ELBOW 7N2444 - Caterpillar

Initial Operation
Before starting the engine, make sure the actuator has been installed correctly. Refer to the Installation procedures in this manual. The procedure below should be used in conjunction with the Operation & Maintenance Manual Starting The Engine procedure. Refer to the Operation & Maintenance Manual for more information.1. Check the oil level of the actuator. Refer to the Operation & Maintenance Section of this manual for more information.2. Properly adjust the linkage. Refer to the Adjust Linkage story in this manual.3. Select a LOW SPEED setting to give low engine speed at initial start-up.
To prevent personal injury, loss of life, and/or property damage when initially starting the engine, be prepared to make an emergency stop. Before starting the engine, make provisions to stop the engine should a runaway or overspeed occur.
4. Start the engine. Refer to the Operation & Maintenance Manual for the complete procedure.5. Adjust the selected speed setting, as necessary, to bring the engine to rated speed.6. Obtain system stability. If less than recommended actuator output stroke is used, it may lead to less than optimum engine stability or response. All operating adjustments of the actuator are made during factory calibration. Additional adjustments are not necessary.Principles of Operation
UG Actuator Schematic Diagram. (1) Terminal Lever. (2) Torque Motor. (3) Loading Spring. (4) Power Piston. (5) Relief Valve. (6) Level Adjust. (7) Range Adjust. (8) Terminal Shaft. (9) Feedback Spring. (10) Torque Motor Beam. (11) Center Adjust. (12) Pilot Valve Plunger. (13) Pressure Reducing Valve. (14) Wash Thru Filter. (15) Gerotor Pump. (16) Drive Input.The UG actuator consists of the following basic components:* Oil Pump (Gerotor Pump) (15)- The oil pump is driven by the actuator drive shaft.* Relief Valve (5)- The relief valve is set to maintain internal operating pressure at 1172 kPa (170 psi).* Oil Filter- The oil filter filters oil to the pilot valve to prevent contamination of the orifice and nozzle. Bypass oil flows through the filter, providing a filter-cleaning function.* Torque Motor (2), Torque Motor Beam (10), Feedback Spring (9), and Loading Spring (3)- These items are used to establish a mechanical position of the pilot valve flapper in response to the DC current being sent to the actuator.* Pilot Valve Plunger (12)- The pilot valve plunger is a follower type valve. The pilot valve plunger duplicates the movement of the torque motor beam, but at a higher force level. The pilot valve plunger controls the flow of oil to and from the servo. The pressure regulator is used to minimize calibration shifts due to speed induced pump pressure changes.* Power Piston (4), Terminal Lever (1), and Terminal Shaft (8)- The terminal shaft converts linear motion of the differential type servo piston to rotary motion of the terminal shaft. This in turn moves the fuel linkage. The terminal shaft position is fed back to the torque motor beam, which provides the proportional control.Increase in Load (Speed Setting)
An increase in the load, or the speed setting, causes an increase in control current from