How To Get The Air Out Of A Hydraulic Cylinder

How To Get The Air Out Of A Hydraulic Cylinder

Before you try to get out the air from any hydraulic cylinder it is very essential to know the type of air that is there in the hydraulics system.

Three types of air are kept in a hydraulic cylinder and they are - entrapped free air, dissolved air, and entrained mixed air.
You can bleed air from the hydraulic system but it can work only for free air pockets in which the air does not mix with the fluid.

If it is a dissolved air then you will be able to remove the air from the hollow ram hydraulic cylinders by raising the temperature of the fluid. Hence, you should continue to raise the temperature until the air gets released. This type of air is released only when it becomes necessary and an example of this type of air is the hydraulic oil that tends to be 10% dissolved air. The mixed air appears to be froth or foam and when it comes to the mixed air you need to pass the fluid through gauze or screen. This is mainly required to blow out the bubbles from the fluid that is there in the hydraulic system. 

Why it is necessary to get out the air from a hydraulic cylinder?

Air entering the hydraulic cylinder may cause several problems that will subsequently lead to system failure. You will find many manufacturers who think that getting the air out from the hydraulic system is not so essential. But as per expert engineers, it is better to get the air out from the hydraulic cylinder. This is because over time air will find its way to get out of the hydraulic system or it will get trapped in the oil. If the air gets trapped in oil then it will be transported back to the reservoir at some point in time. But the air trapped in the hydraulic cylinder can cause several mechanical damages which may ultimately lead to an erratic operation. 

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If there will be air contamination in the hydraulic cylinder then it will cause erosion because of oil collapsing under pressure. Apart from that, due to air trapped in the hydraulic system, it may decrease or lose the lubricity that causes scoring, abrasion, as well as other types of friction which will ultimately damage the surfaces. Moreover, the air contamination in the hydraulic cylinder will cause compression due to which the mixture of air and oil in the hydraulic cylinder may get ignited and burn the seal that may ultimately damage the hydraulic cylinder. 

There are many reasons why the manufacturers say that getting out the air from the hydraulic cylinder is not necessary and one of the biggest reasons may be because that if the cylinder gets damaged then they can sell the replacement parts since most of the parts do not comes under warranty. Apart from that, they may also say so because there is a chance of getting injured when the air bleeds out of the hydraulic cylinder for which they have to pay hundreds or thousands of dollars fine.  That is why they try to convince the people that it is not necessary to get the air out of the cylinder.

Ways to get the air out of a hydraulic cylinder

The following are some essential way about how to get the air out of the hydraulic cylinder:

Gathering supplies: The first thing that you need to do is to gather the necessary tools apart from the hydraulic fluid, tubing, clean materials, and empty bottles.

Working on the level surface: You have to make sure that the surface is at a level if you want to bleed the air easier.

Removing the parts and components: The next thing that you need to do is remove the parts and components from the system for accessing the line that is being bled easier.

Bleeding the farthest lines first: You also need to bleed the line farthest away from the ward as well as work inward. It should be with the lines that are closest to the pump that is bled last. Apart from that, it should only bleed one line at a time.

Keeping the reservoir filled: Before bleeding the air out of the hydraulic cylinder you must make sure that the fluid is in the reservoir. If the fluid does not remain in the reservoir at the time of bleeding then it will introduce more air into the lines and in such case, you have to start again.     

What are the precautions you should take while getting the air out of the hydraulic cylinder? 

When there is trapped air in the hydraulic cylinder often there is abnormal noise. This happens because when the air circulates through the hydraulic cylinder it gets compressed and decompressed which ultimately creates a bang or knocking noise. That is the reason why it is highly required to check out and do a careful inspection of the condition of the system fluid, components, seals so that if there are any signs of contamination or any chances of trapped air it can be identified.

It is also important to know that before the installation the displacement hydraulic cylinder should bled. This is because if any air gets trapped in the hydraulic system it will work as a gas shock absorber. That is the reason why the displacement cylinder should have a breather at the top for dispersing any air. 

Finally, when you will the new hydraulic cylinder you must make sure to check the potential air contamination since it may result in blowing the dirt wiper. Apart from that, the hydraulic cylinder may seal out of its housing extruding past the rod. Hence, if you consider all the things that are mentioned above you will be able to spot the bleeding trapped air early in the hydraulic system. In such a case, it will become possible for you to prevent any kind of damage in the long-term or any chances of operational downtime. 

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