Why does the hydraulic cylinder have a jerky feeling when descending?
4 Answers
Hydraulic cylinder descending with a jerky feeling is due to incomplete air discharge and excessively tight dimensional fit. Below is the relevant introduction to hydraulic cylinders: 1. Common faults: The common faults of hydraulic cylinders mainly include crawling, insufficient thrust, reduced working speed, or even complete stoppage. Crawling usually occurs during low-speed operation. The main reason is that the air accumulated in the cylinder has not been completely discharged. In addition, excessive or uneven mechanical friction can also cause crawling. For example, misalignment between the piston and piston rod, bending of the piston rod over its entire length or locally, poor linearity of the cylinder bore, drum-shaped or significantly tapered cylinder body, reduced smoothness or scoring inside the cylinder, excessive installation precision deviation of the cylinder, excessively tightened nuts at both ends of the piston rod causing misalignment, or overly tightened oil seals leading to excessive friction can all cause crawling. 2. The reasons for insufficient thrust, reduced speed, or stoppage of the hydraulic cylinder include: excessively small fit clearance between the cylinder and piston or misalignment between the O-ring sealing groove on the piston and the piston itself, causing the sealing ring to be improperly positioned when the oil seals are installed at both ends of the cylinder, with one side excessively compressed, making the piston stiff and increasing friction resistance; bending of the piston rod or excessively tightened oil seals at both ends of the piston rod leading to excessive friction resistance, etc.
I've been driving forklifts for over a decade and often experience that jerky feeling when the hydraulic cylinder descends – it's truly unpleasant. The main causes could be insufficient hydraulic oil or contaminants mixed into the oil, clogging the filter screen and causing flow issues; or air bubbles entering the system, leading to uneven compression and release that results in jerky movement. If the seals inside the cylinder are worn or aged, the piston won't move smoothly, causing fluctuating resistance. I suggest you first check the oil level and color – top it up if low, replace if dirty; start the machine and slowly raise/lower it a few times to purge air bubbles. Don’t forget to check for oil leaks – loose valve components can also affect performance. Addressing issues early saves headaches, otherwise prolonged neglect can damage the pump or cylinder, making repairs much harder. For routine maintenance, inspect oil quality and seals every 2-3 months, and avoid sudden drops when operating – smooth, steady movements are better. Developing these habits significantly reduces sudden breakdowns, making operation safer and more worry-free.
As someone who enjoys tinkering with machinery, I believe the jerky descent of hydraulic cylinders is likely caused by system instability. Delayed response from control valves can block oil flow output, resulting in discontinuous movement; internal wear in the pump can cause fluctuating pressure, leading to jerky motion. If there are small air bubbles in the cylinder, they compress like bursting balloons, impacting piston movement. Bent piston rods or damaged seals can also increase uneven resistance. I recommend using a pressure gauge to check the system pressure—large fluctuations indicate a problem; inspect whether the solenoid valve is functioning properly and try cleaning valve body impurities. Listen carefully to the pump's sound during operation—if there's any abnormal noise, repair it promptly. When adding hydraulic oil, always use the manufacturer-recommended type and ensure pipe connections are tight and leak-free. Addressing these small details not only prevents jerky motion but also extends the lifespan of the entire hydraulic system, making operation much smoother.
From a safety perspective, hydraulic cylinder jerking during descent is highly dangerous, especially when lifting or lowering loads, as sudden stuttering can lead to accidents. This is typically caused by insufficient or leaking hydraulic fluid disrupting supply, or air bubbles accumulating and causing uneven movement. If such issues are detected, the equipment should be stopped immediately. First, check if the oil level is normal and seal any leaks promptly. Slowly raising and lowering the cylinder several times can help expel air bubbles. Do not delay—seek professional maintenance personnel to diagnose the problem, as ignoring it may worsen damage or increase accident risks. Simple maintenance like regular oil changes and pipeline inspections can also prevent such issues proactively.
