Method for substantiating the spheres of application of shunting locomotives at sorting stations

Shunting work on sorting wagons is carried out on steeper profiles and requires the operation of shunting diesel locomotives of a higher power. Many sorting operations use double traction of shunting locomotives in conditions of the highly outdated fleet of shunting diesel locomotives. However, the technology of operating two shunting locomotives requires substantiation of its scope of application. In this article, using the example of station "X", the technology of disbanding trains from the sorting hump is investigated in two ways: the first is the existing technology (work on disbanding trains is carried out using two shunting locomotives of the TEM-2 series), shunting locomotive of TEM-7 series. It has been determined that in the existing technology, the required processing capacity of the hill approaches its maximum value. When using the TEM-7 diesel locomotive, the maximum processing capacity of the hill increases by 27%. The sphere of efficiency of the TEM-7 series locomotive instead of two TEM-2 was substantiated by the method of technical and economic calculations.


Introduction
The main function of sorting stations is to sort the wagons according to the directions of travel. The faster the wagons are sorted, the faster the station's performance and the railway as a whole will improve. Currently, there are several studies to accelerate the process of processing wagons at sorting stations using railway automation devices [1-4, etc.]. In particular, most of the research aims to improve the performance of a shunting locomotive at sorting stations [5-9, etc.]. However, in these studies, the scope of applying this or that shunting locomotive is not sufficiently substantiated based on technical and economic indicators. Therefore, it is necessary to substantiate the scope of applying shunting diesel locomotives on the sorting hump, taking into account capital investments.
As you know, the sorting hump has a large profile and, therefore, a shunting locomotive of a higher power is required to sort the wagons. At present, at station "X", due to the outdated fleet of shunting diesel locomotives, the disbandment of trains through the sorting hump is carried out simultaneously by two shunting locomotives the f TEM-2 brand. The introduction of a more powerful locomotive will allow replacing two TEM-2 locomotives, thereby reducing the required fleet by one unit. It is proposed to carry out sorting work at the station with a TEM-7 locomotive instead of two TEM-2. To do this, it is necessary, first of all, to compare the maximum processing capacity of station "X" with the required one, and then to determine the capital costs for the purchase and implementation of a more powerful locomotive. Calculations of existing technology were made according to option I, and the proposed one -according to option II.

Determination of recycling capacity of sorting hump
The maximum processing capacity of the sorting hump depends on the technological cycle of time for the dismantling of one train from the sorting hump, which consists of separate shunting operations and is determined by the formula [10] , ups dis thr cl ar ds where t h/f is duration of i-th half-flight of check-in operation, min; t dm is time for changing the direction of movement of a shunting locomotive, the values are taken for shunting locomotives -t dm = 0.15 min.
The t h/f values are determined by the formula v  [11]  The time for removing the means of securing and coupling the locomotive cl T according to [12] is taken equal to 4.5 minutes for both options.
The technological time of advancing the train onto the sorting hump is determined by the formula where l thr is thrust half-flight length, l thr = 230 m; V thr is thrust speed. The speed of advancing and breaking up depends on the average number of wagons in one uncoupling.
The average number of wagons in one uncoupling is determined by the following formula: where g 0 is the number of uncouplings is determined according to [12] and g 0 = 22. According to [12], knowing wagons, the speed of thrusting and dismantling 3 , where t dis is time to dismantling the train from the hill, excluding the additional time for maneuvers with wagons forbidden to dismount from the hill without a locomotive, min.; Δt dis is the increase in the dissolution time for shuntings with forbidden downhill (FD) wagons, per one train to be dismantled, is taken to be equal to the dissolution time, min.
The time for dismantling trains from the hill, excluding additional time for FD wagons, is determined by the formula where l w is car length, m; V dis is dismantling speed; m c is average number of wagons in the dismantled train. Then the dissolution time taking into account the FD will be equal to: 11.53 11.53 23.06 Technological time for upsetting wagons from the side of the hill to eliminate "opening space" between groups of wagons on the tracks of the sorting yard is determined by the formula According to the first option, two TEM2 locomotives in the sorting yard operate separately during the upsetting operations. Therefore, for the first option, Thus, according to the formula (1), the technological cycle of time for the disbandment of one train from the sorting hump is equal to: -for the first option 17  The maximum processing capacity of the slide is the most important indicator and is determined by the formula [13]:  [13] dis non  =0,03.
Thus, according to the formula (9), the maximum processing capacity of slide is equal to: -for the first option wagons.
The required processing capacity of slide depends on the number of processed trains (N prtr ) and is determined by the formula [13]: where unev k is the coefficient of annual unevenness of wagon-flows.
Currently, the number of processed trains at station "X" will be 26, for such several train-flows wagons.
The calculation results show that the consuming processing capacity of station "X" with the intensive wagon-flows is approaching the maximum. Those, any technical failure of sorting devices, require measures to increase the processing capacity of the station. When a more powerful TEM-7 hump locomotive is used, the maximum processing capacity of the slide increases by 27%.

