The function of the actuator is also important. Engineers must consider the torque required, rated duty cycle, movement rate, inputs and outputs available for control, materials, IP or NEMA rating, and cost. If a problem is encountered that can only be solved by replacing or upgrading the valve or actuator, the replacement may mean much more than the cost of the parts, including labor, down time, lost production, and potential fitment issues after an installation is complete and running. In many cases, replacing a valve can necessitate fully draining a process system if isolation is not possible or practical. For these reasons, proper advance consideration of all factors to correctly select application-specific valve and actuator types is essential.