STUDY OF THE PROCESS OF LOWERING THE “DONBASS-1” COMBINE IN THE KUZBASS MINES

S. D. BATALIN

Introduction

On March 18, 1949, the first “Donbass-1” combine arrived in Kuzbass, where at the S. M. Kirov Mine of the “Leninugol” trust of the “Kemerovougol” combine, personnel were trained and the new machine was mastered. By the end of 1949 the combine had been successfully introduced at a number of mines.

At the present time the “Donbass-1” combine is used in many Kuzbass mines, extracting coal in seams of gentle dip and even, in some cases, inclined dip; moreover, the number of combine faces is continuously increasing.

The working conditions of the “Donbass-1” combine in Kuzbass differ from the working conditions in other coal basins, which has been reflected in the organization of the processes: coal extraction, lowering of the combine, relocation of the face conveyor, and roof control. In addition, in application to Kuzbass conditions, a number of changes have been made to the design of the “Donbass-1” combine; in particular: a new configuration of the movable bar has been designed, the loader motor power has been increased to 19 kW, two rods with disks are used with the hinged folding bar, trimming bars, etc.

The experience of the advanced combine faces of Kuzbass from 1949 to 1953 shows that, thanks to the transition of a number of combine faces to a comprehensive organization of labor based on combining occupations and creating teams in each shift equal in number of people and capable of performing any work taking place in combine faces, productivity increased due to an increase in the combine’s operating time for coal extraction (see Table 1).

Table 1

Summary table of time-study observations of the operation of the “Donbass-1” combine for 1951, 1952, and 3 months of 1953

¹ The process of lowering–raising the combine includes transfer from the working position to the transport position; movement of the combine to the initial position for work; transfer from the transport position to the working position.

From Table 1 it is evident that, with the increase in coal-cutting time, the time for lowering—raising the combine and for scheduled preventive repair also increased. This is explained by the fact that the process of lowering—raising the combine and the repair work were not sufficiently mastered by the combine operators and their assistants in operating the combine, who, before the comprehensive organization of labor, had worked mainly on coal extraction. Even before the emergence of the new form of labor organization, the need to investigate the process of lowering—raising the combine and other work processes in combine longwalls was, and remains today, an urgent task, with the aim of improving the operation of combine longwalls and identifying internal reserves on the basis of studying and generalizing advanced experience.

The principal material for the further exposition is provided by the data of Table 2, from which it is seen that the limits of the indicators are extremely wide. Thus, for example, productive work amounts to from 54 to 98.8%, nonproductive work to 1.2–47%, and downtime to 0–33.7%.

The question arises as to the cause of such sharp fluctuations and what the ways are to reduce the time for lowering—raising the “Donbass-1” combine. We shall try to give an answer on the basis of the analysis presented below.

The operation of the “Donbass-1” combine was observed at various longwall lengths, within the range of 85–170 m.

In order that the duration of the process be comparable, we relate one lowering—raising operation to a 100-meter longwall. These data are given in the last line of Table 2, from which we see that the fluctuations in time for one lowering—raising process range from 167 to 479 minutes, reaching a ratio of almost 1:3.

Such an enormous difference in the time for one and the same process is explained mainly by the different methods used in carrying out individual operations in the lowering process. Even in one and the same longwall, the duration of the lowering—raising process varies within considerable limits when different brigades are working, although the working conditions are identical. Thus, for example, in longwall No. 9 east, with a partial change in brigade composition, the difference in time for one lowering—raising operation reached 1.5 hours (200–290 minutes).

Analysis of the Process of Lowering—Raising the “Donbass-1” Combine

The complex process of coal extraction in a combine longwall includes a number of work processes. If the work of the “Donbass-1” combine in extracting coal (undercutting, breaking, and loading coal onto the conveyor) is regarded as the principal work process, then the process of lowering—raising the combine should be assigned to an auxiliary work process, which was performed during the preparatory shift simultaneously or successively with the process of moving the longwall conveyor. At present, in connection with the transition to comprehensive organization of labor, the process of raising—lowering the combine may be carried out successively with coal extraction in one and the same shift; therefore, reducing the time spent on auxiliary processes acquires exceptionally great importance, since it makes it possible to increase the operating time of the combine for coal extraction.

