 3 (Fig. 1) is a sign of damage, loss of compensating capabilities of the connecting element - the coupling;
4) an increase in vibration at local points indicates damage to the bearing assembly.
Third level of analysis- Preliminary diagnosis of possible damage. The direction of the larger vibration value at the control point with larger values most accurately determines the nature of the damage. In this case, the following rules and axioms are used:
1) values of vibration velocity in the axial direction should be minimal for rotary mechanisms, a possible reason for the increase in vibration velocity in the axial direction is the bending of the rotor, misalignment of the shafts;
2) values of vibration velocity in the horizontal direction should be maximum and usually exceed by 20% the values in the vertical direction;
3) increase in vibration velocity in the vertical direction - a sign of increased compliance of the base of the mechanism, loosening of threaded connections;
4) a simultaneous increase in vibration velocity in the vertical and horizontal directions indicates an unbalance of the rotor;
5) increase in vibration velocity in one of the directions - loosening of threaded connections, cracks in the elements of the body or the foundation of the mechanism.
When measuring vibration acceleration, measurements in the radial direction - vertical and horizontal - are sufficient. It is desirable to carry out measurements in the area of the emission window - the zone of propagation of mechanical vibrations from the source of damage. The emission window is stationary under local load and rotates if the load is circulating. An increased value of vibration acceleration most often occurs when rolling bearings are damaged.
In the general case, the following methods can be used to assess the state of a mechanical system:
1) mutual evaluation - when comparing units and mechanisms of the same type;
2) relative evaluation involves the control of temporary changes;
3) an absolute assessment is carried out by comparing the measured values with standard values.
After analyzing the overall vibration level, 16…20 digital data are converted into 2…3 information messages about the technical condition of the mechanism.
Spectral analysis of vibration parameters is carried out to clarify the cause of damage. Spectral analysis is a signal processing method that allows you to reveal the frequency content of a signal. Such methods of vibration signal processing are known: correlation, autocorrelation, spectral power, cepstral characteristics, calculation of kurtosis, envelope. Spectral analysis has become the most widespread as a method of presenting information due to the unambiguous identification of damage and understandable kinematic dependencies between ongoing processes and vibration spectra.
A visual representation of the composition of the spectrum gives a graphical representation of the vibration signal in the form of spectrograms. By detecting increased vibration amplitudes, equipment malfunctions can be identified. Analysis of vibration acceleration spectrograms makes it possible to identify damage at an early stage. Vibration velocity spectrograms are used to monitor advanced damage. When compiling a fault dictionary, in addition to the oscillation frequency, the amplitude value at a given frequency and the phase are taken into account - the angle of the signal shift of a given frequency relative to the reference signal. The search for damage is carried out at predetermined frequencies of possible damage. To analyze the vibration spectrum, the components of the spectral signal are determined:
1. Turnover frequency - the frequency of rotation of the drive shaft of the mechanism or the frequency of the working process - the first harmonic. Harmonics are frequencies that are multiples of the reverse frequency. They exceed the turnover frequency by an integer number of times (2, 3, 4, 5, ...). Harmonics are often referred to as superharmonics. Harmonics characterize such faults as misalignment, shaft bending, damage coupling, seat wear. The number and amplitude of harmonics indicate the degree of damage to the mechanism.
2. Subharmonics - fractional parts of the first harmonic (1/2, 1/3, 1/4, ... of the rotational speed), their appearance in the vibration spectrum indicates the presence of gaps, increased compliance of parts and supports.
3. Resonant frequencies - the frequencies of natural oscillations of the parts of the mechanism. The resonant frequencies remain the same as the shaft speed changes. Resonant frequencies can appear over the entire frequency range.
4. Non-harmonic vibrations - at these frequencies, damage to rolling bearings appears. With a significant development of damage, harmonic frequencies appear.
5. Tooth frequencies - frequencies equal to the product of the shaft rotation frequency and the number of elements (number of teeth, number of blades, number of fingers). Damage manifested at the tooth frequency can generate harmonic components as the damage progresses further.
6. Side bands - modulation of the process, appear with the development of damage to gears, rolling bearings. The reason for the appearance is a change in speed (increase and decrease) during the interaction of damaged surfaces. The modulation value indicates the source of oscillation excitation. Modulation analysis allows you to find out the origin and degree of development of damage.
