Why should you bleed a hydraulic cylinder?

To keep your hydraulic cylinders working efficiently and safely, it is important to bleed them. Air and debris tend to build up in the cylinder which will degrade the components in the system and increase the risk of malfunctions and damage.  

Hydraulic cylinders are not meant to hold pressurised air only pressurised fluid. This air can contaminate the hydraulic fluid via the pump’s inlet causing aeration, cavitation and/or foaming to occur.  Cavitation causes small vapour filled bubbles which will contaminate the system and will possibly implode when compressed. Foaming causes the equipment to operate erratically as the pump takes in large volumes of air along with the oil.  

When the hydraulic fluid is contaminated this affects other components in the system as well as dramatically changes how the cylinders work.  

Air in the hydraulic cylinders heat up when compressed and can create a dangerous chain reaction. The warm compressed air can dry out lubrication, burn seals and initiate cavitation which leads to the metal components’ erosion. The hot air can even cause hydraulic cylinders to explode if the air mixes with oil in a process known as dieseling.

Hydraulic systems are designed to work with pressurised liquid, knowing how liquid is meant to behave. However, air does not behave in the same way. When air bubbles gather in the cylinders they break up the flow of the smooth fluid, disrupting its behaviour. Think of the brake system on a car; if air gets into the system the brakes will not work as precisely and as responsive as it should creating a risk factor. Bleeding air from hydraulic cylinders in a brake system for cars and arge vehicles such as trucks is very important for road safety.  

Bleeding should take place when abnormal noises occur – this often indicates when there is air in the system. As the air circulates through the system it compresses and decompresses which causes a knocking sound.  

Power Team SA, suppliers of quality hydraulic components and accessories, believes in the maintenance of all hydraulic components and systems – old and new to get the best out of it. By knowing how to maintain hydraulic components the life expectancy of the equipment is extended, doing its job effectively and efficiently for longer.  Power Team SA are always on hand to discuss any hydraulic maintenance questions and through their years of experience, Power Team SA is able to aid in all situations no matter the industry or the equipment.