Bucket wheel excavator

Bucket wheel excavator

 

Fig. 5,2$. General arrangement ol a bucket wheel excavator

(i) Boom which can be raised and lowered (ii) Superstructure with machinery houses, ballast and winches (iii) Under-carriage with crawler travel gear- control equipment, cabins for switch gear, workshops and crew (iv) Operation cabin (v) Discharge end.

Working Ranges (Figures in bracket relate to 700 lit. B. W.E. at Neyveli A - Cutting height (20 m.)

B - Cutting radius C - Dumping radius           D - Dumping height E - Cutting depth (3m),

Neyveli lignite project is the only mining field in India where bucket wheel excavators are used.

A bucket wheel excavator is perhaps the most spectacular of all the excavating machines. It is used for the excavation and removal of soft or unconsolidated overburden, eoal and soft ores in benches of upto 90 metres.

The bucket wheel excavator essentially consists of 3 units:-

(1) the bucket wheel,

(2) The connecting belt to the main crawler mounted carriage, and

(3) the loading belt which disposers pn the excavated material continuously into rail wagons or conveyor belts through hopper cars.

The bucket wheel may be compared with the Persian wheel used in the past on large wells and is a large wheel known as bucket wheel with 6 to 12 buckets. The bucket has a lip with manganese steel teeth for cutting the rock and these are faced with tungsten carbide for hard rocks. The maximum life of teeth with t.c. inserts is 250hours in soft sandstone at Neyveli. The wheel is mounted at the end of the boom which can be (a) pushed out or pulled back (b) lowered or raised, (c) swung through 90° in a horizontal plane depending upon design. The dumps/min by the buckets vary from 70 in small models to 27 in large models, The hourly capacity of an excavator is equal to the total volume of all buckets x wheel speed per hour. The hourly capacities of small models is only 100 m³, but in large models, it is nearly 4000 m³ (3720 m³ solid for 1400 lit. bucket capacity B.W.E.) hr. TK: excavators are crawler mounted. Fig. 5.25 shows relative positions of the various units of a bucket wheel excavator.

The excavated rock is transported by a system of belt conveyors mounted on the machine to hopper cars, belt conveyors or rail wagons.

Power is supplied to bucket wheel excavators at A.C. voltage upto 25 kV though motors operate at 3300 V and 500 V. At Neyveli the B.W. Excavators are supplied electric power at 11 kV through T.R.S. cables and transformers in the machine step down the voltage to 3.3 kV for some motors and to 400 V for some others.