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WIRE ROPE STRENGTH DESIGN FACTORS

Hanes Supply, Inc.

This page is intended to explain Wire Rope Strength Design Factors.

If you have any questions regarding the following, please feel free to call 1-888-426-3755 or e-mail us.


The rope strength design factor is the ratio of the rated strength of the rope to its operating stress. If a particular rope has a rated strength of 100,000 lbs. and is working under an operating stress of 20,000 lbs., it has a rope strength design factor of 5. It is operating at one fifth or 20% of its rated strength.

Many codes refer to this factor as the "Safety Factor" which is a misleading term, since this ratio obviously does not include the many facets of an operation which must be considered in determining safety. Wire rope is an expendable item - a replacement part of a machine or installation. For economic and other reasons, some installations require rope to operate at high stress (low rope strength design factors). On some installations where high risk is involved, high rope strength design factors must be maintained. However, operating and safety codes exist for most applications and these codes give specific factors for usage. When a machine is working and large dynamic loadings (shock loadings) are imparted to the rope, the rope strength design factor will be reduced which could result in overstressing of the rope. Reduced rope strength design factors frequently result in reduced service life of wire rope.

O.S.H.A. (A.N.S.I.) Removal Criteria 5. A.N.S.I. Safety Codes, Standards and Requirements...
Rope must be removed from service when diameter loss or wire breakage occurs as follows:

A.N.S.I.
NUMBER
EQUIPMENT NUMBER OF BROKEN WIRES
IN RUNNING ROPES
NUMBER OF BROKEN WIRES
IN STANDING ROPES
IN ONE
ROPE LAY
IN ONE
STRAND
IN ONE
ROPE LAY
AT END
CONNECTION
B30.2 Overhead and
Gantry Cranes
12 4 Not
Specified
Not
Specified
B30.4 Portal, Tower and
Pillar Cranes
6 3 3 2
B30.5 Crawler, Locomotive
and Truck Cranes
6 3 3 2
B30.6 Derricks 6 3 3 2
B30.7 Based Mounted
Drum Hoists
6 3 3 2
B30.8 Floating Cranes
and Derricks
6 3 3 2
A10.4 Personal Hoists 6* 3 2* 2
A10.5 Material Hoists 6* Not
Specified
Not
Specified
Not
Specified

*Also remove for 1 valley break. OSHA requires monthly record keeping of wire rope condition.

Note: Current industry recommendations and OSHA standards are based upon the use of steel sheaves. The manufacturer of plastic or synthetic sheaves or liners should be consulted for their recommendation on the safe application of their product and possible revision in rope inspection criteria when used with their product.


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“To the extent applicable, all parties agree that they will abide by the provisions 29 CFR Part 471 Appendix A to Subpart A. Additionally, this contractor and subcontractor shall abide by the requirements of 41 CFR §§ 60-1.4(a), 60-300.5(a), 60-300.10 and 60-741.5(a). These regulations prohibit discrimination against qualified individuals based on their status as protected veterans or individuals with disabilities, and prohibit discrimination against all individuals based on their race, color, religion, sex, sexual orientation, gender identity or national origin. Moreover, these regulations require that covered prime contractors and subcontractors take affirmative action to employ and advance in employment individuals without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, protected veteran status or disability.”