Plant layout is concerned with the spatial arrangement of processing e
quipment, storage vessels, and their interconnecting pipework. Decidin
g a good layout is an important activity in the design of chemical and
process plants. A good layout will facilitate a correct operation of
the plant. It will also provide an economic acceptable balance between
the often conflicting constraints deriving; from safety, environment,
construction, maintenance, operation, space for future expansion, and
process relationships such as those determined by gravity now. This p
aper presents a mathematical formulation for addressing the problem of
allocating items of equipment in a given two-or three-dimensional spa
ce. The objective function to be minimized is the total pumping, conne
ction, and floor construction cost. Detailed cost factors are used to
account for the flow direction between two connected units, The proble
m is formulated as st mixed integer linear programming model. Specific
attention is paid to constructing a formulation which is; suitable fo
r the solution of large scale problems. The method presents the rigoro
us solution of problems with about 30 process equipment and of essenti
ally unlimited size problems when the rigorous optimization is combine
d with simple heuristic rules. Three case studies are presented to ill
ustrate the applicability of the proposed approach to retrofit problem
s in multipurpose plants. Trade-offs between capital and operating cos
ts are captured so that the optimal number of required moors maybe det
ermined.