Apr 15, 2020 Aggregates blog

5 tips for energy efficient and productive cone crushing

Mark Kennedy
Mark Kennedy
Senior Technical Training Instructor
It has been estimated that 5-15% of an aggregate producers’ cost can be associated with the cost of electricity. If cone crusher maintenance is neglected, the result will be a detrimental effect on productivity and an overall higher energy cost per ton of material crushed. It’s not uncommon that aggregate producers’ maintenance teams are not fully aware of the maintenance requirements of a cone crusher or its impact on energy consumption. Make sure that at least these five things are checked.
HP3 and HP4 cone crushers pictured on site.
  1. Cone crusher main frame seat liner maintenance

Gap measurements should be taken between the bottom of the Adjustment Ring and the top of the Main Frame to determine if the Adjustment Ring is sitting straight or whether it is tilted. If the Adjustment Ring is no longer resting “straight” on top of the Main Frame, the result will be an inconsistent crusher closed side setting from one side of the crusher to the other. This in turn will result in decreased productivity as well as erratic and possibly excessive power peaks.

A bronze Main Frame Seat Liner is welded to the tapered seating surface of the Main Frame and provides a certain level of protection if the Adjustment Ring bumps, wiggles or moves while crushing is taking place. The Main Frame Seat Liner on most crushers will require replacement at some point in time throughout the crusher’s life.

A HP Series cone crusher is being used and has a total throughput capacity of 300 STPH. Looking at the product gradation table below, let’s say that the “target” closed side setting for this crusher is 3/8” (10mm) [blue box at the top]. You can see that at a 3/8” (10mm) closed side setting, 81% of the crusher product will be 3/8” (10mm) x 0” [blue circle] or 243 STPH (81% of 300 STPH).

This should be considered extremely efficient crushing by anyone familiar with rock crusher applications. But, if the Adjustment Ring becomes tilted by 1/8” (3mm), the closed side setting would now be 3/8” (10mm) on one side of the crusher but 1/2” (13mm) on the opposite side.

Again, looking at the table below, you will see that 66% of the product discharging from the crusher set at a 1/2” (13mm) closed side setting will be 3/8” x 0” [red circle] or 198 STPH (66% of 300 STPH).

That being said, it wouldn’t be fair to suggest that the total 3/8” (10mm) minus production will drop from 81% to 66% as you are still making a good rate of 3/8” (10mm) on the side of the crusher that still measures 3/8” (10mm). To calculate the actual loss of productivity, add 66 and 81 which equals 147, divide this by two which equals 73%. So on average, 73% of the product discharging from the crusher will be 3/8” (10mm) x 0” or 219 STPH. The current 73% production rate compared to the expected 81% represents a 10% decrease in 3/8” (10mm) minus productivity based on a 1/8” (3mm) tilt to the adjustment ring.

Example

The bottom line is that you cannot afford to operate the crusher with a tilted Adjustment Ring due to worn Main Frame Seat Liners. When only “one side” of the Adjustment Ring on the crusher bounces, wiggles or moves during crushing operations, the result, given enough load cycles, will be a tilted Adjustment Ring.

There are two somewhat common reasons why the Adjustment Ring can develop movement on one side of the crusher but not on the other side:

Poor Distribution of the Feed

A condition that exists when the incoming feed material is deep or heavy on one side of the crusher but low or empty on the other side of the crusher. In this case, the Adjustment Ring might bounce, wiggle or move on the side of the crusher getting the heavy load.

Segregation of the Feed

A condition that exists when large stones are entering one side of the crusher, but the smaller stones are entering the opposite side of the crusher. In this case, the Adjustment Ring might bounce, wiggle or move on the side of the crusher receiving the smaller feed. Main Frame seat Liners should be inspected whenever the opportunity presents itself but at minimum, at every mantle and bowl liner change.

Improper Main Frame Seat Liner maintenance will result in a high horsepower consumption at a low crusher throughput tonnage.  This inefficient use of connected horsepower will result in a higher energy cost per ton of material crushed (kW/hr per ton).

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  1. Cone crusher drive belt maintenance

If proper cone crusher drive belt tension and alignment is “not maintained”, the drive belts will slip at the higher power levels and the crusher will inevitably slow down. A slowing crusher will result in excessively high and fluctuating power peaks at a very low crusher throughput tonnage. Improper drive belt maintenance will result in high horsepower consumption at a low crusher throughput tonnage, this inefficient use of connected horsepower will result in a higher energy cost per ton of material crushed (kW/hr per ton).

