Typically, mobile rock crushers feature 3 types of feeders - a belt feeder, an pan feeder, or a vibrating hopper. A belt feeder is commonly used on mini crushers for light. A pan feeder with a static hopper walls is typically being used with a wide range of mobile and portable rock crushing plants.
A belt feeder features static hopper walls and a conveyor belt that conveys the material into the crusher. This type feeder is ideal for light-duty applications such as sand & gravel, asphalt, bricks, and fairly clean concrete. Sharp shot rock or heavy rebar could puncture or damage the conveyor belt. The beauty of the belt feeder is that you can easily reverese the direction in case of a blockage at the crusher inlet.
Small rock crushers with a belt feeder can be easily fed with a skid-steer or mini excavator becauser of the low feed height of this feeder.
Belt feeders are commonly used by mini jaw crushers, most mobile cone crushers, the RM 60 compact crusher, and the RM V550GO! mobile impact crusher.
This is a common setup for a small rock crusher. The hopper, feeder floor, and pre-screen shake as one compact unit. The benefit of this type feeder is that fines can bypass the crusher and merge with crushed material on the bottom of the crusher.
The single piece vibrating hopper is suitable for a wide variety of applications. You will face challanges with dirty wet material as it can build up in the rear or clog the pre-screen grizzly rendering it useless. This type feeder is best fed with an excavataor or small wheel loader. Wide loader buckets could be a problem because you would dump material onto the screening area reducing the pre-screen effectiveness and increasing the risk of a material blockage.
It is commonly used on compact rock crushers.
This feeder setup is common in mobile rock crushing plants and has static side-walls with a vibrating floor that conveys the material forward. Also common, are optional hopper extensions to increase the hopper capacity and facilitate feeding the rock cruhsing plant from the distance. Larger rock crushing plants feature the option of either a vibrating grizzly or a fully independent active pre-screen to improve the scalping action before the crusher inlet.
Larger rock crushing plants are best fed with an excavator or a wheel loader.
Feeding a crusher requires a different approach. You can't feed your small rock crusher like you would feed a dump truck.
Small rock crushers are best fed with an excavator. Using a front-end loader is only recommended for rock crushers with a bigger feed hopper and small consistent feed material such as sand & gravel, shot rock, and asphalt millings.
For instance, a RM 90GO! Compact Crusher features a 34" wide x 25" high inlet opening and is best fed with an excavator that has a 36" wide or 40" wide bucket. If the bucket is much wider than the inlet opening you risk throwing in pieces that are too big. A narrower bucket limits the top size material that goes in and enables you to reach into the hopper to realign material if needed.
| Pros | Cons |
|---|---|
| ➕ More control over material | ➖ Move less material over a great distance |
| ➕ Look into the bucket before feeding material | ➖ Limited reach (depending on the model) |
| ➕ More consistency feeding | ➖ Wait time before dumping a bucket into the feeder (e.g. excavator is too big for the crusher) |
| ➕ Reach into the hopper and realign a piece | ➖ Can't move the finished product effectively (climb off the pile) |
| ➕ Set uncrushables and oversize aside | ➖ Need to build a flat pad on top of the pile |
| ➕ Add a Quick Coupler to change the bucket for a hammer |
Consistency is the aim of the game and slow and steady will win the race. If you dump material right in front of the inlet the entire load comes to crusher at once and your pre-screen - in case your small rock crusher has one - is losing its effectiveness. The feeder will drag out the material over its entire length. Many small rock crushers feature one or two steps where the material tumbles down which improves the pre-screen effectiveness and drag out the material.
No matter if you operate a small rock crusher, or a massive aggregate system you will plug your cruhser. The only thing that changes, is the size of the piece that gets stuck. While it is true that bigger rock crushers take bigger pieces this typically doesn't necessarly translate into doubling or tripling the ideal feed size.
There is a difference between the inlet opening of a crusher, the resulting theoretical maximum feed size, and the ideal feed size. The biggest problem is when 2 large rocks come together and bridge up causing a blockage at the inlet. Without material prep it is one big gamble until this happens. The ideal feed size reflects the restraints of your small rock crusher and the mix of materials in your shovel.
Preparing and downsizing the material to the ideal feed size for your small rock crusher is critical to achieve a high production and low operating costs.
"Your small rock crusher is the most likely your most expensive piece of equipment and you want to run it as efficiently as possible and as short as possible".
While the size shovel defines the overall feeding pace the reach can affect consistencey. When it comes to rock crushing feeding slow and steady wins the race. Consistency can be achieved through material prep and access to enough material in the close vecinity of the crusher. Typically, the excavator is placed on top of a flat pile and feeds material into the crusher. RUBBLE MASTER small rock crushers can track & crush simultaneously so that you can bring the crusher closer to the pile as you keep feeding the material.
The overall positioning affects also operator safety. With impact crushers you want to place the machine off to the side so that rickocheting stones don't damage your excavator cab.
Many operators believe that you have to keep the hopper full to be effective. This is not the case - especially with closed circuit rock crushing systems. You want to watch the output side of the crusher to assess if you are feeding correctly. If you keep overfeeding a small rock crusher you limit the pre-screen capabilities, bog down the crusher, and risk a major downtime because of a material blockage.
Novice operators should keep their cab door open to listen to their small rock crusher. You can hear if you start overfeeding the crusher as the RPM drop. Many crushers feature a feed control system that slows down the feeder in case of overfeeding so that the engine can regain its RPM. If the automated controls need to intervene all the time you should seriously consider changing your feed behavior.
Feeding a crusher requires a different approach and much comes down to operator knowledge. No matter if you have a new crew or are starting out with crushing the way you run affects your bottom line. A crusher operator training may cost a couple thousand Dollars but the payback is fast and you save yourself the hassle of dealing with downtime and damages. Avoiding common mistakes will help you to dominate your jobsite.
RUBBLE MASTER dealers commission new machines with a proper on-site start-up training so you get the most out of your machine from day one. Contact your nearest RUBBLE MASTER dealer for details.
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