Chemical Cleaning of Bearing Shell
Chemical cleaning of bearing shells is a critical process in maintaining the longevity and efficiency of bearings
used in machinery. Bearings, whether in automotive, industrial, or aerospace applications, are subject to wear
and contamination over time, which can degrade their performance. Proper cleaning of bearing shells ensures
that the bearing operates smoothly , reduces friction , and prevents premature failure. Chemical cleaning, in
particular, plays a vital role in removing contaminants like oil, grease, rust , oxidation, and dirt that may affect
the bearing’s performance.
Importance of Chemical Cleaning
Bearings are essential components in machines that help reduce friction between moving parts. Over time,
bearings can accumulate various contaminants such as oils, lubricants , dirt , and even corrosion products. If
not removed , these contaminants can interfere with the proper functioning of the bearing , causing issues
like increased friction, wear, and even catastrophic failure . Chemical cleaning is necessary to ensure that the
bearing shell is free from these contaminants before the bearing is reassembled or reused. It also ensures
that any residues from previous lubricants or cleaning agents are thoroughly removed , allowing for better
adhesion of new lubricants, improving operational efficiency, and extending the lifespan of the bearing.
Types of Contaminants
The contaminants found on bearing shells can be classified into several categories:
Oils and Greases: Lubricants used in the bearings can break down over time or become contaminated with
particles. These oils or greases can affect the bonding of new lubricants or coatings . Rust and Oxidation:
Exposure to moisture , air , and operating conditions can cause corrosion and oxidation on bearing shells ,
leading to pitting and surface damage . Dirt and Particles: Small particles from the operating environment or
previous cleaning processes can accumulate, impacting the performance of the bearing .Scale and Residues:
During operations, scale or residues from various processes can build up on bearing surfaces , which could
negatively impact the bearing’s movement.
Chemical Cleaning Methods
There are several methods for chemically cleaning bearing shells , each suited to different , types of
contaminants. The most common chemical cleaning methods include:
a) Solvent Cleaning
Solvent cleaning involves the use of organic solvents or degreasers to remove oils, greases, and dirt from the
bearing shell. The solvent is typically applied through immersion , spraying, or ultrasonic cleaning, depending
on the size and type of the bearing . Solvents like acetone , trichloroethylene , or specialized degreasers are
used to dissolve and remove oils and grease .Ultrasonic cleaning uses high-frequency sound waves to agitate
the cleaning solution and break down contaminants on the bearing surface . This method is particularly
effective for small or intricate bearing shells where manual cleaning may not be sufficient.
b) Acid Cleaning
Acid cleaning is used primarily for removing rust , oxidation , or scale that may have formed on the bearing
shell due to exposure to moisture or chemicals. A mixture of acids, such as hydrochloric acid or sulfuric acid,
is used to dissolve these contaminants. However , acid cleaning must be carefully controlled , as the wrong
concentration or exposure time can damage the bearing shell, especially if it is made of soft metals or alloys.
After acid cleaning , the bearing must be thoroughly neutralized with a base solution (such as sodium
bicarbonate) to prevent any remaining acid from damaging the shell. Proper rinsing with water is essential
to remove any residue.
c) Alkaline Cleaning
Alkaline cleaning uses solutions with a high pH, such as sodium hydroxide or potassium hydroxide, to break
down oils , greases , and other organic contaminants. This method is often used when more aggressive
cleaning is needed , as alkaline solutions can effectively remove stubborn contaminants .Alkaline cleaners
are typically safer to handle compared to acid -based cleaners but still require careful handling to avoid
surface damage. After cleaning with an alkaline solution , the bearing must be thoroughly rinsed and
dried to prevent any chemical residue from causing corrosion.
Cleaning Process and Precautions
The general process of chemical cleaning for bearing shells involves several steps:
Preparation: The bearing shell should be carefully inspected to identify the type of contaminants. The
cleaning agents should be chosen accordingly . If necessary , the bearing is , disassembled , and any
removable parts (like seals) are taken off. Cleaning : The bearing shell is immersed in or sprayed with the
,chosen cleaning solution. In the case of ultrasonic cleaning, the bearing is placed in a tank containing the
solution. The cleaning time and solution concentration must be carefully monitored to avoid damage.
Rinsing: After the cleaning process , the bearing shell should be thoroughly rinsed with clean water or
solvent to remove any residues of cleaning agents. Drying: It is crucial to dry the bearing shell completely
after cleaning to avoid the formation of rust or corrosion. Drying methods include using air blowers , heat
lamps, or placing the bearing in a drying oven .Inspection: Finally, after the cleaning and drying processes,
the bearing shell should be inspected for any remaining contaminants or surface damage . If any
contaminants remain, the cleaning process may need to be repeated.
Conclusion
Chemical cleaning of bearing shells is a vital process to ensure that bearings operate efficiently and last
longer. It helps to remove harmful contaminants, including oils, grease , rust , and dirt , that can degrade
the performance of the bearing. By using the appropriate cleaning agents and methods—whether solvent
cleaning , acid cleaning , or alkaline cleaning—bearing shells can be properly cleaned and prepared for
reuse or reassembly . Proper cleaning , combined with routine inspection and maintenance , ensures
smooth operation and extends the lifespan of bearings in various industrial and mechanical applications.