Erection accuracy

It should be emphasized that capital cost estimates using installation factors are at best crude and at worst highly misleading. When preparing such an estimate, the designer spends most of the time on the equipment costs, which represents typically 20 to 40% of the total installed cost. The bulk costs (civil engineering, labor, etc.) are factored costs that lack definition. At best, this type of estimate can be expected to be accurate to 30%. To obtain greater accuracy requires detailed examination of all aspects of the investment. Thus, for example, to estimate the erection cost... 

A number of industiy-accepted state-of-the-art 3D computer-aided design (CAD) systems have been used for this purpose. The specification-driven 3D-CAD system allows a computer model to be built to allow extraction of drawings from the model for fabrication and erection. The extracted drawings are enhanced in their accuracy by the computer interference detection system which greatly reduces field rework. 

The cost for piping covers labor, valves, fittings, pipe, supports, and othc rdtems involved in the complete erection of all piping used directly in the process. This includes raw-material, intermediate-product, finished-product, steam, water, air, sewer, and other process piping. Since process-plant piping can run as high as 80 percent of purchased-equipment cost or 20 percent of tied-capital investment, it is understandable that accuracy of the entire estimate can be seriously affected by the improper application of estimation techniques to this one component. 

Table L5. Accuracy (A) and Precision (S) of Lactate Concentrations Determined by the ERECTIC Method versns the Use of TMA as an Internal Standard"...

P(2) All FRP units (including fixings and joints) shall be designed and constructed to ensure compliance with requirements for accuracy in manufacture and erection, and to accommodate permissible deviations in the building structure. Provision shall be made for adjustments, if required. 

Site welding of structures with its attendant difficulties are where possible to be avoided or at least minimized. Instead, site erection should preferably, be based on the bolting together of prefabricated items. This implies prefabrication to close limits of dimensional accuracy with special attention being focussed on interfaces between ... 

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