Plastic tanks are becoming integral to many industrial processes and an understanding of the technology involved in advanced thermoplastic types will help optimise their performance.
But correct material selections and design understanding are critical to successful tank construction – and increasingly so is chemical resistant thermoplastic sheet increasingly supplants steel, stainless steel, fibreglass or similar materials in the chemical vessel, process equipment and tank building industry.
Thermoplastics
The main advantages of properly specified thermoplastics like polyethylene (HDPE), polypropylene (PP) and PVDF include:
- Excellent chemical resistance.
- Predictable service - 20 years or more, depending on application.
- Light weight and easy to construct (butt or extrusion weldable)
- Impact resistant, relatively inexpensive
- Low maintenance
- Very safe
However, because plastics often look the same to the untrained eye, many people new to plastics technology presume that they all function in the same way and offer similar performance over time. This is a fundamental mistake – and one that can not only lead to design failure, but, in the worst instances, profound safety issues. What needs to be understood at the outset is that the physical and chemical property of the plastic product is greatly dependent upon the widely varying polymer used.
Why does it matter? Because knowing the physical characteristics of the plastic involved and having a means of testing, allows people to:
- Match the characteristics of the thermoplastic with the task they are being asked to perform, especially the chemical, its concentration and temperature with which they will come into contact (be it an industrial process water, black water (sewage), grey water (recycled water) or potable water.
- Then build the tanks to a specification – an internationally reliable standard from which you can calculate the ideal materials to use, eliminating otherwise unforeseen safety issues and confidently predict lifespan.
You can thus arrive at a known performance outcome.
Why is this important? Because it is obvious that, while there is wide general awareness throughout Australasia of the benefits of plastics for tank construction, there is also a considerable need for education.
‘Dotmar EPP ’, is currently working with fabricators, end users and specifiers to develop an outline for an official Standard for Australia and New Zealand that reflects world’s best standard, such as the British Standard BS EN 12573 and German DVS 2205.
Using such a Standard involves relatively complex calculations, but this has been simplified through the ‘RITA’ (Rochling Integrated Tank Assist) programme, introduced to Australia and New Zealand by ‘Dotmar EPP’. ‘RITA’ incorporates 21st Century advances in thermoplastic engineering and design, now being widely adopted in Europe.
The programme – developed in conjunction with the Technical Approvals Institute in Germany in accordance with DVS stringent guidelines – streamlines calculation for design and fabrication technique, enabling maximisation of the benefits found in PE and PP, with a proven predicable method for service life under the influence of stress, corrosive chemicals and high temperature.
Test results for periods exceeding 50 years are not yet available because PE, PP or PVDF have not been around that long. However, a natural relationship between mechanical stress and the exposure time to stress at given temperatures has been proved.
As an industry leader, ‘Dotmar EPP’ is also actively participating in the education of tank construction, especially welding, with schools for Fabricators around Australia. These incorporate practical and theoretical tests on fabrication techniques, how to weld and why to weld. Classes of up to 30 are also taught how to test to ensure a known end result, so that safety is built into their outcome.
Dotmar EPP has endeavoured to provide a model for industry by introducing the latest internationally accepted design codes, together with advanced structural analysis techniques to product solutions that incorporate:
- Design by professional engineers utilising the standards BS EN 12573 and DVS2205 or in conjunction with advanced Finite Element Analysis techniques specifically tailored for plastics.
- Fabrication by Australian welders trained and certified to German standards and using state-of-the-art PLC-controlled sheet welding machines.
- A continuous line of quality assurance according to ISO9001 that includes the resin supplier, sheet manufacturer, sheet supplier and the fabricator
- The ability to incorporate, where required, complementary metal products such as mild steel, stainless steel, aluminium or FRP to Australian structural standards, including AS3990, AS 4100, AS 1664 (aluminium) and BS4994 (FRP).
But further work remains to be done. Advances towards uniform standards are increasingly important as engineering thermoplastics play an increasingly important role in enhancing the efficiency and reliability of industrial, water and waste water infrastructures.
These materials will play an increasingly important role in the future of our equipment and our infrastructure. And those who obtain the best advantage from the technology will be those who invest the time to understand the best material for their task.