TECHNICAL REPORT

Oil/Air Lubrication for Steelmaking Equipment Bearings
T. MIYACHI

Recently, oil/air lubrication has undergone an expansion as a bearing lubrication method used in steelmaking
equipment, such as continuous casting equipment. This type of lubrication is attracting more and more customers
as it contributes to energy saving through reduced consumption of lubricant and low torque, and, in addition, it
supplies compressed air to the bearing to prevent infiltration of foreign matter, and utilizes high viscous oil which
can extend the life of the bearing.
We JTEKT have utilized our expertise as a bearing manufacturer to develop an oil/air lubrication device thatis optimal for bearings. This report highlights its usage within steelmaking equipment, particularly on continuous
casting equipment and steel rolling mills.
Key Words: oil/air lubrication, continuous casting machine, steelmaking equipment, energy saving, rolling
bearing life

1. Introduction

2. Overview of Oil/Air Lubrication

The rolling bearings used in steelmaking equipment
are mostly subjected to severe operating conditions,such as exposure to rolling water and heat, therefore
it is extremely important to maintain good lubricationin order to sufficiently satisfy bearing performance.
Oil/air lubrication involves a small amount of oil beingtransported by high-pressure air and is anticipated toextend bearing life as it reduces the infiltration of rolling
water into the bearing and forms a highly-lubricant oilfilm. Moreover, compared to other forms of lubrication,
oil/air lubrication uses a small amount of oil which hasenergy-saving benefits.
As a manufacturer of rolling bearings for steelmaking
equipment, JTEKT began development of oil/air
lubrication technology in 1990 with the aim of improving
bearing lubrication performance. Together withcustomers, we worked on overcoming various technicalissues and improved this technology. As a result, JTEKT’s
technology has been adopted on a truly wide variety ofsteelmaking equipment to date, including continuous
casting machines, steel rolling mills, wire rod/steel rod
equipment and non-ferrous metal rolling mills. This
paper introduces application of our oil/air lubrication
technology on continuous casting machines and steel
rolling mills in particular.

2. 1 Principle and features of oil/air lubrication
Figure 1 shows the transportation principle of oil/
air lubrication. The oil inside the pipe is transported
to the final lubrication point by the frictional force ofcompressed air. Moreover, because the oil is transported
in droplets, there is minimal emission of oil mist, which
does not contribute to lubrication, making it possible tokeep oil consumption to the bare minimum. In addition,
as compressed air, which is the force that transports theoil, is supplied to the bearing, the inside of the bearing isfilled with positive pressure, making it possible to prevent
infiltration of external foreign matter.

Compressed air(continuous supply)

Oil(intermittent supply)
Oil is conveyed continuously
in wave form

Fig. 1 Transport principle of oil/air lubrication

2. 2 Basic components of an oil/air lubrication
systemFigure 2 shows the basic configuration of JTEKT’s oil/
air lubrication system as well as the functions and featuresof each component. A feature of JTEKT’s products is that

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A single pipe can supply multiple bearings and seals.
Oil/airsupply port

Oil/air distributor(developed by JTEKT)

Oil/air distributor
Functions Multi-line distribution of oil/air after mixing unit
Features Quantitative distribution→1 to 4 portions(for continuous casting equipment, etc)
Non-quantitative distribution→1:1 to 1:8(for rolling mill, etc)

Basic layout of oil/air
lubrication system

Quantitative distribution type: Height × width × depth（50mm × 126mm × 65mm）

非定量分配型

Non-quantitative distribution typeOil/air distributor

HousingMixing unit
Oil/air
Mixing unit
Collection tank unit

Mixing unit
AirOilFunctions

Main unit
Air unit

Pump unit●●Dry air

Features

Controller

Quantitative distribution of oil
Mixture of oil and air (generation of oil/air)Function for monitoring oil/air pipes(option)→Dual monitoring function for leaks
and blockages● Oil sight (transparent tube) for visualchecking→Oil/air flow can be checked visually.
●

Controller
Functions●●FeaturesMain unit[Pump unit]●

Functions[Pump unit]●

Supply oil to the mixing unit
● Includes various monitoring
functions for the oil system●Supply air to the mixing unit
● Includes various monitoring
functions for the air system

Applicable for high-viscosity oil→Up to ISO VG680
Automatic recovery function if an error occurs→ Automatic switching to spare pump, etc.

