Charging Metal Props for the Mines of the Leninugol Trust in Kuzbass
Abstract Generated abstract
This article examines the production and charging of simple tubular metal mine props with wooden cores and end plugs at the Leninugol Trust in Kuzbass, where metal supports were introduced to reduce timber consumption, labor demand, costs, and safety risks. It describes the prop design, workshop equipment, wood-processing and hand-charging procedures, and presents a cost breakdown for first-quarter 1940 production. The analysis identifies high administrative, auxiliary labor, and manual charging costs, as well as the rapid deformation and replacement cost of wooden plugs, as key obstacles to wider economic efficiency. It argues that mechanizing charging, eliminating ineffective washers, and reducing plug production costs, especially toward a target of 20 kopecks per plug, would make tubular metal props economically advantageous even in thin seams.
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Charging Metal Props for the Mines of the Leninugol Trust in Kuzbass
V. V. Proskurin
Postgraduate student
The mines of the Leninugol trust alone consume daily about 45–50 carloads of fastening timber, with a haulage distance of more than 500 km; it therefore becomes clear what enormous national-economic importance is attached to the introduction of metal support in the mines of Kuzbass. The use of metal support in stoping and development faces increases its importance for the national economy of the USSR to an even greater degree, since it reduces the cost of supporting the excavated space; moreover, with metal props, workers occupied in timber delivery are freed, and, finally, a greater degree of safety in mining operations is ensured.
At present, in the mines of the Leninugol trust, among the various types of metal props, the most widespread are non-extendable semirigid simple tubular props with a wooden core and two end plugs.
A non-extendable tubular prop is simple in its construction (Fig. 1). It consists of a metal tube (1) with two slots (2), two end wooden plugs (3), a wooden core (4), and two pairs of metal washers (5). Owing to the presence of two wooden end plugs, the simple tubular prop has limited yield within the limits of compression of these plugs, while the wooden core provides it with increased resistance and facilitates repair when it is deformed. The metal washers are intended to make it easy to remove the deformed plugs by means of a wedge driven through the slots (2) in the metal tube.
Fig. 1
Simple tubular props, not charged with wood, are supplied for the Leninugol trust by the Kiselevsk Plant. The manufacture of end plugs, cores, and the charging of tubular props with wood is carried out…
…by the metal-support shop, organized in 1939 under the Coal-Engineering Supply Administration of the Leninugol Trust.
The plugs and cores are made from ordinary dry mine pine props. For processing the wood, two circular saws and three lathes are installed in the shop, driven by motors of 1.5 kW. Mine props of various diameters arrive at the shop. With the aid of circular saw No. 1, props of large diameter are given the form of a squared timber. The resulting slabs are sent to the mines for use as intended. Squared timbers and props of normal diameter are sent for processing on the lathes. On the latter, the plugs are turned into a truncated cone with the diameter of the upper base equal to the inside diameter of the metal pipe, while the diameter of the lower base is 50 mm larger than the upper one. The height of the plug is 150 mm. A prop no more than 1.0 m long may be placed in the lathe, making it possible to turn 6 plugs. The subsequent cutting of the plugs is carried out with circular saw No. 2. The cores are given a cylindrical shape on the lathes, with a base diameter equal to the inside diameter of the pipe, i.e., 100 mm. The length of the core is taken to be 150 mm shorter than the metal part of the prop. Output standards and rates have been established depending on the length of the prop being turned. Charging of the props is carried out by hand with an 8-kg sledgehammer. The distance between the ends of the core and the pipe must be 75 mm. The plugs from the two ends of the pipe are fitted tightly to the core and each protrudes 75 mm beyond the metal part of the prop. Auxiliary workers load the finished products into mine cars and haul them to the warehouse. Imperfections in hand charging sometimes lead to undesirable results requiring the cores to be drilled out. Drilling out of cores or deformed plugs is carried out with a column electric drill fitted with a wood bit.
In the first quarter of 1940, the metal-support shop, headed by a chief and a foreman from the technical supervision staff, worked mainly around the clock. During this quarter the shop chiefly manufactured plugs and cores for tubular props 850–1100 mm long, with an internal diameter of 100 mm.
The annual output of the metal-support shop and the cost of the products manufactured in the first quarter of 1940 are presented in Table 1.
