Glass Fused to Steel Bolted Tanks
Glass Fused to Steel (GFS) is glass that has been fired (heat-processed) in a kiln at a range of high temperatures from 593 °C (1,099 °F) to 816 °C (1,501 °F). There are 3 main distinctions for temperature application and the resulting effect on the glass. Firing in the lower ranges of these temperatures 593–677 °C (1,099–1,251 °F) is called slumping. Firing in the middle ranges of these temperatures 677–732 °C (1,251–1,350 °F) is considered “tack fusing”. Firing the glass at the higher part of this range 732–816 °C (1,350–1,501 °F) is commonly described as a “full fuse”. All of these techniques can be applied to one glass work in separate firings to add depth, relief and shape. Disparate pieces of glass must be compatible in order to ensure they can be fused properly. It is a common misconception that glasses having the same coefficient of expansion (COE) will be compatible. Coefficient of expansion is one indicator that glasses may be compatible, but there are many other factors that determine whether glasses are compatible. If incompatible glasses are fused together, it is unlikely that the fused piece will be able maintain structural integrity. The piece may shatter during the cooling process, or develop stress originating from the point of contact between the incompatible glasses over time, leading to fractures within the glass, and eventually breakage. Generally, kiln-glass manufacturers will rate their glasses for compatibility with other glasses they make. In order to be certain that the glasses they use will be compatible, many glass fusers will adopt one manufacturer’s glasses to use exclusively. The stress in two pieces of incompatible glass that were fused can be observed by placing the item between two polarizing filters. This will show areas of tension which will develop stress and fracture over time.
Glass fused to steel, often referred to as enameled tanks are designed for:
• Storing of liquids (liquid manure, dung water, salt brine, process and fire water, lime milk, liquid fertilizers and other chemicals within the range of chemical resistance of enamel), storm water retention or re-use
• Storing of drinking water ensuring water supply for the public
• Storing of bulk material (grain, limestone, cement, fly ash, carbon black, wood waste,
granulated plastics, salt), and possibly fodder (ensilage, haulage, wet grain crops)
• Process tanks for wastewater treatment plant and for industrial process equipment
• Process tanks for bio gas storage
2. TECHNICAL DESCRIPTION:
An enameled tank consists of a shell and a concrete foundation or steel bottom, optionally of a roof, internal equipment and accessories.
• Enamel = glassy coating with bubble structure with enhanced chemical resistance. The quality of enamel is evaluated in accordance with international recommendations for enamel quality (DEZ, EEA etc.).
• The tank shell consists of enameled plates (plates with a thickness of 3 – 6 mm are made of low carbon steel with a min. yield point Re = 300 MPa), joined together by bolted connections and sealed by permanently flexible sealant. The shell is reinforced with wind- stiffening rings; it is furnished with flanges and connecting elements for internal equipment and accessory. Arranging the plates into rows creates a standard type series of tank diameters and heights.
• The bottom most commonly has a bolted steel floor or is anchored to a concrete foundation or concrete foundation ring with a compacted center surface, which is either in direct contact with the medium or covered by welded or enameled plates. We also manufacture bolted steel bottoms to specification.
• Internal equipment of the tank depends on the purpose of application and specifications. In order to provide for penetrations and entrances of piping the tank is furnished with flanges bolted to the shell.
• Tank accessories consist of ladders (external with or without safety cages and internal), platforms, stairways, manholes (bulkheads), supporting structures, hoppers, thermal insulation and specified other accessories.
• The roof may consist of a geodesic dome, conical enameled self-supporting (even gas-tight) type, or concave enameled or supported or self-supporting made with trapezoidal or sandwich plates, canvas roof of conical or spherical shape. Most commonly specified roof: trough and drain sandwiched insulated panels.
3. CHARACTERISTICS OF THE APPLICATION:
• In principle, enameled tanks are cylindrical above ground tanks consisting of a thin-wall shell, loaded by internal over pressure. Externally the tanks may be exposed to wind pressure only.
• The tank can be used only for the purposes specified in advance in the contract and for the declared medium.
• Burying of the tank underground is possible, but it shall be engineered and approved by the manufacturer or pre-approved licensed engineering firm.
• If the tank bottom is made of concrete then sealing of the joint between enamel and concrete foundation is provided by the manufacturer in accordance with the agreed method of anchoring that has been approved only.
• Concrete foundation slab is designed in accordance with the local foundation conditions and is made of reinforced concrete for water structures with the quality grade of at least C30/37-XA2-C10.2-Dmax 22-S1 as per EN 206-1.
• The height of the tank shell can be additionally modified upon agreement with the manufacturer.
• Exceptionally, the tank shell can be furnished with additional penetrations, but only with the approval of the manufacturer.
• The roofs and shells or platforms can be exposed only to the permitted load specified by the manufacturer.
• Gas-tight roofs shall be protected against unacceptable under pressure and overpressure by safety valves (preferably of a liquid type).
• Tanks designed for storing of media with a risk of dust explosion are equipped with the corresponding quantity of explosion-proof membranes and these tanks shall be furnished with static electricity absorption conductors.
• Every tank shell be connected to the grounding system by installation company, and it shall be equipped with the corresponding lightening conductor bars depending on the length of the tank perimeter as recommended by certified engineer only.
• When the tank is equipped with electrical equipment installed in the tank (pumps, mixers, drives, etc.) then the operators of the tank shall be protected against dangerous contact voltage in accordance with the effective standards for the corresponding power distribution system at no liability to the manufacturer or supplier.
• Arrangement and execution of internal equipment by others shall allow safe operation, maintenance and repairs of this equipment.
• Operation and maintenance of electrical equipment is governed by the corresponding equipment manufacturer electro technical standards and regulations.
• The tanks are usually used for media with pH within the range of 4 – 11 and temperature up to 60 degrees C.
• Internal equipment made of metal of a higher grade than the material of the enameled plates (including stainless steel) can be placed into the tank only after previous approval from the manufacturer.
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