Development of 6-Roller UBE Vertical Mill for Slag / Cement Grinding&Modular Design Concept for UBE Vertical Roller Mills (VRMs)
for Large Cement Plants
Yasuhiro SHIGEMOTO†

Hirofumi KASAI†

Tatsuya HINAUCHI†

This paper introduces the development of the UBE 6-Roller VRM, which achieves higher Milling
Performance at better Cost-Performance, to meet client demand for higher Energy Efficiency andYokozuna size(*) Mill Capacity for increasing Cement Plant capacity. Other advantages include
greater Reliability and easier Maintenance due to greater parts commonality and rationalization
for the VRM range, achieved by the new Modular Design Concept.
(*) Yokozuna is the great champion of Sumo wrestling.

essential countermeasure to suppress mill vibration is to

1． Introduction

increase (improve) friction coefficient of material in theAs a result of the world-wide attention in recent years

grinding area directly beneath the mill roller.

to Energy Efficiency Improvement and CO2 Reduction,

Grinding Forcethe numbers of VRMs adopted for Slag / Cement
grinding are increasing. And effective use of granulated

Compacting Forceblast furnace Slag has been widely promoted, resulting in

Main Roller

further VRM demand for Slag Grinding. More demand for
Sub Roller

Slag Grinding VRMs is anticipated in developing
countries, too, where the trend is to adopt Large Plant
Capacity (5,000 - 10,000 t/day) to meet strong market

De-aerated by Pressing

demand for cement. To meet the increase in plant

Air included in material

capacity, demand for greater milling capacity VerticalFig.1

Mills is also growing rapidly.

Principle of 2-Way System

Under this background, UBE has developed a new

In the 1980s, UBE developed the 2-Way System

6-roller Slag / Cement Mill suitably designed for capacity

shown in Fig. 1, where de-aeration and compaction ofmaximization, higher efficiency and lower cost compared

the raw material bed on the grinding table by sub-roller

to the conventional VRM. The First Development Mill

pressing is achieved, improving the material coefficient of(UM43.6SR) started commercial operation in March 2013,friction.

with excellent performance results as presented in this

The Test Results shown in Fig. 2 demonstrate that thepaper.

higher the degree of grinding bed compaction, the higher

Further, with the recent increase in Cement Plantthe value of the Material Friction Coefficient.

Capacity, larger milling capacity is required. To meet this50Friction coffient of material bed%

increased plant capacity demand, UBE introduces thenew Modular Design Concept, which increases reliability
through commonality of mill parts, and achieves reduced
maintenance cost.
2． Development of New Type Slag / Cement Mill4030201000102030

Compression ratio %Product Fineness of Slag / Cement powder is ultrafine
Fig.2 Compaction Degree of Grinding Bed vs.

(Dp50 = approx. 10 - 15μm), and the occurrence ofvibration can interfere with stable Mill operation.

Friction Coefficient of Material

The140UBE performed further research to investigate theis a UM46.4SN （table diameter: 4,600 mm）, while therelationship between Degree of Compaction & Friction

new mill is a UM43.6SR (table dia: 4,300 mm), or one

Coefficient, and found a link between grinding bed depth

full model size smaller in terms of Table diameter.

and Friction Coefficient of material bed.

Fig.3

In this case, by adopting the 6-roller mill with newdemonstrates that the shallower the grinding bed, thedesign sub-rollers support, compared with thehigher the Friction Coefficient of material bed.

conventional UM46.4SN mill, a 20% reduction of millweight was achieved. Moreover, as secondary effects

Friction coffient of material bed %50%of reduced mill weight, foundation concrete weight
reduced by ▲20%, and Maintenance hoist crane

40%

capacity reduced by ▲40% when compared to a30%

conventional mill.

The reduction in concrete weight inparticular has a considerable cost advantage in terms

20%of initial investment.
Small Compression StrengthMiddle Compression Strength
Large Compression Strength

10%0%

Conventional MillDevelopment MillMil Type

UM46.4SCN

UM43.6SCR

Table Dia.

φ4600mm

Φ4300mmDia.

φ2240mm

φ1800mm

Q’ty

2 pcs

3 pcs

Dia.