The lowering process is subdivided into three main groups: 1) productive work, 2) nonproductive work, 3) downtime. In turn, the groups are subdivided into operations, the operations into methods, and the methods into elements or motions.

Thus, the process of raising—lowering the combine is subdivided as follows: raising—lowering → group of work → operation → method → element or motion. In addition, one or another operation may be performed by different methods.

Table 2

SUMMARY TABLE
of time-study observations of the work of shift crews in lowering and raising the “Donbass-1” combine
in leading combine faces of Kuzbass

Group—Productive Work

The process begins with preparing the combine for lowering—raising, which is divided into the following operations:

Preparing the combine for lowering—raising

(on gently dipping seams)

1. The handle of the controller-loader is placed in the neutral position (switched off).
2. Disconnecting the plug coupling of the loader motor.
3. Disconnecting the emergency “stop” button.
4. Placing the plug coupling and emergency button, together with the flexible cable, on the body of the combine.
5. Disconnecting the sprinkler hose.
6. Disconnecting the loader from the goaf and face sides.
7. Disconnecting the apron.
8. Setting the cutting disks in the position for lowering—raising.
9. Disconnecting the auger (sludge cleaner).
10. Opening the bar lock.
11. Turning and bringing the loader forward in the direction of lowering—raising with the aid of the leading rope.
12. Turning the bar onto the line of the machine’s longitudinal axis.
13. Pulling the combine up to the loader so as to place it in one line with the loader.
14. Installing a support prop for lowering the combine.

Here all the listed operations for preparing the combine for lowering or raising are strictly mandatory; however, their sequence may vary somewhat. In addition, some operations may be combined in time, since the crew usually consists of several people.

In cases where the combine is operating on inclined seams without a loader with a pan, preparation of the combine for lowering and, in general, the lowering operation are simplified.

It should be noted that the time spent preparing the combine for lowering does not depend on the length of the longwall and is determined exclusively by the workers’ skills and by the work methods.

The amount of time spent preparing the combine for raising or lowering in the leading longwalls was distributed as follows:

Average by longwalls—82.
Average of the mean longwall indicators—79.

From these data it is evident that the shortest time observed for preparing the combine for lowering was 56–57 min. A change in the number of workers in the crew has no noticeable effect on the time required to prepare the combine for lowering—raising.

After preparing the combine for lowering, the actual “raising—lowering of the combine” is carried out, which includes:
a) movement of the combine, b) resetting of the prop, and c) operations with the cable and irrigation hose.

The movement of the combine consists of the following operations:

Movement of the Combine

1. Lowering—raising the combine at maneuvering speeds and, as an exception, at operating speeds.
2. Pulling up the cable.
3. Clearing the machine track of squeezed-out coal.
4. Operations with the irrigation hose.

It should be noted that items 1, 2, and 3 are performed simultaneously; moreover, clearing the machine track of squeezed-out coal is not always carried out, since there may be no squeezed-out coal, especially when obtaining an inclined face line by changing the configuration of the ring bar.

In the longwall itself it is necessary to have a hauling rope of normal length, and in some cases to replace the working rope with a rope of smaller diameter; otherwise the time of movement of the combine will increase. In the Kuzbass longwalls, lowering or raising the combine is carried out simultaneously with the loader. The loader moves ahead and is pushed by the end of the bar, but in some cases, when the combine is working with a scraper conveyor, instead of the loader the lowering of the scraper conveyor can be carried out separately.

It should be noted that the time spent on moving the combine during lowering and during raising is practically equal, since raising takes place only at a small dip angle of gently inclined seams.

The amount of time spent on moving the combine during raising or lowering in longwalls was distributed as follows:

Table 3

Since the time of combine movement during raising—lowering falls within 9–16 minutes, where the difference reaches 7 minutes, these operations in the group of productive work cannot yield a noticeable reduction of time in the complete process of lowering—raising the “Donbass-1” combine.

For the same reason, recalculation to a 100-meter longwall was carried out formally; that is, the time spent on setting the prop and pulling up the cable was taken as the same both for a 100-meter longwall and for the lengths of the observed longwalls. This form of recalculation is adopted in all other parts of the combine raising—lowering process.

The operations for resetting the prop are well known from undercutting machines. They consist of:

Relocation of the Thrust Prop

1. Slacking the rope.
2. Knocking out the thrust prop.
3. Extending the rope to its full working length and moving the thrust prop to a new place.
4. Installing the thrust prop.
5. Switching on the working drum to tension the rope to the condition required for lowering or raising the combine.

