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P.O. Box 93
717 N. 15th St.
Bowling Green, MO.
63334
 
    

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Definition of Abbreviations

Grade

Construction

Lay

Core
IPS- Improved Plow Steel
EIPS - Extra Improved Plow Steel
GIPS - Galvanized Improved Plow Steel
EEIPS - Extra, Extra Improved Plow Steel
EEEIPS - Extra, Extra, Extra Improved Plow Steel
FW - Filler Wire
WS - Warrington Seale
SFW - Seale Filler Wire
RR - Rotation Resistant
W - Warrington
S - Seale
RRL - Right Regular Lay
RLL - Right Lang Lay
LRL - Left Regular Lay
LLL - Left Lang Lay
RAL - Right Attended Lay
LAL - Left Attended Lay

IWRC - Wire Rope Core
FC - Fiber Core
Fiber - Hemp or Poly Core
Poly - Polypropylene Core

 

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General Purpose Wire Rope 

6 x 19 and 6 x 37 Class

     The 6 x 19 classification of wire ropes includes standard 6 strand, round strand ropes with 16 through 26 wires per strand. The 6 x 36 classification of wire ropes includes standard 6 strand, round strand ropes with 27 through 49 wires per strand. Although their operating characteristics vary, all have the same weight per foot and the same nominal strength, size for size.

     While the 6 x 19 ropes give primary emphasis to abrasion resistance in varying degrees, the 6 x 36 ropes are important for their fatigue resistance. This fatigue resistance is made possible by the greater number of small wires per strand.

     Although there are exceptions for special applications, the constructions in 6 x 36 classification are primarily designed to be the most efficient for each rope diameter. As the rope size increases, for instance, a large number of wires can be used to achieve required fatigue resistance, and still those wires will be large enough to offer adequate resistance to abrasion.

6 x 19 classification ropes

6 x 19S (Seale)

     In this construction, each strand has nine outer wires over nine smaller inner wires over one large center wire. A comparison of cross-sections shows that these outside wires are larger than those of the 6 x 25FW or 6 x 26WS. Therefore, its resistance to abrasion is increased, but its fatigue resistance is decreased. This is a good rope to withstand abrasion or crushing on the drum.

6 x 25FW (Filler Wire)

     To most wire rope users, 6 x 19 means 6 x 25 filler wire. It is the most common rope in the 6 x 19 classification. This rope has a good balance between both abrasion resistance and fatigue resistance in relation to other ropes.

6 x 26WS (Warrington Seale)

     This construction has better resistance to abrasion than a 6 x 25FW. It also features a compact construction with solid support for the wires; hence, it has a high resistance to crushing. Its number and relative size of the inner wires add to the stability of the strand and gives it a fatigue resistance comparable to a 6 x 25FW.

     A standard 6 x 26WS construction provides the best rope for a wide range of applications. In general, we recommend the use of a 6 x 26WS in any application where a 6 x 25FW is used.

     In most rope sizes, only one 6 x 36 classification rope is made. These constructions were selected to provide fatigue resistance without having wires that are too small.

     The greater number of wires in the 6 x 36 classification makes these ropes more susceptible to crushing. This can be minimized, however, by specifying an Independent Wire Rope Core (IWRC) and by using well-designed sheaves, grooved drums and proper operating techniques.

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Rotation Resistant Ropes

     Rotation-resistant ropes can frequently provide the best and most economical service in specific applications when you choose, handle and use them properly.

     Contra-helically laid, rotation-resistant ropes are different from standard ropes because they're designed to reduce rope torque. Modes of failure and wear for rotation-resistant ropes can differ from those for standard rope constructions. The very nature of these ropes requires special handling, selection and usage not encountered with standard constructions. They are susceptible to kinking, crushing and unbalancing in the form of "core pops" and "birdcages" Use extreme care to avoid operational practices that can possibly lead to these conditions.

     Rotation-resistant ropes should not be used with swivels that allow rope rotation -- or in single part lifts where the load can rotate. Rotation will cause a reduction in strength, unequal loading in the rope and possible rope unbalance. If any significant change in diameter is found in a short length of a rotation-resistant rope, the rope needs to be replaced.

     These ropes should be replaced when you see two randomly distributed crown wire breaks in six rope diameters -- or four randomly distributed crown wire breaks in 30 rope diameters.

     Because rotation-resistant ropes are special, there are separate design, maintenance, inspection and removal criteria established for them by applicable industry regulations and standards.

     We recommend that rotation-resistant ropes be used with a minimum design factor of 5.0.

