Totally Leaking Oil Seal Just Changed? Can't Escape These Problems!

- Dec 13, 2019-

The oil seal is an inconspicuous one of the many parts of the excavator. Because the life of the seal is relatively short, the frequency of replacement is slightly higher. Of course, the price of the oil seal is not expensive, so the cost of replacement is not so high.

But I do n’t know if you guys have found that the same is for the excavator. Some owners change the oil seals much less frequently. They may not change it several times a year. Why? Good oil seal quality? Or is there a trick to using maintenance? Today I will reveal the secrets for everyone.

1. Choice of oil seal structure

The structure of the oil seal is various. Oil seals such as single lip type, double lip type, pressure resistance type, anti-eccentric type, one-way reflow type, two-way reflow type are often used in use; therefore, the structure and form relationship should be correctly selected according to the conditions and uses during use. To the performance and life of the oil seal. If it is used under dusty conditions, the performance of the oil seal will be reduced. An oil seal with a dustproof structure design should be used.

2. Material selection

At present, the commonly used oil seal materials are mainly nitrile rubber, acrylic rubber, polyurethane rubber and other materials; from the perspective of the material formula, hardness, compression set, aging resistance, expansion capacity, abrasion resistance, high and low temperature resistance are all Material requirements for major items. It is important to choose different material formulations under different conditions of use medium, temperature and pressure; and the oil seal lip should have a certain resilience to reduce friction with the shaft and frictional heat. Proper hardness can improve the service life of the oil seal.

3. Interference and eccentricity of oil seal lip and rotation axis

The interference effect between the oil seal lip and the rotating shaft is mainly to make the sealing lip have the ability to follow the axis and the radial runout of the shaft to compensate for the wear of the sealing lip and give the rotating shaft an appropriate radial force during use; There is a certain amount of interference between the oil seal lip and the surface of the rotating shaft. However, when the interference of the oil seal lip on the surface of the rotating shaft is too small, the lip cannot follow or compensate for the eccentricity of the shaft, and a gap will be generated. When the interference of the oil seal lip on the surface of the rotating shaft is too large, the lip will be right. Radial pressure on the shaft surface will also increase. The current oil seal lip interference varies with the diameter of the shaft. The recommended oil seal lip interference is in the range of 0.15 to 0.9 mm.

4.Eccentricity and runout of shaft and surface roughness of shaft

Eccentricity and runout of the shaft are a major factor affecting the service life and leakage of oil seals. Generally, the eccentricity of the shaft can be solved by lengthening the oil seal lip, appropriately increasing the interference amount, and selecting a soft and hard material (refer to NOK's new IUI / IUIS); there are also corresponding requirements for the surface roughness of the shaft. The surface roughness has a certain effect on the wear of the oil seal lip.

5. Installation and storage of oil seals

The oil seals should be stored in a dry and clean environment. The oil seals must be packed, neatly stacked and not stacked randomly. Do not thread or string together to avoid damaging the oil seal lip and affecting the service life. In addition, due to damage to the oil seal lip due to improper installation methods, the sealing effect is also affected, and the service life of the oil seal is easily affected, causing problems such as failure and leakage.

The oil seal can be installed according to the following procedure:

Before installation, carefully check the shaft surface for burrs and machining knife marks to prevent damage to the oil seal lips.

Carefully inspect the oil seal lip for damage and appearance for dust and impurities.

The seal flange is coated with clean grease to facilitate installation and prevent lip scratches during installation; oil seals that are dust-proof should be filled with grease.

For oil seal springs, carefully check the dimensional tolerances for proper installation.

On the edge of the shaft shoulder, in order to facilitate the oil seal installation so that the lips are not damaged, there should be rounded corners or chamfers. When the oil seal installation passes along the shaft, the shaft should be rotated slightly to facilitate the installation operation.

When pressing the oil seal into the hole seat, the diameter of the axial pressure tool should be uniform and smooth. The diameter of the oil seal should be smaller than the diameter of the oil seal. The oil seal should not be installed in the hole seat at an angle.

The oil seal installation should not be interrupted for a long time, so as to prevent the weight of the shaft from compressing and deforming the oil seal and causing damage to the lips. Therefore, to obtain good sealing performance and long service life, we must pay attention to the storage and installation of oil seals.

For example:

We take the oil leak from the oil cylinder as an example. Generally, the poor quality of the oil seal itself is ruled out. The owner replaces the oil seal with a cheap price and no quality assurance. The life of this oil seal is very short.

In addition, if the oil seal of the oil tank leaks, either the external oil seal (often called the front oil seal) is damaged; or the oil cylinder has internal leakage and pressure internal leakage, such as the common excavator arm drop, etc. Internal leakage means that the internal oil seal (often referred to as the rear oil seal) is damaged.

So why does the oil seal always need to be replaced? For the following reasons, you can refer to the daily use to check in.

Reason for oil seal damage:

1. Before installing the oil seal, experienced masters will first handle the burrs at the chamfer of the oil seal joint surface. Do not underestimate this seemingly unnecessary action, but this will greatly reduce the chance of oil seal damage.

2. Before replacing the oil seal of the new cylinder, you may wish to check whether the cylinder has been scratched or scratched. If so, you must handle it properly, otherwise, the piston rod moves back and forth once, even if it is New oil seals will also increase wear, and the oil seals will naturally be damaged over time.

3. Excessive pressure in the hydraulic system will also cause deformation of the oil seal. In simple terms, the system pressure has exceeded the oil seal's oil seal limit. Under high pressure, the oil seal will be deformed and even impacted by high pressure hydraulic oil into several sections.

4. The presence of pollutants, impurities, external dust, and small particles in the hydraulic oil can easily cause the oil seals of the accessories to wear out and must be replaced until they are completely scrapped.

5. There is no need to describe the high temperature of hydraulic oil. There are countless examples of oil seals that must be replaced every year because of high oil temperature and accelerated aging of the oil seal.

6. Long-term purchase and installation of non-genuine oil seals, or the quality of oil seals cannot be guaranteed. In addition to the short life of the seals, the sealing effect must not meet the requirements, and oil leaks are no exception.

To sum up

Regarding the details of the life of the seal and the use and replacement, I will summarize it here for everyone, hoping to attract everyone's attention. In addition, there are many problems caused by seal damage. Welcome everyone to share experience!