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Diameter Of Wire Ropes

The diameter of a wire rope is the diameter of circle which encloses all of the wires.When measuring wire rope it is important to take the greatest distance of the outer limits of the Crowns’of two opposite strands.A measurement across the valleys will result in incorrect lower readings.

Method Of Measuring Diameter

Caliper,fitted with jaws broad enough to cover not less than tow adjacent strands(see figure).

Safety Factor Of Rope

It is diffcult to fix the safety factor for each type of wire rope to be used for various equipments,as this factor depends not only on the load carried,but also on the speed of rope working,the kinds of fitting used for rope ends,the acceleration and arrangements of sheave and drums etc.

The following safety factors are minimum requirements for safety and economy in the common installation.

Rope Characteristics

This chart is purely an attempt to illustrate the relative characteristics of different constructions of wire rope as indicated in the text.No numerical scale is shown or intended.

TENSILE STRENGTH OF STEEL WIRE

Steel wire is made in various tensile strength to meet the different requirements of a particular job.For the production of our ropes,we use wire in the following tensile strength ranges:

1470 N/mm²(=150Kgf/mm²)

1570 N/mm²(=160Kgf/mm²)

1770 N/mm² (=180Kgf/mm²)

1960 N/mm² (=200Kgf/mm²)

2160 N/mm² (=220Kgf/mm²)

In the U.S.A.the various grades are designated as follows:

Traction Steel

Plow Steel(ps)

Improved Plow Steel(IPS)

Extra Improved Plow Steel(EIPS)

The most common grades is "Improved Plow Stell”

Which comes nearest to our 1770 N/mm²(=180kgf/mm²)tensile stength.

TENSILE GRADES

MANUFACTURING STANDARDS


POPE CORES

Ropes are supplied either with fiber or steel core,the choice being largely dependent on the application.

Fiber Core

Fiber cores are mainly made from polypropylene.This material has the advantage that it neither absorbs nor retains

moisture,and thus it eliminates conditions creating internal corrosion,Polypropylene core will have small variations in

size and weight and are less susceptible to damage,especially under moist conditions.

The following precautions must be taken during use:

-Do not use fiber core ropes where these are exposed to high temper atures,i.e.above 90℃,thiswill damage the fiber core.

-The fiber core ropes should not be used when muti-layer winding is required as the fiber cores susceptible to crushing.

Steel Core

The steel core is designated IWRC (Independent Wire Rope Core)and normal construction is 7×7.Steel core proves

advantageous in severe working conditions involving a low factor of safety,small drums and sheaves,high operational

speeds and wide fleet angles.Steel core tends to preserve the circular cross-section of the rope when it is crushed by

over-winding on drums.It also prevents the strands from bridging,(being forcibly against each other)which can result

in fatigue failure of wires.

WIRE ROPE LAY

The direction of lay or rotation of the strands is normally right hand.But some machinery needs left hand lay.

STRAND

Components of the strand

A strand consists of a strand core and a layer or a number of layers

of round wires.The round wire are laid helically around the strand

core.The strand core consists either of a wire(core wire)or a number

of wires or even fiber yarns.

STRAND CONSTRUCTION

Two different types of laying the strand are Equal Lay and Cross Lay.

Strands with Equal Lay Wires

In these constructions the pitches of the various layers of wire are identical as stranding is carried

out in a single operation,therefore,the contacts between wires are linear.Seale,Warrington and

Filler strands belong to this construction.Wires of different diameters are required for these constructions.

As for example: Seale :9+9+1

Warrington :6/6+6+1

Filler :12+6F+6+1

Strands with Equal Lay Wires

All the wires in this type of strand are of equal diameter and for geometrical reasons the number of

wires decreases in each layer,starting from the outermost one,according to an arithmetical progression

based on number(e.g.16+10+3 or 18+12+6+1 or 12+6).In cross lay constructions each layer of wire

is laid up a separate operation with a different length of lay,the result being the crossing of the various

layers of wires.Consequently strong pressure occurs between the wires which may break,especially with

variable with variable loads.

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