The amount of time spent on relocating the thrust prop when raising or lowering the combine was distributed among the faces as follows (Table 4).

Table 4

The fluctuation in the time expended is very considerable (12–40 min). The increase in time is explained by the fact that the length of the prop is poorly selected (it is either too long or too short); sometimes a recess is not made for the prop, and worn props are not replaced in time. All these causes are clearly removable, and they should be assigned to the category of poor-quality work.

Increasing the number of workers in the crew noticeably reduces the time required to relocate the thrust prop. The optimum number of workers in the crew is 3.

Operations with the cable and with the irrigation hose, in terms of the time expended, are considered together, since they are performed simultaneously and are similar in outward appearance. These operations consist of:

Cable Operations

1. Pulling the cable away from the combine.
2. Moving the accumulated part of the cable away from the combine.
3. Carrying the cable around the support props; moreover, these operations may be combined with the movement of the combine, except for carrying the cable around. This operation takes place when the combine is supplied from the side opposite to its travel during coal extraction.

Operations with the Irrigation Hose

1. Disconnecting the hose from the combine when preparing the combine for lowering or raising.
2. Moving the hose to a new place.
3. Connecting the irrigation hose to the combine.
4. Pulling up and fastening the hose to the support.

The amount of time spent on operations with the cable and with the irrigation hose when raising or lowering the combine was distributed by faces as follows:

Table 5

The difference in time is enormous \((62 - 2 = 60\) min. \(= 1\) hour). Even the average of the averages by faces reaches 1 hr. 03 min. (63 min.) instead of the usual 25 min. (average by faces). The reason is that the average of the averages by faces (65 min.) is taken over all crews, including the worst, whereas the table contains data for the best crews; hence the average by faces is 25 min.

A loss of time of up to one hour on operations with the cable and with the irrigation hose is too wasteful for underground work, especially since, as will be shown below, in terms of time it can be combined with other operations. This means that for one hour the combine will be engaged directly in cutting, breaking down, and loading coal, and not standing idle because of auxiliary work.

Increasing the number of workers in the crew noticeably reduces the time of the operation with the cable and with the irrigation hose. The optimum number of workers in the crew is 3.

There is still one more labor-intensive operation—“carrying over the cable.”

It is sometimes unavoidable because of haulage conditions and cleavage characteristics of the roof. In most cases the operation of carrying over the cable can not only be partially combined in time with other operations, but even completely eliminated. The direct lowering–raising is followed by preparation of the combine for work. Operations to prepare the combine for work proceed in the reverse sequence to the operations already described for “preparing” the combine for lowering or raising. However, different amounts of time are spent on these reverse and identical operations. This is explained by the fact that partial dismantling of the combine (“preparation of the combine for lowering or raising”) is always simpler and is performed faster than its assembly (“preparation of the combine for work”). It should be noted that in some well-coordinated crews this difference decreases over time and becomes almost zero, and in some cases, as for example in face No. 9 east, preparation for work is even faster than preparation of the combine for lowering.

The amount of time spent on operations for preparing the combine for work was distributed by faces as follows (Table 6):

Average by faces — 87.
Average of the averages by faces — 126.

Thus, we see that in the best crews the time spent both on dismantling (82 min., see above) and on assembly (87 min.) is the same. But if we take the average of the average indicators by faces, which includes the work of poorer—

crews, 79 min is spent on disassembly and 126 min on assembly, that is, almost twice as much time is spent on assembly.

Table 6

It should be noted that the variation in the time spent on the operation of preparing the combine for work (assembly) is considerably greater (27–171 min) than for the operations of preparing the combine for lowering or raising (56–118 min).

Changing the number of workers in the crew does not have a noticeable effect on the time for preparing the combine for work.

Everything stated about the operations included in the group of productive work on lowering—raising the combine is reflected in Table 7.

Table 7

Productive work on lowering—raising the combine. Mean and extreme time values by crews (according to observations during 1949—1950—1951—1952).

In the further exposition we shall take the mean of the average indicators by face as 100%, where 306 min (5.1 hours) are spent on one complete process of lowering or raising the combine (Table 3). For the best crews it is equal to 227 min (3.8 hours), and, moreover, for them the operations with the cable and hose

irrigation take 21 min.; moreover, as is known, they can be combined in time with other operations.

