1.DIAMETER
The diameter of rope is the diameter of its circumference,
circumscribed to its normal section. This diameter is given in millimeters OR
inches.
A)
PRACTICAL DIAMETER OF STEEL WIRE ROPE
The practical diameter of a rope is measured by following an
established method, its value must be equal to the value of the nominal
diameter (the dimension by which a rope is identified) except for certain
allowed tolerances.
B)
HOW TO DETERMINE THE PRACTICAL DIAMETER
Measurements are taken at two points at least one meter apart
and two diameters are measured at 90° one from the other. The average of the
four values thus obtained is the practical diameter. Usually the practical
diameter is taken from a sample of straight rope not subjected to traction. In
special cases when the tolerance is less than 5% of the minimum guaranteed
breaking strength.
The correct diameter is the
greatest diameter of the rope or strand.
2. CONSTRUCTION AND DESIGNATION
The strand is the simplest construction: it consists of one or
more layers of superimposed wires laid spirally around one or more central
wires or around a fiber core. The construction of the strand is identified by
the number of wires in the individual layers, starting from the outer one(e.g.
12+6+1 or 15+9+FC). FC indicates a fiber core. Distinction is made between
strands with cross laid and equal laid wires.
A)
STRANDS WITH CROSS LAID 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 (18 + 12 + 6 + 1 or 12 + 6). In cross laid 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
loads.
B)
STRANDS WITH EQUAL LAID WIRES
In these constructions the pitches of the various layers of
wires 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.
As for example:
Seale : 9 + 9 + 1
Warrington : 6/6 + 6 + 1
Filler : 12 + 6F + 6 + 1
3. TYPE OF LAY
As already stated, round stranded ropes have both the strands
and the wires in the strands laid helical. Should the lay of the outer wires
in the strands be in the same direction or in the opposite direction to that of
the strands in the rope, the result will be respectively a Lang’s Lay rope or
an Ordinary ( Regular) Lay rope, having a Right Hand Lay or Left Hand Lay
according to the lay of the strands. Right Hand and Left Hand lays are designated
respectively Z and S.
Ordinary Lay ropes are less
likely to kink and untwist, and their Ordinary Lay ropes are less subject to
failure from crushing and distortion. Because the longer length of exposed
outer wires presents greater wearing surface, Long’s Lay ropes have increased
resistance to abrasion. Greater care must be exercised when handling Lang’s Lay
ropes, as they are more likely to kink and untwist than Ordinary Lay ropes. Ordinary Lay ropes are generally used because of their
greater stability; however, Lang’s Lay ropes are preferred for guided loads
such as passenger and freight elevators because the wires have a longer contact
with the sheave grooves and consequently less wear. Given equal construction
and diameter, Lang’s Lay ropes are more flexible than the Ordinary Lay type.
The Steel Wire Ropes we
manufacture are performed according to special methods which give them
stability and eliminate internal stresses.
4. LUBRICATION
Steel Wire Ropes are lubricated as a protection against oxidization
and to reduce friction between wires and strands. Fiber cores are impregnated
for preservation purposes. During the stranding and roping operations, all
wires forming the strand and all strands forming the rope are lubricated. The
type of lubrication varies according to the application for the rope and the
type of plant for which it is intended. During the working life of the rope,
lubrication should be carried out periodically with good quality products
compatible with those used during manufacture and which we shall be pleased to
indicate upon request.
Lubricants used during manufacture shall be free from
solvents, moisture, aromatic compounds, alkaline soaps and acidity both organic
and inorganic. For protection of Steel Wire Ropes against corrosion and
frictional wear, Elephant Steel Wire Ropes have various kinds of lubrication.
5. STEEL WIRE ROPE CORES
The core of a Steel Wire Rope is the central member around which
the main strands are laid. It’s principal function is to support the strands,
and maintain them in their proper position when loads are applied. The three
types of cores commonly used in Steel Wire Ropes are independent Steel Wire
Rope cores (IWRC), wire strand cores (WSC), and fiber cores (FC) of either
natural or synthetic fiber.
A)
Independent Steel Wire Rope Cores (IWRC)
This is a separate Steel Wire Rope used as a core in the main Steel
Wire Rope.
B)
Independent Wire Strand Core (IWSC)
A single strand can be used as the core in a Steel Wire Rope.
The wire strand core may be of the same construction as the outer strands, or
of different construction. A 6-strand rope with a wire strand core of a
different construction from that of the main strands is called a 6-strand rope
with WSC. If the core is of the same construction, the rope is usually called a
7-strand rope-for example, 7x7 or 7x19. Wire strand cores are limited to
standing ropes, and small diameter running ropes.
C)
Fiber Core (FC)
These cores are fiber ropes, made from either natural fibers
such as manila, sisal, jute, or cotton or synthetic fibers such as
polypropylene or polyethylene.
6. ZINC-COATED STEEL WIRE ROPE
Galvanized ropes have their wires uniformly coated with zinc
for protection against corrosion where ropes are exposed to the weather, to
moisture, to salt water or to other corroding agents. Conventional galvanized
ropes have lower strength than bright ropes(uncoated), and their use is usually
limited to stationary installations such as guys, standing rigging, towing
hawsers, mooring lines and the likes.
For hosting equipment in
locations where corrosive conditions are present, heavily lubricated bright
ropes usually are preferred to galvanized ropes.
The wires can be zinc-coated after the last drawing operation (galvanized) or
before and then redrawn (drawn
galvanized).
7. PREFORMED STEEL WIRE ROPE
In a preformed Steel Wire Rope,
the individual wires in the strands, and strands composing the rope, are
properly pre-shaped by preforming head before they are assembled into the
finished rope. Preforming prevents the wire and strands from straightening and
leaves them relaxed in their normal positions in the rope. Preformed ropes have
the following merits as compared with non-preformed ropes;
1) The flexibility is superior to non-preformed ropes, and
during use Steel Wire Ropes kink scarcely ever occurred.
2) Because preformed Steel Wire Ropes have a great endurance to bending, a Steel
Wire Rope’s life will be longer.
3) Broken wire ends do not protrude to injure workmen’s hand, distort adjacent
wires, or cause wear to sheaves and drums.
8. GRADES OF STEEL WIRE ROPE
Elephant Brand Steel Wire Ropes are manufactured in various
Tensile Strength grades to meet the varied requirements of many applications.
Each grade provides a different combination of tensile strength, toughness, and
endurance to abrasion and bending
9. SAFETY FACTORS
The safety factor is the ratio of the strength of the rope to
the working load.
Thus, a Steel Wire Rope with a
strength of 10,000 pounds and a total working load of 2,000 pounds would be
operating a safety factor of five.
It is not possible to establish a uniform safety factor each type of rope-using
equipment, as this factor can safely vary with conditions on individual units
of equipment.
The proper safety factor depends
not only on the loads applied, but also on the speed of operation, the type of
fittings used for securing the rope ends, the acceleration and deceleration,
the length of rope, the number, size and location of sheaves and drums, the
factors causing abrasion and corrosion, the facilities for inspection, and the
danger to life and property.
Kiswire Steel Wire Rope
Distributor UAE
Amzone International Ltd.
M5, Saif Zone, P.O. Box.
8068, Sharjah, U.A.E
Tel: +971 6 55 786 26 |
Ext: 555 | Fax: +971 6 55 786 16
Mob: +971561949348 /
+971507420398
