The October 2005 Power Engineering article by Richard Baker and Jeff Kelly on Valve Vigilance was excellent and timely but with one mistake. Under the heading, “Holding in the motor control contactor,” the article states, “A very common practice used to open or close a stuck valve when the normal push buttons or manual handwheels don’t work is to push in on the open or close motor contactor with an insulated tool. When the contactor is held in, all automatic and safety functions are circumvented except for the motor overloads.” When manually holding the motor control contactor in, ALL the automatic and safety functions are circumvented INCLUDING the motor overloads! The overloads only interrupt the control circuit which by holding a contactor in is defeated. This is a very unsafe practice.
Keep the excellent magazine coming with all the great articles.
Electrician, Belle River Power Plant, Detroit Edison