STEELWORK - Process Plant Steelwork.

Steelwork for process and manufacturing plants varies across a wide spectrum of different industrial uses.Here it is considered to be steelwork that is intimately connected with the support and operation of plant and equipment, rather than simply a steel-framed building envelope constructed over a process plant.

Although the processes and plant vary widely, the essential features of this type of industrial steelwork are common to many applications and are conveniently examined by reference to some typical specific examples. There are many similarities with power station boiler house and turbine house steelwork described later.

Cement manufacturing plant. Typical cement plants are an assembly of functional structures arranged in a manufacturing flow sequence,with many short-term storage and material transfer facilities incorporated into the processes. The physical height and location of the main drums are likely to dictate the remaining plant  orientation.

Vehicle assembly plants. Substantial overhead services to the various assembly lines characterize vehicle assembly plants. It is normal to incorporate a heavy-duty and closely-spaced grid roof structure which also will support  the roof covering.

Reasonably large spans are needed to allow flexibility in arranging assembly line layouts without being constrained by column locations. Automation of the assembly process brings with it stiffness requirements to allow use of robots for precise operations such as welding and bonding. Open trusses in two directions are likely to satisfy most of these requirements, providing structural depth for deflection control and a zone above bottom boom level that can be used for service runs.Building plans are normally regular with rectangular type plan forms and uniformly regular roof profiles.

Nuclear fuel process and treatment plants. Steelwork for nuclear fuel process and treatment plants is highly dependent on the actual process involved, and often has to incorporate massive concrete sections for biological radiation shielding purposes.

Particular points to note are the importance of the paint or other finishes, both from the point of view of restricted access in certain locations, leading to maintenance problems, and also from the necessity for finishes in some areas  to be capable of being decontaminated. Specialized advice is needed for the selection of suitable finishes or to give guidance on whether, for example, structural stainless steels would be appropriate. In addition, certain nuclear facilities must be designed for extreme events, the most relevant of which is seismic loading set by the statutory regulatory body. Frequently designs will have to be undertaken to comply with well-established codes of practice for seismically active zones in, for example, America.

Seismic design requires the establishment of ductile structures to allow high levels of energy absorption prior to collapse, and local stability and ductile connection behaviour become of critical importance. It follows that joint and connection design has to be fully integrated with the structural steel design generally; the normal responsibilities of joint design assumed by the steelwork fabricator may have to be altered on these projects.

Petrochemical plants. Petrochemical plants tend to be open structures with little or no weather protection.The steelwork required is dedicated to providing support to plant and pipework, and support for access walkways, gangways, stairs and ladders. Plant layouts are relatively static over long periods of use, and the steelwork is relatively economic in relation to the equipment costs. It is normal there- fore to design the steelwork in a layout exactly suited to the plant and equipment without regard for a uniform structural grid. Benefits can still be gained from standardization of sizes or members and from maintaining an orthogonal grid to avoid connection problems.The access floors and interconnecting walkways and stairways
must be carefully designed for all-weather access; use of grid flooring is almost uni- versal. Protection systems for the steelwork should acknowledge  both the threat from the potentially corrosive local environment due to liquid or gaseous emissions and the requirements to prevent closing down the facility for routine maintenance of the selected protection system.

Careful account needs to be taken of wind loading in terms of the loads that occur on an open structure and the lack of well-defined horizontal diaphragms from conventional floors.

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