Product Introductions

Low Torque & Long-Lifetime Swivel
Joint LFR JOINT™
1. Introduction
The aging of the population, one of the major social

customers’ maintenance cost reduction and productivity
improvement of facilities using the techniques wehave fostered as a manufacturer of seal products.

issues in Japan, is currently causing a very serious
situation in the manufacturing field as well. In
particular, the aging of experienced workers in themanufacturing field has been progressing, but

2. ‌Issues of conventional
swivel joints
A swivel joint is a collective term for a joint whichof techniques has not been keeping up with the speed

has the ability of continuous rotation and oscillatingof aging. The decline in technical ability in the field ismovement at low speed. It is widely used as analready happening in the production field of every

important part which carries various types of liquids

company. Additionally, the trend of aging population（such as hydraulic oil, air, water, etc.）considered as

is rapidly spreading overseas, and this is also a

blood in each process.

significant issue from the global perspective.

Winter 2019securing enough young engineers and the succession

In such situation, actions to streamline operating costs
at each process are intensifying by considering all theNo.36

various factors together including maintenance offacilities. This is because in order to gain maximum
benefit with limited number of staff, streamlining witha more permanent perspective, which takes man-hour
for maintenance and long-term reliability into account,is now required in addition to short-term cost
reductions in purchasing facilities and materials.
These issues are not only the matters imposed on theequipment that are the main force in a process, butalso items such as sealing materials and joints, whichhave been considered as consumable supplies but
have considerable roles to play.
LFR JOINT™, the swivel joint introduced in this issueof Valqua Technology News, is a solution-type ofproduct developed while collecting customers’comments from the field.
We would like to introduce this product because it is a
product which makes a significant contribution to ourFigure1

Cutaway model of LFR JOINT™
32

Low Torque & Long-Lifetime Swivel Joint LFR JOINT™

For example, swivel joints are applied as joints in theis high. These factors cause the swivel joint to havehose part of robots installed in automatic production

an extremely high rotational resistance and hinderslines of the aluminum diecasting process to reduce thethe intended rotational and oscillating movement.

load on the hose by eliminating twists caused by theIn addition, rubber is generally not a material which is

robots’ complicated movements and high frequency ofresistant to abrasion. Therefore, O-rings are severelyoperation.

worn down, especially under adverse lubrication

However, swivel joints generally have high rotational

conditions at high temperature and high pressure, andresistance and the effect of load reduction on the hose

this results in shortening the life of the swivel joints

is not sufficient, causing premature fractures in thethemselves.

hose. This has been an issue that considerably
decreases productivity of the process.
As another example, under severe environmental

4. Solution by LFR JOINT™

conditions（high temperature, pressurized liquid, dust,

LFR JOINT™ is a swivel joint which solved the long-etc.）such as in steel plants, there were some cases instanding issues with swivel joints and realized bothwhich the interval between maintenance of thelow-torque and long life.

production line became shorter because the sealing

Various innovative designs are applied to the sealingmaterial on swivel joints were quickly worn down.

mechanism and also to peripheral aspects such as theseal groove. In this issue of Valqua Technology News,

Winter 2019the sealing mechanism is explained.

Movement of equipment

5. Sealing mechanism of LFRJOINT™
In order to solve the issues of swivel joints, LFR
SEAL™, a sealing material for rotational movement

No.36

was specially developed for LFR JOINT™. Figure3
shows a cross-section diagram of LFR SEAL™.
Figure2

Example of premature fractures in the hose

ElastomerResin

3. Cause of the issues
The two issues of swivel joints described above, 1）high rotational resistance and 2）short life, are largely
due to the sealing material that is used.
O-rings, mainly made from rubber, are commonlyused as the sealing material for swivel joints. During
low-speed rotation or oscillating movement, this O-ringFigure3

Cross-section diagram of LFR SEAL™

fills the gap by sliding against the rotational axis and5-1）Torque reduction

prevents liquid leakage.

In order to reduce torque in swivel joints, it isHowever, due to the characteristics of rubber

necessary to reduce sliding resistance of the sealingmaterial, frictional resistance when sliding against thematerial, but we considered that sliding resistance isrotational axis is extremely high. Furthermore, thisrelated to friction coefficient, contact area with thetendency is even more significant when fluid pressureother surface（rotational axis）, and tension force. The33

Product Introductions

resulting design was produced by resolving each of5-2）Life prolongationthese factors and is shown in Figure3.

