Big tanks

The Tasman Tank Company, which produces more than 200 large industrial and municipal tanks a year, says advances in specifying, design, protective coatings, manufacture and installation need to be understood to get the best for particular industries and applications. The company says these changes are particularly important to the resources, energy and ‘green’ environmental processing industries.

The design and manufacture of large-capacity industrial tanks is an exacting task. Big tanks today will hold upwards of 10, 20 or even 30,000 tons of liquid.

And not only are they being asked to hold more water and specialised liquids more safely and securely than ever before, but they are expected to do it for longer than ever and in more challenging operating environments. At the technically demanding end of the market, major changes are being driven by the demands of technologies involving zero discharge applications, which are vital to major industries, as well as environmental and process requirements. Many radical advances in big tank design are coming in the area of bolted steel tanks, which have the major advantages of cost-efficient size potential (especially compared with welded) and their ability to isolate diverse liquids through advanced coatings that will not react with the contents over time.

Size, optimum durability and maximum protection for contents really do matter to the food and beverage industry. The tanks have to be big to cope with large-scale industry often in remote locations. Time too is important, an area where bolted steel tanks can shine with off-site prefabrication and modularisation, reduced on-site time and fewer potential interruptions during construction.

If the choice is made to proceed with a bolted steel design, the job only really begins with the production of a cost-efficient structure that looks like it will do the job. Looks can be deceptive. In this expanding industry - as with all rapidly expanding industries - there is a very wide variety of standards of design, production, materials and quality to sort through and it really is a case of let the buyer beware. There are a lot of questions to be asked. The following are some of the important ones.

Does it conform with Australian and New Zealand standards?

This is important. Because of their geographic location and exposure to the elements, the large developments of the resources, energy and large processing industries are often more exposed to risks posed by under-engineered structures. A good example is AS/NZS1170.2:2002 relating to structural design actions - wind actions, including cyclonic loads. Such standards are often not broadly understood, but they need to be because there is no room for shortcuts with quality, safety and structural standards. Any money saved today imposes a disproportionate risk down the line that no professional client would reasonably take.

Fit for purpose cost-efficiency - basic needs

This is really a package of needs, encompassing specification, design, manufacture and construction. The basic needs of many applications will be cost-efficiently met by versatile bolted steel designs incorporating an internal membrane liner. Wall sheet material from The Tasman Tank Company, for example, can range from Galvabond, hot dip galvanized steel to stainless steel. Internal membrane liners include PVC, Aeon, butyl rubber, bolypropylene or Strongline. Roofs - where required - are designed to AS/NZS1170.2 and include monoclad steel, long-life zinc-aluminium and aluminium. It can be very advantageous if, in addition to fabrication to stringent quality and efficiency standards, the manufacturer also offers the option of a complete turnkey site construction service.

Installation

Time-saving and safe site installation can be accomplished using a synchronised, jacking process that allows site crews to install tanks or silos at grade level. This process receives the highest industry ratings for quality control and safety for the on-site construction phase. Jacking tanks and reservoirs from grade reduces the OHS risks associated with working at heights.

Zero discharge

Technically demanding but increasingly common applications can include vacuum and pressure applications, include methane capture, biogas capture, anaerobic and aerobic processes, ultrafiltration, steam and the demineralised water used for turbine cooling. A wide range of tanks can be involved in the one process - and increasingly they must be totally sealed and their contents isolated from outside contaminants and free of elements in the tank’s structure that might react with the contents over time.

One of the major advances in zero discharge applications is fusion-bonded coating systems such as those developed by the Tank Connection group and Akzo Nobel. These factory-applied coatings are particularly suited to totally sealed applications where all the liquids involved in a process are retained on site.

They are also highly applicable to alternative waste treatment facilities (AWTs), an AU$450 billion per annum global industry with plants now being constructed extensively throughout Australia and Europe. These waste treatment systems utilise the latest in factory-coated, fusion-bond systems in the bolted tank construction for the digesters and liquid storage. An AWT can have up to 10 tanks or more for the entire treatment process.

Tank coating

Bonded coatings such as Tank Connection’s LIQ Fusion 7000 FBE coating is approved for potable drinking water with NSF-61 international standard approval. It is suitable for use with all bolted and welded tank linings. LIQ Fusion is designed as an advance on glass/porcelain enamel coatings, utilising the protective properties of an exclusive FBE epoxy powder fused to substrate with a fused external topcoat of SD Polyester. It is designed to outperform earlier systems several times over, with standard warranties on potable water storage starting at three years, triple typical warranties.

LIQ Fusion FBE:

• Does not spall or crack.
• Provides a 'holiday free' coating - it is fusion bonded to substrate surfaces to give total coverage, without blemishes or pinholes or other protective flaws, known as coating holidays.
• Provides complete wraparound on panel edges and in bolt-holes due to the electrostatic applied ‘powder-on-powder’ system.
• Can be repaired (if required) by a documented touch-up procedure.
• Does not require costly and potentially troublesome cathodic protection.

Can the tendering company build what they propose?

Once you have settled on the type of tank you need, then comes the task of selecting the right people to build it. Always check that the companies you are short listing have a track record in your industry. Ask them for testimonials - and follow them up. This can tell you a lot about the way they work, the projects they produce and whether they can blend into your own team and share a project’s common objectives.

Shared objectives for a major project are often every bit as important in achieving on-time, on-budget outcomes for major infrastructure projects, as is the correct selection of the technologies needed to make the project work. A commitment to shared objectives - with the trust and flexibility to accommodate inevitable project changes without recrimination and contractual cost blowouts - can produce major benefits in savings of money and time and achieving ongoing operational efficiencies.

Get an independent engineering assessment

Bring in someone who knows your industry - a quality tank supplier won’t object to having their designs verified.

Conclusion

Tank design isn’t going to get simpler; its complexity is going to increase. As greater environmental, process and energy recapture demands are made of industry, there is going to be an even greater range of specialised storage vessels required. It is imperative you do your homework before you sign on the dotted line.