In most statistical process control(SPC), control charts are used in which samples are taken and a suitable statistic is determined and plotted. In these control charts, control limits, ${mu}{pm}textsc{k{sigma}}$, from which a decision is made are mostly ${mu}{pm}3{sigma}$ and current literature in control charts are mainly concerned with detecting a shift in the mean. Therefore, when $sigma$ is increased considerably after a long time, using control limits set at the first time causes a great deal of economic loss. In this paper the solutions to determine new control limits which maximizes the profit per unit produced and reduce $sigma$ to economically optimal level for a certain cost when $sigma$ is increased due to process deterioration are proposed. By applying new control limits, $alpha$ error decreases considerably compared to apply initial control limits when $sigma$ is increased due to process deterioration. Therefore, false alarm investigation cost drops down to the level of initial a error. And also this solution provides useful information regarding replacement of a process when the process is reviewed regularly.