tank member 61 tank 61 is suspended from a bracket 62 that is attached to the gate operating ring 36 by means of a rod 63 the tank 61 is provided with a fluid fill line 66 which communicates with the interior of the tank a control valve 67 is provided which may be a solenoid actuated valve for automatic operation or manual actuated valve a supply line 68 is connected to the inlet side of valve 67 for supplying fluid to the tank 61 when the valve is opened at the lower end of the tank 61 there is provided a drain line 71 which is connected to a flow control valve 72 the outlet of the control valve 72 is in communication with a drain line 73 in operation a loss of fluid pressure in the servomotors 51 and 52 will be detected by an alarm system not shown this will result in a signal being generated to energize the solenoid of valve 67 to open the valve as a result fluid will flow into the tank 61 filling the tank as the fluid flows into tank 61 the weight of the fluid will effect rotation of the gate operating ring 36 in.