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Mar 30, 2020

Q&A: How to minimize operating costs and ensure trouble-free operation with GP Secondary cone crushers?

Janne Lahtela
Janne Lahtela
Product Specialist, GP Cones and C Jaws
The secondary stage of the crushing process may be demanding for the cone crusher, as there can be variations in the feed flow and the feed size can be anything between extra coarse and fine. Also, possible blockages may limit the capacity of the entire plant. To ensure trouble-free and cost-effective operation, there are certain cone crusher features that help to cope with these mentioned challenges. Here we have a look at some of those features by taking Nordberg® GP Series™ Secondary cone crusher as an example.
Our expert Janne Lahtela, Product Specialist for GP cones and C jaws
Our Metso expert Janne Lahtela, Product Specialist for GP cones and C jaws

We had a chat with our recently appointed Product Specialist for GP Cones and C Jaws, Janne Lahtela, who told us how GP Secondary cone crushers help to reduce operating costs and ensure smooth feed material flow.

Q1: First of all, which cone crushers are we now talking about?

GP Secondaries are engineered for the secondary crushing stage, which in certain applications requires quite specific features from a cone crusher. As a result, they actually look a bit different compared to our versatile cones like the Nordberg® GP Series™, HP Series™ and Metso MX™ cone crushers. Those ones can be utilized in secondary, tertiary and quaternary crushing stages.

That being said, not all secondary crushing applications are the same, and in most of them those versatile cones work tremendously well! But in certain situations, GP Secondaries’ design principles will provide the best performance.

The GP Secondary range includes the GP100S™, GP300S, GP500S™, and the mighty GP7™ models, which are part of the Nordberg® GP Series™ cone crusher product family. As the “S” at the end of their name suggests, they are typically located at the site as a secondary crusher.

Q2: So, there can be different requirements for a cone crusher, if it is operating in the secondary or tertiary stage?

You are correct to a certain extent. The main differences in requirements might come from the process stability or feed size point-of-view, to name a few.

The crushing process may not be stable at the secondary crushing stage. The feed material flow could vary, especially if a surge pin or stockpile is not in use. This means that the crusher may constantly be changing between choke fed, partially full and empty cavity situations.

This variation extends to feed size and gradation as well; it can be anything between massively coarse and fine.

The main feature of the GP Secondaries is the capability to accept extra-large feed material in relation to their physical size. This unique “feed opening to weight ratio” creates numerous possibilities for our customers to optimize their operating expenses and maximize uptime for their whole crushing circuit. In cases where the feed size is the limiting factor, GP Secondaries help to optimize capital expenses too.

Q3: Is the big feed opening beneficial regarding operational expenses and if so, why?

Yes, both directly and indirectly. Directly by the crusher’s excellent performance in its demanding task, and indirectly by how its design positively affects the other crushers around it.

The situation known as blockage, or bridging, is a common challenge in rock crushing. In bridging, too coarse or slabby feed material may get stuck in the feed opening of a cone crusher, thus blocking other material from entering the cavity and limiting the overall capacity of the plant.

Really coarse feed material can be a consequence of using too large double-toggle, short stroke single-toggle or otherwise older technology jaw crusher, which just isn’t capable of reducing the material size enough for the rest of the process, but is too expensive to change to a more suitable one.

In these kind of situations, the big feed opening and lifted spider arms of the GP Secondary cone crusher help by enabling smooth flow of even the coarsest feed material by preventing the formation of blockages.

GP Secondary cone crusher's big feed opening
GP Secondary cone crusher's big feed opening with lifted spider arms maximizes the material flow.

The big feed opening of the GP Secondary is indirectly benefitting the primary crusher, a jaw crusher in this example, which can be operated with a more open closed side setting (CSS). A larger CSS gives the jaw dies significantly longer lifetime, visibly smoother feed material flow and higher productivity for the plant.

Let’s take the Nordberg® C120™ jaw crusher and its jaw die lifetime in the allowed CSS range of 70–175mm (2¾” - 7”)  as an example:

The difference in wear part lifetime is particularly huge, if you don’t have to run the jaw crusher close to its tightest allowed CSS. For example, if you open the setting from 100mm (4”) to 150mm (6”), the crushed tonnage per one set of jaw dies nearly doubles on average, and the relative energy consumption will be lowered as well! This benefit is of course application specific and assuming that there are no other limiting factors for the jaw crusher’s CSS.

Q4: How GP Secondaries help customers to reach trouble-free operation?

In addition of big feed opening, there are also other design features such as steep vertical cavity, that help our customers in different situations to reach trouble-free operation.

More tolerant to fines in the feed

If there is no possibility to add a screen between primary and secondary crushers, it can cause lots of fines to be fed into the secondary cone crusher. GP Secondary, with its steep cavity and the possibility to obtain a shorter stroke, helps to prevent packing issues, and in some cases handle all-in feed.

This can also lead to a situation where less quarry fines have to go to waste and can be made as an end-product.

Managing variable feed rate

Like I already pointed out, it can be a struggle to keep the secondary cone crusher constantly fed with stable feed rate and grading. Any cone crusher works most optimally and produces best capacity, reduction and shape when choke fed. Changeable stroke length in the GP Secondary makes it possible to find the best fit for the available material flow.

That being said, GP Secondaries’ performance is anyhow less sensitive to the feed material level, and they can tolerate on/off feed to some extent.

Reducing fines in the production

Thanks to the steep vertical cavity and kinematics, a GP Secondary cone crusher tends to produce steep particle-size distribution curves; thus, the yield of fines is lowered for the secondary crushing stage. This is especially beneficial for applications such as railway ballast.

Accepting difficult feed material

Sometimes the feed material is slabby, slippery, or moist, which makes it difficult to reach the desired capacity level for the plant. Material with these kinds of properties will flow easily through the GP Secondary’s steep cavity.

Less frequent need to adjust the primary crusher’s parameters

GP Secondaries have constant and large feed opening dimensions across the whole lifetime of their wear parts, minimizing the need to adjust the primary crusher’s parameters during operation or for possible blockages.

As you can have constant feed intake capability despite of liner wear rate, the automatic wear compensation feature from the Metso IC50C™ just eases the operation that much more!

GP Secondary cone crusher's steep cavity
GP Secondary cone crusher has a steep vertical cavity.
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