Advantages over chains Lighter weight Less susceptibility to damage from jerks Silent operation even at high working speeds Greater reliability in operation Wire Ropes Wire rope consists of multiple wires or strands helically wound or ID: 805516
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Slide1
Flexible Load Handling Attachment: Steel Wire rope
Advantages over chains:
Lighter weight
Less susceptibility to damage from jerks
Silent operation even at high working speeds
Greater reliability in operation
Slide2Wire Ropes
Wire rope
consists
of multiple wires or strands, helically wound or laid about an axis. Wires, strands and cores are independent- that interact with each other during service.
Wire ropes are designed in different
steel grades, finishes and a variety of constructions to attain the best balance of strength, abrasion resistance, crush resistance, bending fatigue resistance and corrosion resistance for each application.
Strand
Slide3CORES
Almost all wire
ropes are
laid up over a core, Fibre Core (natural or synthetic), Independent wire rope core or wire strand core (FC, IWRC or WSC):
Core
Wire ropes contd........
Slide4STRAND CONSTRUCTIONS:
Strands are designed with various combinations of wires and wire sizes to produce the desired resistance to fatigue and abrasion. Generally,
a small number of large wires
will have more abrasion resistant and less fatigue resistant than a large number of small wires.
The basic strand has wires of the same size wound
around a centre.
Provides excellent
abrasion resistance but less fatigueresistance. When used with an IWRC, it
also offers excellent crush resistance over drums.
Small wires fill spaces between large wires to produce
crush resistance
and a good balance of strength, flexibility and resistance to abrasion
Outer layer of alternately large and small wires provides
good flexibility and strength
but low abrasion and crush resistance.
Slide5Many commonly used wire ropes use combinations of these basic constructions
Wire ropes contd........
Slide6Wire ropes contd........
Lays of wire ropes
Lang lay is recommended for excavating, construction, and mining applications including draglines, hoist lines. This is because of the
Lang lay ropes are more flexible than regular lay ropes
. They also have greater wearing surface per wire than regular lay ropes
Regular lay or Cross lay
Lang lay or Parallel lay
Alternate lay or Reverse lay
Slide7Strength
can be increased
by:
increasing the diameter of the wire rope increasing the tensile strength of the individual wires decreasing the air voids between the wires using a steel core construction.
Flexibility can be increased by: using more wires of a smaller diameter
decreasing the tensile strength of the individual wires using a fiber core.Robustness, or resistance to physical damage:
increased by using fewer wires of a larger diameter using a steel
coreCoatings can be applied to protect against corrosion.
Characteristics of a wire ropes:(1) Strength (2) Flexibility (3)
Robustness
Wire ropes contd........
Slide8Selection of wire
rope for
a particular
application:
Strength Abrasion resistance
FlexibilityResistance to crushingFatigue strength and corrosion resistanceWire ropes contd........
Slide9Locked-coil steel wire ropes
Applications:
Cable ways, Cable cranes etc.
Advantages:Smooth surface, Tightly packed wires and less flexible
Locked-coil
Semi Locked-coil
Slide10Wire Rope Size Measurement
Wire ropes contd........
Designation of a wire rope:
20 mm
6*19 (12/6/1) wire
Nominal diameter of wire rope : 20 mmNo. of strands: 6 No. of wires in each strand :19.(may be formed by 12
wires over 6 wires with 01 core
wire)
Slide116x7 Class Wire Rope
Strands: 6
Wires per strand: 7
Core: Fiber coreLay: Regular or LangFinish: Bright or galvanized
6x19 Class Wire Rope
Strands: 6Wires per strand: 19Core: IWRC or fiber coreLay: Regular or LangFinish: Bright or galvanized
6x19 Warrington with fiber core
6x19 Seale with IWRC
Stiff rope needs sheaves and drums of large size
.
Slide12Fleet angle in wire rope:
Range of Fleet angle for maximum efficiency and service:
< 1.5
o
for smooth drum< 2o for grooved drum Large fleet angle:
results in excessive rubbing of the rope against the flanges of the drum and the sheave groove, or crushing and abrasion of the rope on the drum.
Slide13Factors Affecting Rope Performance:
Multi-coiling
Bad coiling
Small diameter sheavesOversize grooves
Undersize groovesExcessive angle of fleet
Slide14Factors Influencing the lifetime of wire ropes:
type of wire ropes;
diameter of the drums and sheaves;
reverse bendingspeeds with which the wire ropes run through the sheavesratio between normal working load and the maximum load in the wire ropes;safety factor; being the ratio between the breaking load and the normal
working loadchoice of the hardness in the groove of the sheaves;
fleet-angle between the wire rope and the sheave, respectively between the drum groove and wire rope;greasing or lubrication of the wire ropes and the frequency of greasing or lubrication;mechanical damage
Slide15Selection of drum and sheave diameter
For faster operation of ropes in cranes:
D/d=30
For fast un-loaders: D/d= 36Where,D= sheave diameter or drum diameter, centre to centre of wire rope,d= wire rope diameter.
Slide16Dimension of grooves on drums and in sheaves:
Drum
Sheave
Slide17The End