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| Colliery Engineering | June, 1955 |
Calculations
1. Work done per box — cutting.
| (500 x 9.63) x 66 | = 32.48 h.p. ≡ 35.08 amp. |
| 17.79 x 550 |
2. Work done hauling scraper boxes.
| 9,220 x 0.4 x 66 | = 24.88 h.p. ≡ 26.87 amp. |
| 17.79 x 550 |
3. (a) Work done hauling coal in scraper boxes (based on average load delivered).
| 0.304 x 2240 x 0.67 x 66 | = 3.08h.p. ≡ 3.32amp. |
| 17.79 x 550 |
therefore Average amp. for four scraper boxes = 13.29 amp.
(b) Work done hauling coal in scraper boxes (based on maximum load delivered per trip).
| 0.655 x 2240 x 0.67 x 66 | = 6.63hp ≡ 7.l6amp. |
| 17.79 x 550 |
There are two boxes capable of carrying this weight of coal at any instant,
therefore Amp. required = 2 x 7.16 ≡ 14.32 amp.
(c) Work done hauling coal in scraper boxes (based on maximum capacity of small type boxes).
| 0.494 x 2240 x 0.67 x 66 | = 5.00h.p. ≡ 5.40amp. |
| 17.79 x 550 |
There are two boxes capable of carrying this weight of coal at any instant.
therefore Amp. required = 2 x 5.40 = 10.80amp.
Total possible amperes based on maximum capacity
= 14.32 + 10.80 = 25.l2 amp.
4. Rate of dip along the face 1 in 52.
Weight component acting down face = W sin Θ (Sin Θ = tan Θ for small angles.)
| Total weight down face = 14,367 | 1 | = 276 lb. |
| 52 |
Work done against gradient
| 276 x 66 | = 1.86 h.p. ≡ 2.01 amp. |
| 17.79 x 55 |
Theoretical requirements. Fig. 20.
1. No boxes cutting| amp. | |
| Motor running, gears turning, etc. | 57.00 |
| Ditto plus boxes moving | 83.87 |
| Motor running, plus one box carrying its maximum load of coal (small) | 89.27 |
| Ditto plus two boxes carrying its maximum load of coal (small) | 94.67 |
| Ditto plus three boxes carrying its maximum load of coal (large) | 101.83 |
| Ditto plus four boxes carrying its maximum load of coal (large) | 108.99 |
2. One box cutting
| Motor running, gears turning, etc. | 57.00 |
| Ditto plus boxes moving | 83.87 |
| Motor running, plus one box cutting | 118.95 |
| Ditto plus one box carrying its maximum load of coal (small) | 124.35 |
| Ditto plus two boxes carrying its maximum load of coal (small) | 129.75 |
| Ditto plus three boxes carrying its maximum load of coal (large) | 136.91 |
| Ditto plus four boxes carrying its maximum load of coal (large) | 144.07 |
3. Two boxes cutting
| Motor running, gears turning, etc. | 57.00 |
| Ditto plus boxes moving | 83.87 |
| Motor running, plus one box cutting | 118.95 |
| Ditto plus two boxes cutting | 154.03 |
| Ditto plus one box carrying its maximum load of coal (small) | 159.43 |
| Ditto plus two boxes carrying its maximum load of coal (small) | 164.83 |
| Ditto plus three boxes carrying its maximum load of coal (large) | 171.99 |
| Ditto plus four boxes carrying its maximum load of coal (large) | 179.15 |
The above requirements do not take into account the maximum value of 201 amp. necessary to overcome the small gradient on the face. In this case it is too small to have a significant influence.
Actual requirements
The actual current consumption of the installation was measured on four separate occasions.
The following are average values for the current taken on several dates, together with the number of observations on which the averages are based.
| Monday, May 17, 1954 — 144.38 amp. from 299 observations. |
| Wednesday, May 19, 1954 — 115.14 amp. from 599 observations. |
| Thursday, June 10, 1954 — 120.14 amp. from 424 observations. |
| Tuesday, June 15, 1954 — 136.50 amp. from 260 observations. |
The mean of the means has not been given, as it can be shown statistically that the results given above are all from different populations.
It will be seen that there is very close agreement between the theoretical and actual current consumption of the installation. The individual readings, the averages of which have been given, varied between 90 and 190 amp. again within the theoretical range.
No allowance has been made for the power required to haul the ropes between the engine house and the face. It was impossible to make an estimate of the force required, and as an examination of the arrangements revealed that the ropes were very efficiently supported on well lubricated rollers, it was felt that no large error would result from the omission of this value.
(To be continued)
Drawings and Photographs accompanying the article
Article reproduced from a copy of the magazine held at National Mining Museum Scotland, Newtongrange, Midlothian.
Contains public sector information licensed under the 
