Copyright© 2000-2001 Hanes Supply, Inc. All rights Reserved |
Special Application Wire STAINLESS STEEL CABLES VARIOUS ALLOYS USED STAINLESS STEEL (18-8 Grade) Type 302 stainless steel is the standard alloy for cable. It has about the same strength as galvanized aircraft cable and much better corrosion resistance. It has excellent corrosion resistance in most industrial atmospheres, and good corrosion resistance in seawater and marine atmospheres. Type 302 also has very good corrosion resistance to many chemicals including nitric acid. TYPE 305 Type 305 has better corrosion resistance than Type 302 with 10-15% lower strength. This alloy is primarily used for nonmagnetic cable applications. When sufficiently cold worked, this alloy does not become magnetic. TYPE 316 Type 316 is the standard high corrosion resistant alloy for cable. It is resistant to many of the chemicals in the paper pulp, photographic, food processing and textile industries. Of the commonly used stainless steels, it has the best pitting resistance in marine use. The breaking strength is 10-15% below Type 302. Excellent scale resistance allows its continuous use at temperatures up to 900 degrees F. Corrosion Resistance Chromium in stainless steels is the primary reason for their corrosion resistance. The chrome protects the surface quickly forming an impervious, tenacious oxide film. This acts as a protective barrier against attack. Nickel improves the oxide forming ability of chromium and also gives the stainless steel a broader range of corrosion resistance.
GALVANIZED AIRCRAFT CABLE CARBON STEEL (Aircraft Cable) Galvanized cable has the highest strength and greatest fatigue life of the materials offered. It has good to fair corrosion resistance in rural to industrial atmosphere environments. This material is most widely used for small diameter cables. Tin over galvanized cable offers greater corrosion resistance and reduced friction over pulleys. GALVANIZED IRON (Low Carbon Steel) This is relatively soft and suitable for light duty applications. Very good for seizing, but not recommended for hoisting or use over pulleys.
NYLON COATED CABLES The coating of cables with nylon or other plastic offers a number of advantages. It lengthens the life of a cable by protecting the wires from abrasion; it seals in cable lubricant and seals out grit, dirt and moisture. It protects pulleys and drums from abrasion. It also protects hands, clothing, fabrics or other soft materials which may come in contact with or be used in conjunction with cable. Nylon is the strongest and toughest coating material. It is available in several grades, depending on whether flexibility, toughness, hardness, or outdoor exposure, high or low temperatures or chemical resistance is the primary consideration. Vinyl coatings offer additional advantages. Generally, compared with nylon, they are more flexible, have better resistance to sunlight and are less expensive. Mechanically, however, their uses are somewhat more limited.
Rope Strength Design Factors 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:
*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. Typical evidence of wear and abuse
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