Then the time spent by the best crews on one complete process of lowering or raising the combine is further reduced and will be equal to:

\[ 227 - 21 = 206\ \text{min.} = 3\ \text{hours}\ 26\ \text{minutes}. \]

The considerations set forth are quite realistic and are confirmed by the practical work of the crew in the longwall (Table 2), for which the time for the complete process of lowering or raising is even less (160 min. = 2.67 hours).

Between the time spent by the combine in the longwall on undercutting the coal, breaking it down, and loading it, and the time of the complete lowering–raising process, the ratio most often adopted is 2:1 (two production shifts, one preparatory shift).

In this case, with an 8-hour shift and with the work organized for 1 cycle per day, the time is distributed as follows:

\[ 16 : 8 \]

\[ 2 : 1. \]

In practice it is realized as follows:

\[ 16 : 5.1 = 3.13 : 1, \]

but it can be brought to

\[ 16 : 3 = 5.3 : 1, \]

and in some cases, as, for example, was achieved in longwall 110,

\[ 16 : 2.67 = 6 : 1,\quad \text{and even}\quad 16 : 2 = 8 : 1, \]

that is, it is entirely possible to adopt the ratio

\[ 7 : 1. \]

Under these conditions the distribution of time over the course of a day will be:

\[ 7 : 1 = 21 : 3\ \text{hours} \]

instead of

\[ 2 : 1 = 16 : 8 \]

(which is often encountered in mine practice), that is, with work organized even for 1 cycle per day we can increase the operating time of the combine in coal extraction and significantly improve the quality of planned preventive repair by reducing the time required for the process of lowering–raising the combine.

Such are the results of the analysis of lowering–raising the combine for the group of productive operations.

The number of people engaged in lowering–raising the combine varies by longwall and is distributed as follows (see Table 8):

Table 8

The composition of a crew of 2–4 persons is explained by differences in the organization of labor and in working conditions. Thus, for example, in face No. 9 the absence of a third person was caused by the stability of the side rocks of the seam. However, his absence affected the duration of the operations of resetting the prop and the operations with the cable and the irrigation hose.

Work experience shows that servicing the combine is most practical with 3 workers, for the following reasons. First, if one person is absent during the shift, then lowering and raising can be carried out by 2 workers (with a smaller number of workers the process must already come to a halt). Second, the process of lowering and raising the combine proceeds noticeably faster when there are 3 persons on the shift rather than 2; this shortens the time of preparatory work, and the combine is used in operation most effectively. Third, the third worker is involuntarily trained to work on the combine and can at any moment replace another worker of the crew, one of higher qualification who has, let us suppose, moved to another face. In addition to all this, the third worker can carry out current repairs, which in the course of the combine’s work in the face always arise and which can be done without stopping the combine’s operation. A fourth person on the shift is in most cases superfluous, except when the combine is operated with a safety winch without remote control.

Group of Nonproductive Work

By “nonproductive work” one should understand such work as can either be omitted altogether, or else can be avoided in advance in the process of performing other work connected with it. More precisely, the work should be brought immediately to completion, without returning to it.

Take, for example, the already well-known case of setting a prop. Here it is possible to prepare in advance a prop of the required length; the cuts can be made at once, and not only after the prop has several times come loose or accidentally become fixed; finally, it is possible to replace a worn prop with a new one in advance, rather than spend time on repeated and unsuccessful attempts to set the prop, counting on the next crew to replace the prop, while that crew counts on still another, and as a result production time is wasted uselessly because of sloppiness in the work.

Group—Downtime

The causes of downtime may arise:

1) from the combine, when it is out of order,
2) from the crew, when it is incomplete or insufficiently qualified, and
3) from external influences, for example, when there is no electric power, when there are delays in transporting the mined coal,
4) from poor-quality roof support, as a result of which rock falling from the roof blocks the machine track.

With proper organization of “lowering—raising” and coordination of it with other processes being carried out simultaneously, nonproductive work and also downtime can be completely eliminated.

