How To Test A Hydraulic Cylinder

There are many methods that you can use to test a hydraulic cylinder to determine its function and detect issues. Some of these are simple like the end of stroke bypass test. However, you may not experience any problems if you buy a high-quality hydraulic cylinder but still, there are chances that components may arrive faulty or breakdown during use. These faults come up because of several reasons, for instance: 

• The hydraulic was designed and engineered from a low-grade material by the manufacturer

• The cylinder was forced to do work outside of its tolerance (the most common one)

• A mechanical fault may occur because of excessive use, like a leak.

In some cases, the faults are obvious and sometimes they are not. So, testing your hydraulic cylinder is an important and useful process to check and to eliminate serious faults. If still in doubt, you can consult a professional like ram mount dealers NZ before testing your hydraulic cylinder or swapping a component. As aforementioned, the cause of some mechanical failures is not easily understandable, so simply enhancing components may not solve the issue in some cases or it can even make it worse.


The Common Faulty Area

The common area, or you can say the part that goes wrong in a hydraulic cylinder, is the piston seal, especially in double-acting cylinders. This leakage often occurs because of intense pressure. Also, hoop stress is another common problem that causes ballooning in the cylinder barrel.


The End of Stroke Bypass Test

One of the simplest and effective ways to test hydraulic cylinders or spring ram is by using the end of a stroke bypass test. This test involves pressurizing a cylinder in a test circuit and on the other hand checking for leakages at the seal of the piston.

Leakage detection is done by measuring the difference in pressure between the piston and the cylinder rod side. For most of the units, the ideal ratio is 2:1 for the rod to cylinder. If you find any difference, then a leak is there.

Below is a simplified form of how to conduct the end stroke bypass test yourself:

1. The first step is to open the cylinder’s service ports and put them in the up position

2. Fill the cylinder with fresh hydraulic liquid by using the service ports

3. Create a test circuit by linking the ball valves, directional control valve and relief valve. Make sure to attach a pressure gauge to each end of the cylinder

4. Remove all air from both sides of the cylinder by using the directional control valve

5. After removing air, move the piston shaft into mid-stroke position

6. Apply deliberate pressure at the rod side, alter the relief valve settings until you see the pressure rating on the gauge

7. After pressurizing, centre the directional control valve and close the ball valve.

8. Note the readings displayed on the gauges at the piston seal end and the rod. Compare it with the ideal ratio 2:1 as already mentioned.


Testing regularly will allow you to establish standards for monitor changes and normal operating parameter changes over time. This will make sure that leaks are easier to be detected and the risk of any mechanical failure or any other dangerous outcome is surpassed.

In cases when there is a mechanical fault already, if you deliberately pressurize a hydraulic cylinder in a test environment, it can be hazardous. So, this test should be conducted only by fully trained engineers.

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