Features[Air unit]●[Air unit]●●●

Compatible with a wide range of primary pressures→ Can handle 0.3 MPa or more
Air dryer can also be used (option).

Controlling operation of each oil/air device
Monitoring operation status
Sending and receiving interface signals

Initial oil supply adjustment function→Automatically supplies the amount of oil which is
initially required, and can then adjust the supply
amount thereafter.
● Display of recovery steps→If an error occurs, the steps made to recoverfrom the error state are displayed on theoperation screen.
●

Fig. 2 Basic configuration of oil/air lubrication
Oil/air distributor
Mixing unit

Oil/airHousing
Dry air

Air unit
AirOilCollection tank unit

Example of oil/air lubrication system layout

Pump unit
Controller
Main unit

Fig. 3 Basic layout for oil/air lubrication in continuous casting equipment

each component has a high degree of freedom allowing
it to be flexibly applied to suit the scale of the relevant
steelmaking equipment.

3. Application to Steelmaking Equipment
3. 1 Application to continuous casting machines
Figure 3 shows the basic configuration for an oil/air
lubrication system used for continuous casting machines.

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Continuous casting machines use a large quantity ofbearings therefore, as Fig. 3 shows, oil/air is distributed
into multiple channels using the oil/air distributor after
the mixing unit. The oil/air distributor is small and has
no operating parts therefore it can be directly installed
into regular segments. Moreover, for continuous castingmachines, two approaches are used; one where the oil
supplied to the bearings is collected back into the tank(Fig. 3) and the other where the oil is discharged from theJTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)

−Oil/Air Lubrication for Steelmaking Equipment Bearings−

10080806060404020200

WearCorrosion Breakage Deformation

Other

Cumulative percentage, %100

Percentage, %oil seal installed in the housing.
In continuous casting machines, the following benefits
can be anticipated when oil/air lubrication is applied.
1) Longer intervals between segment replacement due toextended bearing life.
2) Prevention of sudden accidents due to reduced bearingbreakage.
3) Reduction of operating costs due to reduced lubricant
consumption.
4) Reduction of maintenance cost due to reduced manhours for disassembling and washing bearings.
5) Improved environment due to collection of oil.
Figure 4 provides one example of the results of asurvey into the factors for bearing replacement whengrease lubrication is used. The corrosion and the wear
account for around 70% of disposal factors. If oil/airlubrication is used, the infiltration of cooling water isprevented due to the supply of compressed air and oil film
strength is improved through the application of lubricant
with high extreme-pressure performance, therefore
corrosion and wear issues are significantly improved.
Figure 5 is an example of comparing the bearing wear
amount of grease lubrication and oil/air lubrication. In
the case of oil/air lubrication, bearing wear is notably
reduced, therefore it can be said that applying the oil/
air lubrication method to continuous casting machines
greatly contributes to improving bearing life.
JTEKT believes that oil/air lubrication, which is aneffective bearing lubrication method for continuous
casting machines, should be developed further, and assuch, we are pushing forward with total engineering
including peripheral components such as bearings, oilseals and housing.

