What is a sealing ring dynamic seal?
Definition
Dynamic sealing, as the name suggests, refers to a sealing form that can maintain the sealing effect during the relative motion of the seal. The dynamic seal of the seal ring achieves its sealing function through the sealing effect produced by the contact between the seal ring and the moving fitting surface. This form of sealing is widely used in various machines and equipment, such as hydraulic cylinders, pneumatic cylinders, valves, pumps, etc., to ensure that these equipment will not leak during relative motion.
Classification
Sealing ring dynamic seals are mainly divided into two categories: reciprocating dynamic seals and rotating dynamic seals.
1. Reciprocating seal:
Commonly used in the seal between the piston and the cylinder barrel in hydraulic and pneumatic cylinders and the seal between the piston rod and the cylinder head.
2. Rotary seal:
Commonly used in the seal between the rotating shaft and the housing, such as bearing seals, shaft end seals, etc.
How to improve dynamic sealing performance?
Improving the dynamic sealing performance of O-rings is a comprehensive task, involving material selection, design optimization, installation and maintenance, and working environment control. The following are some specific measures and suggestions:
Material selection
1. Medium-resistant materials:
According to the properties of the working medium (such as oil, water, gas, chemicals, etc.), select O-ring materials with good tolerance to the medium. For example, for hydraulic oil, you can choose nitrile rubber (NBR); for high-temperature environments, you can choose fluoro rubber (FKM) or silicone rubber (VMQ).
2. Wear-resistant materials:
In dynamic seals, friction will occur between the O-ring and the moving parts. Choosing materials with good wear resistance can extend the service life of the O-ring and reduce the risk of leakage. For example, hydrogenated nitrile rubber (HNBR) has good wear resistance.
3. Temperature-resistant materials:
Choose appropriate materials according to the operating temperature range. In high-temperature environments, materials with good high-temperature resistance should be selected; in low-temperature environments, materials with good low-temperature resistance should be selected.
Design optimization
1. Groove design:
Reasonably design the size and shape of the installation groove to ensure that the O-ring can produce appropriate compression deformation after installation and fill the gap between the sealing surfaces. Parameters such as the width, depth and fillet radius of the groove should be optimized according to the size and hardness of the O-ring.
2. Pre-compression control:
Pre-compression is an important factor affecting the sealing performance of O-rings. Excessive pre-compression will cause premature failure of the O-ring, while too little pre-compression may cause leakage. The pre-compression should be reasonably determined according to the working pressure and the properties of the medium.
3. Dynamic sealing design:
For sealing occasions with rotation or reciprocating motion, the dynamic sealing performance of the O-ring should be considered. Specially designed O-rings, such as O-rings with spiral or corrugated shapes, can be used to adapt to the deformation and vibration of moving parts.
Working environment control
1. Working pressure control:
Strictly control the working pressure of the system to avoid exceeding the bearing capacity of the O-ring and causing sealing failure. Devices such as pressure sensors or safety valves can be used to monitor and control the working pressure.
2. Movement speed control:
According to the material and size of the O-ring, the speed of the moving parts should be reasonably controlled. Too fast movement speed will cause premature wear and failure of the O-ring, while too slow movement speed may affect the sealing effect.
3. Temperature control:
For high-temperature or low-temperature environments, appropriate temperature control measures should be taken. For example, in high-temperature environments, cooling devices can be installed or high-temperature resistant materials can be used; in low-temperature environments, heating devices or low-temperature resistant materials can be used.
4. Medium cleanliness control:
Ensure the cleanliness of the working medium to avoid impurities entering the sealing area and affecting the sealing effect of the O-ring. The cleanliness of the medium can be controlled by using filters or regular replacement of the medium.
Installation and Maintenance
1. Correct installation:
Before installing the O-ring, make sure the sealing surface is clean and free of impurities, scratches, or damage. Use appropriate installation tools and methods to avoid scratching or twisting the O-ring. Make sure the O-ring is correctly installed in the groove without twisting or offset.
2. Regular inspection and replacement:
Regularly check the sealing effect of the O-ring. If leakage or damage is found, it should be replaced in time. At the same time, check the wear of the groove and sealing surface, and repair or replace it if necessary.
3. Lubrication and protection:
In some cases, an appropriate amount of lubricant can be applied to the surface of the O-ring to reduce wear and friction heat. For O-rings exposed to harsh environments, protective measures should be taken, such as adding a protective cover or applying a protective coating.
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