NUT 6V8190 - Caterpillar

Introduction
For Specifications with illustrations, make reference to SPECIFICATIONS for D379B, D398B, D399 GENERATOR SET ENGINE ATTACHMENTS, Form No. SENR2546. If the Specifications in Form SENR2546 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.Woodward UG8 Governors
SCHEMATIC OF UG8 LEVER GOVERNORWoodward UG8 Dial And Lever Governor
The UG8 Dial Governor is a mechanical-hydraulic governor. A hydraulic activated power piston is used to turn the output terminal shaft of the governor. A lever on the terminal shaft is connected to the fuel rack by a linkage rod. The governor has a separate oil supply and oil pump. The governor oil pump and ballhead are driven from a shaft in the governor drive housing. The shaft is driven by the fuel pump drive shaft.The oil pump gives pressure oil to operate the power piston. The drive gear of the oil pump has a bushing in which the pilot valve plunger moves up and down. The driven gear of the oil pump is also the drive for the ballhead.An accumulator is used to keep a constant oil pressure of approximately 120 psi (830 kPa) to the top of the power piston and to the pilot valve.The power piston is connected by a lever to the output terminal shaft. There is oil pressure on both the top and bottom of the power piston. The bottom of the piston has a larger area than the top.Less oil pressure is required on the bottom than on the top to keep the piston stationary. When the oil pressure is the same on the top and bottom of the piston, the piston will move up and cause the output terminal shaft to turn in the increase fuel direction. When oil pressure on the bottom of the piston is directed to the sump, the piston will move down and cause the output terminal shaft to turn in the decrease fuel direction. Oil to or from the bottom of the power piston is controlled by the pilot valve.The pilot valve has a pilot valve plunger and a bushing. The bushing is turned by the governor drive shaft. The rotation of the bushing helps reduce friction between the bushing and the plunger. The pilot valve plunger has a land that controls oil flow through the ports in the bushing. When the pilot valve plunger is moved down, high pressure oil goes to the bottom of the power piston and the power piston will move up. When the pilot valve plunger is moved up, the oil on the bottom of the power piston is released to the sump and the power piston moves down. When the pilot valve plunger is in the center (balance) position, the oil port to the bottom of the power piston is closed and the power piston will not move. The pilot valve plunger is moved by the ballhead assembly.
SCHEMATIC