4 ødeleggende hydrauliske gripefeil du må kjenne til

28. august 2024

The maintenance of hydraulic grabs for cranes is essentialto ensure their normal operation and extend the service life of the equipment. Hydraulic grabs are often prone to various failures when used in work. Most of the hydraulic grabs failures of common crane hydraulic systems in equipment are caused by overheating of hydraulic oil, air intake, pollution, and oil leakage. Due to the failure of the hydraulic system, the failure of the main system will directly lead to the failure of the main system, resulting in more serious economic losses. Therefore, it is important to analyze the causes of these hydraulic grabs failures and take corresponding preventive measures. This article will introduce 4 common failures and their repair methods in detail.

Hydraulic Grabs Failure 1: Air enters the hydraulic system

AIR 1

Cause hydraulic grabs failure:

  • Hydraulic grabs cylinder piston moving position.
  • The hydraulic cylinder of the hydraulic grabs vibrates or even makes abnormal noises.
  • The hydraulic cylinder of the hydraulic grabs produces local strain and sintering.
  • As a result, the centerline of the hydraulic cylinder of the hydraulic grabs is not parallel to the guide rail of the guide sleeve and is skewed.
  • The volumetric efficiency of the hydraulic pump of the hydraulic grabs decreases, the energy loss increases, and the hydraulic system cannot exert its due efficiency.
  • The thermal conductivity of the hydraulic oil in the hydraulic cylinder of the hydraulic grabs deteriorates, and the oil temperature rises, causing chemical changes.
ReasonSolution
Air is inhaled due to loose joints or damage to oil seals and sealing rings.Each joint should be fastened firmly and ensure that the fuel tank is well sealed, to prevent external air from entering and polluting the system, and exhausting at the same time.
The oil-absorbing pipeline and the pipeline connecting the system are worn, scratched, or corroded, causing air to enter.Reasonably design the structure of the hydraulic system to rationalize the layout of the pipeline.
Air bubbles generated by inattention during refueling are brought into the fuel tank and mixed into the system.Exhaust treatment is required to keep the pipeline clean and reduce external corrosion.
Foreign objects and moisture are mixed in the hydraulic cylinder, resulting in local strain and sintering.The inner wall of the cylinder needs to be polished and the cause of foreign matter mixing needs to be found.
Improper installation of the hydraulic cylinder results in the centerline and the guide rail of the guide sleeve not being parallel. Need to reinstall.
The sports seal is too tight. Need to adjust the seal.
The piston and piston rod have different shafts.Need to be corrected according to the installation instructions.
The guide sleeve and the cylinder are not on the same axis.Need to be corrected according to the installation instructions. 
The piston rod is bent.You need to follow the installation instructions to straighten the piston rod.
The cylindrical degree of the inner diameter of the cylinder is extremely poor.Need to boring and grind cylinder cylinder, re-match the piston.
The sliding surface fits too tightly or the surface is brushed.Need to sharpen the sliding surface.
If the piston seal is damaged, the oil in the high-pressure chamber will quickly drain back to the low-pressure chamber, making a “roar” sound.Piston seals need to be replaced.

Hydraulic Grabs Failure 2:Hydraulic system pollution

Hydraulic system pollution

Cause failure:

  • Pollutants will clog the hydraulic components of the hydraulic grabs in and out of the oil or gaps between them, causing movement failure, affecting working performance or causing accidents.
  • It may also cause clogging of the filter and may cause the filter to completely lose its filtering effect, , causing a vicious circle of the hydraulic system of the hydraulic grabs.
  • The hydraulic oil and water of the hydraulic grabs are mixed.
ReasonSolution
There is a lot of dust in the operating environment, and the outside of the system is not clean.When the hydraulic system is operating in a site with serious dust pollution for a long time, try to filter the oil once every 2 months, and replace the oil inlet filter once in about half a year.
Impurities are brought into the system during refueling, oil surface inspection, and maintenance operations.During maintenance, pay attention to the cleanliness of the oil cylinder and try to carry out it in a dust-free environment.
If the temperature is too high, the hydraulic oil will deteriorate. If the temperature is too high, the speed at which the hydraulic oil will deteriorate will be accelerated.If this happens, the electro-hydraulic grab should be cooled down.
Hydraulic oil and water are mixed, and if there is water in the hydraulic system, this phenomenon will be caused.The sealing of the hydraulic system of the electro-hydraulic grab should be checked.
If there are impurities in the fuel tank of the electro-hydraulic grab, the hydraulic oil will be contaminated by impurities and deteriorate.Check and maintain a clean environment in the fuel tank in time, and check regularly.

Hydraulic Grabs Failure 3:Hydraulic system oil leakage

Hydraulic system oil leakage

Cause failure:  

