GB191107309A - Improvements in and relating to Valve Gear for Hydraulic Turbines. - Google Patents

Abstract

7309. Gelpke, V. March 23. Regulating. - Relates to valve-gear for hydraulic turbines in which a by-pass valve opens a free or non-working way for the water when the throttle valve is closed by the governor, whereby " waterhammer " shocks are avoided, after which the by-pass valve is gradually and automatically closed. The by-pass valve is operated by a rod a, Fig. 1, at the end of which is mounted a hollow member formed with a piston b working in a chamber c. A hollow piston-valve s admits oil from a chamber c<1> to either side of the piston b alternatively. The valve s carries a piston made with a small perforation, and working in a cylinder m, the vertical position of which is determined by the movements of a rod t actuated by the throttle-valve governing-mechanism. The oil, after operating the piston b, flows away through a pipe l. The method of working is as follows: When the speed of the turbine exceeds a predetermined limit, the throttle-valve is closed and the rod t is moved in the direction of the arrow, whereupon the cylinder m is raised. Owing to the restricted leakage of oil through the piston n, the valve s is also raised, whereupon oil is admitted beneath the piston b and the by-pass valve opened. The leakage of oil through the piston n continues, and, under the action of gravity, the valve s gradually falls and the device resumes the normal position, as shown. A weight g may assist the valve s to fall. In a modification, the valve s, Fig. 4, is actuated by a differential piston n<1> subjected below to a constant oil pressure, and subjected above to an oil pressure which is varied by the amount of leakage permitted. This variable oil pressure is attained by the incoming oil passing through a restricted opening f<3> in the supply pipe f<2>, while the oil leaks away through ports r<1> controlled by the pilot valve a<2> of the governor-controlled throttle-valve mechanism B.