φ1700mm

φ1120mm

By adopting smaller grinding rollers, theoretical mill

Q’ty

2 pcs

3 pcs

capacity is decreased, but by increasing the number ofMill Weight100%

80% (▲20%)

Crane 100%

Crane 60%

05101520Layer Thichness h（mm）

Fig.3

Measuring results for Friction coefficient ofmaterial bed

MainRoller

This test result, clearly demonstrating the relationshipbetween bed depth and Friction Coefficient (Fig.3),
inspired UBE’s decision to develop a new VRM withSubRoller

smaller rollers but larger capacity than ever before.

rollers from 4 to 6-rollers, mill capacity is maintained.
Moreover, as the new 6-Roller Mill employs the 2-Way
System, and the support structure of the new, low-load
Sub-Roller configuration has also been refined, millweight and cost are reduced, while the same mill
performance as a larger mill is achieved.

Accordingly, aOthers

new concept, down-sized mill has been successfully
developed.
2.1. Results of Development

FoundationFoundation

mass 100%mass 80%

2.1.1 Comparison of Specification and Cost of Mill
Table 1 Comparison of Specification and Cost

Table.1 is a Specification Comparison of Conventional(Slag 90T/H, Clinker 120T/H base)& newly Developed Mill.
Note: Table 1 presents performance figures for arepresentative mill (Slag Grinding Capacity: 90 T/H,Clinker Grinding Capacity: 120 T/H), where mills of thesame model achieve very similar production results.
The new 6-roller Mill’s greatest advantage is Mill
down-sizing. By combinations of Table size, Roller size
and number of Rollers, Mill down-sizing has beenachieved relative to the conventional mill of same millcapacity. In the case of ‘Table 1’, the conventional mill2

2.1.2 Performance of UM43.6SR

Table 2 shows actual operation data comparison ofUM46.4SN (Conventional Mill) & UM43.6SR

An order for the first UM43.6SR Slag Mill was received(Development Mill)

from China, and mill trial operation started in
December 2012.

Conventional MillDevelopment
Mill

Mil Type

UM46.4SN

UM43.6SR

Capacity

96T/H

99T/H

Fineness

4,200cm3/g

4,205cm3/g

Mill

25.3kW/t

24.9kW/t

Sep.

1.4kW/t

1.3kW/t

Fan

8.0kW/t

7.8kW/tP.C. Total

34.7kW/t

34.0kW/t

Vibration

25～50μm

15～35μm

Remarks

After 1000h
Operation

After 1000h
Operation

In March 2013 mill performanceacceptance was completed.

P.
C.

Table 2Difference+3%-2.0%

Actual Operation Data of Slag Grinding

As per Table 2, the UM43.6SR Mill Capacity increased
approximately 3%, and Power Consumption decreased
about 2% compared to UM46.4SN. Superiority of thenew UM43.6SR mill design is confirmed by this data.
Further, regarding mill vibration, which was anotherperformance improvement target of this project, thenew mill ran at lower vibration as expected. It may be
assumed that this is a result of the shallower grinding
bed depth and higher Coefficient of Friction in the newmill in comparison to the conventional mill.

The

reduced mill vibration and improved grinding efficiency
have resulted in a significant performance improvementof the newly developed mill over the conventional mill.
Accordingly, the first operating 6-Roller Slag Mill has
achieved all of the mill performance targets establishedin the development stage, to the great satisfaction of thecustomer.
Furthermore, UBE has received an order for the same

Fig. 4 Slag Grinding Plant and 6 Roller Millmodel UM43.6SCR Slag / Cement Mill for Australia, withmill scheduled to start operation in early 2014.

3.

VRM Proposal for New Large-Capacity Cement Plants
Recently, with increasing Cement Plant Capacity, verticalmills are being used not only for raw material and coal
grinding, but also for cement grinding.

3Fig 5 shows a typical VRM arrangement for new cement

improving standardization of key parts and interchange

plant.

ability, thereby improving reliability at a lower equipment
cost.

Details of this design method are as follows.

(Please refer to Fig.6, 7 & Table3)
Raw Mill

Cement Mill

4 Rollers (2+2)

4 Rollers
1 Set of Raw Mill

1 Set of Coal Mill

2 Sets of Cement Mill

Fig.5 Typical VRM Arrangement for Large Cement Plants
The larger cement plant capacity becomes, the larger
mill capacity must also become, and such over-sized
VRMs require special engineering, and special parts andsupport machinery.

