by Colleen Suo
In December we reviewed KPI-JCI Resource Development Manager Erik Schmitd’s seven best practices for optimal crusher maintenance. This month, we’ll look at some elementary dos and don’ts of crusher maintenance, beginning with horizontal shaft impactors.
• Check the rotor for wear after making speed adjustments. This will ensure you are not over-penetrating into the blow bars, thus wearing the rotor.
• Check for excessive horsepower draw or loss of production after making an apron or curtain adjustment. Improper settings can cause high horsepower demand and lower production rates.
• Provide well-graded input feed to the crusher. Is what’s going in pre-sized to help maximize production and minimize wear costs?
• Be sure to properly prep the feed, especially if you’re working with recycled concrete. Do you have the ability to deal with some of the uncrushables and get rid of some of the steel beforehand? This can reduce plugging in the chamber as well as blow bar breakage.
• Monitor daily wear of the crusher. Processing abrasive material, tight settings and uncrushables can accelerate wear.
• Make adjustments to the aprons in small increments. This will allow you to achieve your desired results faster.
• Lubricate the crusher bearings daily per the OEM recommendations. New grease will keep dirt out of the bearings, extending the life of the bearing.
• Flip the blow bars before they are less than ¾-inch above the rotor, being sure to readjust the aprons before re-starting crushing operations. As you’ve worn your blow bar, you’ve changed your close side setting.
• Lastly, don’t exceed a reduction ratio of 12:1 – 18:1, as excessive reduction ratios can reduce production rates and shorten the life of your crusher. What is setting your topside feed?
Schmidt’s top 10 cone crusher maintenance tips
• It is no surprise the first tip is doing comprehensive daily inspections. Visual inspections can catch a majority of potential failures that could end up costing big in preventable downtime. Visual inspections should be performed inside areas that can’t normally be seen such as discharge areas, drive guards and inspection covers, which can identify wear, build-up and loose or missing components.
• Next on the list of tips is to check for bowl float, also known as ring bounce (among other things). Most cone crushers use some sort of tramp iron relief system (TIR) to allow uncrushables to pass through the crushing chamber. TIR systems were not designed to be continuously overloaded. This often happens when a crusher is operating outside of its designated parameters, such as proper reduction ratio, liner configuration or excessive fines getting into the chamber. Bowl float is a symptom of a different problem. Check out the feedstock – is it fines-heavy? Then you could have a screening problem, not a bowl float problem. There were many application-related scenarios mentioned that can cause bowl float, which included moisture content (heavy clay) or possibly the wrong liners being installed. Schmidt stated the most common cause of bowl float is operating the crusher at too small of a closed side setting.
• Housekeeping goes hand in hand with the visual inspections. Material build-up is pretty much inevitable in the aggregate business and will find its way into guarding – shrouds and any other horizontal surface on the framework. Schmidt said it could be anything in the chamber causing damage: flashing off a skirt board or conveyor – even a root ball can slip by, and if it goes unnoticed for a prolonged period of time it will wear away the crushing edges of the cone. Operators should be very familiar with the “as-manufactured” profile of their crusher so they will recognize potential problem areas and make corrections before production is disrupted.
Material can build up in places quickly if it is wet or sticky. Schmidt suggested some operations might have to do more than one visual inspection per day depending on what is being processed. Build-up can take out rollers or head/tail pulleys. It can rip up belting and cause tracking problems as well – so it’s easy to see how it wouldn’t take long to cause damage to a cone crusher. Build-up in the discharge area can also cause wear.
• Once again, fluid contamination (fuel, hydraulic and oil/lubricants) was brought to the forefront of crusher maintenance procedures. Schmidt suggested any bulk fluids going into storage tanks should be pre-filtered when stored and again when servicing equipment. He mentioned that as emission standards drive engine producers to manufacture cleaner engines (Tier 3, interim and 4 Final), the fuel atomization is accomplished by very high-pressure injection systems. Dirt, dust, water or cross contamination in these systems will cause damage – extensive and expensive. One way to prevent this situation is to do routine analysis on maintenance fluids and fuel.
• Misapplication of equipment includes operating a crusher outside of the designated parameters. All crushers have limitations – capacity, feed size, closed-side settings, material being crushed and environmental issues. Misapplication can cause internal damage that won’t manifest itself right away, so the failure occurs long after the initial damage.
• Do not wear the manganese liners beyond the scheduled replacement. Again, keeping an accurate log (amp draw or bowl float) and daily visual inspections will assist in this task. Schmidt said, according to manufacturers, a manganese liner should be considered worn out when its weight equals 40 – 60 percent of when it was new.
Since it is not practical to stop operations and weigh the liners mid-lifecycle, he suggested keeping track of weight before and after replacement so you can get an idea of the lifespan of the liners for your particular application.
• Inspect discharge and feed areas. If the discharge belt is not running, the crusher will fill and get plugged with material – and often times, the operator cannot see the discharge belt. Schmidt recommended having adequate clearance for the material to exit and transition to the discharge belt. He also recommended keeping the feed height into the crusher at a minimum and to be sure it is centered, stating that a rock box or ladder may be necessary to ensure this. If a blockage does occur, Schmidt said an operator should never restart the crusher without a thorough inspection inside to verify any damage or trapped material between the wedgeplate (eccentric) and cone head. He said they should turn freely of each other with consideration given to the anti-spin mechanism.
• Keeping daily records is key (refer to Part I). Things suggested to track include normal operating temps, luge oil flow (gpm), lube oil filter restriction, crusher coast downtime from shutdown, running amps when empty and amounts of oil used or added. By doing this, PMs can be identified and planned for before a failure occurs.
• Be aware of cold weather start-up issues where applicable. Schmidt mentioned one of the advantages to operating a machine equipped with roller bearings (such as the brand he represented) is the ability to operate within wider temperature ranges, requiring a minimum amount oil flow in order to begin crushing – not a minimum operating temperature. A few hints offered to facilitate quicker start times in colder climates included placing a tarp or slab of plywood over the crusher opening to retain heat, change to synthetic oil when possible (always check with the manufacturer or operating manual first) and install or use an oil recirculating kit.
• Lastly, Schmidt recommended using the correct lube oil. Don’t go cheap concerning the lifeblood of our machinery. Follow the OEMs’ recommendations for types and brands. For cones with roller bearings, making sure the product is equipped with the EP (extreme pressure) additive package is critical.
Many of the points Schmidt made during the presentation are common sense-based and are hopefully not only being put into practice but have become part of the work routine. The main take-away from the presentation is the importance of preventative maintenance and record keeping, helping you to become intimately acquainted with the equipment. It sounds cliché, but it is a good life practice – if you take care of your equipment, it will take care of you. In the case of aggregate production, it will protect your large investment and provide a good living for you and your crew. n