Conclusions and Recommendations

The duration of the process of lowering and raising the “Donbass-1” combine is affected by the following factors and characteristics:

1) choice of the machine track,
2) number of people,

3) the position of the magnetic starter relative to the direction of travel of the combine,

4) the presence of a detachable bar, and

5) the sequence and overlapping in time of individual operations, as well as the methods used to carry out the operations.

1. The choice of a new or old machine track depends on coal squeezes and on the behavior of the roof. A new machine track has considerable advantages, since in this case the following processes can take place simultaneously: lowering the combine and transferring the face conveyor, which cannot be achieved with the old machine track. The old machine track may be used for lowering the combine only as a forced measure when the new machine track is blocked, clearing which would require considerable time.

2. The optimal number of people, as a rule, should be 3; a fourth person in the shift is needed when the combine is operated with a safety winch without remote control.

3. If the magnetic starter is located on the side of the coal-cutting direction, lowering the combine is considerably simplified, and the total lowering time is substantially reduced. If the magnetic starter is located on the opposite side, the lowering time of the combine is extended to as much as one hour per shift, owing to the laborious operation of carrying the electric cable around the support posts.

In longwalls 170–240 m long, electric cables made of two sections connected by a bus box are sometimes used; this creates an additional expenditure of time on operations with the cable, which can be avoided with a one-piece cable.

1. The presence of a detachable bar eliminates the possibility of its catching on the upper part of the support on uneven ground, which reduces the time spent on additional lowering–raising operations of the combine, as occurs in the case of a non-detachable bar, when it is necessary to cut out the upper members and sometimes to reset the supports in order to avoid a possible rope break.

2. A rational sequence and overlapping in time of individual operations, as well as the use of the most effective methods in carrying out operations, make it possible to reduce the time for lowering–raising the combine to 2–3 hours.

This gives a ratio between the operating time of the combine (undercutting, breaking down, and loading coal onto the face conveyor) and the time of the complete lowering–raising process, under a three-shift operating regime per day, of 21 hours : 3 hours = 7 : 1, instead of 16 hours : 8 = 2 : 1, which had previously existed in a number of combine longwalls; and only thanks to the introduction of complex organization of labor has this ratio in combine longwalls become, on average, about 3 : 1. Consequently, the potential of internal reserves for increasing the productivity of the “Donbass-1” combine is still far from being fully used, since, with an entirely possible reduction of the combine lowering–raising process to 2–3 hours, combine productivity under a three-shift regime can increase by 20–30%, and under a two-shift operating regime by 40% and more.

As for the other work processes carried out during the lowering–raising period of the combine, such as transferring the face conveyor and controlling the roof, the first of these can be performed simultaneously and coordinated in time with the process of raising–lowering the combine, and in some cases, when using a flexible conveyor of the SKM-1 or SKM-2 type moving after the travel of the combine during coal extraction, it can be entirely eliminated.

The process of roof control depends on the properties of the coal and the rocks lying in the roof. In mechanized longwalls of the Kuzbass, three methods of roof control are known.

1. Smooth lowering of the roof, using as special supports wooden packs or cribs made from rail cuttings. This method is used in those cases when the roof is somewhat below average stability and the coal, under high pressure from the overlying rocks, breaks down well after undercutting by the circular cutter bar. With this property of the coal, when artificial caving is used, after the longwall has been set down, the pressure on the coal seam at the face line decreases sharply, and the coal breaks down poorly, wedging the bar with the disks; as a result the electric motor overturns, and consequently operation of the combine becomes extremely difficult, especially when extracting the first strip after setting down.

This method of roof control can be carried out in parallel with the processes of lowering–raising the combine and extracting coal; consequently, it is not an obstacle to increasing the operating time of the combine.

1. Artificial caving, using packs or cribs as special supports and setting down after a certain number of cycles. Since the setting down of the longwall is not carried out every day, it therefore has no substantial effect; and when work is done on a discontinuous week, setting down may be performed on nonworking days.

2. Partial caving with packing of gob strips. This method of roof control is very simple and can be carried out simultaneously with any processes, but it is very labor-intensive, and therefore it is not advisable to use it.

From what has been said it is clear that increasing the productivity of mechanized longwalls by reducing the time spent on auxiliary processes is entirely possible within the range of 20 to 40%, especially when small-scale mechanization is used (a jack with a drive from an electric drill for moving the conveyor drive and turning the combine) and flexible mobile conveyors.

Noted Misprints