The advantages of Polyurethane

3 June 2013

Local industries can substantially reduce the unpredictable downtime periods and delays on overall return-on-investment caused by premature plant abrasion, by making use of wear protection products manufactured by polyurethane expert UMP.

UMP director Trevor Carolin notes that the properties of polyurethane, its chemical composition and its suitability to applications are often misunderstood.”Polyurethane is often wrongly perceived as a plastic, which it is not. It is an organic polymer containing the urethane group that is core to the chemical structure and is grouped with rubbers, due to the fact that both are elastomers and made from reacting a polyol with a diisocyanate,” he explains.

Carolin highlights the fact that chain extenders are added to increase the molecular weight of the pre-polymer in order to form a usable elastic polymer. “Polyurethane wear solutions are among the most effective of these, helping to not only meet the plant’s projected time to break even, but also substantially reducing the expenditure required to operate the plant.”

According to Carolin, the variations of polyurethane composition make it suitable as an abrasion resistant and load bearing material for the mining industry and, due to its chemical resistance, as a versatile material for the chemical industry too. “The major advantages of polyurethane include; tensile and tear strength elongation, in addition to rebound, chemical and solvent resistance.”

When production chemistry is scientifically matched to the application, Carolin points out that polyurethane can play a key role in assisting plant managers and maintenance engineers in protecting the plant from downtime due to either erosive or abrasive wear.

Pipeline protection

With process plants today being designed for higher throughput, the life expectancy of modern mining plants has ultimately shortened, says Carolin. “Equipment is being designed for a certain life expectancy and no more. For this reason, engineers are moving away from traditional rubber lined steel pipes, and towards more cost effective lining alternatives. It is, however, important to realise that rubber lined steel pipes still have a place in plant sectors that have a short life expectance i.e less than 5 years and energy consumption is not an issue.

Carolin states that polyurethane has been proven to be cost effective in terms of proofing the pipe against abrasion and energy efficient due to it low coefficient of friction, up to 5 times better than rubber. Through better engineering design one can ensure that the pipeline achieves the required durability that correlates with the projected life of plant. “The most cost effective lining material on the market today is polyurethane, but for the lining to meet expectation, its composition and the actual lining of the pipe must be undertaken by a competent company.”

According to Carolin, high density polyethylene (HDPE) is the major competing material against polyurethane in the local market. “When applied correctly, a polyurethane lined pipe can outperform its competitors by a factor of three when conveying mine tailings and other process media. A test conducted at a phosphate plant in South America with 16mm ore pumped at 3m/s, revealed that polyurethane lined pipes in this application outlasted HDPE by factor of 24,” he continues.

Carolin suggests that if a steel polyurethane lined pipe commands a 41 percent premium over its closest rival, HDPE, the total life cycle cost over a given period would work out to approximately 47 percent to that of HDPE. “This assumes that polyurethane is a minimum of three times more wear resistant and does not take into account polyurethane’s superior performance with regards to high velocity, large particle sizes and bends. UMP’s branded Redline polyurethane in particular allows for a thinner lining and a range of thicknesses to suit either the internal pipe diameter or the specific wear protection required. What’s more, it delivers benefits that include shatter proofing and immunity to thermal and external shocks,” he adds.

General protection

Polyurethane wear protection also plays a fundamental role in chutes and other steel channels with rectangular or multi angular sections. Carolin explains that wear protection for these shapes is achieved by making use of UMP’s range of Armadillo protective chute linings, which delivers a life cycle cost advantage of more than 30 percent.

“Armadillo can be installed as a chute liner at the UMP factory and onsite, or it can be fabricated as a drop-in liner for ease of replacement. The major benefits of Armadillo include; resistance to impact and abrasion, excellent tear and cut properties and a low coefficient of friction in chutes and bins,” Carolin adds.

Despite the distinct advantages of polyurethane as a wear resistant material, Carolin warns that it is of the utmost importance for plant managers to deal with an experienced wear protection company that acts as a consultant, rather than just a seller.

“Users should remain alert to the fact that polyurethane is a chemical with numerous variants, and that the incorrect grade of material will have disastrous consequences. They should also work to narrow down the choice set of possible polyurethanes, and then undertake field tests to determine which one will deliver optimum results. The customer can benefit substantially by applying the best solution for its particular application,” he concludes.

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