A dumper is a valve used to stop a fluid or adjust the amount of fluid in a duct or hopper. It is also used for switching of fluid transportation. Dumpers are mainly installed on air ducts, exhaust ducts, and dust-collector ducts in ironworks, cement factories, petrochemical plants, power plants, paper mills, pollution prevention facilities, waste incineration plants, and so on. Since complete blockage is required, a Power Cylinder with a press stopping mechanism is used to open/close a dumper. It is also important to select a Power Cylinder with a large starting torque because opening/closing a dumper requires a large starting force.