0Investigation period:
Approx. 3 years

Replacement factor

Fig. 4 Factors for replacement of spherical roller bearings

Oil/airSpherical roller bearings

Cylindrical roller bearings with self-aligning ring

4040

Period of use approx. 1 year

303020201010-0-0-10-10-20No wear

-30-20-30-40-40

Grease64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104mm40

Period of use approx. 1 year

3030201010-0-00-10No wear

-200mm

25.020Period of use approx. 6 months

100-10-10-30

Period of use approx. 1 year1040

20-2020Approx. 35µm of wear

-20-30-40-40
64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104mm-10Approx. 10µm of wear-200mm

25.0

Fig. 5 Wear comparison after field test

Oil/airsupply port

Oil/air distributor (developed by JTEKT)

Mixing unit

Oil/airDry air

Air unit
AirOilPump unit
Controller

Collection tank unit

Main unit

Fig. 6 Basic layout of oil/air lubrication in rolling equipment

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Table 1 Comparison of lubrication methods for bearings for rolling equipment backup roll
Oil/air lubrication

Oil mist lubrication
Small-sizedEquipment
scalePipe size

Internalbearing
pressure
Lubricantconsumption
amountOils used

Small-sized

Forced circulation lubrication

Small-sizedMedium-sizedtankLarge-sizedtank

・Can be used with 1 unit
・No direction limit with smalldiameter pipe
Approx. 30 kPa

・A unit is required for eachstand・Pipe direction is downward
Approx. 5 kPa

HighInternal pressure 0 kPa

Low
Consumption amount 3

Consumption amount 1

・High viscous oil (VG680)
can be used
・Extreme-pressure oil.
Synthetic oil can be used

・Unit is larger
・Pipe diameter is larger

・Limited to mist oil3. 2 Application to rolling mills
Figure 6 shows the basic configuration of an oil/airlubrication system on a steel rolling mill main body as
one example of application.
The application of oil/air lubrication to steel rollingmills, in terms of the rolling mill main body, is suited
to bearings for backup rolls which have a low rollreplacement frequency. In rolling mills, the following
benefits can be anticipated when oil/air lubrication isapplied.
1) Longer intervals between segment replacement due toextended bearing life.
2) Prevention of sudden accidents due to reduced bearing
breakage.
3) Simplification of the area around equipment through a
compact lubrication unit design and smaller pipes.
4) Reduction of operating costs due to reduced lubricant
consumption.
Table 1 shows the results of a comparison between oil/
air lubrication and other lubrication methods.
Currently, the two mainstream lubrication methods
for bearings used in rolling mill backup rolls are forced
circulation lubrication and oil mist lubrication. There arefew cases where oil/air lubrication is adopted. However,
it is believed that the adoption of oil/air lubrication willserve the purpose of future environmental improvements
and reduce of operational costs.

Consumption amount 2・VG220 to 460of the rolling mill, such as the conveyance table. In thecase of conveyance tables, the following benefits canbe anticipated when oil/air lubrication is applied, which
reduces the maintenance cost.
1) Improved bearing life due to a high sealing function.
2) Reduced motor power consumption due to low torque.
3) Reduced adhesion of leaked oil to products due to oilcollection.
4) Reduced costs involved in processing oil discharged inequipment periphery due to oil collection.

4. Conclusion
The effectiveness of oil/air lubrication in steelmaking
equipment has been verified through various technologicaldevelopments and advancements thereof.
As a result, this lubrication method is now recognizedby various customers involved with continuous castingmachines and other steelmaking equipment. Moving
forward, JTEKT wishes to further leverage its knowledge
as a bearing manufacturer to further pursue the potentialof oil/air lubrication, which contributes to stableequipment operation and energy-saving.

3. 3 Other examples of application
Places for application of oil/air lubrication other than
the rolling mill main body include peripheral equipment

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References
1)
2)

T. Miyachi, T.Uranishi: JTEKT ENGINEERINGJOURNAL, No. 1010E (2013) 42.
JTEKT CORPORATION : Oil/Air Lubrication System
for Industrial Equipment, CAT. NO. B1019. (in Japanese)

T. MIYACHI**JTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)

Industrial Machinery Application Engineering Dept.,
Bearing Operations Headquarters

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