Device for hydraulic testing of plunger pairs

4.2 Purpose

The device is intended for determination of hydraulic density of plunger pairs of fuel pumps. The action of the device is based on measuring the time during which a certain amount of mixture compressed in the working space of the plunger pair to a certain pressure leaks through the gap between the plunger and the plunger sleeve. The plunger vapors are tested for tightness using a mixture of diesel oil and fuel with a viscosity of 36 * 106 m2/s.

Principle of operation

The housing 3, by means of half-rings 12, is fixed on a plate 1, which can be located on a locksmith table. In the housing 3, there are four cells, in one of them a test pair 8 is installed, which by means of a clamping nut 10 is fixed in the housing 3. Using the fixing screw 2, we clamp the plunger pair, previously pouring a mixture of diesel oil and fuel into it. Then, a force is applied to the end of the plunger along its axis by pressing the lever 5, the pushing projection 6 presses on the plunger, and a test stopwatch is simultaneously turned on. The mixture in the plunger sleeve is compressed and under pressure leaks through the gap between the plunger and the sleeve. As the mixture leaks, the plunger moves. At the moment when the oblique edge of the plunger reaches the cut-off hole of the bushing, the mixture remaining in the above-plunger space rushes into this hole, and the plunger will begin to move quickly. At this point, turn off the stopwatch. The permeation time of the mixture characterizes the hydraulic density of the plunger pair. The smaller it is, the smaller the hydraulic density of the pair, and vice versa.