TEST RESULTS OF THE RPU-3 PROTOTYPE EXPANDER

O. D. Alimov, D. N. Malikov, E. I. Podkorytov

Expanders of the RPU type were created as a result of creative collaboration between the Tomsk Polytechnic Institute and the Anzhero Machine-Building Plant [1—4].

The RPU-3 prototype expander is a lightened modification of the RPU-2 expander (with a diameter of 1300–1500 mm), a pilot batch of which underwent industrial tests in the mines of Kuzbass in 1961 with positive results. The RPU-2 expander operates as part of a set with the SBM-3u machine.

The RPU-3 expander is intended for driving raise workings in coal (furnaces) with a diameter of 1000–1200 mm. With a BSA-6 or BGA-2 drilling rig, a borehole 500 mm in diameter is drilled from bottom to top, and then on the return stroke, using the RPU-3 expander, it is reamed to a diameter of 1000–1200 mm. Obtaining a borehole 1000–1200 mm in diameter is ensured by two pairs of replaceable bits rotating about their own axes and about the axis of the borehole.

With an initially drilled borehole diameter of not less than 400 mm, the LBS-4 machine can also be used as the drive for the RPU-3 expander.

The RPU-3 expander has the following technical characteristics.

The main purpose of the industrial tests was to determine the operational—

capability of the RUP-3 expander, its technical possibilities, and its design advantages and shortcomings.

Testing of the RUP-3 expander was first carried out at the Taibinskaya mine of the Kiselevskugol trust, where in July 1962 a borehole 32 m long was driven in seam III Vnutrennii. The expander operated in combination with a BSA-6 drilling machine. During the process of enlarging the borehole, the power at the terminals of the BSA-6 machine motor was measured.

Owing to the temporary cessation of preparatory work at the Taibinskaya mine, testing of the RUP-3 was continued at mine No. 5–6 of the Prokopevskugol trust, where in October–December 1962 four boreholes were driven in the Lutuginskii seam and two boreholes in the Moshchnyi seam.

The total length of the workings driven was 256 m; their diameter was 1000 mm.

The seams mentioned above have the following characteristics.

Seam III Vnutrennii: thickness 3 m; coal of medium hardness without rock inclusions; dip angle 71°.

Lutuginskii seam: thickness 3.5 m; coal of medium hardness with pyrite inclusions; dip angle 67°.

Moshchnyi seam: thickness 13 m; hard coal with abundant pyrite inclusions; dip angle 69°.

In seams III Vnutrennii and Moshchnyi, the RUP-3 expander operated in combination with a standard BSA-6 drilling machine having two feed speeds for drilling and one—10.4 cm/min—for reaming the borehole.

In the Lutuginskii seam, the RUP-3 expander operated in combination with a BSA-6 machine adjusted for two expansion modes. In this machine, on the recommendation of TPI, the Anzherka plant changed the ratio of the numbers of teeth in one of the pairs of reducer gears. As a result of this very simple adjustment, the BSA-6 machine came to have four feed speeds: two—10.4 and 20.8 cm/min—for drilling, and two—9.9 and 20.3 cm/min—for expansion in reverse travel (for details see [4], Table 32, variant III). In the process of reaming boreholes with the RUP-3 expander, both feed speeds were used, depending on the nature of the face being broken.

All BSA-6 machines operating with the RUP-3 expander were equipped with non-blown “Kuzbass” motors rated at 8 kW.

Of the 7 boreholes, three were driven from an intermediate drift, and the rest from a conveyor drift; among the latter, one borehole was driven under an installed shield support (the expander was installed under a section of the shield and raised along the same borehole to the lower drift).

For transporting the expander along the drift, bringing it to the mouth, and installing it on the drill string, in some cases a telescopic thrust “stand-boom” manufactured in the TPI laboratory was used. The stand-boom considerably facilitated rigging work. The drilling installation was serviced by two people.

The lengths of the individual boreholes and the labor expenditures for driving them are presented in the table. It follows from this table that, even taking into account considerable delays not attributable to the workers and the absence of experience in operating the RUP-3 expander, the rate of expansion of the working averaged 9.6 linear m per shift with two workers employed, or 20% higher than the driving rate specified by the standard for expanding a borehole by the drilling-and-blasting method. (The standard for expanding a furnace by the drilling-and-blasting method is 7.7 linear m per shift per one drivage worker, with a blasting specialist participating for approximately 0.5 shift.)

