Hydraulic Clamping Fundamentals

displacement volume available from your power supply, the system will eventually compress the air in a system and build hydraulic pressure. However, if powering your system with a non-reciprocating power source such as a single shot air / oil booster, it may not have enough useable oil volume to replace the void caused by compressing the air. To bleed the air from a hydraulic system, connect to the power supply and fill with hydraulic fluid at as low a pressure as practical. While under pressure, loosen (crack) a fitting at the furthest point from the power supply and allow the foamy air to escape (as air is lighter than the liquid, it will tend to “migrate” to the highest point in the system, which is the next most common point to start bleeding from the system). Repeat the bleeding procedure at each device working your way back to the power supply, or lowest point in the system. Once you have bleed the system of air, more hydraulic fluid may need to be added to your power supply to compensate for the oil that has been lost during the filling of the system as well as bleeding procedure. To fill, and bleed the air from a system utilizing a screw pump, install a "T" fitting in the screw pump’s pressure outlet port (on block style pumps, the alternate side port may be used instead of installing an additional fitting). With the unused port of the "T" fitting unplugged, totally advance the screw pump piston (rotate hex clockwise) to push the air out of the screw pump pressure chamber. While retracting the screw pump piston (rotate hex counter clockwise), pour oil into the open port of the "T" fitting to fill the screw pump pressure chamber (alternately, connect any hand, air or electric pump to deliver fluid to the system).

Plug the open port of the "T" fitting and loosen (do not remove) the fitting connection at the device in the system that is furthest from the screw pump. Advance the screw pump piston, compressing the oil in the system and driving the air out at the loose device fitting. (If using alternate pump to pre-fill system, bleed air from the device fitting until fluid shows no signs of air bubbles escaping from the loosened fitting). Tighten the device fitting and repeat the process as necessary to purge the maximum amount of air as possible (bleeding the air from the system is complete when clear fluid is expelled at the loose fitting.

Hydraulic Clamping Fundamentals Rev - D

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