Power Shovel

Submitted by:Arpit Saini (CO13214)Ashi Gupta (CO13215)

Definition

Power shovel  (also stripping shovel or front shovel or electric mining shovel) is a construction equipment whose purpose is to excavate the earth and load it into the trucks or other pull equipment waiting nearby.

Types

Type of power shovel is described by its mounting -

1. If it is mounted on crawler track, it is called crawler-mounted power shovel.

2. If it is mounted on rubber tyred wheels it is referred as wheel-mounted power shovel.

Wheel mounted power shovelCrawler mounted power shovel

Size of power shovel Size of power shovel is indicated by the size of

dipper generally expressed in cubic meters. They are available in size 3/8, ½, ¾, 1, 1 ¼, 1 ½, 2 and 2 ½ cubic meter which come under the category of standard power shovels.

Modern bucket (dipper) capacity ranges from 8 cubic metre to 80 cubic metre.

Basic parts

Click icon to add picture1. The mounting (crawler track or rubber tyred wheel)

2. Cab3. Boom4. Dipper stick5. Dipper 6. Hoist line

          

OperationThe shovel operates using several main motions:• hoist - pulling the bucket up through the bank (i.e. the bank of material being dug)• crowd - moving the dipper handle out or in to control the depth of cut and when positioning to dump• swing - rotating the shovel between digging and dumping• propel - moving the shovel unit to different locations or dig positions

Working

Support cable

Angle of swing

Hoist cable

Boom

Dipper stick

cab

Selection of type and size

Best type is decided after considering various techno-economic factors :

a)Job location Numerous Small jobs – Rubber tyred Large job – Crawler mountedb)Type of footing Soft and muddy soil – Crawler mounted

.

For selecting the best size of the shovel for the given job, the following factors must be

examined :

a)  The cost of per cubic meter of output : Minimum cost per cubic metre of output.

Size of job Cost of transporting Depreciation rate Downtime cost – Time lost during repair & adjustments Cost of wage – Less for large shovel Cost of drilling , blasting, excavating- Less expenditure

for large size shovelb)  The job/site conditions  For high lifts to dump - long boom of a large shovel. For excavating blasted rocks, hard and tough bed of

soil - large size dipper. High hourly output - large shovel Size of hauling unit determines size of shovel.

OPTIMUM  DEPTH OF CUT

The optimum depth of cut is that depth which produces the greatest output and at which the dipper comes up with full load without excessive downward pressure and tension. This depth varies with the type of the soil and the size of the dipper.

OUTPUT OF POWER SHOVEL

Output of shovel = bank measure capacity of dipper x 3600/cycle time in second (m3/hr)

In general cases, Output of shovel = 

Loose volume of dipper /   (1 + Swell fraction)  x Actual time in seconds per hour /

Cycle time in seconds x efficiency

Expressed in cubic meter/hr

           

Factors affecting the output

a) Class of material According to Power Crane and shovel association, USA - Moist loam or light sandy clay > Sand and gravel > good common earth > Hard , tough clay > Wet, sticky clay > Poorly blasted rock

b) Depth of cutDepth shallow – output reducedDepth greater – output increased

c) Angle of swingHorizontal angle (ex-pressed in degrees) between the position of the dipper when it is excavating and the position when it is discharging the load. The output of shovel is inversely proportion of the cycle time and thus to the angle of swing.

d) Job conditionsJob conditions may be classified as excellent, good, fair and poor depending upon the situations of work site and climatic condition

e) Management conditions Excellent management conditions yield

maximum output while poor one may yield the minimum.

f) Size of hauling unitsSmall size of hauling unit – small shovel size

g) Skill of OperatorSkillful operator – output increases

h) Physical condition of the shovelGood condition – output increasesBad shape – subjected to wear and tear

Applications Suitable for dragging softer material. Can remove big size boulders with prior

loosening. It is used in various types of jobs such as

digging in gravel banks, clay pits, digging cuts in road works, road side berms etc.

It is very useful for excavating trenches . It is mostly used in the excavation for canals

and depositing on the embankment without hauling units.

Used for excavation and removal of overburden .

Shovel digging overburden

Thank you