Method for substantiating the scope of efficiency of a shunting locomotive of TEM-7 series
The capital expenditures for the purchase and implementation of the TEM-7 locomotive can be determined by enlarged meters. The cost of TEM-7 locomotive at the Central Bank rate as of 21.02.2021 is estimated at 4.61 billion soums [14]. To conduct an economic assessment, it is necessary to determine the operating costs of using the locomotive. Depreciation deductions are calculated using the formula: where CFA is the cost of fixed assets; а depr is depreciation rate, %. For operating fixed assets, the full replacement cost is taken, for commissioned objectsthe initial one use depr T a % 100  ., (11) where Т use is useful life, 20 years. . , sum (12) where ∑ACF depramortized cost of fixed assets; к cpre is coefficient taking into account the costs of current repairs (taken 0.34) 4

,bil. Sum
To assess the quality of proposed event, it is necessary to take into account the costs of maintaining two TEM-2 locomotives. The cost of TEM-2 locomotives, taking into account their service life, is 2.03 billion soums [15].
Depreciation costs for two TEM-2 locomotives will be: ( The transition to the second option leads to savings on the wages of driver and driver's assistant, as well as on diesel fuel. The TEM-7 shunting locomotive consumes more fuel than the TEM-2. Therefore, the savings from fuel savings are not taken into account and the savings from the wages of driver and the assistant driver for the year E wt is calculated by the formula: , sum (13) where E w are saving on wages of driver and driver's assistant per day, sum; Saving on the wages of driver and assistant driver we take 19576817 sums per month [16], in 19576817/30 = 652561 sums per day. The total total annual expenses for the maintenance of TEM-2 locomotives with drivers and driver assistants will be: ).
The total cost of maintaining a shunting locomotive per day can be defined as the sum of costs associated with the operation and downtime of locomotive, where  ot Mh are locomotive-hours of operation of shunting locomotive per day; loc shun e is cost of 1 locomotive-hour of work (accepted 218913 sum), sum.
Costs associated with the operation of locomotive by options: After calculations, it can be concluded that the organization of station based on the use of TEM-7 locomotive can provide monetary savings, taking into account deductions for depreciation and maintenance in the amount of 1.918 billion sums in a year.
The calculation of the payback period for the introduction of TEM-7 locomotive at the sorting stations is as follows: the net present value by years (NPV) is calculated, and the first positive value of NPV will correspond to the payback period, in terms of resulting savings. Net Present Value can be calculated using the following formula [17]: where C rc are reconstruction costs (capital costs), sums; R t is total annual savings from the introduction of a new locomotive into operation, sums; E is the discount rate; we take 0.12; t are years.
The calculation results are summarized in Table 1. At costs in the initial year. the calculation is made according to the formula: For the 4th year of project NPV=1.214billion sum. The exact value of payback period of capital investments is calculated using the following formula. years: where is last year in which the NPV balance is negative (NNPV ): is the year in which the NPV balance became positive (PNPV ).

Results and Discussion
The results of calculations to substantiate the scope of application of shunting diesel locomotives at the sorting stations showed that today the required processing capacity of hill at station "X" is 1704 wagons and the maximum processing capacity of hill is 1738 wagons. When using the TEM-7 diesel locomotive. the maximum processing capacity of the hill increases by 27% and will amount to 2217 wagons. According to [18], the annual growth in the traffic volume is 8%. Consequently, after a year, the technology of disbandment with two shunting locomotives will not master the volume of processed wagon-flow. The introduction of a more powerful locomotive of the TEM-7 series helps to preserve the processing capacity of the roller coaster for another 3 years. When two shunting locomotives TEM-2 are replaced by one TEM-7 at the "X" sorting stations due to investments in the purchase of a new TEM-7 locomotive, the payback period of the project will be 3 years and 1 month. This shows the feasibility of introducing a shunting locomotive TEM-7 at station "X".

Conclusions
To date, most of the shunting locomotives of the fleet have exhausted their standard service life. The technical condition of locomotives, which has exhausted this period, in most cases allows them to remain in operation, provided that the serviceability of vehicles is maintained by appropriate types of repair. The desire to reduce costs and improve operational efficiency determines the need for railways in rational traction facilities for shunting wagon sorting. Based on the foregoing, a variant of efficiency of replacing the TEM-2 shunting locomotive with TEM-7 is considered. The savings from replacing the existing two shunting locomotives of TEM-2 series with a locomotive of TEM-7 series will amount to 1.918 sums per year. The payback period will be 3 years and 1 month. The presented method of choosing the type of rolling stock for servicing the sorting hump operation of station makes it possible to determine an economically feasible option for organizing shunting operations. taking into account the characteristics of possible types of rolling stock.