544,648. Turning gear for turbines. BRITISH THOMSON-HOUSTON CO., Ltd. Oct. 18, 1940, No. 15422. Convention date, Oct. 19, 1939. [Class 7 (v.)] [Also in Group XXVI] The rotor of an elasticfluid turbine is slowly rotated during shutdown periods by turning-gear apparatus, which is automatically coupled to the rotor at a predetermined minimum speed of the rotor during the shutting-down operation, and is uncoupled in response to a pre-determined acceleration of the rotor when the latter is operated under its own power. The turning- gear comprises an electric motor 13 driving through a bell 50 and speed-reducing gears 51 ... 55, the gear 55 being movable into mesh with a gear 56 on the turbine rotor by means of a lever 60 fulcrummed on the shaft of the gear 54 and actuated by the armature 63 of an electro-magnet 64. The gear 55 is biassed to the disengaged position by a spring 65 attached to the lever 61. The normal lubricating system for the bearings 16, 17 of the turbine 10 comprises a reservoir 18, a main oil pump 19, conduits 22, 24, 25 andreturn conduits 26, 27. During operation of the .turning-gear, an auxiliary oil pump 29 driven by one of the motors 38, 39 discharges through a connection 32 and a pressure-responsive device 34 into the conduits 24, 25. The device 34 has a contact 35 closed on the occurrence of a pre-determined oil pressure and a flow-responsive device 36 in the return conduit to the oil reservoir 18 has a contact 37 closed by oil pressure. The control system for the motors 13, 38, 39 is shown diagrammatically in Fig. 3 and comprises DC mains 75, 76 and A.C. mains 77, 78. A push-button 79 energizes a relay 84 latched in by a catch 85 and opening contacts 86 to deenergize the relay winding 83. Relay contacts 88 in the circuit of a latch-tripping solenoid 89 are closed for later energization by a pushbutton 90. The relay also closes at 92 the circuit of a speed-responsive device 41 connected to the winding 94 of an auxiliary relay 95 controlling circuits for energizing the auxiliary pump motors 38, 39. These circuits comprise a line 99 through relay contacts 96, 98, 101 and the winding of a relay 102 which closes at 103 a holding circuit for the relay and at 104 the circuit for an A.C. contactor 105 which completes at 106 the circuit of the A.C. motor 38. If the A.C. supply fails, the D.C. motor 39 is switched in by means of a relay 108. The line 99 is also connected through line 119 and contact 121 of relay 122 to the winding of a time-delay dropout relay 118 operating to close a contact 123 in the circuit of a control relay 124 for the turning- gear motor 13. This circuit includes the contacts 35 of the oil-pressure responsive device 34, contacts 37 of the oil-flow responsive device 36, and a contact 125 closed by the auxiliary relay 95. The relay 124 energizes' a contactor 128 connecting the motor 13 at 129 across the A.C. mains, and completing at 131 the circuit of the relay 122, so that the relay 118 is de-energized and drops out after a delay due to a time-delay device 132. A contact 133 of the relay 122 completes the circuit of a timedelay drop-out relay 135 acting to complete at 137 the circuit of the solenoid 64, which acts on the lever 61 and gear 55 to couple the turning gear to the turbine shaft. The lever 61 shifts the position switch 66, breaking at 70 the circuit of the relay 135 and at 68 the circuit of the speedresponsive device 41 on the turbine shaft, but closing at 71 the circuit of the tripping solenoid 89, which can then be energized by the push button 90 if it is desired to bring the motor 13 and the turbine to rest. On starting the turbine under power while the motor 13 is rotating, the gear 55 is thrown out of engagement and the speed-responsive device 41 de-energizes the relay 95, so that the motor 13 and the auxiliary pump motor are de-energized on the opening of contact 96 of relay 97. When the steam supply to the turbine is cut off, the device 41 energizes the relay 95 and the motor 13 and the appropriate pump motor are restarted and the gear 55 re-engaged for rotating the turbine slowly.