DESPITE being one of the driest countries on Earth, many people are surprised to learn that Australians are among the highest per capita users of water in the world.
As world population has tripled, and water use has increased six-fold over the past century, we in Australian have overdrawn our water resources to the extent that we are taxing major river systems beyond sustainable extraction limits - while also using more ground water than ever before.
Australia's water use has in fact increased 65 per cent since the early 1980s, according to the Federal Government's National Land and Water Resources Audit.
Small wonder then that the spotlight is being thrown on the efficiency of our water and waste water infrastructures - not only of our potable water supply and sewerage systems, but also the performance of systems that re-use effluent in this sunburnt country (particularly in sectors such as mining, agriculture, recreational facility, electricity and gas, metals, forestry and water supply).
Engineering thermoplastics have an increasingly important role to play in enhancing the efficiency and reliability of such infrastructures. Any engineer who has ever seen the havoc wrought on metals and other decay-prone materials used near water, waste water and recycling process solutions needs no introduction to the challenges of these aggressive environments.
The potent cocktail of liquid and chemicals poses an ongoing challenge to government and private industry engineers alike charged with the responsibility of maintaining infrastructure and machinery in top condition - without incurring massive maintenance budgets to do so (or suffering the political backlash when something breaks down).
The problem is not only the major plant involved - the big ticket items in primary and secondary treatment plants - but also the myriad of ancillary items involved in each stage, in settling, feeding, filtering, screening, pumping and conveying solutions and sludges from one point to the next. After all, any chain is only as strong as its weakest link.
Answers to many of these problems are being provided by advanced technology engineering plastics, such as the versatile families of Polystone, Ertalon and Nylatron plastics.
Apart from their obvious advantage of resistance to corrosion and fouling, their low friction, low weight and low wear characteristics help produce high reliability and long operational life.
These attributes - combined with non-toxicity, excellent strength, dimensional stability and cost-efficiency - are among the primary reasons why they are replacing metals, old-generation plastics and more expensive products that have been used for decades.
These super plastics (explained further below, and at www.dotmar.com) are finding expanding uses in such areas as pumping stations, sewage treatment plants; primary, secondary and tertiary treatment processes; conveyors; filters; and river and ocean discharges, including underground and underwater. Recent examples include:
* DAF (Dissolved Air Flotation) clarifiers, where Polystone 7000SR has been used to fabricate sprockets and wear shoes. Differently formulated Polystone 7000 has been applied to under-chain wear strips, while the ubiquitous Nylon has demonstrated its value in sprockets. Bar and step screens have also employed Polystone 7000SR vanes.
* Sedimentation tanks. Here Polystone 7000SR sprockets appeal because of their light weight, ease of installation, corrosion resistance, lubricity and economical replacement benefits. Ertalon 6PLA side tracking wheels offer similarly excellent corrosion protection in this application, as well as UV resistance, noise and weight reduction (and they don't require lubrication either)
* Centreless screw conveyor linings. These have employed dual layer/dual colour Ultra High Molecular Weight Polyethylene (UHMWPE). The dual layer acts as a wear indicator, with the 9mm top layer in brown or black and a 3mm bottom layer in yellow or green. Apart from the non corrosion benefits, the UHMPWE offered noise suppression, wear resistance and was easy to manufacture and install. Similarly, Nylatron MC901 was used for hangar bearings in screw conveyors, where its non-lubrication qualities were valued - and it was kind to the counter face of the screw.
* Belt dewatering equipment. Polystone Ultra has been selected here because it is non-corrosive, kind to the belt and highly resistant to abrasion (qualities which also were employed in a scraper for removing dewatered sludge from the belt).
* Blue metal filtering sprinklers. Ertalyte TX thrust washers were employed because - in addition to self-lubrication and wear resistance - they offered no moisture absorption and outstanding strength and creep resistance.
* Fine screen drum filters. These have benefited from Ertalon 6PLA and Nylatron MC 901 being used as strong, impact and wear resistant sacrificial components (which also don't need lubrication and don't corrode). Ertalon 6XAU has also been used in drum support rollers.
* Tertiary treatment chemical dosing ponds. Slide strips for gate and Penstock valves have been fabricated from Polystone 7000, which has a low coefficient of friction and offers economical service with high resistance to wear and abrasion. The material is used in this application by OEMs.
Engineered from stock shapes from Dotmar EPP's national network, long-life plastics such as Polystone, Ertalon and Nylatron are extreme plastics for extreme performance.
Polystone materials are recognised for their dramatic ability to lower operating costs through the reduction of abrasion and corrosion in any waste water processing environment. This is achieved through taking advantage of distinctive material characteristics and innovative machining to harness critical features:
• Low weight and easy handling.
• Very high chemical resistance.
• Very low moisture absorption and biologically neutral.
• Excellent abrasion resistance through a very low coefficient of friction.
• Corrosion protection through the elimination of electrolytic interaction.
• Stability and durability through a range of operating conditions.
The family of products made from this virtually unbreakable material include Polystone 7000SR, which is prized in water applications for its abrasion resistance combined with lack of corrosion and no moisture absorption.
Lightweight and economical to replace in applications such as valves, Polystone 7000SR complements materials such as Polystone Ultra, which is especially formulated for optimum sliding characteristics and resistance to wear and abrasion.
This means it is ideally suited to mechanical transmission support products and to flow promotion. Polystone 7000 and Polystone Ultra are used for change parts in which they offer light weight and easy fitting.
Ertalon (commonly recognised as nylon) is widely applicable to original equipment manufacture and maintenance requirements.
Ertalon stock shapes can be engineered to suit applications requiring a whole host of performance characteristics (including high mechanical strength, stiffness, hardness and toughness, fatigue resistance, high mechanical damping ability, good sliding properties, noise damping, electrical insulating, dielectric properties and excellent wear resistance).
Besides not needing lubrication or maintenance, Ertalon LFX shows excellent wear resistance, even in dirty environments. Ertalon LFX wear strips, for example, offer higher load carrying capacity than even the UHMWPE materials they typically replace, with improved wear resistance under load. Ertalon LFX lasts 3-4 times longer than UHMWPE.
Because the composition of members of the Ertalon family can be changed to suit different applications, materials such as Ertalon 6PLA can be custom-engineered for ideal combinations of corrosion resistance, UV resistance, noise reduction, weight reduction and elimination of lubrication needs.
This means they can be custom-formulated to indoor, outdoor, exposed or permanently immersed needs. Their strength, wear resistance and impact resistance also makes them highly useful for sacrificial components.
Ertalyte TX (in addition to being self-lubricating) offers a strong combination of wear resistance, strength and creep resistance and no moisture absorption in the many applications to which it is put in water and processing plants.
The Nylatron family of thermoplastics can also be formulated for outstanding performance characteristics suiting different applications, such as wear resistance and fine motion control.
Members of this family have some outstanding particular performance characteristics - Nylatron703 XL, for example, features 'Zero Slip-Stick' performance for precise and efficient motion control of machinery components.
Widely applicable to the water, waste water and processing industry is Nylatron MC901. In addition to being easy to manufacture and install (plus offering wear resistance, corrosion resistance and strength) components made from this material are kind to the counter faces of machinery in which they are used, enhancing overall service life.
Local supply of all the engineering plastics described ensures shorter delivery times compared with overseas OEMs - and enhanced ability to modify designs through the local supplier.
Engineers should consult appropriate technical guidance for which engineering plastics suits particular applications (one such resource being http://www.dotmar.com.au).
*Aldo Mostacci, BE (MECH), is engineering manager for plastics engineering specialist Dotmar EPP .