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On almost all projects all over the world, process engineers, project engineers, and cost professionals approach the initial development of process plant projects in terms of geographical boundaries known as ISBL (inside battery limits) and OSBL (outside battery limits). First the ISBL is defined, then the OSBL is defined to support the ISBL.
As simple as this concept is, confusion still abounds. "Could diere possibly be more than one ISBL and one OSBL on most projects?"
Traditionally, ISBL is thought of as the process portion of a production facility, or that part where chemical reactions or refinements occur. The process area is where the real product is created.
ISBL comprises one or more geographical boundaries, imaginary or real, enclosing a chemical plant being engineered and/or erected, established for the purpose of providing a means of specifically identifying certain portions of the plant, related groups of equipment or associated facilities.
The OSBL, although not as well defined, is traditionally thought of as the non-process/infrastructure that is necessary to support of the process. OSBL generally consists of:
feed product storage/purification;
final product storage, packaging, and distribution facilities;
utilities and distribution systems;
interconnecting pipe racks (racks between process areas);
any structures not providing support or access to the process
equipment; and
administrative, maintenance, and storage buildings.
PROCESS FACTORS
Figure 1 is a sketch illustrating the traditional definition of ISBL and OSBL. In diis first sketch, a heavy dashed line represents the graphical boundary of the battery limits that encompasses a 15M X 50M area.
Process equipment is geographically located inside die 15M X 50M boundary (inside the battery limits) and the tank storage, electrical transformer utility, wastewater treatment plant, etc. are located outside the boundary (outside the battery limits). Some pipe, valves, and instrumentation are also located inside die boundary.
A common method of conceptual cost estimating is to use a "Lang Factor" as a multiplier applied to the cost of the major equipment located inside the boundary, to quickly obtain the total installed cost of everything inside the boundary [I]. The Lang Factors are based on the historical costs of specific process equipment located witìiin predefined boundaries [2].
One of the world's greatest project analysts: R. C. Floyd, clarified die definition of ISBL and OSBL. He...