The operating point of a chemical process is usually computed by optimizing a steady-state objective function, e.g., the profit, subject to some characteristics of the plant. However, the resulting point typically lies in the boundary of the operating region. The presence of disturbances can easily cause constraint violations. Thus, it is necessary to move the operating point away from the active constraints into the feasible region (back-off). The magnitude of this back-off has direct economical meaning. The purpose of this paper is to use a Canonical Piecewise Lineal approximation to compute the back-off.