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Common Failures And Cause Analysis Of Hydraulic Hoses

Common Failures And Cause Analysis Of Hydraulic Hoses

  • Categories:Company News
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  • Time of issue:2021-04-03
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(Summary description)Common Failures And Cause Analysis Of Hydraulic Hoses


Hydraulic hose is an important part of construction machinery such as concrete pumps, excavators, loaders, etc. However, it is often not valued by people. When there are leakage, cracks, cracks, loosening and other faults in use, it is often not analyzed The reason for the failure is simply to replace the hose, and the same failure will be repeated shortly after use. The loosening or rupture of hydraulic hoses not only wastes oil and pollutes the environment, but also affects work efficiency, and even causes accidents, endangering the safety of humans and machines.
 
Reasons for failure analysis of hydraulic hoses: improper use, unreasonable system design and unqualified hose manufacturing, etc.
 
I will discuss it in detail below based on my experience in actual work.
 
First, analyze the characteristics of the pipe. The hoses are divided into rubber hoses and plastic hoses. Plastic hoses are cheap and easy to install, but they have poor carrying capacity and are easy to age. They are only suitable for oil return pipes or drain pipes. Rubber hoses are divided into high pressure hoses and low pressure hoses. High pressure hoses are generally composed of It is composed of four parts: outer rubber layer, steel wire reinforcement layer, middle rubber layer and inner rubber layer. The inner rubber layer is in direct contact with the hydraulic oil, and one is made of synthetic rubber. The bearing capacity of the hose depends on the reinforcing layer, which is the skeleton of the hose, usually braided or wound with steel wires. Most of the medium and high pressure use steel wire braid as the skeleton, and the high pressure and ultra high pressure mostly use the steel wire winding skeleton. The outer rubber layer is generally made of rubber with good abrasion resistance and corrosion resistance to ensure that the reinforcement layer is not mechanically damaged, chemically corroded, damp and rusted. The low-pressure hose uses braided cotton and twine instead of braided steel wire, and is generally used for low-pressure oil return. pipeline.
 
Hose failures are generally manifested in the following four aspects: failure of the outer rubber layer, failure of the inner rubber layer, failure of the reinforcement layer, failure of the rupture. The causes and countermeasures of hydraulic hose failure are as follows:
 
1. Failure of the outer rubber layer
 
(1) Cracks appear on the outside of the hose
 
The main reason for the appearance of cracks in the hose is that the hose is bent in a cold environment. If you find cracks on the outside of the hose, pay attention to observe whether there are cracks in the inner rubber of the hose and decide whether to replace the hose immediately. Therefore, do not move the hose or dismantle the hydraulic system at will in a cold environment, and do it indoors if necessary. If you need to work in a colder environment for a long time, you should switch to a cold-resistant hose.
 
(2) The bubbling on the outer surface of the hose is caused by the unqualified production quality of the hose or improper use during work. If bubbling occurs in the middle of the hose, it is mostly a hose production quality problem, and qualified hoses should be replaced in time; if bubbling occurs at the joint of the hose, it may be caused by improper installation of the joint. There are often two types of hose joints: detachable and withholding. The detachable pipe joint is made into a hexagonal shape on the outer jacket and the joint core, which is convenient for frequent disassembly and assembly of the hose; the crimping pipe joint is composed of the joint jacket and the joint core, and the outer rubber layer must be peeled off during assembly, and then crimped on the special equipment , So that the hose can get a certain amount of compression.
 
(3) The hose is not broken but a large amount of oil seepage. The hose has a lot of oil seepage but no rupture is found. The reason is that the inner rubber is eroded and scratched when the high pressure liquid flows in the hose, until the large area of ​​the steel wire layer leaks out. Oil oozing. This failure usually occurs at the bend of the pipe, the hose should be checked and replaced, and the bend radius of the hose should meet the technical requirements during use.
 
(4) The outer rubber layer of the hose is severely deteriorated, and the surface has microcracks. This is a manifestation of the natural aging of the hose. Due to aging and deterioration, the outer layer is continuously oxidized to make the surface covered with a layer of ozone, which thickens with time. As long as the hose is slightly bent during use, tiny cracks will occur. In this case, the hose should be replaced.
 
2. Failure of the inner rubber layer
 
(1) The inner rubber layer of the hose is hard and cracked: the main reason is that the rubber product is added with a plasticizer to make the hose flexible and plastic. But overheating

Common Failures And Cause Analysis Of Hydraulic Hoses

(Summary description)Common Failures And Cause Analysis Of Hydraulic Hoses


Hydraulic hose is an important part of construction machinery such as concrete pumps, excavators, loaders, etc. However, it is often not valued by people. When there are leakage, cracks, cracks, loosening and other faults in use, it is often not analyzed The reason for the failure is simply to replace the hose, and the same failure will be repeated shortly after use. The loosening or rupture of hydraulic hoses not only wastes oil and pollutes the environment, but also affects work efficiency, and even causes accidents, endangering the safety of humans and machines.
 
