What are the applicable standards for using a gear-operated valve instead of a standard handwheel with a rising stem?
The handwheel or lever on manually operated valves is designed so that reasonable effort by the operator(s) is sufficient to operate the valves. MSS SP-91: Guidelines for Manual Operation of Valves provides recommendations in this regard. This standard defines an operator as a person who can apply approximately 670 N (150 lbf) of force to a lever with an effective length of 300 mm (12 inches).
EP GP 62-01 also provides guidelines for the use of a handwheel operator. According to this standard, the force on the handwheel/lever required to operate new valves should be limited to 360 N (80 lbf). If the force exceeds this value, a gear operator must be used.Gear Operated Butterfly Valve