Plunger and Barrel Assembly

Fig. 5 Plunger and Barrel Assembly:

The pump plunger and the pump barrel, Fig. 5, together form the plunger and barrel assembly. The plunger is fitted so perfectly into the barrel that it seals even at very high pressures and low speeds. No additional sealing is required for this purpose. Slight leakage losses are necessary with regard to the lubrication of the plungers.

Fig. 6 Machined Grooves in the Plunger and Barrel Assembly:

Apart from a vertical groove the pump plunger is also machined on its side, Fig. 6. The diagonal edge formed on the wall of the plunger is known as the helix.
Due to the precise matching of pump plunger and pump barrel it is important that only complete plunger and barrel assemblies be replaced, under no circumstances just plunger or barrel alone.