The main purpose of lip seals is to avoid contamination and maintain the working fluid. They can be used in various mechanisms – from slow-moving to high-speed rotation, as well as temperatures below zero and to more than 260 °C.
To work effectively, the lip seal should maintain proper contact with the rotating part. This will depend on the correct choice, installation, and care of the seal after installation.
SELECTING A LIP SEAL
Maintenance of the function of the lip seal begins with the process of selecting the material. When choosing a material, you must consider the operating temperature, the type of working fluid, and the scope of the seal. The most common material for a hydraulic cuff is nitril (Buna-N). This material works well at temperatures from -40 °C to 135 °C. Nitrile lip seals are used in industry both in new equipment and as repair kits for used vehicles. They have excellent resistance to machine oil, water and hydraulic oils, but what really distinguishes these seals is their low cost.
Each type of rubber has special properties and exact temperature ranges. Be sure to take into account the work process and the environment before choosing the seal material, as the correct material can prevent costly damage.
DESIGN OF A LIP SEAL
After selecting the seal material, the next step will be to consider its design. Today’s lip seals have several parts that affect the sealing operation. The seal may have a spring element in its construction. A leakproof seal will usually be less costly and will be able to hold viscous materials such as grease at slow speeds of the shaft. Typical applications are conveyors, vehicle wheels and lubricated components. Spring seals are commonly used with oils and can be used on a wide range of equipment.
Checklist for installing a lip seal
- If you pull out the lip seal and see the recess on your shaft, it’s probably due to contamination. Without good ventilation, all the dust and dirt entering your equipment can destroy not only your bearings and gears, but also your shafts and lip seals. Of course, it is always better to rule out the possibility of contamination than to try to remove it afterwards. Too tight fitting between the lip seal and the shaft can also create a groove.
- Excessive temperature is the main cause of seal failure. As the temperature rises, the lubricating film becomes thinner, which leads to dry running conditions. Elevated temperatures can also lead to cracking of the elastomer or the formation of bubbles. The life of the nitrile seal is halved with each temperature increase of 57 degrees.
- A low oil level can be another factor in reducing the life of the lip seal. In such a situation, the seal eventually becomes firm and can not follow the shaft, which will lead to a leak.
- Cold temperatures can make the seal brittle. Choosing the right lubricant and seal material can help in operating in colder conditions.
- Seals can also become unusable due to the shaft beating. This can be caused by misalignment, imbalance of shafts and manufacturing inaccuracies. Different elastomers will carry a different beat amplitude. Adding a spring ring will help in this case.
- Excessive pressure is another potential cause of failure of the lip seal. When using with a higher pressure, a special seal design should be used.
LIP SEALS 14896-84
Lip seals 14896-84 are designed to seal the gap between the cylinder and piston (plunger, rod) in hydraulic devices operating in reciprocating motion with a relative displacement of not more than 0.5 m / s, at a pressure of 0.1 to 50 MPa, temperature from -60 °C to 200 °C, a stroke of up to 10 m and a response frequency of up to 0.5 Hz.
Seals, depending on the design and the value of the acting pressure, are made of three types:
Type 1 – for a pressure of 0.1-50 MPa (1.0-500 kgf / cm2)
Type 2 – for the pressure of 0.25-32 MPa (2.5-320 kgf / cm2)
Type 3 – for pressure of 1,0-50 MPa (1,0-500 kgf / cm2)
Instead of seals type 2, it is allowed to use seals type 3, which are interchangeable with seals type 2.