Comprehensive Guide to Cone Crushers and Vertical-Shaft Impact Crushers, and Why They Are Used Together in Crushing-Screening Plants

In this article, we will mainly examine the working principles, structure, components, and capacity and power calculations of cone crushers and tertiary-type vertical-shaft impact crushers, which are an inseparable pair as secondary and tertiary crushers in aggregate plants where volcanic rocks such as basalt, granite, diabase and the like are crushed. We will explain the reason why they are used together. We will give examples from the plants in which they are used.

Hydrocone Cone Crushers

Cone crushers are compression crushers.

Figure 1 shows the cross-sectional view of the hydrocone-type cone crusher and the main components that make it up. Bearing-mounted inside the lower body, driven by a bevel-gear system and rotated at a certain gyration speed, is the part called the eccentric; the main shaft of the crusher is mounted eccentrically inside it. The main shaft is also mounted inside the spider bearing located at the top of the upper body. The main shaft rests on the step bearing located on the hydroset piston connected to the lower body of the crusher. This bearing carries the axial loads on the main shaft. On the conical hub connected to the main shaft, the conical moving jaw (mantle) is fixed. On the inner part of the upper body, a fixed jaw (concave) — also conical and with a special form — is fixed.

The hydroset system is a hydraulic cylinder that adjusts the gap between the moving jaw (mantle) and the fixed jaw (concave) — that is, it controls the product size.

Figure 1. Cross-sectional view and components of the Hydrocone cone crusher — In Figure 1 we see the cross-sectional view of a horizontal-shaft tertiary impact crusher and the main components of the crusher.

During operation, the moving jaw approaches and recedes from the fixed jaw along the full 360° circumference, applying pressure to the material. In other words, we can define the cone crusher as a jaw crusher with an infinite number of jaws.

We see the crushing principle of the cone crusher in Figure 2.

Figure 2. Explanation of the cone crusher crushing principle

The Rose & English capacity formula

Q = \frac{W_{i} \cdot D \cdot ρ_{s} \cdot \sqrt{L_{M A X} - L_{M I N}} (L_{M A X} + L_{M I N}) \cdot K}{2 \cdot \sqrt{\frac{R}{R - 1}}}

W_i:Bond work index

D:Bowl diameter

L_MAX:Open-side setting (OSS)

L_MIN:Closed-side setting (CSS)

R:Reduction ratio

K:Statistical factor. For soft materials such as coal and coke, K = 0.5, and for hard materials such as quartz and granite, K = 1

ρ_s:Specific gravity of the crushed material

The Rose & English motor power formula

P = W_{i} \cdot Q \cdot [\frac{\sqrt{F_{80}} - \sqrt{P_{80}}}{\sqrt{F_{80}}}] \cdot \sqrt{\frac{100}{P_{80}}}

P:Motor power,kW

W_i:Bond work index

Q:Capacity,TPH

F₈₀:The size through which 80% of the feed material passes,micron

P₈₀:The size through which 80% of the crushed material passes,micron

Cone crusher gyration speed formula:

n \geq \frac{665 \cdot (\sin α - μ \cdot \cos α)}{\sqrt{d}}

n:Cone crusher gyration speed (number of revolutions),RPM

μ: The coefficient of friction between the steel and the crushed material (between 0.2 and 0.3)

d: Maximum product size,cm

α:The angle that the crushing-cone surface makes with the horizontal

Crushing force calculation

F_{B} = {[{(\frac{2191878 \cdot N}{n \cdot x \cdot \sin β})}^{2} + {(\frac{2411065,8 \cdot N \cdot \tan α}{n \cdot x \cdot \sin β})}^{2}]}^{0,5} \cdot \frac{9,81}{1000}

n:Gyration speed,RPM

F_B:Crushing force,kN

N:Motor power,kW

x:The dimension between the cone lines,mm

α:Half of the cone angle

β:Gyration angle

Tertiary-Type Vertical-Shaft Impact Crushers

The Working Principle of Tertiary-Type Vertical-Shaft Impact Crushers

The rotor of these crushers is closed and completely lined as a stone box. The rotor acts as a high-speed stone pump; by giving a high velocity to the material entering it, it provides a high-speed stream of stone toward the crushing-plate group formed by the rock shelf attached to the body, thereby achieving rock-on-rock crushing. The velocity of the particles thrown from the rotor can rise to values of up to 100 m/s.