7. Vibration electrical origin typically seen at 50Hz, 100Hz, 150Hz and other harmonics. The frequency vibration of electromagnetic origin disappears in the spectrum when the electrical energy is turned off.
8. Noise components arising from jamming, mechanical contacts. They are characterized by a large number of components of various amplitudes. With knowledge of the components of the spectrum, it becomes possible to distinguish them in the frequency spectrum and determine the causes and consequences of damage (Fig. 15).
Rules for the analysis of spectral components
1. A greater number of harmonics characterizes greater damage to the mechanism.
2. Harmonic amplitudes should decrease as the number of harmonics increases.
3. Amplitudes of subharmonics should be less than the amplitude of the first harmonic.
4. An increase in the number of side bands indicates the development of damage.
5. The amplitude of the first harmonic should have a greater value.
6. The modulation depth (the ratio of the harmonic amplitude to the amplitude of the sidebands) determines the degree of damage to the mechanism.
7. The amplitudes of the vibration velocity components should not exceed the allowable values adopted in the analysis of the overall vibration level. One of the signs of the presence of significant damage is the presence in the vibration acceleration spectrum of components with values above 9.8 m/s2.
The record of each spectrum consists of 800...6400 lines that determine the frequency and amplitude of the components. Analysis of one spectrogram allows forming 2…4 informational messages. These messages may be the same or different from the mechanism checkpoint information messages.
Analysis of the temporal shape of the vibration signal
The vibration signal can be represented in a temporal form, which is the main form of representation of the temporal signal. The most effective use of the analysis of the temporal shape of the vibration signal for diagnosing transient, non-stationary, shock processes. For this, periods of 30 ... 400 μs are used, the number of measurements is 10000 ... 16000 or more. Examples of the time form of the vibration signal are shown in Figure 16.
Time waveform change analysis allows for early fault detection. The difficulty of the analysis lies in the absence of rules for formalizing and processing temporary realizations of the parameters of fast processes. In many ways, this process is subjective and depends on the experience of the specialist. The spectral components of the vibration signal often remain virtually unchanged due to the averaging of the vibration signal necessary to obtain a reliable estimate. At the same time, the analysis of the actual signal provides additional information about the technical condition of the mechanism.
Time Signal Analysis Rules
1. It is necessary to evaluate the repeatability of the parameters of the oscillatory process. The same influences must correspond to the same realizations of the oscillation parameters. You can use a comparative analysis of the same type of processes at different points using a two-channel vibration analyzer.
2. Evaluation of the symmetry of the signal relative to the zero (initial) level of fluctuations. The presence of a symmetrical signal indicates a good condition (the ideal case is a sinusoidal waveform - absolutely symmetrical), deviations - increase the degree of asymmetry. Diagnostic parameters for analysis are positive and negative values of oscillation amplitudes. The reasons for the asymmetry are the non-linearity of the characteristics of the system, the anisotropy of the details of the bearing unit.
3. The most significant is the time of calming the system after the disturbance. Systems with low stiffness and low damping properties will have a longer decay time. It is necessary to determine the causes that reduce the stiffness and the damping properties of the system. It is possible to evaluate the stability of the damping properties of a mechanical system by determining the oscillation decrement as the natural logarithm of the ratio of two subsequent amplitudes.
The nature of the change in the temporal implementation of the vibration signal when changing the speed of the mechanism is also a diagnostic feature:
1) if, when changing the rotational speed, there is an increase in vibration in a linear relationship, the cause of the damage is mechanical damage to the parts;
2) if, when changing the rotational speed, there is an increase in vibration in a quadratic dependence, the cause of the damage is the unbalance of the rotor;
3) if an increase in vibration occurs exponentially with a change in rotational speed, the cause of damage is a crack in the body part or in the base;
4) a sharp decrease in the vibration of the electric motor when the power is turned off (Fig. 17a) - a sign of damage to the electrical part of the engine;
5) a gradual decrease in vibration when the mechanism stops (Fig. 17b) - a sign of damage in the mechanical system.
6. Formation of visual signs of damage
External signs of destruction of parts always leave characteristic traces, which can be used to determine the cause of damage. Knowing the cause allows you to establish the necessary actions to prevent similar failures or improve the reliability of the node. After a breakdown, a visual inspection of the damaged part is carried out. According to the traces of wear, the type of wear, the nature of the acting forces on the bearing, the nature of the contact of the surfaces mating with the bearing are determined. This approach was used to develop a classification of damage to rolling bearings (Table 3).
