The increasing amount of inferior expanded metal products being offered on the South African market is raising concerns about the reliability of these products when they are installed in safety-critical applications.

The increasing amount of inferior expanded metal products being offered on the South African market is raising concerns about the reliability of these products when they are installed in safety-critical applications.

Expanded metal meshes are produced by cold-stretching and flattening solid sheets. No material is lost during the manufacturing process, even though the original sheet of metal can be expanded by up to ten times its original size, resulting in a mesh that is considerably lighter than the equivalent area of steel plate.

Raising the reason behind the concern, Lance Quinlan, national technical sales consultant at Andrew Mentis, says that while expanded mesh can never unravel, when the metal is over-expanded the strands become narrower, the spaces between strands increases and the strength of the knuckle centres in the mesh is diminished.

“Expanded metal is a very versatile product with literally thousands of applications. In many of these functions the strength of the mesh is not a predominant issue — for instance, general racking, trays, shelves, architectural decoration, outdoor furniture and certain enclosures and partitions. 

“However, where expanded metal is being used for worker safety applications such as walkways and catwalks, guardrails and protection cages, filter and machine motor covers, lift side walls and ladder rungs, a structural failure resulting from sudden impact or subtle degradation could have catastrophic consequences.,” he explains.

With inferior expanded metal, personnel are exposed to potential injury and if pieces of damaged mesh are sucked into machinery the damage, downtime and associated costs would be significant.

Quinlan says that the main reason for over-expanding metal is to save costs, but this renders the product sub-standard.

“The industry needs to be aware of this when making a purchase decision based on price alone and must always ensure that the product is fit for the purpose intended,” he continues. “Often a close visual inspection will determine if there are any cracks between the knuckles and if the strands appear too thin.”

The SABS standard 190: Part 1 – 1983 specifies the required dimensions for expanded metal products, but Quinlan says not all manufacturers comply.

Andrew Mentis regularly submits expanded metal samples to the SABS and its manufacturing facility is audited to maintain current certification verifying that these products meet the criteria for shortway, thickness and bendability.

Andrew Mentis, an ISO 9001 certified operation, has been a longstanding supplier of expanded metal products to major operators in the mining, petrochemical and power sectors.

With extensive experience in the various applications of expanded metal, Andrew Mentis manufactures Mentex® raised and Flatex® flattened meshes. Typically, both Mentex® and Flatex® are manufactured from high quality local mild steel, but can also be manufactured from any other ductile metal. The product is typically supplied unpainted, but readily lends itself to any of the normal finishing processes such as painting, stove enamelling, plating and galvanising.

These products are available in a comprehensive range of sizes, mesh sizes and thicknesses and can be fabricated in any form. The mesh can be bent, shaped to radii, angled or notched, while maintaining its inherent rigidity. It is also available in various sizes, from mini meshes, with small openings of 1.4 mm by 2 mm and with a thickness of 0.4 mm to larger meshes with 115 mm by 300 mm openings and a thickness of 6 mm.