Due to lack of common parts, in the5 Rollers

6 Rollers (3+3)

10% Down Sizing

20% Down SizingFig 5- & 6-Roller Mill Design

event of mill breakdown, there is the risk of long term
plant shut-down.

Accordingly, the End User is faced

By changing the conventional 4-roller design to thewith the dilemma of opposing requirements: Large

5-roller raw mill, a 10% down-sizing was achieved, andCapacity Production and Security of Common Spares.

by changing the conventional 4-roller cement mill to theIn order to reduce risk of long-term shutdown, Mill

new 6-roller mill, a 20% down-sizing was achieved while

Users stock many key spare parts (for example: bearing,

maintaining the same grinding capacity in both cases.

cylinder, etc.), however, maintaining a lot of spare parts

Raw Mill

Cement Millstock for each different VRM is not good economics.
From this viewpoint, VRMs installed on new Cement
Plants in recent years must not only have thecharacteristics of Large Capacity and High EfficiencySame(low power consumption), but also High Reliability with

Gear Reducer

Low Initial Investment and Low Maintenance Cost.
In order to meet the above mentioned demands, UBE
has conducted new research into a modular mill concept,and introduce herewith VRM combinations to meet ofplant capacity with each mill size as follows.
3.1 Modular concept design

SameRoller Module

UBE has been designing the VRMs Rollers inaccordance with

Modular design concept. In otherwords, if roller size is same even for different table size,
same roller assembly, same swing lever assembly andsame tension device are used. By adopting this design
method, parts standardization is achieved.
The following example is a combination of Raw Mill &5 Rollers

Cement Mill suitable for new, large capacity Cement

6 RollersPlants, comprised of a 5-roller Raw VRM and 6-roller
Fig.7 Modular Design Concept of VRM

Cement VRM, having 2-way systems with small roller
size. With this adaptation the mill is able to be

As just described, by changing to smaller, modular

down-sized and used for the large Cement Plant, whileroller mill design, the same grinding roller modules are4

used for both raw and cement mills, and parts

4. Conclusioncommonality is achieved.
Further, by matching mill power and table rotation

UBE has supplied over 500 VRMs for Cement Plants,speed, identical reduction gear units are used on theSlag Grinding Plants and other plants all over the world.

three VRM: (1) set of 5-roller raw mill, and two (2) sets ofFrom a strong experience base, UBE will continue to6-roller cement mills.

develop VRM technology in order to supply larger size,
more energy efficient, better cost performing VerticalRoller Mill,

3.2 Combination of mills for new, large cement plantstandard.

Table3 shows typical ‘Mill sizing Table by Module
Concept （Example）’.
Raw Mill(１ Set)
5 Roller Type

Cement Mill(2 Sets)
6 Roller TypeMill Capacity

750 T/H

260 T/H x 2Mill Type

UM63.5

UM61.6 CR

Roller Size

φ2500 x 5

Reduction
Gear

6,000kW
23.1rpmφ2500 x 3
φ1900 x 3
6,000kW
23.1rpm

Mill Capacity

580 T/H

200 T/H x 2Mill Type

UM59.5

UM56.6 CR

Roller Size

φ2240 x 5

Reduction
Gear

5,100kW
23.8pmφ2240 x 3
φ1700 x 3
5,100kW
23.8rpm

Mill Capacity

400 T/H

150 T/H x 2Mill Type

UM53.5

UM50.6 CR

Roller Sizeφ1900 x 5

ReductionGear

3,800kW26.7rpm

Plant
Capa.

10,000T/D

7,500
T/D

5,000T/Dφ1900 x 3
φ1500 x 3
3,800kW26.7rpm

Table 3 Mill sizing Table by Module Concept （Example）
3.3 Advantage of Module design concept
As per above-mentioned, by adopting small roller
module, new concept VRMs are able to keep mill
performance while down-sizing the mill, and the initialinvestment for the project is may be reduced.
And through standardization of parts, End Users canmanage spare parts and trouble-shooting more easily,
thereby ensuring mill availability and reliability.

Due tocommonality of spares, quantities of contingency spareparts can be reduced, so the cost burden for spares isalso is lower.

5whilemaintaining

UBE’s

highquality