GRADE 130/140 (2160 N/mm2) EXTRA EXTRA IMPROVED PLOW TYPE (EEIPS)
GRADE 120/130 (1960 N/mm2) EXTRA IMPROVED PLOW TYPE (EIPS)
Used in the manufacture of wire ropes for special installations where maximum rope strength is required and conditions of use permit some applications such as mine shaft hoisting where increased tonnages on existing skips and drums can be tolerated, and where other conditions such as sheave and drum diameters are favourable to its use.
GRADE 110/120 (1770 N/mm2)IMPROVED PLOW (IPS)
Has a remarkable combination of high tensile strength, tough wearing qualities and excellent fatigue resistant properties. By far the largest tonnage of wire rope is made of this strength grade.
Types of Core
An important point to consider is the selection of the proper type core required in the rope. Wire ropes are made with either fiber core or steel wire core.
Fiber Core (FC)
This core is made of either natural fibers or polypropylene and offers greater flexibility than the Independent Wire Rope Core.
Independent Wire Rope Core (IWRC)
This core is usually composed of a separate 7 x 7 wire rope designated as IWRC. The steel core increases the strength by 7% and the weight by 10%. These steel cores provide more substance support than fiber cores to the outer strands during the rope’s operating life. Steel centers resist crushing, are more resistant to heat and increase the strength of the rope
The design factor, being the ratio between the minimum breaking load of the rope and the working load limit (WLL), tells at what percentage of its ultimate strength a wire rope is operating. The Design Factor takes into consideration both normal rope wear and potential stresses in various applications. The best practice in determining an adequate design factor is to analyze the specific conditions involved in each individual installation. The normal design factor used with wire rope is 5:1.
Proper alignment of sheaves is essential. The main sheave should line up with the center of the hoisting drum, otherwise both the rope and sheave flanges will be subjected to severe wear and rapid deterioration will occur. If rope speeds are high, sheaves should also be balanced.
Wire rope products will break if abused, misused or overused. Regular inspection and maintenance are necessary. Attachments such as hooks, shackles etc. must have at least the same working load limit as the wire rope used. Consult industry recommendations and standards before using.
Where a wire rope leads over a sheave and on to a drum, the rope will not remain in alignment with the sheave groove, but will deviate to either side depending upon the width of the drum and its distance from the fixed sheave, often called the “lead” sheave.
The angle between the center-line through the “lead” sheave and the center-line of the rope leading to the drum is called the Fleet Angle.
Experience provesw that the best wire rope service is obtained when the maximum fleet angle is not more than 1 1/2 degrees for smooth drums, and 2 degrees for grooved drums. Fleet angles of 1 1/2 and 2 degrees are the equivalents of approximately 38 feet and 29 feet, respectively, of lead for each foot of drum width either side of the center-line of the lead sheave.
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