Recently, our teams have been spending a lot of time with mining customers who have been looking for specific solutions to improve the reliability of critical processing equipment such as crushers.
Crushers are an important part of the processing side of the operation, and keeping those machines online is essential to any productive operation.
To help with this challenge, we wanted to flashback to a productivity tip from 2018 that focuses on crusher design, wear challenges and lubrication best practices. Enjoy!
There are three main types of crushers – jaw crushers, cone crushers and impact crushers.
Jaw crushers: In jaw crushers, a large feed opening receives material. There are two outer bearings located on either side of the main frame to support an eccentric shaft. There are also two inner bearings – known as “pitman” bearings – that support a moveable jaw. The reciprocating motion of the shaft moves the pitman against stationary jaw and as material reaches the bottom of the chamber, it fractures. Jaw crushers typically use spherical roller bearings, which support radial loads and misalignment. These bearings also operate under moderate speeds and loads, with occasional load spikes.
Cone “gyratory” crushers: In a cone crusher, the main shaft is housed in a frame attached to a mantle. A pinion shaft assembly drives a bevel gear that rotates the cone. As material presses against the bowl, it is crushed into smaller pieces. Cone crushers have two radial and two axial bearings. The radial bearings are cylindrical roller bearing, while the axial bearings are tapered thrust and cylindrical thrust bearings. These bearings operate at moderate speeds but support heavy loads as well as occasional shock loads.
Impact “hammer” crushers: Hammer mills are typically used as secondary crushing. They have high rotational speeds with variable loading conditions and use spherical roller bearings to handle radial loads and shaft misalignment. These bearings are of split pillow block design and provide support during crusher operation.
Crusher bearing wear
Crusher bearing damage is often a result of contamination, improper lubrication, and metal-to-metal wear. Common wear modes include:
Abrasive wear and debris denting caused by contamination.
Adhesive wear stemming from poor bearing surface finish, excessive loads or the use of a wrong viscosity oil, all of which can result in metal-to-metal contact.
Fretting or fretting corrosion, which typically results from a loose fit, leading to relative motion between the bearing and the shaft or housing.
To help protect against these wear modes, it’s critical to use the right lubricant products.
Oils: As a general rule, operators should use extreme pressure fortified gear lubricants with a minimum viscosity of 22 cSt at the bearing operating temperature. This typically demands an AGMA 3 EP or 4 EP gear oil. The lube oil should operate in a range between 10 and 50 degrees Celsius. Operators should also implement a routine oil sampling program to effectively monitor oil and crusher condition, as the demanding operating conditions of this equipment can lead to sudden changes in performance.
Greases: Operators should look for lithium or calcium soap-based greases that have a base oil viscosity of ISO 220 to 460 and that contain extreme pressure additives. In some cases, operators may use greases that contain a molybdenum disulfide additive to protect against adhesive wear. Most crusher bearings should be frequently re-greased to ensure proper lubrication and the purging of external contamination.
I hope that this tip provided a helpful summary of proper crusher lubrication. If you have any questions or additional thoughts, please leave a comment below.
Very Useful Info. Am awaiting for my POP to be signed by customer in 2 cases where in customer realized bearing failure reduction & also increased ODI.