CST flat steel decks used on API 12B oil field tanks
Sloped Steel Decks or Roofs
CST’s supported and unsupported flat steel decks, or roofs, provide an economical solution to many liquid and dry containment needs where safe, regular access to accessories on the deck is desired. Based on years of experience and field-proven assembly this type of cover is an excellent option for numerous applications.
Flat steel decks were one of the CST’s earliest designs for tanks covers and is still used often today. At CST we have optimized the design through finite elements analysis, proprietary design programs, new materials and almost 100 years of field experience. CST’s flat deck roofs can be usually constructed up to 32 feet (9.8 m) and up to 100 feet (33.8 m) supported, but spans in access of 120 feet have been constructed. Supported decks can be center column supported or contain multiple columns depending on the size and loading.
CST’s flat decks can be deigned to accommodate a variety of accessories from valves to hatches. Safe and easy access to these accessories for regular maintenance and use is often important, so CST’s near-flat design and standard safety railing designs are significant benefits.
Externally Supported Roofs (ESR)
CST’s ESR is built to accommodate higher static and dynamic loads, applications with higher pressures and vacuum conditions, and where a smooth inner roof surface is beneficial. These roofs are specifically designed for applications where a center mixer is requires to be carried by the roof. With a newly designed center ring installation and service of center supported loads is easily accomplished.
Design and cost optimization has made CST’s new ESR a high quality, highly competitive cover solution for the digester and other market’s needs. When CST redesigned its ESR, higher performance was not the only result. The new ESR has approximately 30% fewer parts, which makes it even easier to assemble.
CST’s ESR is designed with a smooth, unobstructed inner surface. This smooth surface is ideal for applications where corrosion of internal structural members is a concern, maintenance of internal structural members is cost prohibitive and ease of cleaning is desirable.
Since its origin as a dry silo cover, the knuckle roof’s application has greatly expanded to a variety of liquid and dry storage needs. For small diameter tanks in an areas of higher environmental loads but minimal dynamic loads, a knuckle roof is the most economical cover. Easy installation adds to the cost benefits of this type cover.
Having been integrated onto silos and tanks for over 60 years, there is a tremendous amount of field data validating the knuckle roof designs. Knuckle roofs have a proven life expectancy even in extremely demanding applications such as leachate tanks and digesters.
Knuckle roofs are limited to 31 ft (9.5m) in diameter which makes them ideal for silo covers. Most sizes are predesigned and have reduced manufacturing times. Unlike flat steel roofs knuckle roofs have a high slope. This makes knuckle roofs an ideal solution silos and small diameter tanks in high snow load areas. Its steep slope also minimizes the need for internal structural support but may also be a hindrance to regular access or access with loads.
CST’s knuckle roofs are predominantly manufactured in Vitrium glass-fused-to-steel. They can also be manufactured in stainless steel and other materials. CST’s engineers can match the customer’s needs with the material and design to meet the application requirements.
CST’s trough deck covers are primarily designed for areas with low environmental loads where cover cost out drives total containment and durability requirements. Minimal construction costs, locally available components and no special construction tools make this the ideal solution for moderate diameter, less stringent applications.
When the diameter is small and the loads are minimal, beams can be used to span the tank and, thus eliminate the need for any internal, vertical support columns. For higher load applications and when tank diameters are larger, internal beams can be supported by vertical columns. These columns do add to the complexity of cleaning and maintenance needs.