Patent GB-1397618-A (GB)
Title: Turbine comprising a safety device
IPC: F03B3/06
Filed: 1972-09-25
Abstract: 1397618 Hydraulic turbines - control TITOVI ZAVODI LITOSTROJ 25 Sept 1972 44227/72 Heading F1T The invention relates to a hydraulic turbine and to the control thereof by variation in the pitch of the runner blades. The turbine shown is of the Kaplan type in which the pitch of the runner blades 132 is controlled by means of a servomotor 5, movement of the servopiston in a downward direction to open the blades being effected by supply of servofluid to the space 52 above the piston, and movement in an upward direction to close the blades being effected by supply of servofluid to the space 53 below the piston. Flow of servofluid is controlled by a main distributer valve 2 comprising a piston-rod 22 carrying two pistons 24, 25, fluid under pressure being supplied to inlet 215 and delivered at 212 or 213 depending on the position of the piston valve, the fluid passing to chambers 531 or 521 to control the servomotor 5. In accordance with the invention, a safety distributer valve 3 is disposed between the distributer valve 2 and the servomotor 5, also a second valve 4 is connected to the safety  distributer valve 3. The valve 3 comprises a pistonrod 32 carrying an upper piston 33, an intermediate piston 34 and a lower piston 35. A chamber 315' is connected through inlet 315 to the outlet 212 of the main distributer valve 2 while a chamber 311' which is connected to the chamber 315' is connected through outlet 311 to the chamber 531 and so to the "closing" chamber 53 of the servomotor. Similarly chamber 316' is connected through inlet 316 to the outler 213 of the main distributer valve and chamber 312' which is connected to chamber 316' is connected through outlet 312 to the chamber 521 and so to the "opening" chamber 52 of the servomotor. A further chamber 313' is connected through outlet 313 to a drain. The lower piston 35 is formed with a bore 353 within which is disposed a fixed sleeve 36. The lower piston is also formed with two further bores 351 and 352, bore 351 inter-connecting an annular recess 354 in the piston with a chamber 314' and so with an outlet 314, and the bore 352 inter-connecting the bore 353 with an annular recess 314" in the wall of the housing 31. Oil under constant pressure is supplied at inlet 41 and passes through bore 361 in the sleeve 36 to the bore 353. The inlet 41 is connected to the chamber 411 of the valve 4, the valve comprising a piston valve having pistons 4a, 4b mounted on a common rod, the piston 4a being acted on by fluid under pressure supplied through line 44 from the pressure device of the turbine governor and the piston 4b being acted on by a spring. Oil at constant pressure is supplied through inlet 42 to chamber 421; an annular recess 431 also the space at the end of the piston 4b are connected to drain pressure. In the position of the safety distributer valve shown, oil under pressure can pass from the main distributer through 213, 316, 316', 312', 312, 521 to the opening space 52 of the servomotor 5; also oil can discharge from the closing space 53 through 531, 311, 311', 315', 315, 212 to drain at 214. In the event of increased turbine speed the pressure of the servofluid in the closing chamber 53 of the servomotor increases and this increase in servofluid pressure is communicated to the space 336 above the piston 33, the valve assembly 32 moves downwardly, and as soon as the sealing edge 36c is opened and the edge 355 closed, the valve moves completely down. The servofluid in the chamber 53 is drained out through throttle 37 and the runner blades are fully opened. When the servopiston 51 rests on the bottom of its cyclinder and ceases to pressurize the servofluid, the fluid pressure in the space 336 above the piston 33 is reduced and the fluid-pressure in space 353 lifts the piston assembly 33, 34, 35 back to its upper position. The valve assembly 4a, 4b moves to the right due to increased oil pressure in line 44, closing off oil pressure line 42 and opening chamber 411 and so chamber 353 to drain.