In addition to the material entering the rotor, a certain amount of material is also sent in a controlled manner from outside the rotor, providing a density in the crushing chamber and thereby improving the energy transfer. By controlling the amount of this material sent from outside the rotor, together with variables such as the rotor diameter and rotor speed, variables such as product grading, capacity and the amount of wear are brought under control.

Figure 3 shows the crushing principle of tertiary vertical-shaft crushers.

Figure 3. The working principle of tertiary-type vertical-shaft impact crushers

The Main Components of Tertiary-Type Vertical-Shaft Impact Crushers

Figure 4 shows the main components of the tertiary-type vertical-shaft impact crusher. In summary, the main components of these crushers are:

The crushing chamber group
The roof group
The main shaft group
The base group

It is made up of these groups.

Figure 4. Components of the tertiary-type impact crusher

The rotor is like the "heart" of a tertiary-type vertical-shaft impact crusher. Its task is to give the feed material the kinetic energy that will be converted into the stress energy required for it to break — that is, to accelerate it. The feature of tertiary-type crusher rotors is that their rotors are of the closed type; the throw shoes in open rotors are replaced by the stone accumulations that form inside the rotor. The rotor generally has 3 ports with a 120° angle between them. At the port outlets, the stone accumulations form between the tungsten carbide tips and the trail plates located at the edge where the material is thrown out at high speed.

Figure 5 shows the view and components of the tertiary-type vertical-shaft impact crusher rotor; Figure 6 shows the general view and components of the crushing chamber of the tertiary-type vertical-shaft impact crusher.

Figure 5. View and components of the tertiary-type vertical-shaft impact crusher rotor

Figure 6. General view of the tertiary-type vertical-shaft impact crusher crushing chamber

Capacity and Power Analysis in Tertiary-Type Vertical-Shaft Impact Crushers

Analysis with the Bond formula

In tertiary-type vertical-shaft crushers, when calculating the unit crushing power, the Bond formula gives a result quite different from the actual value. Therefore, as is known, it is a formula based on the work index W_i.

W = 11 * W_{i} * (\frac{1}{\sqrt{P}} - \frac{1}{\sqrt{F}})

N = W * Q

W:The approximate specific energy requirement for crushing,kWh/t

W_i:Work index

P:The square-mesh size through which 80% of the product (the material coming out of the crusher) passes –micron

F:The square-mesh size through which 80% of the material fed to the crusher passes –micron(the fine material should have been screened out of the feed material)

N:Required motor power,kW

Q:Capacity,tonnes/hour

If we examine the product curves in tertiary vertical-shaft impact crushers, in the first part the curve largely proceeds with a low gradient — that is, in this part the reduction ratio is low — and toward the last part the gradient increases and the reduction ratio increases. For this reason, when applying the Bond formula, instead of P₈₀ it is necessary to use a value between P₃₅ and P₄₀.

For quick calculations, Graph 1 can be used.

Table 1 shows the work index and other physical properties of various materials.