It can be said that improving the durability of thesealing material is an effective means for life

Ⅰ.Friction coefficient

prolongation of the swivel joints because the life of

Resin of low friction coefficient was compounded withswivel joints is deeply related to leakage from sealingelastomer by forming them simultaneously inside thematerial.

sealing where the other surface（rotational axis）This sealing employs resin for the sliding face of thecomes in contact.

sealing and its durability is superior to an O-ringwhich slides on a rubber face. Also, as described inⅡ.Contact area

5-1, the mechanism to reduce torque decreases friction

When fluid pressure is applied, a tilt generated by theheat generated during the sliding of the sealing andtapered face of the non-pressurized side coming into

this reduces abrasion and fatigue of the sealing

contact with the groove face makes it possible tomaterial.

control the contact area of the arc sealing face that isin contact with the rotational axis. Thus, the increasein the contact area resulting from increased pressure
can be suppressed as shown in Figure4.

6. Effects of LFR JOINT™
6-1）Increasing the life of accessories suchas hose material

Fluid pressure

Figure6 shows a comparison of rotational torque ofLFR JOINT™ and a conventional swivel joint with anO-ring. It shows that torque rises only slightly with

The tapered face ofthe non-pressurizedside comes in contact
with the groove faceFigure4

Control of the contact area

Ⅲ.Tension force

The volume of external diameter of elastomer at thebase was reduced and the inner face and the outer

Rotational torque（N·m）

LFR JOINT™, even if fluid pressure is increased.

No.36

LFR JOINT™
Swivel joint with an O-ringface that become the sealing face were designed to bearc-shaped to reduce tension force.
Pressure（MPa）
ReducedvolumeFigure6Comparison of rotational torqueThis considerably reduces the rotational load on
accessories such as hose material.
In market performance, the lifetime of hoses wasactually extended, and the life-prolongation effect evenreached a maximum of ten times longer in somecases.

Figure5Winter 2019

Tilting of thesealing

Suppresses
increase ofcontact area

Shape of external diameter of elastomer part34

Low Torque & Long-Lifetime Swivel Joint LFR JOINT™

6-2）Life improvement of joints
Figure7 shows a product life comparison of LFRJOINT™ and a swivel joint with an O-ring, andTable1 shows the test conditions.

O-ring for conventional swivel
joints（leakage after approx. two
hundred thousand times ofoscillation）

LFR SEAL™ attached to LFR JOINT™
（capable of continuousoperation even after approx.
four hundred thousand times ofoscillation）

This shows that maintenance costs for joints can be
reduced because the life of LFR JOINT™ is more thanDurability for numberof times（oscillation）

double when compared to our conventional joints.
Approx.
over 400
thousandtimes

Figure8

Approx. 200
thousandtimes
Swivel joint with an O-ring

Figure7
Table1LFR JOINT™

Life comparison

Test condition for life comparison

 omparison of sealing cross-sections before andCafter life testing

7. Conclusions
The Valqua Group aims to evolve into an“H&Scompany”that provides not only sealing products but

Winter 2019

FluidAir

Pressure0.7 MPa

unit product that is a part of our strategy.

Temperature

120℃

We will continue to develop products to meet market

Angle of oscillation

90 degrees

demand, but also dig out unmet needs together with

Diameter of rotational axis

φ42

our customers and work hard to provide true

Also, Figure8 shows a comparison of the cross-also peripheral services and this product is our firstsolutions by merging innovative technologies andservices.

sections of the sealing material before and after life

No.36

testing. The thinner line represents the cross-section
before the test and the solid line after the test.
The O-ring for conventional swivel joints was severely
worn away after approximately two hundred

8. References１）Akihiro Nagano, Valqua Technology News, No.30,
9-13, 2016

thousand times of oscillation and this abrasion causedleakage. On the other hand, LFR SEAL™ attached toLFR JOINT™ did not show any major abrasion evenafter approximately four hundred thousand times ofoscillation and was still capable of continuousoperation.

＊LFR JOINT and LFR SEAL are trademarks of VALQUA, LTD.

Ryosuke Nishi
Research and Development Headquarters
Product Development Division 135