Reasons for failure analysis of hydraulic hoses: improper use, unreasonable system design and unqualified hose manufacturing, etc.
 
I will discuss it in detail below based on my experience in actual work.
 
First, analyze the characteristics of the pipe. The hoses are divided into rubber hoses and plastic hoses. Plastic hoses are cheap and easy to install, but they have poor carrying capacity and are easy to age. They are only suitable for oil return pipes or drain pipes. Rubber hoses are divided into high pressure hoses and low pressure hoses. High pressure hoses are generally composed of It is composed of four parts: outer rubber layer, steel wire reinforcement layer, middle rubber layer and inner rubber layer. The inner rubber layer is in direct contact with the hydraulic oil, and one is made of synthetic rubber. The bearing capacity of the hose depends on the reinforcing layer, which is the skeleton of the hose, usually braided or wound with steel wires. Most of the medium and high pressure use steel wire braid as the skeleton, and the high pressure and ultra high pressure mostly use the steel wire winding skeleton. The outer rubber layer is generally made of rubber with good abrasion resistance and corrosion resistance to ensure that the reinforcement layer is not mechanically damaged, chemically corroded, damp and rusted. The low-pressure hose uses braided cotton and twine instead of braided steel wire, and is generally used for low-pressure oil return. pipeline.
 
Hose failures are generally manifested in the following four aspects: failure of the outer rubber layer, failure of the inner rubber layer, failure of the reinforcement layer, failure of the rupture. The causes and countermeasures of hydraulic hose failure are as follows:
 
1. Failure of the outer rubber layer
 
(1) Cracks appear on the outside of the hose
 
The main reason for the appearance of cracks in the hose is that the hose is bent in a cold environment. If you find cracks on the outside of the hose, pay attention to observe whether there are cracks in the inner rubber of the hose and decide whether to replace the hose immediately. Therefore, do not move the hose or dismantle the hydraulic system at will in a cold environment, and do it indoors if necessary. If you need to work in a colder environment for a long time, you should switch to a cold-resistant hose.
 
(2) The bubbling on the outer surface of the hose is caused by the unqualified production quality of the hose or improper use during work. If bubbling occurs in the middle of the hose, it is mostly a hose production quality problem, and qualified hoses should be replaced in time; if bubbling occurs at the joint of the hose, it may be caused by improper installation of the joint. There are often two types of hose joints: detachable and withholding. The detachable pipe joint is made into a hexagonal shape on the outer jacket and the joint core, which is convenient for frequent disassembly and assembly of the hose; the crimping pipe joint is composed of the joint jacket and the joint core, and the outer rubber layer must be peeled off during assembly, and then crimped on the special equipment , So that the hose can get a certain amount of compression.
 
(3) The hose is not broken but a large amount of oil seepage. The hose has a lot of oil seepage but no rupture is found. The reason is that the inner rubber is eroded and scratched when the high pressure liquid flows in the hose, until the large area of ​​the steel wire layer leaks out. Oil oozing. This failure usually occurs at the bend of the pipe, the hose should be checked and replaced, and the bend radius of the hose should meet the technical requirements during use.
 
(4) The outer rubber layer of the hose is severely deteriorated, and the surface has microcracks. This is a manifestation of the natural aging of the hose. Due to aging and deterioration, the outer layer is continuously oxidized to make the surface covered with a layer of ozone, which thickens with time. As long as the hose is slightly bent during use, tiny cracks will occur. In this case, the hose should be replaced.
 
2. Failure of the inner rubber layer
 
(1) The inner rubber layer of the hose is hard and cracked: the main reason is that the rubber product is added with a plasticizer to make the hose flexible and plastic. But overheating

  • Categories:Company News
  • Author:
  • Origin:
  • Time of issue:2021-04-03
  • Views:0
Information

Common Failures And Cause Analysis Of Hydraulic Hoses


Hydraulic hose is an important part of construction machinery such as concrete pumps, excavators, loaders, etc. However, it is often not valued by people. When there are leakage, cracks, cracks, loosening and other faults in use, it is often not analyzed The reason for the failure is simply to replace the hose, and the same failure will be repeated shortly after use. The loosening or rupture of hydraulic hoses not only wastes oil and pollutes the environment, but also affects work efficiency, and even causes accidents, endangering the safety of humans and machines.
 
