Beside undesirable operational characteristics such as jolting movement, air may also cause damage to the hydraulic cylinder and its sealing elements.
If hydraulic oil containing air bubbles is compressed very quickly, the bubbles heat up so much that the air-gas mixture could spontaneously combust. This causes a very high local increase in both pressure and temperature which may damage the seals. This is called the Diesel effect.
Also, a cylinder filled with nothing but air in the cushioning is not functional. Even a single extraction at full operating speed may damage the cylinder.
Prior to start-up, cylinders must be vented manually.
The venting process
Venting of hydraulic cylinders is vital for a correct function. By cycling the cylinder several times over the entire stroke in both directions at the lowest possible pressure, the air is purged and residual air is dissolved in the medium and transported to the tank. The venting screws are designed in such a way that they only have to be unscrewed by one turn to allow the air to escape.
Usually, hydraulic cylinders are provided with special venting screws on both sides.
The venting holes are suitable for measuring couplings and for the application of venting sets. With the Hänchen venting set, a hydraulic cylinder can be vented cleanly and conveniently without additional tools and without leaks or drops.
Venting set
If measuring couplings are attached in the venting ports of the hydraulic cylinder, the venting set can be plugged in directly.
The Hänchen venting set consists of
• Wide neck bottle with air filter G1/8
• Measuring hose M16x2 for measuring coupling