Wire rope and cable, is there a difference? The terms are often used interchangeably, but are they different? Each is considered a machine. Wire ropes are usually ⅜” in diameter or larger, while cables or cords are smaller. Though this little distinction exists in aircraft and marine cables, wire ropes and cables are synonymous in most other ways.
A strand is made up of two or more wires twisted around a center wire. Each strand is made up of 7, 19, or 37 wires. Cable or wire rope is made when a group of strands is twisted around a center wire or rope. They are named for the numbers of wires and strands. A 7×7 cable has 7 strands with 7 wires in each strand wrapped around a central core. A 7×19 cable would include 7 strands with 19 wires in each cable.
Different wire rope applications require different demands for abrasion, strength, and corrosion resistance. Different materials are used to meet different needs. Sizes under ⅜ “ are considered aircraft cable, sizes over 3/8 “ in diameter are considered wire rope.
- Stainless Steel – Type 302, made up of 18% chromium and 8% nickel alloy, is the most common grade because of its high strength and resistance to corrosion. When non-magnetic properties are required, type 305 is employed. Other common types used in wire rope are 304, 305, 316, and 321. Each has specific advantages and disadvantages. Stainless steel is the stronger of the two, so its cost is higher but well worth it.
- Galvanized Carbon Steel – To protect from the elements, a coating of zinc is applied to wire ropes used in the making of this wire rope. It is the wire rope of choice when strength is necessary, but corrosion resistance is not significant enough to warrant the use of stainless steel. Galvanized carbon steel is the go-to for cost-effectiveness.
If you require flexibility, you need wires that have more strands, more strands equal more flexibility. Look for 3×7, 7×7, and 7×19; these will give you more flexibility. However, as the degrees of flexibility increase, the abrasion resistance decreases. These cables are most useful where you require continuous flexing. Basic cable construction:
- 1×7 cable – This cable offers the least stretch and is stiff in larger diameters, but is stiffest in smaller diameters.
- 1×19 cable – This cable is still reasonably flexible, yet it resists compressive forces. It is smooth on the outside, and sizes above 3/32” diameter are the strongest.
- 7×7 cable – Good for use over pulleys. Strong and durable with high abrasion resistance and flexibility.
- 7×19 cable – Best to use over pulleys with the most significant stretch of all cables in addition to being the strongest having the most flexibility.
It is essential to correctly estimate the qualities necessary for the work the wire rope will be doing. To decide the importance of the essential attributes to do the job, you need to look for quality and figure out whether it can withstand how it will be used and the length of time it can be used in this capacity. In choosing a wire rope for the job at hand, these four things must be considered:
- Sufficient strength to lift the load and then some, keeping safety in mind. Always overestimate.
- Sufficient flexibility for continued bending
- Abrasion resistance
- Resisting abuse: crushing and distorting the rope
Make sure the rope you will be using has the strength to carry your load. Many factors go into this decision:
- How many ropes will be used?
- What angle will they be using to lift?
- What sling configuration will be used?
- Which machine will be doing the lifting?
Whether it is a crane, a pulley, or some other machine, be sure to choose the proper size, construction, and grade of wire rope appropriate for the job.
Silver State Wire Rope
To find the wire rope or cable you need for the job, contact us at Silver State Wire Rope for all of your wire rope and rigging needs. We have all sizes of cable and wire rope; whether you need it for aircraft, marine, or land use, we have it all!