February 1, 2014
Proper care — and application — will keep your primary jaw crusher properly feeding the production cycle.
When it comes to maintaining a jaw crusher and securing the most uptime possible, the key is to develop a proactive preventive care program and become properly trained on the equipment, according to industry expert Wade Lippert.
Lippert, a field service representative for KPI-JCI and Astec Mobile Screens, has been servicing aggregate equipment for 25 years. In his years of experience, Lippert says he often comes across tunnel-visioned producers who are solely focused on one specific part of an operation — like how large material can be and still be fed into a crusher.
What they should be concerned about, Lippert says, is how much production can be achieved and the best way to achieve it. That all boils down to maintenance and education.
“There has to be investment in a comprehensive maintenance and training program,” Lippert says. “Too often, I am told how much downtime a producer is experiencing and how much that downtime is costing them, and yet I find they are not taking care of the equipment. Investment in maintenance is considered an operating expense that can affect your bottom line, positively or negatively.”
But maintenance is far more extensive than just greasing bearings and miscellaneous “housekeeping,” Lippert says.
“If you purchase a piece of equipment, you expect a certain amount of longevity in the equipment,” he says. “This applies to anything you buy. If you purchase a vehicle, you need scheduled maintenance like fluid changes, tire checks, and, yes, housekeeping. If these basic practices are not performed, the vehicle will fail you, as well as affect the resale value dramatically. These fundamentals in vehicle maintenance are understood by most and considered common sense. The same fundamentals can be applied with crushing equipment, but with much more attention to detail.”
Because of the violent nature of a jaw crusher, the equipment — regardless of application or manufacturer — will fail at some point without preventive care. But a proper maintenance program can help producers avoid costly breakdowns by repairing problems in their infancy. This could be something as minor as a loose or missing bolt, a broken weld, a loose belt, or a buildup of material that is allowed to remain, Lippert says. When taken care of daily, they remain small issues that can be immediately resolved to avoid downtime, but, over time, they can affect the longevity of the equipment.
Factory training and education goes hand-in-hand with a preventive care program in extending the lifespan of a piece of equipment. While new technology can greatly enhance the efficiency of an operation, it can also add a challenge to those who have not been exposed to it.
“There is often a fear associated with new technology, and the fear provides lack of understanding in how the equipment works,” Lippert says. “But if proper training and education is provided, the fear disappears and is replaced with an understanding of how the equipment functions. Technology can either be friend or foe. Become educated, and it will profit you. Cling to ignorance, and technology will eat your lunch.”
Avoid oversized feed
To establish a preventive care program that will extend the lifespan of a jaw crusher, producers must go beyond greasing bearings daily and consider the application of equipment. Although daily greasing is vital to a jaw crusher’s survival, it’s only part of a much bigger picture, Lippert says.
“The way the jaw crusher is applied is as important to maintaining the jaw as a good grease interval,” he says. “The jaw crusher is most often the primary crusher in a quarry or recycling operation. It is asked to perform the first stage of crushing, which can be the most difficult stage of product reduction. However, it is too often misapplied by feeding too large of material. This creates loss of production and the potential to damage the crusher.”
Every producer seeks high production in order to achieve the best bottom line, but when oversize material is fed into the crusher, the opposite can occur, Lippert says.
“Oversize material can cause what we call ‘black belt,’ which is essentially caused when an oversized rock is introduced into the jaw, but is too large to fit into the chamber,” he says. “This causes an interruption in crushing, which equals no production. It also imposes stress to the crusher as the rock is pounded against the area of the pitman known as the pitman barrel, which is where the shaft and bearings are located. Pre-sizing material is vital to providing the proper feed and achieving high production. A general rule of thumb is to keep the maximum feed size under 80 percent of the jaw opening or gap as measured from the top of the stationary die to the top of the moving die.”
Keep fines manageable
Although too large of material can cause problems for the producer, too many fines can also affect crushing performance. An excess of fine material will fill in all of the voids, which are necessary for the material that is being crushed to expand into. This creates an event called compaction. Compaction amplifies the forces in the crushing chamber, up to five times the normal crushing forces. As with any force that is generated, the energy must find a point of release, which is usually in the jaw base structure or in the shaft and bearings. Over time, this can cause damage, Lippert says. Excessive amounts of fine material also limit production because these fines are taking the place of otherwise crushable larger rock.
Compaction can also be caused by improper use of the jaw die or plates. The corrugations of the jaw dies are crucial to the jaw performance, as the corrugations provide the expansion room needed as well as the leverage required to break the rock. Jaw dies should be flipped or replaced once the remaining corrugations get to about 20 percent of their beginning dimensions or irregular wear is detected. The wear of a jaw die should be gauged by the remaining corrugations at the bottom, not the overall weight of the jaw die itself.
Aim for attrition crushing
If the proper feed size is introduced into the jaw and the jaw die maintenance is performed as recommended, the result will be a higher output, and true attrition crushing will take place. Attrition crushing, or rock-on-rock crushing, helps with output gradations and improves wear cost for the producer, as more of the wear takes place on the rock rather than the jaw dies.
As with all crushers, the maintenance of a crusher depends on how it is applied and taking a proactive approach to maintenance items like wear parts. Replacing wear parts before they are worn out costs less and improves the crusher’s performance, ultimately saving money, increasing uptime, and providing crusher longevity, Lippert says.
Although the fundamentals of jaw crusher maintenance apply to all jaw crushers, it is important to consider each scenario according to each specific producer when it comes to preventive care, he adds.
“Every producer needs to consider what he can do to improve his situation by adding to or developing a program that will work for his specific needs,” Lippert says. “Every customer is unique in that there are no two identical applications, both in material and in people themselves. But there are similarities that can be the foundation for building a good maintenance program, so it is important to remain flexible. Keeping an open mind to suggestions may save you money and make you more profitable. It also serves as a morale booster to the employees asked to operate and maintain the equipment, and maintaining good employees will help in assuring that proper maintenance is being performed.
“In short, investment in maintenance is both a financial and a personal commitment to man and machine, which translates to a positive work environment and a profitable bottom line.”
Michelle Cwach manages the communications and media relations for KPI-JCI and Astec Mobile Screens. She can be reached at 605-668-2606 or firstname.lastname@example.org.