Wire Rope Warning
GENERAL INFORMATION ON WIRE ROPE
The three basic components of a typical wire rope. (Fiber core is shown.)
Wire rope consists of three basic components.
2. Strands, formed by wires, laid helically around a core.
3. Core, or center.
Steel grades in wide use today are IPS (improved plow steel), EIPS (extra improved plow steel), sometimes also referred to as XIPS, XIP, or EIP, as well as EEIPS (extra, extra improved plow steel.)
Its function is to provide proper support for the strands under normal conditions. Three types of core (or center) are commonly used.
1. Fiber Core (F.C.), usually polypropylene (P.C.), sometimes hemp (H.C.) and sisal.
2. Independent Wire Rope Core (IWRC)
3. Wire Strand Core (WSC)
IWRC and WSC are sometimes referred to as steel wire core or steel center.
Expressed in numbers of strands x number of wires. 6 x 25 indicates that the wire rope consists of 6 strands, which in turn have 25 individual wires. Constructions are grouped into classes:
6 x 7 Class: Containing 6 strands that are made up of 3 through 14 wires, of which no more than 9 are outside wires.
6 x 19 Class: Containing 6 strands that are made up of 15 through 26 wires, of which no more than 12 are outside wires.
6 x 36 Class: Containing 6 strands that are made up of 27 through 49 wires, of which no more than 18 are outside wires.
8 x 19 Class: Containing 8 strands that are made up of 15 through 26 wires, of which no more than 12 are outside wires.
19 x 7 Class: Containing 19 strands, each of which is made up of 7 wires.
8 x 19 and 19 x 7 class wire ropes have rotation-resistant properties, excluding elevator ropes. Other common constructions are 7×7 and 7×19 galvanized cable, which is sometimes referred to as “aircraft cable” although it is not intended for aircraft use. Also, 1×7 and 1×19 strand wire ropes, as well as 7x7x7, 7x7x19 cable-laid wire ropes. Many others exist, some for highly specialized applications only. Note that any class denotes the nominal number of wires in each strand. The actual number of wires may be different. For example, 6×36 class: strands most commonly consist of 36 wires, or 31, or 41.
They refer to different types of arrangements of wires and their diameters within a strand. Common strand patterns are Filler Wire, Seale, Warrington and combinations thereof.
Indicates how the wires have been laid to form strands and how the strands have been laid around the core. A right regular lay rope (RRL; the most common) has its strands laid right on the rope – similar to threading a right-hand threaded bolt. Regular means that the direction of the wire lay in the strand is opposite to the direction of the strand lay in the rope. (The wires in regular lay rope appear to be in line with the axis of the rope).
Caution: When combining seperate ropes in a single line application always use ropes of the same lay pattern. Different lays can increase rotation at connection points decreasing rope efficiency.
Right Regular Lay (RRL)
Right Lang Lay (RLL)
Left Regular Lay (LRL)
Left Lang Lay (LLL)
A manufacturing process wherein the strands and their wires are permanently formed – during fabrication – to the helical shape that they will ultimately assume in the finished wire rope. Proper preforming prevents the strands and wires from unlaying during normal use. The vast majority of wire rope sold today is preformed.
Wire rope is either sold as “bright” (or “black”) – meaning uncoated, or galvanized for better corrosion resistance. “Drawn Galvanized” wire has the same strength as bright wire, but wire, “galvanized at finished size” is usually 10% lower in strength. Plastic coated wire rope is also available, usually galvanized or stainless steel cable. The most common plastic coatings are nylon in either clear or white, although other materials and colors are available. These coatings do not add strength to the wire rope itself.
During fabrication, wire ropes receive lubrication. The kind and amount depends on the rope’s size, type and use, if known. This in-process treatment will provide the finished wire rope with ample protection for a reasonable time if it is stored under proper conditions. But, when the wire rope is put into service, the initial lubrication will normally be less than needed for the full useful life of the wire rope. Because of this, periodic applications of a suitable wire rope lubricant are necessary.
ORDERING WIRE ROPE:
Construction, lay, core, finish and other factors mentioned above impart greatly differing characteristics to different wire ropes. They must be understood and considered when selecting wire rope. There is no perfect wire rope for all applications; usually some less desirable properties are traded off for other, more desirable ones. Refer to the Wire Rope Users Manual by the Wire Rope Technical Board for a better understanding of wire rope properties and consult professional help when in doubt.
Lacking a complete description of the wire rope desired, a supplier can make several assumptions:
1. If direction and type of lay are omitted from the rope description, it is assumed to be right regular lay (RRL).
2. If finish is omitted, this will be presumed to mean ungalvanized, “bright” finish.
3. If no mention is made with reference to preforming, preformed wire rope will be supplied.
4. If a supplier receives an order for 6 x 19 wire rope he may assume this to be a class reference and is, therefore, legally justified in furnishing any construction within this category.