Characteristics of Rolling Mill Oil Film Bearing Seals

Sep 18, 2023

Oil-film bearings, also known as liquid friction bearings and ideal sliding bearings, are one of the key core components of modern rolling mills. Science and technology advancements are raising demands for high-quality rolled products, particularly thin plate precision, with speeds surpassing 100 m/s. Oil-film bearings have the characteristics of a large load capacity (more than three times larger than rolling bearings), a long service life (theoretical life is 10–15 years), a wide speed range, and strong impact resistance, which rolling bearings do not have. The application of the industry is becoming more extensive.

The normal operation of the oil film bearing can't be done without a good seal. The working environment of oil film bearings used in rolling mills is poor, especially in hot rolling, where a large amount of cooling water and, scale and other sundries may enter the oil film bearings at any time, threatening the safe operation of the oil film bearings. Preventing lubricating oil leakage and cooling water and other impurities from entering the lubrication system is an important part of rolling mills' oil film-bearing seal. The seal of rolling mill oil film bearing refers to the seal inside the bearing parts, including the static and rotary seals.

The characteristics of the rotary seal of oil film bearings in rolling mills mainly include three points: one is the seal of two-way media (water or emulsion and lubricating oil); the other is that the pressure difference on both sides is not large, but there is spray or splash; and high-speed rotation.

The rotary seals of rolling mill oil film bearings are lip seals. The lip seal mainly relies on the sharp corner of the sealing lip to press on the sealing coupling surface. Theoretically, it should be a line contact, but it is a narrow-band contact with sufficient pressing force, and the distribution of contact stress is peak-like. For lip seals, the pressure should not be too tight, and the contact zone should not be too wide. Analysis from the dual angles of lubrication and sealing shows that if the pressure is too tight, the seal and the coupling surface will be in a semi-dry friction state, aggravating the wear and heat of the seal and shortening the service life. If the pressure is too wide, it may form a thick wax lubrication state and thus leak oil outwards, reducing the sealing effect.

FV oil film bearing adopts the design of a type sealing device, which has good overall performance of the sealing mechanism, easy installation and disassembly, and long service life.

The design of the DF-type sealing device fully considers the following factors:

When the oil film bearing works, a large amount of lubricating oil with a certain speed sprays outward from the taper sleeve and the bushing. The oil sealing system, the first barrier of the oil film bearing, should play a blocking role.

Many cooling water rushes to the oil film bearing. Once it enters the lubrication system, it will cause serious adverse effects and often require multiple water-sealing lines.

There is relative rotation between the roll and the bearing box, the tapered sleeve, and the bushing. Although the static sealing safety performance is good, it cannot completely solve the oil film-bearing sealing problem. The design of the dynamic seal should reduce the loss of dynamic friction as much as possible while ensuring the safety of the seal. The combination of the labyrinth shielding loop (or other non-contact shielding barriers, such as the oil-throwing lip) and the contact dynamic seal meet this requirement.

There are many large-diameter seals in the sealing device of the oil film bearing. The linear speed of the dynamic seal contact part is high, and the lip shape, interference, and lip material of the dynamic seal contact part need more attention.

The oil-film-bearing sealing device belongs to the seal on heavy equipment. It is not easy to install and disassemble, and the convenience of operation needs to be considered. It integrates static seal, lip dynamic seal, and labyrinth seal and combines the functions of sealing oil and water. With the central flange of the sealing cover as the dividing line, the two sides constitute the water sealing defense line and the oil sealing defense line, respectively.

FV Bearing has been focusing on the research and production of rolling mill bearings for many years. It has mature technology and practical experience in oil film bearings. Our oil film bearings are exported to Poland and other European countries and run well.