Summary on the theme of master's work
Contents
- Introduction
- 1. Collection and analysis of domestic and foreign information on occurrence of defects in overhead cranes
- 1.1 Defect relation to overhead cranes
- 2. Increasing the lifetime of the bridge crane by increasing the frequency of inspections
- 2.1 Coefficients showing the effect on the frequency of inspections
- 2.2
The schedule of inspections
- References
Introduction
Overhead cranes are an integral part of the handling, storage operations. In the shops of enterprises, warehouses, ports, the most widely used bridge cranes, by which they can raise and lower heavy loads, as well as their movement. Overhead cranes are designed for general performance for loading and unloading both indoors (workshop, warehouse, etc.), and in open racks. Overhead cranes are used, for example, in the halls of power machinery, industrial workshops and metallurgical enterprises.
Condition crane fleet Ukraine obsolete cranes are used in excess of, in frequent breakage. Approximately 80-90% of the park - it taps that exhausted their standard life.
Time operating overhead cranes often have damage associated with improper handling of construction of bridge cranes, as well as irregular intervals inspections. At untimely inspection crane components, mechanisms may, in some cases, the entire bridge crane may fail. And with frequent inspections are increased costs for overhead crane. Therefore conduct timely inspections of the bridge crane is an urgent task.
1. Collection and analysis of domestic and foreign information on occurrence of defects in overhead cranes
1.1 Defect relation to overhead cranes
Issues of elimination of defects and strengthen metal structures to ensure their reliability and durability of a number of scientists involved. Among them Val V., E. Gorokhov, Uvarov B., V. Plotnikov, Belsky M., A. Lebedev and others [1,6,8].
Scientists in their work pay great attention to design solutions to strengthen steel structures. Significantly fewer questions reflected the choice of technology to eliminate the existing defects, structural damage and reduce the life of factors overhead crane. Therefore it is necessary to analyze the defects arising in overhead cranes.
Defects that arise during operation of the bridge crane in the mode of operation similar lightweight secondary mode. Yakhnin R. in his work "Repair of metal bridge cranes" notes which defects occur in the middle overhead cranes and heavy-duty 5-ton capacity [8]. Defect relation bridge crane shown in draw. 1 and draw. 2.
Draw. 1. Defect relation bridge cranes heavy duty 5-ton capacity (animation, volume–58КB)
Draw. 2. Defect relation bridge cranes medium-duty 5-ton capacity (animation, volume–108КB)
Analysis has shown that the most common defects bridge cranes heavy and medium modes 5-ton capacity are mechanisms of movement and lifting, 33% and 42%, respectively. Also worth noting is that the metalwork and electrical lead to problems in heavy 27% and 22% and an average of 18% and 17% of operating modes. Safety devices and cable-beam system with a ratio of defects within 10%.
2. Increasing the lifetime of the bridge crane by increasing the frequency of inspections
2.1 Coefficients showing the effect on the frequency of inspections
To reduce the number of generated defects and breakdowns that occur during the operation of the bridge crane is necessary to develop the optimal frequency of inspections based on the developed factors that affect the incidence of these failures [1]. You also need to determine the factors that affect the valuation of the life of the bridge crane before and after their service life, which is 16 years.
To account for the influence of real life on the standard life using a range of standard formulas [11], but in this mathematical model, there are some inaccuracies in particular, do not take into account all factors that may affect the frequency of inspections.
Utilization payloads:
Utilization during the year:
Utilization during the day:
Where Qср - the average weight being lifted for a change, t; Q - rated load, t; tс and tг - respectively the number of hours of work per day and tap the number of days in the year of the crane.
The average number of cycles per hour:
Where Zц - the number of inclusions per cycle Zц = 6 ... 12, cyclic duration for which the mean-shift mechanisms in the number of inclusions hour nch up to 240
Number of cycles for the life of the crane on the rules Gosgortechnadzor:
Mode loading crane depends on the coefficient of load distribution Kp:
Where C1 - the average number of cycles with the private level load mass P1; CТ - the total number of cycles over the lifetime of the crane; P1 - the value of individual private goods (load level) for a typical application of the crane; Pmax - maximum weight load (nominal load), which is allowed to raise the crane; m = 3.
To account for the influence of real life on the standard life using a range of standard formulas [2], but in this mathematical model, there are some inaccuracies in particular, do not take into account all factors that may affect the frequency of inspections. Lifetime by the rules correspond to groups Gosgortechnadzor classification [3]:
For factors affecting the service life of the bridge crane, you can enter a factor which shows the influence of factors on the service life of the bridge crane. This ratio varies from 0.92 to 1.0 - the lower chapel explained maximum possible deviation that does not disrupt operation of the bridge crane. With excellent (new) condition tap coefficient taking 1.0.
For the lower limit of the state of the bridge crane to do the calculation. When evaluating the bridge crane accept that his condition is equal to or higher than 60%. This is because the condition of the crane at least 60% will experience unstable operation, as in some cases the valve can not operate normally. Based on the 10 coefficients, which can reduce the lifetime of the tap assume that four of them are minimal, i.e. crane operation is 60%. Since the lower limit is 0.92:
Where ni - this coefficient shows the effect on the state of crane.