Table 1
| No. | Cost item | Plugs: costs per unit, kopecks | Cores: costs per unit, kopecks | Charging: costs per unit, kopecks | Costs for initial charging, kopecks | Note |
|---|---|---|---|---|---|---|
| 1 | Forest materials | 5.36 | 25.60 | — | 30.96 | For charging one prop, two plugs and one core are used |
| 2 | Auxiliary materials | — | — | 6.98 | 6.98 | For charging one prop, two plugs and one core are used |
| 3 | Electric power | 2.71 | 11.81 | 0.95 | 18.18 | For charging one prop, two plugs and one core are used |
| 4 | Wages of production workers | 9.85 | 16.86 | 29.24 | 65.80 | For charging one prop, two plugs and one core are used |
| 5 | Wages of shop workers subject to allocation | 3.81 | 5.74 | 5.88 | 19.24 | For charging one prop, two plugs and one core are used |
| 6 | Wages of administrative and technical personnel, junior service personnel | 6.67 | 10.41 | 17.22 | 40.97 | For charging one prop, two plugs and one core are used |
| 7 | Additional wages | 1.78 | 2.83 | 4.48 | 10.87 | For charging one prop, two plugs and one core are used |
| 8 | Payroll charges | 2.29 | 3.58 | 5.62 | 13.78 | For charging one prop, two plugs and one core are used |
| 9 | Labor-safety expenses | 0.48 | 1.06 | 1.74 | 3.76 | For charging one prop, two plugs and one core are used |
| 10 | Depreciation of equipment | 0.16 | 3.51 | — | 3.33 | For charging one prop, two plugs and one core are used |
| 11 | Wear of low-value inventory | 0.47 | 2.13 | 2.31 | 5.38 | For charging one prop, two plugs and one core are used |
| 12 | Horse-yard services | 0.10 | 1.56 | 5.98 | 7.74 | For charging one prop, two plugs and one core are used |
| 13 | Heat treatment | 0.72 | 10.91 | — | 12.35 | For charging one prop, two plugs and one core are used |
| Total | 34.4 | 96.00 | 80.4 | 245.2 |
It is evident from Table 1 that the cost of the initial charging of a prop is 2 rubles 45 kopecks. In analyzing the cost of the initial charge, the expenditure item for the wages of administrative-engineering and junior service personnel, by virtue of its large amount, inevitably draws serious attention to itself—40.97 kopecks for charging one prop. The direct wage costs of production workers for charging props by hand with a sledgehammer, amounting to 29.44 kopecks per prop, also indicate the need to introduce a mechanical method of driving in the cores (a press and other types of mechanization). Expenditures on auxiliary materials (washers), since they have not justified their main purpose in the mines, should be reduced to zero.
If the cost of manufacturing the cores and the cost of the charging itself, together amounting to 1 ruble 76 kopecks per prop, may at first win favor by their low cost for one prop-setting operation (with 100–150-fold use of the metal prop), then the cost of manufacturing the plug, which is deformed after 1–2 prop-setting operations, cannot satisfy the requirements of the mines. The cost of the plug must be reduced. In the second quarter of 1940 the shop, as a result of putting into practice a number of rationalization proposals, achieved a reduction in direct wage costs from 9.85 kopecks to 7 kopecks per plug. This is, of course, little. A further reduction in the cost of manufacturing the plug is necessary, and it should proceed along the following lines:
1) reducing the costs of maintaining administrative-engineering and junior service personnel;
2) reducing the costs of maintaining auxiliary labor;
3) through savings in timber materials and electric power.
Indeed, the cost of turning a plug in the first quarter of 1940 amounted, in direct wages, to 9.85 kopecks (see Table 1), while the costs of delivering the timber to the lathe, removing shavings, and delivering the finished plug to the finished-goods warehouse amounted to 3.81 kopecks per piece; still greater costs fell on the maintenance of administrative-engineering and junior service personnel, which amounted to 6.67 kopecks per plug.
A reduction in the cost of manufacturing plugs will undoubtedly have its effect on lowering the cost of manufacturing cores and of the charging operation.
Reducing the cost of the plug from 34.4 kopecks to 20 kopecks is the primary task of the metal-support shop. The possibilities for this exist. With a plug cost of 20 kopecks, the economic advantage of using simple tubular props with end plugs is obvious even in seams of low thickness.