A perfectly functioning hydraulic system is crucial for the performance and longevity of a scissor lift table. However, as soon as air enters the system, this can cause malfunctions and loss of performance.
Correct bleeding ensures that your lift table works efficiently and safely. Read on to find out the most important aspects of bleeding!
How does air get into the hydraulic system?
Air can enter the hydraulic system of a scissor lift table in various ways. The most common causes are:
1. Loosening of hose connections
Whenever a hydraulic connection is loosened, there is a risk of air entering the system.
2. Refilling hydraulic oil
If hydraulic oil is filled too quickly or improperly, it can foam up and trap air bubbles. These bubbles only escape slowly, which can lead to loss of performance and malfunctions. Therefore, refilling should always be carried out slowly and in a controlled manner.
3. Maintenance and repair work
Work such as replacing seals, cleaning valves or retightening hydraulic fittings can introduce air into the system unnoticed. It is particularly important to bleed the system after replacing seals in order to avoid air pockets.
4. Microcracks in hoses or seals
Hydraulic hoses and seals age over time. UV radiation, mechanical stress and strong temperature fluctuations can cause tiny cracks. Even if no oil is leaking, air can be sucked into the system through these cracks.
5. Loose connections
If hydraulic screw connections or other connections are not properly tightened, small leaks can occur, allowing air to enter the hydraulic system.
6. Outgassing of the hydraulic oil
Hydraulic oil always contains a small amount of dissolved air. Strong temperature fluctuations or overheating can cause this air to settle as bubbles in the system.
7. Defective hydraulic pump
A worn or damaged hydraulic pump can draw air into the system on the suction side or at the shaft seals. Signs of this are:
- irregular movements of the lift table
- loss of power
- increased noise development
8. Oil level too low
A low hydraulic oil level can cause the pump to suck in air and introduce it into the system. This is one of the simplest causes of air pockets - and can be easily avoided by regularly checking the oil level.
In addition, a low oil level can lead to overheating, which accelerates wear on the pump and cylinders.
How does air in the hydraulic system make itself felt?
Air in the hydraulic system can significantly impair the function of a scissor lift table. Typical signs of air pockets are:
- Spongy response behavior: The lift table reacts with a delay when the hydraulic motor starts up.
- Irregular movements: Sudden changes in lifting or lowering speed.
- Noise development: Loud bubbling or knocking indicates air bubbles in the system.
- Vibrations: Noticeable shaking during operation of the lift table.
If one or more of these symptoms occur, the hydraulic system should be bled immediately.
What problems do air pockets cause?
Air in the hydraulic system of a scissor lift table can impair the functionality and service life of the components. The most common problems include:
1. Inaccurate movements
As air is much more compressible than hydraulic oil, power transmission is imprecise. This can lead to fluctuating or uneven stroke movements, which are particularly problematic in precision applications.
2. Cavitation and material damage
Air bubbles in the hydraulic system can expand in areas with low pressure (e.g. on the suction side of the pump) and collapse again when the pressure rises. This phenomenon generates microscopic shock waves that can damage the material of the pump and other components.
3. Noise and vibrations
Typical signs of air pockets in the hydraulic system are bubbling, knocking or humming noises. These are not only annoying, but can also be an early warning sign of impending damage to the pump or other hydraulic components.
4. Corrosion due to moisture ingress
Air contains moisture that can collect in the hydraulic system. This moisture promotes the corrosion of metallic components. It is particularly critical that rust particles are distributed in the hydraulic oil and can damage valves, seals and pumps.
5. Safety risks due to uncontrolled movements
Uncontrolled or delayed movements of the scissor lift table pose a considerable safety risk. This is particularly critical in applications where people are working with the lift table. Unexpected movements can lead to injuries or accidents.
6. Uneven lifting movements with multiple cylinders
In the case of scissor lift tables with several hydraulic cylinders, air in the system can cause the cylinders to be supplied with uneven pressure. This causes the lift table to lift asymmetrically, which places an uneven load on the structure. This increases the mechanical stress on individual components and can lead to their failure in the long term.
7. Foam formation and decreasing lubricity
If air remains in the hydraulic system for a long time, it can lead to foam formation. This foam not only impairs the efficiency of the hydraulic fluid, but also reduces its lubricity. Insufficient lubrication increases wear on pumps, cylinders and valves and, in the worst case, can lead to failure of the entire system.
How do you bleed the hydraulic system of a scissor lift table?
Hydraulic lift tables work with closed hydraulic circuits in which air cannot escape by itself. Manual bleeding is therefore required.
Step-by-step instructions for bleeding our scissor lift tables:
Attention: For lift tables with several cylinders, all cylinders must be bled in sequence!
- Switch on the lift table.
- Position the maintenance supports.
- Raise the table to its maximum height.
- Slightly open the bleed screw on the cylinder (highest point) until oil escapes. Collect the escaping oil with a cloth.
- As soon as only bubble-free oil escapes, close the bleed screw.
- Lower the table onto the maintenance supports and raise it again.
- Repeat the bleeding process until no more air escapes.
- Remove the maintenance supports.
- Bring the table to a resting position and check the oil level. If necessary, top up with hydraulic oil.
- After bleeding, carry out a few test movements to ensure that the lift table is working smoothly.
Conclusion
Air in the hydraulic system of a scissor lift table can cause inefficient operation, uncontrolled movements and even safety risks. Regular maintenance and professional bleeding are crucial to avoid these problems and extend the service life of the lift table.
ℹ️ Tip: Pay attention to the typical causes and symptoms of air pockets to keep your hydraulic system in optimum condition at all times.
Comments (0)
No comments found!