Hydraulic Cylinder Troubleshooting: Why Your Cylinder is Drifting/Creeping

Hydraulic cylinders are among the most important components of mobile and industrial equipment that are designed to hold the position or support the weight with precision. If you notice the cylinder moving slowly (or drifting/creeping) even though it's supposed to be stable, it's an indication of a leak within the internal structure. The drift can be dangerous, decrease efficiency at work, and also waste energy.

Finding the root of cylinder movement is vital to ensure a successful repair. This article outlines the most common causes and ways to recognize them.

The Four Principal Reasons for Cylinder Drift

Cylinder drift happens because high-pressure fluid has escaped an internal seal and thereby equalizes that pressure across the rod and piston sides, which allows loads to be moved.

1. Problems with Piston Seals (Internal Cylinder Leak)

This is the main reason for piston drift. The piston seals were designed to stop fluid from flowing from the high-pressure side of the piston to the lower-pressure side. In time, heat, wear, and dirt degrade these seals.

• The How To Test (The Isolation Test):

  1. Completely extend or retract the rod (e.g., expand and retract the rod).

  2. The cylinder is isolated by closing off the flow at the cap and rod ports (usually with a shut-off valve located near the inside of the cylinder).

  3. Be sure to check the Cylinder.

  4. When the piston is still slipping or sputtering after it has been isolated, the issue is almost likely to be related to the piston seal. The fluid is flowing past the damaged seal, causing the cylinder to drift.

2. Diritial Control Valve (DCV) Spool

The valve that controls direction is responsible for controlling fluid flow towards and away from the cylinder. In a neutral or hold position, its internal spool seals pathways of flow. In the event that its seals have been damaged or the spool/bore has worn down, a small amount of fluid could leak.

• What to test:

  1. Conduct your Test of Isolation in the manner described in the previous paragraphs.

  2. In the event that the cylinder ceases to drift after the lines have been separated, then the leak occurs in the downstream of the cylinder, usually the DCV. Fluid is leaked into the valve's spool, which allows for the movement of the cylinder.

  3. Notice: This is a typical issue with older spool-type valves. Removing or replacing the valve is essential.

3. Pilot Operated Check Valve, or failure of the load-holding valve

Load-holding valves (often an operator-operated check valve and counterbalance valve) are designed to secure the cylinder and stop sudden drops, particularly when used in mobile equipment or for applications that involve massive loads.

• The reason for failure: These valves can fail when the seals have been damaged or when dirt (like pieces of debris) is deposited on the seat surface, hindering the valve from closing and retaining the pressure.

• What to test:

  1. When the DCV isolation test results are negative (meaning that the DCV is in good working order), be sure to focus on the valve that holds the load.

  2. Find signs of leakage from the outside around the body of the valve or perform tests for the decay of pressure on the valve.

  3. Troubleshooting Tips: If the drift is not consistent, look for any debris or contamination within the valve.

4. External leaks (Less Common Cause of Drift, however important)

Although external leaks are primarily responsible for the loss of fluid in the system, as well as pressure major water leak from the high-pressure part of the unit may cause drift because it allows the pressure to drain away more quickly than the pump could be able to compensate.

• Where to Look: Inspect all hose fittings, rods, and seals (wiper seals) for obvious leakage of hydraulic fluid.

• Safety Warning: Never use your hands to look for tiny high-pressure leaks. Utilize a piece of wood or cardboard, because pinhole leaks could cause an injury to the body caused by a fluid.

Prevention is the Best Cure

To reduce the drift of your cylinders and extend the longevity the life of hydraulic parts:

1. Maintain Cleanliness of Fluids: The most common cause of contamination is the leading cause of destruction of valves and seals. Make sure you have a strict filtering system and regular oil analysis.

2. Regular visual checks: Look for scoring on the rod of the piston, indications of leaks outside, and listen out for unusual sounds of operation.

3. Use the right fluid: Ensure you are using the right type and viscosity of hydraulic fluid, as recommended by the manufacturer.