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Is an Impact Crusher Right for my Quarry?
Posted by Bert Hart

7 minutes read

The difference between a good and excellent tool is what it's used for. Knowing which crushing plant to use is similar; all are good, but which option helps best achieve your product and spec?

The goal is to sell rock/gravel, not just buy a crusher; the crushing plant is the means to that end. In this article, we'll be discussing Mobile Impact Crushers and some questions we can answer to determine an Impactor's suitability to your quarry. (We use quarry broadly here, it could equally apply to a contractor or recycler.)

What is the feed material?

This is one of the most important questions to ask when choosing an Impactor. Some materials can be prone to very high wear and end up being a very expensive crush. We always emphasise profitability per tonne.

If the feed material lacks enough fines and requires multiple crushing passes, an Impact Crusher is an ideal solution. Its crushing system lends itself to producing a good envelope of material sizes from a single pass. Learn how they work in this article →

Sedimentary rock tends to break in layers resulting in 'slabby' end product with compression-based Crushing Plant (e.g. Jaw Crushers and, to a lesser extent Cone Crushers). Impactors produce the best shape in these applications as 'slabby' material is not generated near the same degree from an impact. A primary HSI Impactor can be utilised in this scenario crushing or a tertiary VSI after another plant.

 

What are the specification requirements?

HSI Impactors are classified as primary and secondary capable crushers; Impactors can be directly fed, or chain fed down the line for further shaping if required.

An Impactors big strength is the ability to do both primary and secondary duties in one pass, typically achieving what a Jaw and Cone Crusher together would produce.

Their multi-role reputation is due to an Impactors superior shaping ability and resistive crushing.

An Impactor gets a better product shape thanks to the effect of Autogenous crushing that occurs in the chamber. Autogenous Crushing is the rock on rock impacts that happen in an impactor's high-speed environment; rocks bounce off each other, shaping them, and produces an ideal cubical shape.

Increased fragmentation resistance of crushed materials is also part of an Impactors list of benefits. Impactors break up material at its weakest points, meaning the material passing through has reduced fragmentation attributes. 

A sufficient Cubical Shape, Fragmentation Index and Sizing Envelope are important in meeting today's strict specifications placed upon quarries.

These three attributes make an Impactor a compelling crushing solution.

 

What are the versatility requirements?

Mobile Impact Crushers are the most versatile mobile crushing plant; what a quarrying business needs to ascertain: how often will the mobile plant be shifted to a different site? And how often will it be required to move on-site?

An Impactor fulfilling the role of a primary and secondary crusher will halve two machines' potential transport cost. The more often movements are needed, the more savings there is.

Impactor vs other machines for transport

What about feed variation? An Impactor can handle a wide spread of material types and sizes like alluvial, face rock and concrete.

Where it would suffer is on the extreme ends of the feed size, very large, or very fine material (in context to the Impactors specified ability), Impactors will start to wear more rapidly in these scenarios.

A one-stop shop crushing machine is the Impactors strength.

Cubical Shape Index - Impactor vs Cone

The shape index graph shows how 'slabby' an end product is based on EN933-4 standard. The higher the index number the less cubical a product is. Lower is better.

Cubical Shape

L.A Fragmentation Index - Impactor vs Cone

The L.A. test determines how resistant a crushed material is to fragmentation and is based on the EN 1097-2 standard. The higher the index number the less resistant the crushed material is to fragmenting. Lower is better.

LA Fragmentation

Operating costs

The cost per tonne operating an Impact Crusher is relatively low when considered in context.

The wear part cost is perceived as high, and it is higher than a Jaw and Cone when looked at separately, but versatility is its strength and with an Impactor doing the job of both, the cost is low.

Consider there is only one machine to replace wear parts on, transport, fuel, maintain, run, and invest in.

When calculating which type of Crusher you are investing in, calculating your total cost per tonne and thus profit, will give you the best base to compare the benefits of a machine to the business.

Impactor Chamber

Ease of use

At Equip2, we spend a lengthy amount of time training new plant operators on using an Impact Crusher and how to get the most out of them. It can be a steep learning curve, particularly coming from the 'set and forget' nature of Jaw and Cone Crusher setups.

An Impactors versatility means it has more adjustability, and understanding these functions and how to work them to produce products to the desired specification is where the time goes learning and experimenting.

However, once mastered, a skilled Impact Crusher operator can produce some accurately specced products. Another weak point here is that just one primary operator tends to work with an Impactor; swapping operators on and off won't allow them the time to master it adequately.

Additionally, an Impactor also requires more maintenance attention; wear parts need regularly checking along with drive components. This doesn't always go well with some operators, so a maintenance schedule and a responsible maintenance person will all help keep the plant running at its peak with no unexpected downtime.

 

Is an Impact Crusher right for my business?

To summarise, an Impact Crusher has more versatility than a Jaw and Cone Crusher since it can simultaneously perform primary and secondary duties. 

We're big fans of Impact Crushers because they produce excellent results for our customers and have thus far; been unbeatable as a total machine solution. 

Want more information on Crushing Solutions or a Consultative approach to choosing your next machine? We can help by providing a profitability calculator, production forecast and a full costing run down.

Impactor Model

Rockster R700S

Portafill MI-7R

Keestrack R3h/R3e

Keestrack R5/R5e

Keestrack R6/R6e

Weight

22,500kg

20,000kg

30,200kg

50,170kg

61,000kg

Transport without permit****

Ideal Reduction Ratio

1:12

1:12

1:12
1:20 (Closed Circuit)

1:12
1:20 (Closed Circuit)

1:12
1:20 (Closed Circuit)

Ideal End Product

10-120mm

10-120mm

10-150mm

10-150mm

10-150mm

Inlet Size

710mm x 650mm

810mm x 600mm

770mm x 960mm

800mm x 1,050mm

970mm x 1,300mm

Pre-Screen

Post-Screen Capable*

Magnet Belt

Tonnes per hour**

150

150

250

350

400

Optimal Annual Production***

135k Tonnes

135k Tonnes

270k Tonnes

315k Tonnes

360k Tonnes

*Post screen is optional - we supply post-screen equipped Impactors by default
**when processing optimal size of feed and output, results can vary
***Assume 1,000 working machine hours at 90% optimal production per hour
**** Based on standard weights and dimensions, please check with the transport company as permit requirements vary by region and can change

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