Basic terms and definitions

 
 

What is a wire rope?

 

Steel wire ropes consist of very few components but each of those vary in their specific properties so a very large number of different wire ropes can be made for specific purposes. The three basic components are:

Wire – the basic component of the wire rope. Wires are manufactured from different materials, in different diameters, grades and finishes.

Strand – consists of a number of wires stranded helically in one layer or more around a center wire (king wire). Strands are manufactured in many different constructions. They can be laid in right or left direction, parallel or cross lay.

Core – the core can be made of fiber or from steel wires. Some wire rope constructions do not have a core at all.

Wire rope – consists of a number of strands, normally 6 or 8, laid helically around the core. Single layer ropes consists only of one layer of strands. Rotation-resistant ropes have two layers or more.

 
 

Diameter:

The actual rope diameter is defined as the diameter of the circumscribed circle of the rope. According to most standards it is taken as the average of four measurements taken at two locations 1 m. apart (about 3') at perpendicular planes.

When measuring the diameter with a regular caliper, make sure to measure the largest dimension on the rope.

It is better to use a caliper with wide jaws that cover 2-3 strands at the same time.

 

Tolerance table

 
               

 

Materials:

 

Steel wires:

Wires are purchased according to established standards (ISO 2232, ISO 4101) in finished condition. Any thermal treatment or coating required is done by the supplier.

Wires can be in different grades (breaking strength) and finishes.

 
Grade:

 The grade of the wire is the minimum breaking strength. The most common grades used are:

  • 1370 N/mm².
  • 1770 N/mm².
  • 1960 N/mm².
  • 2160 N/mm².

Other grades are used for some special applications.

 
The North American market uses a different scale of grades according to U.S. federal specification RR-W-410:
  • Traction Steel
  • Mild Plow Steel (MPS)
  • Plow Steel (PS)
  • Improved Plow Steel (IPS)
  • Extra Improved Plow Steel (EIPS)
  • Extra Extra Improved Plow Steel (EEIPS)

The most common grade for general purpose wire ropes is IPS which is quite close to 1770 N/mm². Grade EIPS is close to 1960 N/mm².

The actual strength of the steel in these grades varies with the wire diameter.

 

Finish and Material:

The most common materials and finishes are:

 

Uncoated (bright) steel wire – wire ropes made of uncoated wires are used in applications in which the ropes are normally discarded because of wear and fatigue and not due to corrosion. Even with these ropes, some corrosion protection can be achieved by proper lubrication of the ropes. According to ISO 2408 this finish is designated by the letter U.

Zinc coated steel wire (drawn galvanized) – These wires are coated before the final drawing. The result is a zinc coated wire with a very smooth surface. There are two types of finish: Quality B is the most common, it has a thinner zinc coating but the same mechanical properties as an uncoated wire. Quality A has thicker coating but lower mechanical properties.

According to ISO 2408 this finish is designated by the letter B or A respectively.

Hot dip galvanized steel wires – These wires are coated after the steel wire is drawn to the final diameter. The result is a zinc coating that is significantly thicker than quality B or quality A but the mechanical properties are also much lower. These wires are used mostly for applications where the main concern is corrosion resistance as in mast stays etc.

Stainless steel wires – these are normally made of AISI 302/304 or AISI 316. AISI 302/304 offers higher breaking strength. AISI 316 offers better electrolytic corrosion resistance which makes it more suitable for marine applications.

Other coatings – other coatings such as brass or Zn95/Al5 alloy are used for special applications.

 
Fiber core:
Synthetic fiber core – for most applications the fiber core is made of synthetic material, mostly polypropylene. The basic components are fibrillated film or mono-filament yarns. The cores are manufactured according to our specifications that are based on the relevant standards and our extensive experience. According to ISO 2408 synthetic fiber cores are designated SFC.
Natural fiber cores – These are used mostly for elevator ropes. We manufacture these cores from high quality impregnated sisal yarns. The cores are made in one continuous length without any splices in the strands. According to ISO 2408 natural fiber cores are designated NFC.
According to the current standards cores can be made also from manila fiber but this fiber is not common and it is not used by Wire Rope Works Messilot Ltd. Other types of fiber that where used in the past are cotton, hemp, jute and other soft fibers but these are not allowed by the current standards.
 
Lubricants:

 A wire rope is a "machine" made of many separate metal parts (wires). When a rope is loaded or unloaded or when it wraps around a sheave or a drum the wires move slightly. Like in any other machine, without lubricant this relative movement results in friction, high internal stresses and wear. Lubrication between the individual wires and between the strands is critical for the service life of the rope. Lubricants also provide some corrosion protection.

All wire ropes made by Wire Rope Works Messilot Ltd. are lubricated during the stranding operation so that every wire is coated with lubricant.

Fiber cores are also lubricated with the required amount of lubricant.

Different types of lubricants are used depending on the intended use of the rope and customer requirements.