ROCK NAME	ROCK TYPE	WORK INDEX W_i	SPECIFIC GRAV. (t/m³) ρ	BULK DENS. (t/m³) γ	ABRASION INDEX A_i	COMPRESSIVE STRENGTH MPa
Andesite	Volcanic	16 ± 2	2,6-2,8	1,6	0,5	170 - 300
Amphibole	Metamorphic	16 ± 3	2,8 – 3,0	1,7	0,2 - 0,45	-
Sandstone	Sedimentary	10 ± 3	2,7	1,6	0,1 - 0,9	30-180
Basalt	Volcanic	20 ± 4	2,9 – 3,0	1,8	0,2 ± 0,1	300 – 400
Limestone	Sedimentary	12 ± 3	2,7	1,6	0,001 – 0,03	80 - 180
Carbon	Sedimentary	14 ± 4	1,0 – 1,8	0,8	-	-
Clinker	-	-	-	1,2	-	-
Coke	-	-	-	0,6	-	-
Diabase	Volcanic	19 ± 4	2,8-2,9	1,7	0,3 ± 0,1	250 - 350
Diorite	Volcanic	19 ± 4	2,7 – 2,8	1,6	0,4	170 – 300
Dolomite	Sedimentary	12 ± 3	2,7	1,6	0,01 – 0,05	50 - 200
Gabbro	Volcanic	20 ± 3	2,9-3,0	1,8	0,4	170 – 300
Gneiss	Metamorphic	16 ± 4	2,7	1,6	0,5 ± 0,1	200 – 300
Granite	Volcanic	16 ± 6	2,7	1,6	0,55 ± 0,1	200 – 300
Hematite	Sedimentary	-	5,1	2,2 – 2,4	0,35 ± 0,2	-
Magnetite	Sedimentary	-	5,7	2,2 – 2,4	0,50 ± 0,2	-
Marble	Metamorphic	12 ± 3	2,7	1,6	0,001 – 0,03	80 - 180
Porphyry	Volcanic	18	2,7	1,6	0,1 – 0,9	180 – 300
Quartzite	Metamorphic	16 ± 3	2,7	1,6	0,75 ± 0,1	150 – 300
Syenite	Volcanic	19 ± 4	2,7 – 2,8	1,6	0,4	170 – 300
Silex (Hornfels)	Metamorphic	18 ± 3	2,8	1,65	0,7	150 - 300

Table 1 Work index and other physical properties of various materials

Graph 1. Unit crushing power in tertiary-type VSI crushers as a function of rotor tip speed

The Reason for Using a Cone Crusher as Secondary and a Vertical-Shaft Impact Crusher as Tertiary

Since the cone crusher is a compression crusher, the product obtained from it has internal stresses and hairline cracks. It also has a flaky structure, and its flatness and elongation ratios are not at the desired level. For these reasons, it cannot be directly screened and used in concrete and road construction. The product obtained from the cone crusher needs to be crushed again in a third stage with an impact-type crusher, freed from its internal stresses and made cubical.

As we mentioned earlier, cone crushers are used as effective secondary crushers for hard and abrasive volcanic rocks such as basalt, granite, diabase and river stone. Behind these crushers, a horizontal-shaft impact crusher is generally not used. Instead, vertical-shaft impact crushers designed according to the rock-on-rock crushing principle are used.

Example Plants Where a Cone Crusher Is Used as Secondary and a Vertical-Shaft Crusher as Tertiary

1- A basalt crushing-and-screening plant with a 200 TPH product capacity for producing concrete aggregate

The plant uses an 1100×900 jaw crusher with a 132 kW motor, a cone crusher equivalent to the METSO HP 300 with a 200 kW motor, and a vertical-shaft crusher with a Ø990 rotor diameter and 2×250 kW motors.Figure 5 shows the plant flow diagram, Graph 2 shows the product curve for a 60 m/s tip speed.

Figure 5. Flow diagram of the basalt concrete-aggregate production plant

Graph 2. Output curve of the VSI crusher with a Ø990 rotor diameter

2- A river-material crushing-screening-washing plant with a feed size of 0–300 mm

In the plant, river material with a maximum feed size of 300 mm is crushed and concrete aggregate is produced. Being flowing river material, it is not very dirty. After the natural sand is separated, a jaw crusher and a cone crusher are used to reduce the stone to a size that the vertical-shaft crusher can crush. The plant feed capacity is 300 TPH; after 108 TPH of 0–4 natural sand is taken, 192 TPH of crushed-stone concrete aggregate is produced.

Graph 3 shows the river-material feed curve, Figure 6 shows the plant flow diagram, Graph 4 shows the vertical-shaft crusher output curve.