A series of low temperature destruction tests by Bridon®1 on galvanised and bright, 6x36 IWRC, RHO, grade, 16mm ropes exhibited consistent increases in breaking strength, typically between 5.5% to 5.9% at -50°C. This testing data showed no evidence of unusual fracture characteristics. This finding is similar to tests on multi-strand ropes reported by Buschmann show increased breaking load when testing ropes at temperatures between -90° and -120°C.
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There is only limited published physical property data to reliably quantify the behavior of individual carbon-steel wires at low temperatures. However, the data consistently shows the following differences at -60°C compared to properties measured at +20°C:
a. an increase breaking strength
b. a drop in relative ductility
c. the ductile-brittle transition temperature increases with carbon content
d. cold-drawn steel wires have a fine grain size which reduces the ductile-brittle transition at sub-zero temperatures.
Research conducted by Boleantu and Babeu on reverse bends and torsion tests on individual carbon-steel wires did not show a brittle transition at test temperatures of -60°C. However, it is reasonable to assume that when a wire is elastically or plastically deformed in any mechanical test the heat generated will increase the temperature of the test sample, as it would when working in a rope.
In plain carbon steels, the notch sensitivity increases at reduced temperatures4. While notch sensitivity and low impact resistance can be a problem in steel plates at low temperatures to date no correlation has been found with strands formed from steel wires in a rope.
Notch sensitivity is a characteristic that is not usually associated with wire and wire ropes for the following reasons:
• no sharp notches are present on the wire surface after the manufacturing process
• the rigidity of each steel unit is small
• because each wire is a single element the failure of a wire does not create a stress concentration in the adjacent wires giving no propagation of the fracture.
Consequently, it is important to prevent mechanical handling and service damage to the wire surface which can act as notches e.g. through de-icing.
Attempts at British Ropes (Bridon®) to complete bend fatigue tests on wire ropes at temperatures below 0°C have been unsuccessful because it was not possible to maintain testing temperatures. This was attributed to the friction between the rope and the capstans and internal friction in the wire rope combining to heat the test sample and raise its temperature. Another important observation from the dynamic tests was the behaviour of the lubricant.
It is essential to use suitable rope lubricant compatible with sub-zero applications. Wire rope lubricants can become ineffective at low temperatures due to flaking or cracking resulting in the rope operating similar to a dry rope. This can reduce the fatigue life significantly. Bridon® can lubricate ropes with Brilube® 8 or Brilube® 16, which operate up to -50°C. Bridon® also offers a novel Bristar® polymer core, called Bristar® Polar, which is designed to support the rope at -50°C.
Factors that should be recognized when operating the ropes at low temperatures include:
a. shock loading and removal of ice by mechanical methods must be avoided to minimize notch sensitivity
b. special consideration should be given to the choice of lubricant, and periodic re-application of a service dressing
c. approach choice of polymer core
d. care in the choice of termination method relating to the risk of severe shock loading on an anchorage point
Based on Bridon® test reports describing measurements of rope strength at low temperatures, and information from open-literature, the available evidence supports the conclusion the Bridon® steel wire rope is well suited to operating under sub-zero conditions, assuming that ropes are properly inspected, maintained and handled. Evidence suggests that strength of Bridon® wire rope will not deteriorate at operating temperatures of -40°C. While consideration must be made when operating the ropes to prevent shock loading and mechanical damage to the steel wires, no evidence of a brittle transition has been located for wire ropes at sub-zero temperatures. To extend durability in fatigue, it is essential that the correct lubricant is3 applied and maintained to avoid flaking during sub-zero service.
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Stainless steel wire rope and galvanised steel wire rope are used for various industrial applications including rigging, lifting, utilities, marine and infrastructure projects, and it can be used in and around commercial and domestic properties.
This wire rope guide will help you make an informed decision before you buy either stainless steel wire rope or galvanised steel wire rope.
Although simple in its appearance, wire rope is a complex mechanical device that makes lifting, moving or supporting a load simple. Wire ropes are available in various compositions to suit different purposes. For example, wire rope can be rigid, flexible, restrict rotation and have features that limit corrosion, abrasion and crushing. In particular, it is common for wire rope to be fabricated from stainless steel or galvanised steel.
