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(a) Breaking Strength. All hoisting wire rope shall be of such breaking strength as to provide a minimum factor of safety of seven. The factor of safety (F) shall be calculated by the following formula:
SN f = -- W
S = Manufacturer's rated breaking strength of one rope.
N = Number of parts of ropes under load.
W = Maximum static load imposed on all ropes with the platform, cage, or bucket, and its rated load at any position in the hoistway.
(b) Wire Rope Inspection.
A representative of the user of the material hoist shall be appointed and this representative shall keep written reports of the rope condition on file at the work site. The representative shall have the authority to order wire rope replacements and keep unsafe wire rope from being used.
(2) Periods of Inspection.
Inspection periods shall be set-up for each material-hoist wire rope. The frequency of inspection shall be determined by consideration of environment, degree of hazard to materials, frequency of operation, and the frequency with which the rope is subjected to its capacity limits. Inspections shall be made not less often than once each 30 days.
(3) Method of Inspection.
The working length of the wire rope shall be unwound from the hoist drum. Thorough inspection shall be made of the rope sections that pass over sheaves, drums, or contact saddles, or which make opposing turns. The rope close to end attachments shall be carefully inspected.
(4) Inspection of Used Wire Rope.
A used wire rope shall be thoroughly inspected prior to installation.
(5) Inspection of Wire Rope on Idle Equipment.
The wire rope on equipment that has been idle or shutdown for a period of one month or more shall be completely inspected prior to operation.
(6) Surfaces Contacted by Wire Rope.
Sheaves, guards, guides, drums, flanges, and other surfaces contacted by wire rope during operation should be examined at the time of inspection. Any condition harmful to the rope in use at the time should be corrected.
(c) Wire Rope Removal and Replacement.
Wire rope with one or more of the following defects shall be removed or replaced immediately:
(1) Corrosion. Severe corrosion shall be cause for replacement. Any development of slight corrosion should be noted and watched closely.
(2) Broken Wires. One or more valley breaks shall be cause for replacement. (A valley break is a wire break occurring in the valley between two adjacent strands.)
Six randomly distributed broken wires in one rope lay, or three broken wires in one strand in one rope lay, shall be cause for replacement. (A rope lay is the length along the rope in which one strand makes a complete revolution around the rope.)
(3) End Attachments. Development of broken wires in the vicinity of attachments shall be cause for replacement. If this condition is localized in an operating rope and the section in question can be eliminated by making a new attachment, this can be done rather than replacing the entire rope.
(4) Abrasion. Abrasion, scrubbing, flattening, or peening causing loss of more than one-third of the original diameter of the outside wires shall be cause for replacement.
(5) Kinking. Severe kinking, crushing, birdcaging, or other damage resulting in distortion of the rope structure shall be cause for replacement.
(6) Heat. Evidence of any heat damage resulting from a torch, or any caused by contact with electrical wires shall be cause for replacement.
(7) Reduction of Rope Diameter. Reduction from nominal diameter of more than 3/64-inch for diameters up to and including 3/4-inch; 1/16-inch for diameters 7/8 to 1 1/8 inches; and 3/22-inch for diameter 1 1/4 to 1 1/2 inches shall be causes for replacement. Marked reduction in diameter indicates deterioration of the core.
(d) Wire Rope Installation. Hoisting ropes shall be installed in accordance with the wire rope manufacturer's recommendations. The hoisting ropes shall be secured to the drum by clamps or by an approved equivalent means.
(e) Drums and Sheaves.
(1) Pitch diameters of drums shall be a minimum of 24 times the nominal rope diameter. The drum flange shall extend at least 2 inches radially beyond the last layer of rope when all rope is coiled on the drum.
(2) The winding drum shall have not less than three turns of rope when the platform, cage, or bucket is at the lowest point of travel.
(3) All hoisting wire rope shall be improved plow steel grade or stronger, and equal in flexibility to 6 x 19 classification wire rope. The joining of hoisting ropes by splicing is prohibited.
(4) There shall be at least 4 feet of clearance between the cathead sheave and the hoisting-rope fastening on the platform, cage, or bucket when either is at the uppermost terminal or landing.
(5) The arc of the bottom of the sheave groove shall be smooth and concentric with the bore or shaft of the sheave. The center line of the groove shall be in a plane perpendicular to the axis of the bore or shaft of the above sheave.
(6) Sheave grooves shall be machined or cast, providing the bottom of the groove has a radius subtending an arc of 150 degrees and conforms to Table 1.
Table 1 Groove Radii for New and Reconditioned Sheave Grooves Wire Rope, Root Nominal Groove Radius Diameter Minimum Maximum 1/4 .140 .150 5/16 .170 .180 3/8 .205 .215 1/2 .265 .275 5/8 .330 .340 3/4 .390 .400 7/8 .460 .475 1 .525 .540 1 1/8 .585 .600 1 1/4 .655 .670
(7) Load-bearing sheaves for wire rope shall be grooved to accommodate the rope and shall have a diameter at least 20 times that of the wire rope. For minimum tread diameter of sheaves see Table 2. (The diameter of a sheave is measured at the bottom of the grooves.)
(8) Sheaves intended for use with fiber rope shall not be used with wire rope.
(9) Defective and worn sheaves that may cause equipment failure or damage to the wire rope shall be replaced. If pillow blocks are used, they shall be mounted on top of beams and securely bolted. Open bearings shall not be used.
(10) No snatch blocks or hood-type sheaves shall be used on any hoist tower.
Table 2 Minimum Ratio of Rope Diameter to Sheave Tread Diameter Diameter Minimum of Hoisting Tread Diameter Rope of Sheaves* (Inches) (Inches) 1/4 5 5/16 6 1/2 3/8 7 1/2 1/2 10 5/8 12 1/2 3/4 15 7/8 17 1/2 1 20 11/8 22 1/2 11/4 25
* Based on 20 times rope diameter.
(11) All sheaves shall be of iron or steel.
(12) All sheave bearings shall be lined with babbit, or other equivalent bearing metal, or have ball or roller bearings.
(13) Sheave bearings shall be provided with adequate means for lubrication.