  • The hydraulic cylinder of the hydraulic grabs can move, but the speed of movement is too slow. 
  • Once a serious leakage occurs in the hydraulic system of the hydraulic grabs, the pressure of the system will be insufficient, causing the bucket to fail to open and close normally.
  • Hydraulic oil leakage can also cause environmental pollution, affect production, and even have serious consequences that cannot be estimated.
ReasonSolution
The brutal operation of hydraulic components in the assembly, excessive force will deform the parts, especially by beating the cylinder block and sealing flange with copper rods, etc.Full attention should be paid to the design and processing of sealing parts in the design and processing links.
To choose the correct assembly method. 
Parts are damaged by collision during work, which will scratch the sealing element and cause leakage.Choose the right seal to extend its aging time.
Pay attention to the protection of the seal to avoid it being scratched by other parts.
There are dust and impurities in the use environment and leakage occurs if a suitable dust-proof seal is not selected.When selecting and designing seals, consider the compatible type of hydraulic oil and sealing material, load conditions, working speed, changes in ambient temperature, etc., and choose reasonable seals and suitable dust-proof seals.
Parts are deformed or damaged.Need to be corrected or replaced directly.
The oil supply of the hydraulic pump is insufficient, causing the pressure to not go up.Troubleshooting the hydraulic pump.
Caused by excessive system leakage.Check the sealing performance of each component and pipeline.
There are rod cavities and rodless cavities in the cylinder, that is, part of the pressure oil in the high-pressure chamber leaks from the piston seal to the low-pressure chamber.The piston sealing assembly needs to be replaced.
The cylinder or piston of the oil cylinder is over-worn.You need to consider whether to sharpen it or replace it directly.

Four leakage methods of hydraulic system

  • Gap leakage:There are two main types of gap leakage in the hydraulic system of construction machinery, leakage at the fixed seal (static joint surface) and leakage at the moving seal (dynamic joint surface). The leaking parts of the fixed seal mainly include the joint between the cylinder head of the hydraulic cylinder and the cylinder; the motion seal mainly includes the piston of the hydraulic cylinder and the inner wall of the cylinder cylinder, between the piston rod and the cylinder head guide sleeve. The size of the gap leakage is related to factors such as pressure difference and gap.
  • Porous leakage:Various cover plates in hydraulic components, due to the influence of surface roughness, it is impossible to fully contact between the two surfaces. In the microscopic depressions where the two surfaces are not in contact, many voids of various cross-sectional shapes and varying sizes are formed. The cross-sectional size of the voids is related to the surface roughness. Multiple voids leak and the liquid needs to flow through many curved voids. During the sealing performance test, it takes a certain holding time before the leakage can be revealed.
  • Mucus attachment leakage:There is a certain adhesion between the viscous liquid and the solid arm. After the two come into contact, a thin layer of liquid is adhered to the solid surface. If the film on the solid surface is thicker, the oil film will be scraped off by the sealing ring due to mutual movement. Adhesion leakage. The basic way to prevent adhesion leakage is to control the thickness of the liquid adhesion layer.
  • Power leakage:On the sealed surface of the rotating shaft, if there are traces of spiral processing when the shaft rotates, the liquid flows along the groove of the spiral trace under the action of the rotating force of the rotating shaft. If the direction of the spiral trace is consistent with the direction of rotation of the shaft, power leakage will occur due to the “pump oil” effect of the spiral trace. The characteristic of power leakage is that the higher the speed of the shaft, the greater the leakage. To prevent power leakage, the presence of “pump oil” processing traces on the sealing surface of the shaft and the lip of the sealing ring should be avoided, or the principle of power leakage should be used, and the oil pumping effect of spiral traces should be used to pump the leaking oil back to prevent leakage.

Regarding the leakage method, you can refer to this article to learn more:Leakage and its effects in various hydraulics driven system

Hydraulic Grabs Failure 4 : Hydraulic oil overheating

Hydraulic oil overheating

Cause failure

  • The viscosity of the hydraulic oil and the working efficiency of the hydraulic system have all decreased, and even the machinery and equipment cannot work properly in severe cases.
ReasonSolution
The ambient temperature is too high, and the high load is used for a long time, which will make the oil temperature too high.It should be avoided to work continuously and under heavy loads for a long time. If the oil temperature is too high, the equipment can be operated at no load for some time, and then work after the oil temperature drops.
The heat dissipation performance of the fuel tank is poor, causing the oil temperature in the fuel tank to be too high.The volume of the fuel tank, that is, the heat dissipation area, should be increased, and an oil cooling device should be installed.
Improper selection of hydraulic oil, the quality and viscosity grade of the oil does not meet the requirements, or the mixing of different grades of hydraulic oil causes the viscosity of the hydraulic oil to be too low or too high.Choose hydraulic oils that meet the standards, and do not mix two brands of hydraulic oils.
The environment of the construction site is harsh. With the increase of the working time of the grab crane, the oil is easily mixed with impurities and dirt. The contaminated hydraulic oil enters the mating gap of the pump, motor, and valve, which will scratch and destroy the accuracy and roughness of the mating surface, causing leakage to increase and the oil temperature to increase.Regularly overhaul the grab, replace the new hydraulic oil in time, and keep the oil in the hydraulic cylinder clean.

Understanding the common failures of these 4 hydraulic grabbers can not only help you respond quickly when problems occur, but more importantly, it can ensure the safety and efficiency of operation.Through regular maintenance and timely resolution of these problems, you can extend the service life of your equipment, reduce downtime, and increase productivity.

If you want to learn more about how to optimize the performance of grab cranes or need professional repair and maintenance services, please contact us immediately. Let us help you keep your essential touipment in the best condition and ensure the smooth operation of your business!

cindy
Cindy
Hva skjer: +86-19137386654

Jeg er Cindy, med 7 års arbeidserfaring i kranindustrien og samlet et vell av faglig kunnskap. Jeg har valgt de tilfredsstillende kranene for 1000+ kunder. Hvis du har behov eller spørsmål om kraner, ta gjerne kontakt med meg, jeg vil bruke min ekspertise og praktiske erfaring til å hjelpe deg med å løse problemet!

TAG: traverskran,grab gantry crane,hydraulic failure,overhead kran

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