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Physical Address: Tel: (032) 459 2383 STM Tanks Physical Address: Tel: (012) 719 9052/3/4 Associated Company Grotto Defranceschi - manufacturers of stainless steel wine, fruit & beverage and dairy tanks.
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Double-wall Steel Underground Storage Tank
Built to Last a Lifetime
Double-wall Steel Underground Storage Tanks (USTs) were pioneered in Germany in the mid-1960's, primarily out of concern for protecting the environment. Their double-wall structure provides secondary containment, significantly reducing the liklihood of stored product accidently leaking into the underground environment in which they are placed.
The thinking behind this concept is simple: should the outer steel tank corrode, a result of the metal's reaction with oxygen and water found in the soil in which it is buried, the product will remain safely contained within the inner steel tank. Double-wall Steel UST's carry favour in countries governed by the European Union (EU), where they are highly prized for their strength and ruggedness.
Forgeweld has been manufacturing robust Double-wall Steel USTs since 1998, mostly for the export market. To date, we have produced units conforming to US, French and, now, the new European CEN codes.
Rugged, Robust and Strong
Forgeweld Double-wall Steel USTs are classified as secondary containment technology, consisting of a steel primary tank enclosed within a steel secondary tank. An interstice is formed between the inner steel tank and outer steel tank which can be electronically monitored for product leakage. After tank installation, this interstice is filled with a liquid consisting of two parts water and one part glycol; any loss of liquid level or pressure will activate an alarm, informing personnel that a leak is present. If required, Forgeweld Double-wall Steel Tanks can be delivered to site with the interstice already filled with monitoring fluid.
A 2.5mm composite (Firbreglass-reinforced Polyester Resin or FRP) or 0.8mm polyurethane coating can be applied to the outer steel wall to provide corrosion protection. The corrosion coating is checked for discontinuities over 100% of the tank surface by a 35 000 volt holiday test, and the polyurethane coating by a 6 000 volt holiday test.
Apart from the position of the interstitial monitoring apparatus, Forgeweld Double-wall Steel USTs are similar in configuration to the Permatank® and Forgeweld Composite Tanks. Sizes can be produced to order, however, we recommend that 40m³ be considered the maximum due to mass considerations involved in transporting and shipping them - Double-wall Steel USTs are heavier than a Permatank® Jacketed or Forgeweld Composite UST of the same size.
Forgeweld Double-wall Steel USTs are fitted with manholes incorporating fittings and unions to accomodate filler, dip and breather and suction (pump) apertures. Units are generally fitted with 25mm sockets for monitoring the interstice topside at each end, as well as with dished or flanged ends. Each tank has lifting lugs and a manufacturer's nameplate containing data relating to the tank and its manufacturer.
Internationally accredited
The carbon steel plate used to manufacture all structural components of our Double-wall Steel USTs is South African made, complying with SABS Grade 300WA and Grade 43A of the applicable British Code.
Forgeweld Double-wall Steel USTs are manufactured according to European Union CEN Standard Workshop Fabricated Steel Tanks, Part 1: Horizontal Cylindrical Single Skin Tanks for the Underground Storage of Flammable and Combustible Water Polluting Liquids (Reference ENG 12285-1).
As well as being certified by the United States standards authority, the Underwriters Laboratory, we hold certification from independent auditors testifying that we exercise all necessary quality control features when undertaking their fabrication.
Durable and Maintenance-Free
Forgeweld Double-wall Steel USTs are extremely storng and durable. No cathodic protection nor maintenance is necessary. The presence of a measurable, held vacuum means that there is no need to site leak-test them after installation (burial), as called for by many codes or standards covering the installation of storage tanks. Our double-wall Steel USTs are completely compatible with the storage of all blends of conventional and oxygenated fuels, including methanol.
We encourage all our customers to read the applicable codes - the protection of property, people and environment is everyone's responsibility. Copies are available from Standards South Africa or see www.stansa.co.za