Drive belt condition, alignment and tension should be checked on a weekly basis (40 hours). A “pulse input speed sensor” can be used to warn operations of a slowing crusher. This speed sensor will also extend drive belt life as the maintenance department will get the opportunity to service (retighten) the drive belts prior to belt failure or prior to crusher stall out.

Plant production rate 400 STPH, crushing 8hrs/day, 5d/week, 50w/year with an average product sale price of $6.00/ton

  1. Cone crusher hydraulic power unit maintenance

Improper hydraulic power unit maintenance can cause the pump and motor assembly to cycle more often than it should or worst-case scenario, to run continuously throughout the day. This inefficient use of connected horsepower will result in a higher energy cost per ton of material crushed (kW/hr per ton). It will also result in a shorter life cycle of the hydraulic power unit ancillary components, such as: the pump, motor, coupling, motor starter, pressure switches, solenoid valves, seals, packings, etc. The hydraulic power unit should be inspected on a daily basis (8 hours) for, filter condition, breather condition, leaks, loose connections or unusual noises.

Looking at the table below, let’s use a “pump cycle time” of one pump cycle for every one hour of operation as the base value, this would be very typical of a new crusher supplied with a new hydraulic power unit. But due to “maintenance neglect”, abnormal and excessive oil leakage is now causing the hydraulic power unit to cycle once every five minutes of operation, the energy cost will be “twelve times higher than normal”.

 

  1. Cone crusher discharge compartment maintenance

If the under-crusher discharge compartment is not properly maintained and material builds up on the crusher arms or the countershaft box, crushed product will be restricted from exiting the crushing chamber, this will result in a low crusher throughput tonnage at an extremely high-power level. This inefficient use of connected horsepower will result in a higher energy cost per ton of material crushed (kW/hr per ton). The under-crusher discharge area should be inspected for built-up material on a daily (8 hour) basis.

The table below clearly demonstrates that you can’t afford not to inspect the under-crusher discharge area both from an energy conservation standpoint and a lost productivity standpoint. The table is based on using an HP400 cone crusher, 400 horsepower drive motor, operating at a 1/2” (13mm) closed side setting, running at 80% rated power (320 HP), crushing 250 STPH, operating 8 hours per day, 5 days per week and 50 weeks per year.

  1. Cone crusher lubrication pump maintenance

If the crusher lube oil pump is not properly maintained and the flow rate decreases due to internal pump wear, circulating lube oil temperature will increase. The increase in crusher drain oil temperature will cause the oil cooler fan motor to cycle on and off more frequently throughout the day or in worst case scenario, to run continuously. This inefficient use of connected horsepower will result in a higher energy cost per ton of material crushed (kW/hr per ton).

Approximately 70% of the total lube oil flow rate is being used to keep the cone crusher cool. When the actual lube oil flow rate decreases below 70%, the crusher will operate warmer than previously. If the cone crusher package lube system has been neglected on the maintenance side, and the lube oil is allowed to become contaminated, the end result will be rapid and abnormal lube pump wear and a decrease in the total amount of lube oil flow.

As an example, let’s say that the correct pump flow rate to a HP300 cone crusher is 30 GPM. The crusher will require approximately 70% of proper flow to keep it cool (21 GPM), but let’s says that the actual pump flow rate has decreased to 19 GPM due to internal pump wear.

The crusher will operate with higher drain line oil temperature due to the inability of the lower flow rate to keep the crusher cool. With the crusher operating warmer than normal, the radiator type oil cooler fan will cycle on and off more often than in the past or in worst case scenario, it will run continuously throughout the day.

 

Summary

“Maintenance neglect” in the five areas listed will, without a doubt, result in a higher energy cost per ton of material crushed (kW/hr per ton) and in many cases a decrease in cone crusher productivity. This list should get you thinking about other components within the aggregate plant that also, “if neglected”, could result in a very inefficient use of electricity.

Some aggregate producers make enough profit each year to offset “maintenance neglect”. At best, such organizations are earning less profit then they otherwise might enjoy. At worst, a declining profit margin and increased competition eventually will catch up with them.

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