It is impossible to control the physical processes occurring in the contact zone of the gearing during operation. At the same time, the type of wear, the nature of destruction, the distribution of acting forces makes it possible to obtain information about the operating parameters and the nature of aging.
When developing the classification of damage to gears (Table 4), the following factors were taken into account: the value of the applied force load; external factors; immobility of the landing surfaces of the gear and shaft; state of contact surfaces; mutual arrangement of shafts; uniformity of applied forces; formation of fatigue cracks.
Limits of use of gears at various types wear are formulated in the rules of technical operation:
If the tooth is broken, there are cracks near the base of the tooth, or plastic deformation of the tooth material, the gear wheel must be replaced;
With smallpox chipping, replacement is necessary if the working surface of the teeth is damaged by more than 20%, with a depth of chipping pits - more than 5% of the tooth thickness;
With abrasive wear - tooth wear by 10 ... 20% of the tooth thickness;
In case of hardening, scuffing on the working surface of the tooth - in case of damage to more than 20% of the working surface area;
The presence of tint colors on the working surface of the teeth is not allowed; - according to the location of the contact spot - the contact spot should be at least 25 ... 60% in height and 30 ... 80% in width of the tooth.
The proposed classification of damage allows you to consistently investigate deviations in the operation of gears and make timely decisions to increase the service life of gears.
7. Formation of information flows
The main product of the diagnostic service is information on the technical condition of mechanical equipment. The timely use of this information determines the effectiveness of the repair service. Information about the actually detected and repaired damage, the work carried out allows us to assess the accuracy of the diagnosis and make adjustments to the diagnostic models and decision rules. In fact, it is necessary to formulate requirements for the sources and amount of information used for repairs.
There are three main sources of information about the technical condition of the equipment and the causes of malfunctions:
Failure analysis;
Results of technical diagnostics;
Determining the causes of breakdowns.
Traditionally, failure analysis considers the transition from a healthy state to an unhealthy state. This leads to consideration of past states, without the certainty of repeating combinations of factors and operating conditions prior to failure. Failure is a consequence of the development of damage under the influence of the interaction factors that have developed at the time of failure. Carrying out repair actions changes the existing impact of factors, leading to a change in the nature of damage accumulation. Therefore, the use of traditional approaches in determining the problems of failure analysis, associated with the determination of the distribution laws of the probability density of failure flows, in relation to metallurgical machines does not allow obtaining reliable estimates of reliability parameters.
From the point of view of cybernetics, a failure should be considered as an error in the reliability control system of a complex of metallurgical machines, due to a mismatch between the tasks set and the internal state of the mechanism. Therefore, along with the concept of failure, it is necessary to take into account the repair actions carried out, the deviations from the working state that were noticed and eliminated, which did not entail a downtime of the workshop. Only with this consideration, failure analysis can be an effective means of monitoring the reliability of mechanisms. Therefore, maintenance work carried out by the repair service can provide information about possible emergency stops. The initial data in this case are the work carried out to eliminate the comments of the technological personnel; violations of operating modes; additional maintenance work. Like any complex system, a complex of metallurgical machines must have the properties of a simple failure flow and stationarity. Therefore, deviations from the traditional scope and type of maintenance work may precede pre-failure conditions.
The results of technical diagnostics should provide information on the category of technical condition, possible damage and recommendations on the time and types of repair actions. The frequency of diagnosis should be determined based on the rate of development of the most characteristic damage. It is necessary to distinguish two levels in assessing the state of the mechanism - indicator and diagnostic.
The results of the inspection of the mechanism during the repair, the work carried out to restore the working condition, are necessary for the organization feedback between the diagnostic service and the repair service. The effectiveness of diagnosing is largely determined by the level of mutual understanding and trust between the specialists of these departments.
A practical solution to the problem of forming information flows is presented in the form of an information management system for the repair service (Fig. 18).
The system consists of the following main components:
The static part, which includes information that is relatively unchanged over time - data from regulatory and technical documentation, operating experience, base of equipment defects, etc.;
Dynamic part - data that accumulate or change over time, characterizing the actual state, workload of machines, the results of inspections and repairs, lubrication, diagnostics;
The information part - the formation and presentation of final information: schedules for repairs, lubrication, diagnostics, analysis of the possibility of fulfilling an order based on data on the current actual state of the equipment and predicted work, development of other reporting documentation.
