Fault diagnosis of hydraulic cylinder

Answer:

False action or malfunction There are several reasons for and how to handle it: (1) the core of the valve is jammed or blocked. When the flow valve or the directional valve core is stuck or the valve hole is blocked, the hydraulic cylinder is prone to malfunction or malfunction. At this time, the pollution of the oil should be checked. Check whether the dirt or colloid sediment is stuck or blocked valve holes; Check the body's wear and tear, clean, replace the system filter, clean the tank and replace the hydraulic medium. (2) piston rod and cylinder jam or hydraulic cylinder block. At this point, however, the hydraulic cylinder does not move or move very little. Then should check if the piston and piston rod seal is too tight, whether sediment into the dirt and glue: whether the axis of the piston rod and cylinder of the wearing parts and seal failure, whether the load is too big.

Do not drive the load at work The main reasons are: the stop-position of piston rod, insufficient thrust, falling speed, and unstable work. (1) internal leakage of hydraulic cylinder. The internal leakage of hydraulic cylinder includes hydraulic cylinder seal, piston rod and sealing gland seal and piston seal and the leakage of excess and so on. The reason of the piston rod and packing gland seal leakage, sealers crease, squeezing, tearing, wear, aging, metamorphism and deformation, etc., a new seal should be replaced at this time. The main cause of the piston seal overwear is that the speed control valve is misregulated, causing excessive backpressure and sealing parts or hydraulic oil pollution. The second is the quality of the material in the assembly and the sealing material. The result is that the action is slow and weak, and the damage of the piston and cylinder can be caused when serious, and the "pull cylinder" phenomenon occurs. The processing method is to adjust the speed control valve, and the control installation instructions should be done with the necessary operation and improvement. (2) leakage of hydraulic circuit. Includes valves and hydraulic pipe leaks. The repair method is through the control of the reversing valve and the leakage of the hydraulic connection line.

Hydraulic system control pressure is too low. The resistance of throttle in the control line may be too large, the flow valve is misregulated, the control pressure is not suitable, the pressure source is disturbed. The control pressure source should be checked at this time to ensure that the pressure is adjusted to the system. (4) air in the hydraulic system. The main reason is that there is a leak in the system. At this time, the liquid level of the hydraulic tank should be checked, the sealing parts and the pipe joint of the hydraulic pump suction side, and the oil suction strainer is too dirty. If this is the case, the hydraulic oil should be replenished, the sealing and the connection of the pipe should be processed, and the coarse filter will be cleaned or replaced. (5) the hydraulic cylinder initial movement is slow. In low temperature, the hydraulic fluid is large and the fluid is poor, causing the hydraulic cylinder to move slowly. Improved method is to replace glue good hydraulic oil temperature performance, can use in the low temperature heater heating or by machine itself to improve the oil temperature of startup, system normal working oil temperature should be kept at about 40 ℃

Seal quality is directly related to slippage or crawling. When the o-ring is used under low pressure, it is relatively easy to slip or crawl because of the difference between the high pressure and the friction resistance of the u-shaped ring. U-shaped seal surface increases with the increase of pressure as the pressure, although sealing effect also increase, but the dynamic and static friction resistance is larger, the difference between the internal pressure increases, the influence of rubber elasticity, the contact resistance is increased due to the lip margin, sealing ring will be tilting and lip edge elongation, also easy to cause slipping or crawl, can be used to prevent the tilting bearing ring keep its stability. 4. Hydraulic cylinder body inner hole surface scratch and the adverse effects of rapid repair method: (1) scratches grooved extrusion materials scrap foam can embed seals, runtime to work in the damaged seal parts at the same time, may cause new scratch area road. To make the surface roughness of the inner wall of the cylinder, increase the friction and make it easy to creep. The internal leakage of the hydraulic cylinder increases the efficiency of the hydraulic cylinder. The main reasons for the scratches on the inside of the cylinder are as follows.

The piston slides or crawls Hydraulic cylinder piston slippage or crawling will make hydraulic cylinder work unstable. The main reasons are as follows: (1) the internal astringent of the hydraulic cylinder. Inside the hydraulic cylinder parts, assembly parts deformation, wear or shape tolerance overrun, resistance is too large, the hydraulic cylinder piston speed as stroke position varies, slip or crawl. Most of the reason is that because of the poor assembly quality, the surface has a wound or sintered iron filings, which makes the resistance increase and the speed decreases. For example: piston and piston rod are different heart or piston rod bending, hydraulic cylinder or piston rod is the position deviation of the guide, the sealing ring is carried too tight or too loose. The solution is to repair or adjust, replace damaged parts and remove iron filings. (2) poor lubrication or hydraulic cylinder bore. Because the piston and cylinder, guide rail and the piston rod are relative motion, if the aperture is super bad, bad lubrication or hydraulic cylinders will aggravate the wear, reduce the centerline of the cylinder linearity. In this way, when the piston is working in the hydraulic cylinder, the friction resistance will be small when it is large, causing slip or crawling. The method of elimination is to repair the hydraulic cylinder first, and then the piston, the piston rod, and the guide sleeve should be adjusted. (3) the hydraulic pump or hydraulic cylinder enters the air. Air compression or expansion causes the piston to slip or crawl. The elimination measures are to check the hydraulic pump, set up special exhaust, and operate the whole trip round and back several times.