19 x 7 Non-Rotating

     In an application where a single-part hoist rope is used to lift a free load -- or where rotation-resistant properties are essential for rope performance -- the 19 x 7 can be used. Its rotation-resistant characteristic is achieved by laying six strands around a core strand in one direction, then laying 12 strands around the first operation in the opposite direction. Thus, when the rope is in tension, opposing rotational forces are created between the inner and outer layers.

     In addition, frequent and regular inspection for broken wires is critical when using this rope. Due to its design, the 19 x 7 construction has a relatively low reserve strength. This can result in short service life between the point in time when the broken wire removal criteria are met and when actual rope failure occurs.

8 x 25 Rotation Resistant

     In a multi-part wire rope system where the blocks have a tendency to twist -- or for a single-part hoist line that doesn't require the degree of rotation-resistant properties found in a 19 x 7 rope -- the 8 x 25 Resistwist rope has found successful application. The rotation-resistant characteristic is achieved by laying the eight outer strands around an independent wire rope core so these strands are in the opposite direction to the lay of the core. Thus, when the rope is in tension, opposing rotational forces are created between the core and the outer strands.

     Though not as rotation-resistant, the 8 x 25 Rotation Resistant rope is more stable than a 19 x 7 rope. It also has increased resistance to bending fatigue and crushing. This is achieved through the use of eight-strand construction with an independent wire rope core.

     Like any application where an installation's rope type is changed, the 8 x 25 Rotation Resistant rope should be substituted only after carefully comparing specifications and strength requirements.

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HOW TO CALIPER WIRE ROPE
Rope diameters are determined by measuring the circle that just touches the extreme outer limits of the strands - that is, the greatest dimension that can be measured with a pair of parallel- jawed calipers or machinists caliper square. A mistake could be made by measuring the smaller dimension.

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SELECTING PROPER WIRE ROPE

To get the best service of wire rope on any specific installation, the following five principal factors should generally be considered. The proper choice of rope could be made by correctly estimating the relative importance of each of these requirements. Finally the rope should be selected which would have the qualities most suitable to withstand the combined effect of the destructive factors which may be encountered.

TENSILE STRENGTH
After giving consideration to the factor of safety the rope should have sufficient strength to withstand the maximum load to be applied.

ABRASIVE RESISTANCE
Abrasive wear removes metal from the cross section of outer wires of a wire rope where it is exposed. Larger diameter wires offer greater metallic area to withstand abrasive wear. Resistance to abrasive wear can be determined by three principal factors: (i) Diameter of outer wires, ( ii) Grade of wire, (iii) Distribution of wearing surface. In short, resistance to abrasion wear in proportion to the severity of the abrasive factors, to which the rope is to be subjected, should be considered.

FATIGUE RESISTANCE
Bending fatigue is caused by the action of bending of wire rope around sheaves, drums, etc. Apart from load, speed which the wire rope has to encounter is also an important factor. There is a definite relationship between the diameter of outer wires of rope and diameter of the sheave or drums, etc. which effect the service life of rope. In short, ability to withstand the effects of bending and vibrations to be encountered, should be considered.

CRUSHING STRENGTH
There are two principal detrimental effects when wire ropes are subjected to the action of lateral forces. First, the wires become damaged by radial pressure and second, the cross section of wire becomes distorted. Ropes that vibrate in a span often strike repeatedly against external objects causing flattening of wires. When rope is repeatedly flexed, cracks develop in the hardened surface of wires. Wire breakage follows thereafter. In the second case, the wires, strands and the core are disturbed from their proper shapes and position resulting in premature wire breakage. Therefore, it is necessary to select a wire rope which has sufficient lateral stability to withstand the crushing forces it may have to encounter. Generally Regular or Ordinary lay ropes are preferable to Lang's Lay ropes and similarly six strand ropes are recommended over eight strand ropes because of their more lateral stability.

CORROSION
A large number of wire ropes fail because of corrosion which may be either external, internal, or both. Normally corrosion takes place because of acid of alkaline atmosphere which is due to sea, air, industrial fumes or other conditions. In most cases corrosion cannot be completely eliminated but it can be resisted by cleaning and lubricating rope or by using galvanized ropes. In short, a rope which would have adequate resistance to corrosive factors should be selected. Though there would be a number of other factors which would influence the life of a rope, the above factors are generally important. In certain cases these properties are contradictory. For example, increasing the diameter of the outer wires of a rope increases resistance to abrasion, but decreases resistance to bending fatigue. It is, therefore, very important that the ultimate selection of rope must be a most acceptable compromise. Each of the desirable characteristics should be attained to the maximum degree possible without excessive sacrifice of the other required properties.

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