Reasons for failure analysis of hydraulic hoses: improper use, unreasonable system design and unqualified hose manufacturing, etc.
 
I will discuss it in detail below based on my experience in actual work.
 
First, analyze the characteristics of the pipe. The hoses are divided into rubber hoses and plastic hoses. Plastic hoses are cheap and easy to install, but they have poor carrying capacity and are easy to age. They are only suitable for oil return pipes or drain pipes. Rubber hoses are divided into high pressure hoses and low pressure hoses. High pressure hoses are generally composed of It is composed of four parts: outer rubber layer, steel wire reinforcement layer, middle rubber layer and inner rubber layer. The inner rubber layer is in direct contact with the hydraulic oil, and one is made of synthetic rubber. The bearing capacity of the hose depends on the reinforcing layer, which is the skeleton of the hose, usually braided or wound with steel wires. Most of the medium and high pressure use steel wire braid as the skeleton, and the high pressure and ultra high pressure mostly use the steel wire winding skeleton. The outer rubber layer is generally made of rubber with good abrasion resistance and corrosion resistance to ensure that the reinforcement layer is not mechanically damaged, chemically corroded, damp and rusted. The low-pressure hose uses braided cotton and twine instead of braided steel wire, and is generally used for low-pressure oil return. pipeline.
 
Hose failures are generally manifested in the following four aspects: failure of the outer rubber layer, failure of the inner rubber layer, failure of the reinforcement layer, failure of the rupture. The causes and countermeasures of hydraulic hose failure are as follows:
 
1. Failure of the outer rubber layer
 
(1) Cracks appear on the outside of the hose
 
The main reason for the appearance of cracks in the hose is that the hose is bent in a cold environment. If you find cracks on the outside of the hose, pay attention to observe whether there are cracks in the inner rubber of the hose and decide whether to replace the hose immediately. Therefore, do not move the hose or dismantle the hydraulic system at will in a cold environment, and do it indoors if necessary. If you need to work in a colder environment for a long time, you should switch to a cold-resistant hose.
 
(2) The bubbling on the outer surface of the hose is caused by the unqualified production quality of the hose or improper use during work. If bubbling occurs in the middle of the hose, it is mostly a hose production quality problem, and qualified hoses should be replaced in time; if bubbling occurs at the joint of the hose, it may be caused by improper installation of the joint. There are often two types of hose joints: detachable and withholding. The detachable pipe joint is made into a hexagonal shape on the outer jacket and the joint core, which is convenient for frequent disassembly and assembly of the hose; the crimping pipe joint is composed of the joint jacket and the joint core, and the outer rubber layer must be peeled off during assembly, and then crimped on the special equipment , So that the hose can get a certain amount of compression.
 
(3) The hose is not broken but a large amount of oil seepage. The hose has a lot of oil seepage but no rupture is found. The reason is that the inner rubber is eroded and scratched when the high pressure liquid flows in the hose, until the large area of ​​the steel wire layer leaks out. Oil oozing. This failure usually occurs at the bend of the pipe, the hose should be checked and replaced, and the bend radius of the hose should meet the technical requirements during use.
 
(4) The outer rubber layer of the hose is severely deteriorated, and the surface has microcracks. This is a manifestation of the natural aging of the hose. Due to aging and deterioration, the outer layer is continuously oxidized to make the surface covered with a layer of ozone, which thickens with time. As long as the hose is slightly bent during use, tiny cracks will occur. In this case, the hose should be replaced.
 
2. Failure of the inner rubber layer
 
(1) The inner rubber layer of the hose is hard and cracked: the main reason is that the rubber product is added with a plasticizer to make the hose flexible and plastic. But overheating of the hose will cause the plasticizer to overflow. In addition, when the overheated oil passes through the cylinders, valves or other components in the system, if a large pressure drop occurs, the oil will decompose, causing the rubber layer in the hose to oxidize and become hard. In this case, first check whether the working temperature of the system is normal, whether the valve throttling and the oil suction passage of the pump are unblocked, etc., remove all the factors that cause the oil temperature to be too high and cause the oil to decompose, and then replace the hose. If only the inner rubber under the rupture of the hose is hard, but the upper part is kept well, this is because the rupture of the hose is too flat, bent or twisted, which causes the oil to heat up and accelerate oxidation, causing the inner rubber to hair hard.
 
(2) The inner rubber layer of the hose is severely deteriorated and obviously swelled: The inner rubber layer of the hose is severely deteriorated. The obvious swelling is caused by the incompatibility of the inner rubber material of the hose with the oil used in the hydraulic system, and the hose is deteriorated by chemical action. . If this happens, check the fuel tank, because there may be broken rubber pieces at the oil return port. In this regard, check whether the compatibility of the system oil and the inner rubber material of the hose and the working temperature meet the standard.
 
