VALFLON™ lined steel pipes
Gasketless mechanism
1. Introduction

3．M isalignment of gasket may lead to gasket
protruding into the inner pipe and may adversely

VALFLON™（PTFE）has anti-corrosive properties andaffect inner environment due to fluid accumulation

does not elute of metal ions. VALFLON™ lined steel

4．High-level skill（techniques）to precisely align gasket

pipes are used for the transport of chemical solutions

and transfer of those skills（techniques）（strong acid, alkali, solvents, etc.）manufactured atWinter 2022
No.42

chemical plants and in piping that handles high-purity

For connection of pipe components, to avoid

items for the semiconductor industry. Other than

misalignment within the flow route, the center axes of

VALFLON™ piping materials, lines with corrosive fluid

the connecting flanges need to be placed facing eachthat cannot be carried by metal tubes use glass lining

other to allow flow, and also the center axis of the gasket

pipes and karbates. However, these have low mechanicalthat is the containment section must also be placed instrength, and are easily damaged if used as scaffoldingalignment with the central axis of the flange. However,or receives impact during piping work. In addition, if

there is a problem that high skill（technique）is required

there is a concentration of stress due to land subsidence

for connecting the pipes with high precision alignment ofor earthquakes, it has the disadvantage of possibly

flange and gasket. First, the flange that is formed as one

causing unanticipated accidents. VALFLON™ pipingwith the piping component or fixed at the open end of

material, utilizing the superior flexibility of VALFLON™,

the piping component, gaskets are a different material

is appropriate for these uses. Recently, in thefrom pipe components and second, there is no gasket

semiconductor industry, VALFLON™ piping material isseat to fix the position or determine the alignment ofused for handling high purity chemical solutions.

gaskets on the flange flare surface.

As the connecting structure of such VALFLON™ piping

For pipe installation devices, even if the pipe routes arematerial, flanges are installed at the connecting pipe

connected through a central axis, if the gasket isends and a gasket is placed between the flanges at theinstalled misaligned, part of the open ends of the gasket

pipe connection to be tightened. In this report, we willbore would protrude into the tube. There is an issue

introduce a“gasketless mechanism”that does not placethat protrusions of the gasket would increase the flowa gasket in between the flanges.

resistance of the liquid within the pipet and substancesthat flow with the liquid may accumulate at the2. Outline of gasketless mechanism2-1）Problem to be solved
1．There is no specific installation position for gaskets
or seat for fixation
2．Misalignment of gasket may lead to decrease in
sealability
21

protrusions and lead to worsening of the innerenvironment. Other than this, piping connections thatuse conventional gaskets close the connecting section byplacing each flange surface in contact with the opposite
side of the gasket, and crushing the two gaskets fromboth sides by tightening the flanges. In other words, thetwo flange surfaces have a structure that do not come inProduct Introductions

contact because of the gasket in between. Suchconnecting devices have issues because they may

Convex side

Flange No. 1

Concave side

Flange No. 2

decrease in pipeline sealing properties due to reasons
such as a gasket that is not installed in the appropriate
position leading to uneven flange tightening.
Figure1 and 2 show a photograph and diagram of thepipe junction.
Flange flare side

Figure3

Diagram of junction

After flange tightening, the lined junction is astructure that minimizes misalignment.
Figure4 and 5 show a photograph and diagram of thejunction after tightening.
Figure1

Photograph of the pipe junction

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FlangeFlangeFlange flare side

Flange flare side

No.42
VALFLON™（PTFE）

VALFLON™（PTFE）
GasketFigure2

Diagram of pipe junction

Figure4

Photograph of junction after tightening2-2）Measures to solve the issues
To solve the above issues, VALFLON™（PTFE）that isFlange No. 1

Flange No. 2
Metal touch junctionused in sections of the flange No. 1 formed at theopening of the tube No. 1 and flange No. 2 formed at theopening of tube No. is pressure bonded together and thishas a metal touch junction that connects the metal of theflange flare that seals the surrounding area of thepipeline junction and the flange section that does nothave VALFLON™（PTFE）lining.
In the above piping device, the metal section of flange
No. 1 and flange No. 2 have a concave-convex shape thatis a structure that relieves misalignment of the pipes atFigure5

Diagram of junction after tightening

the tightening section. Figure3 shows the junction.
22

VALFLON™ lined steel pipes Gasketless mechanism

3. Effect anticipated for gasketless steel pipes⑴ By connecting flange surfaces without a gasket in
between the flanges, the occurrence of variability inmaintain sealability with no problems without gaskets.
Table1Pressure resistance/leakage test conditions

Pressure（MPa）

Retention time（min）

Fluid

Pinholeinspection

1.5

10

Water

AC15KVthe tightening state at the flange surface due totightening tasks can be lowered and tightening
precision can be improved.

Water
pressure⑵ The housing section that was formed in a sectionof the flange houses the lining used for a section of
the flange surface, and the lining that is pressure
bonded due to the tightening of the flanges seals theMetal touch mechanism

Figure6

Diagram of pressure resistance/leakage testarea around the pipeline connecting section andrealizes a piping device that has simple installation

4-2）Heat cycle test

procedures while maintaining the sealability of

After connecting the pipes, the heat cycle was repeated toflanges.

confirm whether leakage may occur due to stress relaxationof the sealing surface. Table2 shows the conditions for thea separate component such as gaskets, it isheat cycle test and Figure7 is a diagram of the heat cycle

unnecessary to determine the position of the gasket

test.

against the flange surface or maintain that state

As a result of the heat cycle test, it was confirmed that

until tightening. Therefore, work efficiency

sealability could be maintained without any problems.

Winter 2022

⑶ Regarding the connection of pipes, by not having

improves and it is possible to improve the precision

Table2of tightening tasks without depending upon theassembly operator’s skill（technique）.
⑷ Gasketless mechanism can prevent flow resistancewithin the pipeline by gaskets that were tightened

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in a misaligned position and prevent theConditions for heat cycle test

Pressure（MPa）

Retention time
（min）

①０．
６MPa

３０

②０．
６MPa

１５

※Test is implemented by 100 repeats of⑸ After connection of pipes, by not having a gasket
in between, it is unnecessary to do retightening tomaintain sealability.

①→② as 1 SET

Confirmation ofsealability after test

accumulation of substances that are contained in thefluid.

Fluid
１６５℃
saturated steam
Water at room
temperature

Pressure（MPa）

Retention time（min）

Fluid

Pinholeinspection

1.510

Water

AC15KV

Saturated steam⑹ Metal touch mechanism can reduce the looseningof bolts due to vibration because there is no gasket
in between.

Output

4. Sealing performance

Metal touch mechanism

4-1）Pressure resistance and leakage tests
Standard tests and inspections for lined pipes wereconfirmed for gasketless mechanism. Table1 shows thepressure resistance and leakage test conditions andFigure6 shows a diagram of pressure resistance andleakage tests. It was confirmed that it is possible to23

Water at room temperature

Figure7

Diagram of heat cycle testProduct Introductions

5. Conclusions
VALFLON™ lined pipes with gasketless mechanism is awith further improvements, we aim to complete
products that would be a mainstay of lined pipes andmake products that our customers are satisfied with.

product that was produced with the customer’s
viewpoint, such as pipe installation and flange tightening
control in consideration. In addition, it has the safety
features because of its fire-safe property that wouldminimize the possibility of spreading fire. In the future,

6. References
1）V alqua Handbook Technology Edition （Pipingmaterial products）

Nobuyuki Kawai
VALQUA METAL TECHNOLOGY CO., LTD.
Production Division

Winter 2022
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