CLAMP 1695723 - Caterpillar

General:
This pneumatic speed setting assembly is used to change the speed setting of SG or PSG governors by means of an air signal, either from a pneumatic controller-as in a process control system-or from a pressure regulator for simple remote speed adjustment. This assembly can be furnished on any SG governor not equipped with a speed adjusting motor, and on any PSG governor except one with two position speed droop, with bi-metal type temperature compensation, or with a speed adjusting motor. When this speed setting-assembly is used, an external speed adjusting shaft is not supplied and the cover is machined for mounting the assembly.The direct type speed setting assembly increases governor speed setting as the air pressure signal increases. The assembly responds to an air pressure change as small as .05 psi. While the most commonly used assembly receives an air pressure signal of 3 to 15 psi, assemblies using signals in other ranges are available (e.g., 6 - 30 psi, 9 - 15 psi, 3 - 20 psi, 5 - 60 psi). The speed range obtainable varies from about 10 percent to 80 percent of the high speed setting; speed can be set accurately only at one end of the speed setting range. Contact us for help in selecting the correct assembly for a particular application.Hysteresis in terms of rpm increases as the speed range increases. (A hysteresis loop is a plot of the speeds obtained at various control signal pressures; one portion is recorded as speed setting signals are being increased, the other portion as the signals are being decreased.) In a governor using a speed setting assembly with a speed range of 2850 to 3350 rpm, the hysteresis in rpm is less than one-half of one percent of high speed setting; with a range of 2370 to 3370 rpm, the hysteresis in rpm is about three-fourths of one percent of high speed setting.Operation:
The pneumatic speed setting assembly consists essentially of a diaphragm, housing, oil reservoir, adjusting screws and a rod extending down through the cover to the governor floating lever. The air signal pressure acts on one side of the diaphragm and causes it to move against the force of an opposing spring. Movement of the diaphragm is transmitted by the diaphragm rod to the governor floating lever. Motion of the floating lever increases or decreases the speeder spring force. The change in speeder spring force represents the change in speed setting.To prevent hunting which would occur because of air compressibility if the air pressure were supplied directly to the diaphragm, the space above the diaphragm is filled with oil and is connected through an orifice with an oil reservoir. The air pressure signal is applied to the top surface of the oil in the reservoir and the pressure signal is transmitted by the oil to the diaphragm.Installation:
The pneumatic speed setting assembly cover has two tapped holes for the oil reservoir; selection of the proper tapped hole for the oil reservoir depends on whether the