Stainless steel wire rope is very common and used in many commercial and industrial applications. Stainless steel has chromium added to the steel to provide some degree of protection against rust and corrosion. Stainless steel is not immune to those environmental effects but is better protected than pure non-treated steel. Stainless steel wire rope is used predominantly in applications where it is not exposed to the outdoor elements to avoid rust or corrosion damaging the wire rope.
Stainless steel wire rope is available in grades 304 and 316. 304 grade stainless steel is standard whereas 316 grade stainless steel is ideal for use in and around marine locations. 304 grade stainless steel contains approximately 18% chromium and 8% nickel while 316 grade stainless steel contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum is added to help resist corrosion to chlorides (like sea water, chlorides and de-icing salts).
Galvanised wire rope is steel wire rope coated in a layer of zinc. The coating helps protect the steel from moisture in the air to prevent the wire rope from being susceptible to rust. This type of wire rope is ideal for use in marine locations where the wire rope is exposed to wet, damp and humid conditions. Galvanised wire rope helps to prevent the inner steel degrading from rust deposits.
While galvanised wire rope provides this benefit, it is not ideal for use in certain circumstances. These circumstances include: applications in and around salty sea water, use where corrosive chemicals are being handled, when food or medical products are being handled, applications where aesthetics are important and a shine is required, and others. In these circumstances it is preferable to use stainless steel wire rope.
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The main difference between stainless steel and galvanised steel wire rope is the tensile strength. Given stainless steel is steel combined with chromium when the steel is in liquid molten state, this provides additional strength compared to galvanised wire rope composed of steel and a coating of zinc. Stainless steel wire rope is favoured by many for this very reason and during the wire rope’s service life, if maintained well, it performs highly effectively in various applications.
In addition to strength, here are a few other differences:
Galvanised wire rope is steel wire hot dipped in zinc or electro-galvanised to protect the steel from rust and corrosion. This treatment provides a coating only and protection to the internal steel wire will no longer exist if the coating is breached. We stock galvanised wire rope available in fibre core or steel core, in 6×7, 6×19, 6×24, 6×25, 6×36, 7×7, 7×19 constructions.
Each type of wire rope construction is suited for different purposes and it is important that you check your standards, regulatory requirements and industry codes to ensure the correct wire rope is used. A wire rope with a thicker diameter will be more abrasion and crush resistant, whereas a thinner diameter will provide flexibility, bendability and not suffer fatigue.
Fibre core wire ropes are used where flexibility in handling, moving or supporting a load is required. Fibre core wire ropes are not suited for applications where there is prolonged outdoor exposure or crushing against other objects. On the other hand, steel core wire ropes have a higher tensile strength and are better suited to applications where there will be abrasions and crushing.
We stock stainless steel wire rope available in grades 304 and 316 in 1×19, 7×7 and 7×19 constructions. Each type of wire rope construction is suited for different purposes and it is important that you check your standards, regulatory requirements and industry codes to ensure the correct wire rope is used.
Here is an overview of the stainless steel wire ropes we stock:
– 1 x 19 construction: this type of wire rope consists of a single strand with 19 wires. Given the number of wires formed into the rope, it offers a high breaking load and is the least flexible wire rope construction. It will not bend around corners or angles and is ideal for straight line applications to support objects.
– 7 x 7 construction: this type of wire rope consists of 7 strands of 7 wires. It is not as flexible as the wire rope with a 7 x 19 construction but still has bendability characteristics.
– 7 x 19 construction: this type of wire rope consists of 7 strands with 19 wires each. This combination offers the greatest flexibility and is the most common and versatile in industrial and commercial applications. The wire rope is ideal for applications where there are bends and turns in the system. This type of rope also has some stretch in it.
The benefits of galvanised wire rope are:
The benefits of stainless steel wire rope are:
At Keble’s Trading, we are a wire rope supplier that has been in business for 33 years. Supplying Melbourne with high-quality wire rope that has been selected to meet the needs of our customers, we understand what matters most.
If you are interested in a long-term relationship with us, you can open an account with us, and we will assign an account manager to give you a single-person contact for all your needs. Enquire today by calling 067 687 or visiting one of our four showrooms today.
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