| 摘要 |
PURPOSE:To prevent the occurrence of water hammering due to closing of a downstream valve, by operating effectively a pilot valve or the like in accordance with increase or reduction of the quantity of water to be used to not only maximize the quantity of water supply with the adjustment of the quantity of water supply but also prevent the oscillation and the noise due to the variation of pressure in a duct. CONSTITUTION:When a primary-side pressure is reduced because of the increase of the quantity of water to be used and becomes lower than set pressures of pilot valves B and C, the valve B is closed, and the valve C is opened, and the internal pressure of a cylinder 13 is reduced up to an air pressure through a pipe 43, a pipe 51, a valve port 56, and a discharge pipe 53, and a valve body 7 is moved upward. Thus, no water flows from a discharge pipe 33 after a valve port 11 is opened to its full width. Meanwhile, when the quantity of water to be used is reduced, the primary-side pressure rises and becomes higher than set pressures of valves B and C, and the valve B is opened, and the valve C is closed, and therefore, the quantity of water flowing out from the valve port 11 is reduced. The oscillation and the noise due to opening and closing operations of a main valve accompanied with the variation of pressure in the duct are prevented by a needle valve provided in the main valve, and water hammering due to closing downstream valves is prevented. |
