Traditional methods of storage tank or silo construction, whether in concrete or steel, present a number of Health and Safety challenges on site. Martin Grant explains how an alternative technology is minimising these risks, while at the same time providing a faster and more convenient method of construction.
In industry, agriculture and water utilities, the proper storage and processing of solids and liquids places extremely demanding requirements on the holding tank, especially if toxic or aggressive substances are likely to be present. This means that their fabrication and erection are critical processes that cannot be compromised.
Adding to this complexity of large tank builds is compliance with Health and Safety regulations, such as The Working at Heights Regulations introduced in 2005, which have played such an important role in reducing on site accidents.
In concrete tank construction, whether jumpforming, slipforming or building from pre-cast blocks, working at height is an inevitable part of the process, as it is with large, bolted steel section, tanks. It is against this background of more traditional, complex tank construction methods that an alternative system of tank and silo building has come to the fore. At its foundation is the Dual-Seal System for joining metal. Developed by Lipp GmbH, this patented system is based on a double edge folding principle to ensure optimum, safe storage for solid, liquid or even gaseous substances.
While the sealing system is innovative, the assembly process that it enables is even more so, and the Lipp Dual-Seam System is believed to be the fastest, simplest way to build reliable containers and tanks. The size of the containers is variable anywhere between 3m and over 40m in diameter, with tank heights of up to 40 metres.
A key part of the tank’s strength comes from the steel composite used in construction. The steel composite, Verinox, uses galvanised steel on the outer layer and stainless steel on the inner, providing both strength and corrosion resistance at sensible costs. The process starts with the fabrication of the appropriate quantity of Verinox composite stainless steel band, supplied on site in a coil. Also delivered to the site is the transportable assembly system, conceived and developed by Lipp. The composite steel band is fed into the assembly device at ground level, which begins to mechanically pull the band through it. As the steel band rotates through the assembly device, the storage tank cylinder emerges, spiralling upwards from ground level with the assembly device forming the Dual-Seam seal as it goes.
While the tank construction is still at low level, the roof can be added. After that, the spiral form continues building upwards and the process of tank erection is entirely automated. Not only is the construction process fast and safe; it also eliminates the need for nuts and bolts, which can be a point of structural weakness and the need to work at height with all the risks that can present. In addition, being built around a circular former, the potential for the tank to be constructed with a profile that is not quite perfectly round is eliminated; such ‘out of true’ construction can again be a potential point of structural weakness that can lead to catastrophic failure.
With the Lipp Dual-Seam System and the method of container construction, outstanding quality and extreme stability are ensured. The spiral construction method ensures that even the largest containers are resistant to horizontal pressure, providing the highest levels of storage safety.
Most importantly, without the need for cranes and other heavy plant and no requirement to work at height, the automated on-site production method itself is much safer, while at the same time being faster; which means reduced risk with lower assembly and installation costs.
Martin Grant is with Lipp Systems.