3. Faults manifested in the strengthening layer
 
(1) The hose is broken, and the braided steel wire near the breach is rusty. The hose is broken, and the outer rubber layer is peeled off for inspection. It is found that the braided wire near the breach is rusty. This is mainly because the layer is affected by damp or corrosive substances, which weakens the strength of the hose and causes it to rupture under high pressure. This kind of situation is usually accompanied by cracks, scratches or severe deterioration of the outer rubber layer, which makes the outer layer lose its protective effect on the reinforcing layer. In this regard, it is necessary to check and eliminate all adverse factors such as mechanical damage to the outer rubber layer, chemical corrosion, high-temperature baking, etc., and then replace the hose. However, there are cases where the outer rubber layer is maintained well and the reinforcement layer is rusted and cracked, and the rupture is usually within 200mm from the hose connector number. The reason is mostly that the connector is unqualified, and moisture enters the inner edge of the jacket, causing The reinforcement layer absorbs moisture, which causes rust to reduce the pressure resistance of the hose and rupture.
 
(2) The hose reinforcement layer is not rusty, but the reinforcement layer has irregular wire breakage. The hose was broken, and no rust was found in the reinforcing layer after peeling off the outer rubber layer, but irregular broken wires appeared in the length direction of the reinforcing layer. The main reason was that the hose was subjected to high-frequency impact. There are many intersections between the steel wires of the braided reinforcement layer. When the pressure in the pipe changes greatly, these intersections will also move with the change of the pipe diameter, and the steel wires will rub against each other. If the hose is subjected to high-frequency shock pressure, frequent friction occurs at the intersection, causing the steel wire to break. For hoses that are often subject to high-frequency shocks, steel wire-wound skeletons should be used as the reinforcement.
 
4. Failure manifested in the rupture
 
(1) The hose is broken in one or more places, the cracks are neat, and the other parts are kept in good condition. The main reason for this phenomenon is that the system pressure is too high, which exceeds the pressure resistance of the hose. If the system pressure meets the requirements, check whether the actual pressure resistance of the hose used meets the design requirements.
 
(2) Torsion occurs at the rupture of the hose. The reason for this phenomenon is that the hose is excessively twisted during installation or use. After the hose is twisted, the structure of the reinforcement layer is changed, and the gap between the braided steel wires increases, which reduces the pressure resistance of the hose, and the hose is easy to rupture under high pressure. Therefore, in the process of using or storing the hose, do not subject the hose to torsion torque. When installing the hose, try to keep the axis of the two joint numbers on the moving plane to avoid the hose from being twisted during movement.
 
(3) The steel wire is crimped at the rupture of the hose, and there is obvious necking near the rupture. The reason for this phenomenon of loose reinforcement is that the hose is excessively stretched and deformed, and the layers are separated, which reduces the compressive strength. The hose will shrink or stretch in the length direction under the action of high pressure, and the general expansion and contraction amount is +2% to 4% under normal conditions. If the hose is selected too short during installation, it will be greatly stretched during work, and failures such as cracking or loosening will occur in severe cases; in addition, if the span of the hose is too large, the weight of the hose and the weight of the oil will also be affected. It will give the hose a larger tensile force, and the above failures will also occur in severe cases. Solution: If it is pulled too tightly during installation, a new longer tube should be replaced; if the span is too large, an intermediate support clamp should be added.
 
In summary, through the above analysis, the following matters should be paid attention to when using hydraulic hoses in the future:
 
①Hose arrangement should try to avoid heat source and keep it away from the performance of engine exhaust pipe. If necessary, a casing or a protective screen can be used to prevent the hose from deteriorating due to heat.
 
② Where hoses must be crossed or may rub against the mechanical surface during work, protective devices such as hose clamps or springs should be used to prevent the outer layer of the hose from being damaged.
 
③When the hose must be bent, the bending radius should not be too small, and should be greater than 9 times the outer diameter. There should be a straight section at the junction of the hose and the joint that is more than 2 times the outer diameter of the pipe.
 
④When installing the hose, avoid being in a tensioned state. Even if there is no relative movement at both ends of the hose, keep the hose slack. The tensioned hose will expand under pressure and reduce its strength.
 
⑤Do not twist the hose during installation. A slight twisting of the hose may reduce its strength and loosen the joint. The joint should be tightened on the hose during assembly, not on the joint.
 
⑥ If the hose is configured on a key component, it is recommended to check or replace it regularly.

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