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Locomotive Haulage in Mines

In case of rope haulage, the power to move the load is available from external fixed motor to the haulage. While in case of locomotive haulage, the driving unit i.e. locomotive is coupled to a train due to which more safety can be attained.

The locomotives are very flexible in nature & they can be used for men transport also. The rail transport finds its main application as gathering and haulage in the underground mines and tunnels. The rope haulage system works on track, and so is the locomotive haulage.

The locomotive haulage is best suited as a long distance haulage with a gradient in the range of 1 in 200 to 300.

However, gradient up to 1 in 30 for a short distance can also be negotiated by this system. The system is flexible, comparing to rope and belt conveyor systems.

Tractive effort

It is the total force delivered by the motive power of the locomotive, through the gearing, at wheel treads. When this force is greater than the product of locomotive weight and the coefficient of adhesion between the wheels and rails, the wheels will slip, i.e. it will roll. This can be numerically expressed as:

Total or maximum tractive effort

TE = Wʟ C

Whereas: C is the coefficient of adhesion whose value depends upon the condition of track, and whether it is sanded or not. Wʟ is the weight of locomotive.

Drawbar pull

This is the force exerted on the coupled load by a locomotive through its drawbar, or coupling, and is the sum of the tractive resistance of the coupled load. The drawbar pull that a locomotive is capable of developing is determined by subtracting the tractive effort, from the sum of the tractive resistance of the locomotive. This resistance is offered by the several sources: rolling resistance, which the entire train offers, is equal to weight of the train in tons. (i.e. weight of locomotive + weight of mine cars with pay load) multiplied by a frictional coefficient m which could be 10-15 kg/ton.; Curve resistance which can be ignored gradient resistance and the force required to provide acceleration to the motion (as given in the formulae specified below).

Drawbar pull

= R₀Wᴛ

Wᴛ is weight of trailing load, i.e. weight of train in tons. T.

R₀ is running resistance/t in kg.

Example

An 8 t locomotive has a coefficient of adhesion 0.18 and a coefficient of rolling resistance 100 N/tonne mass. The maximum tractive force available to haul the trailing load in kN along a straight track is ____

Solution

W = mg = (8 x 1000) x 9.8 N = 78400 N

Total roller resistance = 8 x 0.18 = 800 N

Draw bar pull (DBP) = Tractive effort - pull required to move the loco

= μW - pull = 0.18 x 78400 – 800

= 13312 N = 13.3 kN

Example

A 10,000 kg locomotive runs at a speed of 3 m/s along a level track. The coefficient of adhesion at the track is 0.23, and the rolling resistance of the locomotive is 90 N per 1000 kg. The maximum power available for hauling the train in kW is ____

Solution

W = mg = 10,000 x 9.8 = 98000 N

V = 3 m/s

μ = 0.23

Rolling resistance = 90 N/1000 kg

Hence, Rolling resistance for 10,000 kg locomotive = 90 x 10 = 900 N

Tractive effort (TE) = μW

= 0.23 x 98000 = 22540 N

Drawbar pull (DBP) = TE - pull (or rolling resistance)

= 22540 – 900 = 21640 N

Now, Power = DBP x V

= 21640 x 3 = 64920 W ≈ 65 kW 

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