Excluding downtime, the rate of reaming averaged 13.4 linear m, and for the “reaming” operation, taking coal loading into account, 18.2 linear m per shift. Time-and-motion observations show that there are real possibilities for increasing the productivity of drillers by approximately 1.5 times compared with the level achieved.

Results of industrial tests of the RUP-3 prototype reamer

* Installation of the reamer and drilling-in were carried out under the shield.
** Installation of the reamer and drilling-in were carried out by machinists without an instructor.

When feeding the reamer to the face at a rate of 10.4 cm/min, the power consumed by the drilling rig varied over a wide range: when the reamer operated in clean coal of medium hardness it amounted to 2.5–3.5 kW, and in hard coal with large pyrite inclusions it reached 15 kW.

When driving a working through clean coal of medium hardness, the power of the BSA-6 machine drive (8 kW) provides the reaming process at a feed rate of 20.3 cm/min.

During operation of the RUP-3 reamer it was established that its design is fully serviceable and ensures the driving of boreholes in the most difficult mining and geological conditions, where the use of existing reamers of the same diameter is impossible.

The operating principle of the RUP-3 reamer provides the teeth with high wear resistance. During the reamer tests, only one tooth failed. When reaming a 70 m borehole in coal with abundant pyrite inclusions, the width of the cutter dulling land was 2.5–3.0 mm. With such wear, the teeth can be resharpened 4–5 times without loss of their operating efficiency.

The RUP-3 reamer provides a smoother load on the drilling machine compared with existing reverse-stroke reamers.

During the tests, the following principal shortcomings of the RUP-3 reamer were identified.

1. The bevel gears from the drill string to the crowns had a large

clearance, as a result of which the gears, being in mesh over one third of the tooth height, quickly failed.

1. During operation of the expander, the pin connecting the expander with the drill string fell out, and the screws connecting the skids with the expander body unscrewed spontaneously.

2. The taper of the expander drive shaft is too small, which makes it difficult to install the latter on the drill string.

3. The coupling has no neck for a pipe wrench, as a result of which unscrewing the coupling from the string becomes impossible under underground conditions.

4. The planetary reduction gear has excessive strength and, consequently, increased overall dimensions and weight.

Conclusions

1. The use of the RUP-3 expander in combination with light rotary-drilling machines ensures mechanized driving of raise workings, eliminates drilling-and-blasting operations, and thereby increases labor safety and improves the operating qualities of raise workings. At the same time, unproductive expenditures for lowering the drill string are also eliminated (which occur with the drilling-and-blasting method of expanding ovens).

2. The design of the expander is serviceable.

3. The principle of coal destruction by the RUP-3 expander is effective and less energy-intensive in comparison with existing expanders. Operation of the expander showed that the durability of the teeth when working in coal with large inclusions of kolchedan (up to 50% of the face area) is entirely satisfactory.

4. The manufacturing quality of the RUP-3 prototype expander is low; two pairs of bevel gears in the reducer did not have normal meshing, as a result of which the expander failed twice.

5. When the expander is operating in kolchedan occupying from 30 to 50% of the face area, the drive power of the BSA-6 machine (8 kW) is insufficient. It is necessary to increase it to 10–11 kW. In the future, it is advisable to produce the BSA-6 machine with four feed speeds.

6. To ensure smoother operation of the expander in kolchedan, the number of teeth in the bit must be increased to 8 (instead of 6), with a corresponding increase in the number of revolutions of the driver.

On the basis of the test results, the commission adopted the following decision: in order to determine the durability of individual units of the expander, to test it more fully at the other mines of the trust, and to determine the range of spare parts for it, it is advisable to produce in the first quarter of 1963, for the Prokopyevskugol trust, an industrial batch of 15 RUP-3 expanders, taking into account the elimination of the shortcomings noted above.

References

1. Alimov O. D., Karminskii V. N., Malikov D. N., Device for expanding raise boreholes. Author’s certificate, No. 111963, 1956.

2. Alimov O. D., Malikov D. N., Experience in driving raise workings without the presence of people at the face. Proceedings of Higher Educational Institutions. Mining Journal, No. 2, 1960.

3. Malikov D. N., Investigation of means and methods for mechanizing the driving of raise workings in the mines of Kuzbass. Author’s abstract of dissertation, Tomsk, 1961.

4. Alimov O. D., Basov I. G., Gorbunov V. F., Malikov D. N., Drilling machines, Gosgortekhizdat, 1960.