We drove for a long time to the lake. The driver carefully placed the trailer on the ramp. When the axle falls into the water, the Hot Wheels bearing hub simultaneously falls into the water. The rapidly compressing air and grease inside the hub creates a vacuum as the heat from the bearings is cooled by the lake water outside the hub. If the seals cannot hold a vacuum, the hub can suck in water and contaminants.High Quality Nitrile Rubber Cassette Oil Seal Type
Although this is an extreme case, this type of contamination can occur in all bearings if the seals are in poor condition. Obviously, the most important part of a bearing is the seal. If contaminants can get on the contact surfaces or if the grease is drained, the bearing will not last long.
Some new seals are made using hydrogenated nitrile butyl rubber. The manufacturer states that the material will not be attacked and degraded by synthetic fluids and additives that attack traditional nitrile compounds. In addition, the material is highly resistant to abrasives that can penetrate other joints causing leaks.
Today, most seals are referred to as “lip seals” because their lip rests on the outside diameter of the shaft. This “rubber” (nitrile, polyacrylate, silicone, etc.) edge is glued to a metal sheath that is inserted into a hole in the part to be sealed. The suspension spring enters the groove behind the lip, helping the lip maintain contact with the shaft. Sometimes you will find a ring of sealant around the outside diameter of the body to help seal the metal body to the hole where the seal is installed. In other cases, the metal shell is completely covered in the same material that the lip itself is made from.
Some lip seals have their own built-in dust seal, which is a small extra lip that faces the outside of the housing. This little lip does not hold the spring. Some bearing seal manufacturers make seals with three different lips.
The seal must always be installed with the sealing lip facing the fluid to be sealed. This is because the lip is designed in such a way that the pressure applied to the seal from the “wet” side increases the pressure exerted by the lip on the shaft. If the seal is installed backwards, pressure on the “wrong” side of the lip will cause it to pull away from the shaft, causing leakage. On most seals the right side is obvious, but on others it is not.
Most seals are designed so that the “back” (liquid-facing side) of the housing is open. The front is closed and can be engraved with a part number. However, some seals are very symmetrical and special attention must be paid to the correct orientation of the lip.
Some seals are even designed for a specific rotation. They may have an arrow showing rotation. Oriented seals may have small diagonal ridges near the lip. These ridges act as microscopic “threads” that help draw fluid away from the edge as the shaft rotates. Some seals have a sine wave lip design that creates a resonant mode as the shaft rotates. This helps tighten the lip, drawing oil away from the lips and reducing leaks.
After removing the seal, inspect the hub and spindle surfaces where the lip is located for damage. If the surface is scratched, pitted, or too rough for a new seal, you have several options. Minor scratches or corrosion can usually be removed with sandpaper. Surfaces should not be treated with anything rougher than sandpaper. Sometimes the lips of hardened old seals will wear the grooves in the sealing surface. If you can catch nails in the groove after sanding the shaft with sandpaper, the groove is too deep to be accepted.
Whatever it is, replacing a hub or spindle can be very expensive in terms of both the cost of the hub and the cost of replacing it.
Check the seal itself to determine the cause of the failure. If the seals are hardened and/or worn out, it’s just the sacrilege of age. If the seal lip is very soft and swollen, it may have been damaged by an incompatible lubricant.
If the seal is relatively new, it may not have been installed correctly. Installation failures include torn edges, dents from improper installation tools, misalignment, raised fasteners, damaged burrs, and missing compress springs. Careless installation may cause the compress spring to fall out of the groove. Also, check for signs of heat damage.
Then make sure you have the correct seal. Check the fit of the shaft and housing. Lubricate the lip with whatever fluid you will be working with before installing the seal. If the seal is installed dry, the lip will overheat as soon as the shaft starts to rotate.
Install the new seal in place using the seal installer. If the seal must be installed on a rough part of the shaft (such as a spline), wrap masking tape around the rough area to get to where it should be to prevent damage to the seal. Do not strike the seal directly and never use a punch or punch to install the seal. Indenting the seal body with a punch can cause the lip to deform and the seal to leak. Make sure you insert the seal into the hole correctly and push it in correctly. As a general rule, the seal should be hammered in until it is flush. There are some exceptions, so it’s best to check the depth before removing an old filling.
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Post time: Jul-31-2023