Crane and Hoist Canada

Troubleshooting hydraulic cylinder drift

March 22, 2023  By Emily Newton

Emily Newton

Keeping your hydraulics working is crucial for crane operators

What is the easiest way to find the cause of hydraulic cylinder drift? The most straightforward approach is applying the process of elimination to the most common causes. Here’s how mechanics can identify and recognize them.

Identifying Hydraulic Cylinder Drift

Hydraulic cylinder drift occurs when a cylinder can’t achieve hydraulic lock. This can happen for various reasons, but it typically has something to do with a fluid leak. Failed seals anywhere in the cylinder can be responsible for a leak, although multiple causes exist.

When a piece of machinery is experiencing hydraulic cylinder drift, the cylinder will often droop or sink downward outside normal movement. Since fluid is leaking somewhere in the system, the cylinder can’t maintain the pressure required to support force on it as usual. Cylinder drift leads to poor equipment performance and poses a serious safety risk. There are a few key symptoms to look out for.

Symptoms of Hydraulic Cylinder Drift

Different cylinder types will present various symptoms of drift. This is important to keep in mind since how a drift presents itself can say a lot about what is causing the issue.


Special Case: Double-Acting Cylinders

Some types of cylinders are more difficult to diagnose than others. For example, double-acting cylinders can have a failed port seal that causes cylinder drift but goes unnoticed. A double-acting cylinder can still tenuously achieve hydraulic lock unless another seal fails.

As a result, cylinder drift can go unnoticed for longer in double-acting cylinders. The main symptom to look out for is unusual fluctuations on the pressure gauge. The pressure may rise and dip erratically as the malfunctioning cylinder attempts to establish hydraulic lock after momentary drift.

It may be more immediately noticeable when a single-acting cylinder, such as a tie-rod, experiences drift. There are several main symptoms to look out for, particularly jerky or uneven motion. This could feel like the cylinder slipping as it tries to bear a load.

Failed piston seals can be similarly difficult to spot, even in single-acting cylinders. If a cylinder is experiencing drift but there’s no immediately obvious cause, keep an eye on the pressure gauge. Abnormally high pressure can hint at an internal issue, such as a piston seal failure.

Single-Acting Hydraulic Cylinder Drift Symptoms

It may be more immediately noticeable when a single-acting cylinder, such as a tie-rod, experiences drift. There are several main symptoms to look out for, particularly jerky or uneven motion. This could feel like the cylinder slipping as it tries to bear a load. The movement is caused by the drop in pressure when the cylinder can’t achieve hydraulic lock.

Unusual motion doesn’t have to be jumpy, though. Never ignore any slow drifting or slipping. Drooping cylinders are a common sign of a drift issue. One cylinder may be unable to evenly support the load in equipment that uses multiple cylinders, indicating potential drift.

Finally, always take fluid leaks seriously. Excessive or persistent leakage often indicates that hydraulic drift occurs due to a failed seal. This applies to double-acting cylinders, as well.

Troubleshooting and Repair Strategies

There are a few main causes of hydraulic cylinder drift. Checking a few mechanical components should reveal what’s happening in a specific cylinder. Note any known leaks and the type of irregular movement the cylinder is experiencing.

Contaminated Hydraulic Fluid

One of the first things any mechanic should do when investigating cylinder drift is check the hydraulic fluid itself. Contaminated fluid can ruin seals over time and cause erratic motion from improper viscosity. The most common contaminants include water, air, particulate debris and chemicals.

Anything that isn’t the intended hydraulic fluid can cause cylinder malfunctions. Cylinders are designed to pressurize a certain kind with specific qualities, but contaminants cause alterations that lead to pressurization issues. There are many possible causes for fluid contamination, including poor maintenance practices, wear and tear of other parts, and improper fluid storage.

One of the first troubleshooting steps should be to service the faulty cylinder and refill it with fresh hydraulic fluid. Double-check the manufacturer’s recommended type since the wrong kind can also cause cylinder drift. It’s important to take extra care when cleaning and refilling the cylinder to ensure fresh contaminants don’t sneak in with the new fluid.

Failed Rod Seal

A failed seal rod is one of the most common causes of cylinder drift. This malfunction is often hard to miss since it tends to cause noticeable fluid leakage and may even spray fluid. Failed rod seals have distinct drift behaviour, as well. The cylinder may initially drift but eventually stabilize when the rod stops moving.

The rod seal is probably due for replacement if the cylinder demonstrates this drift-and-halt motion. It’s a good idea to check for fluid contamination during replacement and refill the cylinder with clean hydraulic fluid. Double-check the manufacturer’s specifications to verify that the right replacement seal is used. Incorrect or poorly installed seals can cause hydraulic cylinder drift.

Valve Leak

A hydraulic cylinder’s valve seals are directly responsible for maintaining pressure, so they can easily cause drift. There are many possible reasons why a valve seal could fail, including worn-out parts and contaminated fluid. A leaky seal compromises pressurization, leading to the slipping experienced in cylinder drift.

Cap-side valve seals tend to be the more common causes of cylinder drift. However, rod-side valve leaks can also cause it in certain situations. This happens most often in cylinders oriented with the rod side downward.

Valve leaks can be tricky to catch since various issues can cause a seal to fail. For example, poorly manufactured valves are more likely to use cheap seals or include less precise machining. A low-quality valve can leak from the first day it is installed. Similarly, installing the wrong type can cause improper performance, including cylinder drift.

The hydraulic fluid itself can also cause valve seal failure. Contamination can break down the internal components of any cylinder, leading to mechanical failure. The longer contaminated fluid goes unchecked, the more likely a seal will fail.

Perform a thorough inspection of the valves if they’re the suspected cause of drift. It’s a good idea to double-check the hydraulic fluid for contamination. Check each valve for any possible mechanical issues before inspecting the seals. Damaged seals should be fairly easy to notice, but keep an eye out for any chips, nicks or material decay. Check for contaminants and debris, as well.

If the cylinder is still experiencing drift after replacing the valve seals and checking the hydraulic fluid, there could be another mechanical issue.

When in Doubt, Trace the Fluid Exit Path

One of the simplest ways to troubleshoot hydraulic cylinder drift is to trace the fluid exit path. It’s usually due to some type of leak, except for contaminated hydraulic fluid. Finding it is all about observation.

If it isn’t immediately obvious what is causing the cylinder drift, test the cylinder as safely as possible and monitor how the fluid is moving. After each test round, check every possible exit point for signs of leakage. Eventually, it should become clear where fluid is being pushed out of the cylinder, revealing the failed part.

Keep in mind the possibility of an internal leak, as well. They usually show up on the gauge as erratic pressure changes.

Repairing Hydraulic Cylinder Drift

Hydraulic cylinder drift can happen in any piece of machinery. The important thing is to pay attention to the key signs and catch the problem early. Troubleshooting involves eliminating the most common causes until the right one is found. Prioritize good maintenance practices after making repairs to help prevent further problems.

Emily Newton

About the author: Emily Newton is the Editor-in-Chief of Revolutionized Magazine. She regularly covers news and trends in the construction and industrial sectors.

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