FABRICATION
Drawings
Installation Drawings. Current industry practice is for the designer to prepare plans and sections or isometric drawings of the required piping system. These, together with line specifications, outline all the requirements needed for the fabrication and installation. Usually the weld bevel requirements for field welds are specified to assure compatibility between all the system components to be field welded.
Frequently the shop welding bevels are left to the discretion of the fabricator, provided, of course, the required weld quality is attainable. Location and numbers of field welds are an economic consideration of available pipe lengths, shipping or heat-treating limitations, and field installation limitations.
Shop Details. A piping system prefabricated at a commercial pipe fabrication shop is usually divided into subassemblies or spools. The manner in which a system is divided depends on many factors: available
lengths of straight pipe, dimensional and weight limitations for shipping and heat treatment, field welding clearance requirements, and sometimes scheduling needs. Bending, forging, special heat treatment, cleaning, and as much welding as possible are normally performed in the shop. Every attempt is made to minimize the number of field welds, but this must be balanced economically against the added costs of transportation and greater field rigging problems because of larger, heavier, more complex assemblies. Where the site conditions are adverse to normal field erection practices, much of the plant can be fabricated in modules for minimal onsite installation work. Once the number and locations of field welds have been decided, the fabricator will prepare detailed drawings of each sub assembly.
Each sub assembly drawing will show the required configuration; all necessary dimensions required for fabrication; reference to auxiliary drawings or sketches; size, wall thickness, length, alloy, and identification of the materials required; code and classification; reference to special forming, welding, heat treatment, NDE, and cleaning requirements; need for third-party inspection; weight and piece identification
number.
Drawings
Installation Drawings. Current industry practice is for the designer to prepare plans and sections or isometric drawings of the required piping system. These, together with line specifications, outline all the requirements needed for the fabrication and installation. Usually the weld bevel requirements for field welds are specified to assure compatibility between all the system components to be field welded.
Frequently the shop welding bevels are left to the discretion of the fabricator, provided, of course, the required weld quality is attainable. Location and numbers of field welds are an economic consideration of available pipe lengths, shipping or heat-treating limitations, and field installation limitations.
Shop Details. A piping system prefabricated at a commercial pipe fabrication shop is usually divided into subassemblies or spools. The manner in which a system is divided depends on many factors: available
lengths of straight pipe, dimensional and weight limitations for shipping and heat treatment, field welding clearance requirements, and sometimes scheduling needs. Bending, forging, special heat treatment, cleaning, and as much welding as possible are normally performed in the shop. Every attempt is made to minimize the number of field welds, but this must be balanced economically against the added costs of transportation and greater field rigging problems because of larger, heavier, more complex assemblies. Where the site conditions are adverse to normal field erection practices, much of the plant can be fabricated in modules for minimal onsite installation work. Once the number and locations of field welds have been decided, the fabricator will prepare detailed drawings of each sub assembly.
Each sub assembly drawing will show the required configuration; all necessary dimensions required for fabrication; reference to auxiliary drawings or sketches; size, wall thickness, length, alloy, and identification of the materials required; code and classification; reference to special forming, welding, heat treatment, NDE, and cleaning requirements; need for third-party inspection; weight and piece identification
number.
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