The software must include:
- "Information about equipment" - a static database designed to enter, store and view information about equipment;
- "Accounting for operating hours" - a dynamic database designed to enter and store information about the actual duration of the machines, provides access to the auxiliary mode "History", which allows you to determine the average workload of the mechanism;
- "Condition control" - a dynamic database designed to store information about the results of diagnosis, performed maintenance and repair operations, as well as lubrication;
- "Schedule of works" - provides access to the schedule of maintenance, repairs, lubrication, and diagnostics, automatically generated based on dynamically adjusted repair cycles;
- "Technological control" - the main module information subsystem, designed to assess the possibility of fulfilling the plan (order), based on the remaining resources of machines, the selection of alternative replacements based on the division into functional groups, within which partial or complete interchangeability of machines is implied.
8. Formation of criteria for assessing the quality of the repair
The effectiveness of repair work depends on three main factors:
Timeliness; - determination of types and volumes of repairs;
The quality of the repair work.
Regarding these factors, it is necessary to develop evaluation criteria. For the timeliness of the repair, the basic rule is "it is better to repair an hour before failure than a minute after." Sometimes an excessive amount of repair work should prevent the possibility of damage to body parts. Several rules can also characterize the quality of the repair performed: failure-free operation during the overhaul period, repetition of failures - the result of poor repair quality; improvement of diagnostic parameters after repair, in particular energy ones.
This work actually forms the methodological basis for carrying out repairs according to the state. The development of this document and implementation must be carried out at the enterprises of the metallurgical industry of Ukraine.
Thus, the concept of technological safety of mechanical equipment of metallurgical enterprises can be formulated as follows: ensuring the trouble-free operation of a complex of metallurgical machines in the overhaul period by carrying out preventive repairs of equipment based on information about the technical condition of the mechanisms.
Literature
1. Rules for the technical operation of the mechanical equipment of blast furnace shops. VNIIOCHERMET. - M.: Metallurgy, 1968. – 212 p.
2. Rules for the technical operation of the mechanical equipment of open-hearth shops. VNIIMEKHCHERMET. – M.: Metallurgy, 1979. – 202 p.
3. Rules for the technical operation of the mechanical equipment of blooming and continuous billet mills - M .: Metallurgy, 1979. - P. 192.
4. Rules for the technical operation of mechanical equipment of sinter plants. VNIIMEKHCHERMET. - M.: Metallurgy, 1985. - 143 p.
5. Rules for the technical operation of mechanical equipment of converter shops of metallurgical enterprises. VNIIMEKHCHERMET. – M.: Metallurgy, 1984. – 79 p.
6. Regulations on scheduled preventive repairs (PPR) of mechanical equipment of ferrous metallurgy enterprises of the USSR (2nd edition), approved. April 20, 1972, VNIIOchermet, 1973.
7. Temporary regulation on maintenance and repairs (TO and R) of mechanical equipment of enterprises of the system of the Ministry of Ferrous Metallurgy of the USSR. - Tula, 1983. - 390 p.
8. Grebenik V.M., Tsapko V.K. Reliability of metallurgical equipment (assessment of operational reliability and durability). - M.: Metallurgy, 1980. - 344 p.
9. Organization of maintenance of metallurgical equipment / V.Ya. Sedush, G.V. Sopilkin, V.Z. Vdovin and others - K .: Technique, 1986. - 124 p.
10. Grebenik V.M., Gordienko A.V., Tsapko V.K. Improving the reliability of metallurgical equipment: a Handbook. - M.: Metallurgy, 1988. - 688 p.
11. Belodedenko S.V., Ganush V.I., Filipchenkov S.V., Tsybanev Yu.G. Models of the probability of failure-free operation and safety in assessing the technical condition // System Technologies. - 2010 - No. 2 (67). – S. 159–166.
12. Belodedenko S.V., Ugryumov D.Yu. Efficiency of predicting the durability of rolling equipment units and deformation fatigue criteria // Metallurg. and mining. prom. - 2003. - No. 5. – S. 86–90.
13. Regulations on the maintenance of equipment of enterprises of the mining and metallurgical complex. Order of the Ministry of Industrial Policy of Ukraine No. 285 dated 15.06.2004
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