Kф=0.72, will determine the lower limit of the performance of the crane.
The coefficient of the new crane will be able to change slightly, because all units and mechanisms are in excellent condition. Table 1 shows the wear factors as a bridge crane.
| Percentage of wear mechanisms of the bridge crane, % | Coefficient showing the influence on other factors, depending on the state of the crane, Кф | condition crane | Characteristics of the physical condition |
| 0…5 | 0,96…1.0 | New | New just installed and not yet exploited. Is in excellent condition |
| 5…20 | 0.91…0.96 | Good | Former crane operation, completely remodeled or renovated, in excellent or good condition. |
| 20…40 | 0.84…0.91 | satisfactory | Used one, requires some repair or replacement of individual small parts (vkladyschi, bearings, etc.) |
| more 40 | 0.72…0.84 | conditionally suitable | Former operation, requiring repair or replacement of major parts (engine, etc.) |
Table 1 shows the ratios that demonstrate the effect on coefficients taken into account factors that affect the service life of the crane. The coefficients are shown in Table 2 were obtained by calculating the factors that determine the state of the crane. Above are 10 factors (coefficients), which range from 0.92 to 1.0 - is the extent in which the possible use of an overhead crane. Using a crane, in which four factors affect the operation of the crane and constitute 0.92, defines the lower limit of a crane - conditionally suitable condition.
Table [11] shows the correspondence modes of bridge cranes during their operation. For example, the selected bridge crane 5 tons and having a plurality of classifications A5 will work 13.3 years from 16 years of their service life in the mode of A5, after 13.3 years this crane can be operated in a more serious mode. This can lead to failure of the bridge crane.
Example, in Table 3, the coefficient Kф = 0.72, standard life of 16 years, ie Crane conditionally suitable for operation and service life will be equal:
Where CH - standard life Кф - coefficient showing the effect of factors on the performance of an overhead crane.
Based on these data we can conclude that this method [11] does not take into account some factors affecting the life of the crane.
2.2 The schedule of inspections
In the operation of overhead cranes plays an important role periodicity condition crane inspections. At untimely examination may have some problems associated with the performance of the crane. Thus, in case of delay inspections may fail mechanism node or the entire bridge crane, and with frequent inspections spent more money. Therefore, for each machine you need to develop your schedule inspections, which differs from the standard. Example of a standard technical survey can be seen in Drawing 3.
On the bottom axis represents the term in which the checks, measured in years. For example, after 16 years of their service life (Cн), the crane is subjected to overhaul (Inspection). In Figure 3 indicates : Repair - Kaп.рем., Primary inspection - Обс.1, retested - Повт.2 and further the operation of the crane - t, it depends on the condition of the crane. In the period of their service life to the attention of not undertake minor inspections - Checking Lube, removable inspection and other inspections. This diagram is constructed in the form of decreasing levels since lifetime achievement at each stage decreases.
To conduct inspections of the bridge crane, which is operated should use pattern 4.
The diagram shows the recommended timing of the technical inspections. For example, the standard life may vary from 11.5 to 16 years, as in the diagram added further re-examination after the operation, but with an interval of 1 year.
In writing this essay master's work is not completed. The final version of the work can be obtained from the author or supervisor after December 2014.
References
- Бельский М.Р., Лебедев А.Н. Усиление стальных конструкций. – К.: Будівельник, 1981. – 117 с.
- Металлические конструкции: Общий курс: Учебник для вузов / Г.С.Ведеников, Е.И. Беленя, В.С. Игнатьева и др.; Под ред. / Г.С. Веденикова. – 7-е изд., перераб. и доп. – М.: Стройиздат, 1998. – 760 с.
- Пчельников С.Б. Обеспечение надежности специальных промышленных зданий: Дис...кCта техн. наук: 05.23.01 / ДонНАСА. – Макеевка, 2007. – 177с.
- ДБН 362C92. Оцінка технічного стану сталевих конструкцій виробничих будівель і споруд, що знаходяться в експлуатації / Держбуд України. – К.: Укрархбудінформ, 1995.
- Modes of operation and performance of overhead cranes [Electronic resource].– Mode of access: Overhead cranes
- Плотников Василий Андреевич. Горизонтальные поперечные воздействия мостовых кранов на подкрановые конструкции : Дис. ... канд. техн. наук : 05.23.01 Магнитогорск, 1998 152 с. РГБ ОД, 61:99-5/1223-7
- Парницкий А.Б., Шабашов А.П. Мостовые краны общего назначения. М.: Машгиз - 1961.
- Промышленный транспорт –11 вып. М. 1988.
- Способ снижения раскачивания грузозахватного органа мостового крана Maeda Minoru, “Кэйсо, Instrumentation” 1987г.
- Lifetimes of hoisting cranes [Electronic resource].– Mode of access: Terms manual
- Котельников В.С., Шишков Н.А. Комментарий к правилам устройства и безопасной эксплуатации грузоподъемных кранов–Москва: МЦФЭР, 2007. – 720с.