draglines (fabil & venkatesh)

DRAGLINESBy

FABIL T (MT15CTM003)KONE VENKATESH(MT15CTM009)

INTRODUCTION

• Draglines are used to excavate material and to load it into hauling units, such as trucks or tractor-pulled wagons, or to deposit it in levees, dams, and spoil banks near the pits from which it is excavated.

• The dragline is designed to excavate below the level of the machine.

INTRODUCTION

• A dragline usually does not have to go into a pit or hole in order to excavate. It operates adjacent to the pit while excavating material from the pit by casting its bucket. This is very advantageous when earth is removed from a ditch, canal, or pit containing water.

INTRODUCTION

• Frequently, it is possible to use a dragline with a long boom to dispose of the earth in one operation if the material can be deposited along the canal or near the pit. This eliminates the need for hauling units, thus reducing the cost of handling the material.

TYPES OF DRAGLINES

Draglines may be divided into 3 typesCrawler-mountedWheel-mounted, self-propelledTruck-mounted

Truck-mounted

Wheel-mounted

Crawler-mounted dragline

Crawler-mounted dragline

• Crawler-mounted draglines can operate over soft ground conditions that would not support wheel-or truck-mounted equipment.

• The travel speed of a crawler machine is very slow, frequently less than 1 mph, and it is necessary to use auxiliary, hauling equipment to transport the unit from one job to another.

Basic components of draglines

THE SIZE OF A DRAGLINE

• The size of a dragline is indicated by the size of the bucket, expressed in cubic yards (cu yd).

• Most draglines may handle more than one size bucket, depending on the length of the boom utilized and the class and weight of the material excavated.


• In practice, the combined weight of the bucket and its load should produce a tilting force that is not greater than 75% of the force required to tilt the machine.

• A longer boom, with a smaller bucket, will be used to increase the digging reach or the dumping radius when it is not desirable to bring in a larger machine.


Relationship between bucket size and boom length and angle

OPERATION OF A DRAGLINE

• Digging is accomplished by pulling the bucket toward the machine while regulating the digging depth by means of the tension maintained in the hoist line.

• When the bucket is filled, the operator takes in the hoist line while playing out the dragline.


• The bucket is so constructed that it will not dump its contents until the drag line tension is released.

• Hoisting, swinging, and dumping the loaded bucket follow in that order; then the cycle is repeated.

• An experienced operator can cast the excavated material beyond the end of the boom.

OUTPUT OF DRAGLINES• The output of a dragline will vary with the following factors:

– Class of material– Depth of cut– Angle of swing– Size and type of bucket– Length of boom– Method of disposal, casting, or loading haul units– Size of the hauling units, when used– Skill of the operator– Physical condition of the machine– Job conditions

Factors affecting dragline production

• Depth of cut• Angle of swing• Size of bucket• Length of boom• Job condition• Physical condition of machine

Depth of cut & Angle of swing

• The ideal production of draglines are provides by the manufacturer

for working at optimum depth and 90° angle of swing, also assumes 100% efficiency, for actual operation the depth & angle of swing will be different it is adjusted by swing depth factor.

Size of bucket & Length of boom

• Should match properly to obtain best action and operating efficiency

• most of draglines can handle more than one bucket size depending on the weight of boom and material handled

• since maximum lifting is limited to the force which will tilt the machine the size of bucket should be reduced when long boom is used for high unit weight material.

Production• The output of a dragline should be expressed in bank measure

cubic yards (bcy) per hour. This quantity is best obtained from field measurements.

• To estimate dragline production using the tables1) Determine the ideal output of the dragline for the machine

size and material (Table 3-7)2) Then adjust this value by multiplying it by a swing-depth factor

(Table 3-9) and a job efficiency factor, as shown in Equation Expected production = Ideal output × Swing-depth factor × Efficiency

• Table 3-7 presents ideal dragline production capability based on digging at optimum depths with a swing angle of 90°.

• The table also assumes maximum efficiency, 60-min hour.

• For any other depth or swing angle, the ideal output of the machine must be adjusted by an appropriate depth-swing factor.

• The effect of the depth of cut and swing angle on dragline production is given in table 3-9(swing depth factor)

• To use Table 3-9, first determine the optimum depth of cut for the machine by material involved from Table 3-8

• then, divide the actual depth of cut by the optimum depth and express the result as a percentage.

• The appropriate swing-depth factor is then obtained from Table 3-9,

EXAMPLE

• Determine the expected dragline production in loose cubic yards (LCM) per hour based on the following information. – Dragline size = 2 cu yd (1.53 m3)– Swing angle = 120o

– Average depth of cut = 7.9 ft (2.4 m)– Material = common earth– Job efficiency = 50 min/h

Solution Ideal output =230 BCY/h (176 BCM/h)

(Table 3-7)Optimum depth of cut = 9.9 ft (3.0 m)

(Table 3-8)Actual depth/optimum depth = 7.9/9.9 × 100

= 80% [= 2.4/3.0 × 100

= 80%]

Swing-depth factor=0.90 (Table 3-9)Efficiency factor =50/60 = 0.833Estimated production = 230 × 0.90 × 0.833

= 172 BCY/h [= 176 × 0.90 × 0.833

= 131 BCM/h]

Safety

• Keep personnel away from the swing area of dragline• The crane operator must not swing the boom and

bucket, whether loaded or empty, over the top of trucks and drivers.

• Another common accident, with cranes equipped as draglines is where a machine falls into the excavation it is digging. These accidents often happen when ground conditions deteriorate after a rain. Before working ground condition need to be checked.

draglines (fabil & venkatesh)

Engineering