Non-stagnant piping system

The present invention relates to a non-stagnant piping system and it is an object of this invention to provide a piping system such that the fluid inside the upstream side piping of a valve portion and inside the valve will not become stagnant in a super pure water line and chemical solution, etc., regardless of whether the valve is in a closed or opened state. A diaphragm valve 3 having a by-pass means 3b installed on the upstream side of the valve portion 3a is mounted in the sub-line 2 branched from the main line 1 in the piping system, and a pressure reducing unit 4 having a pressure reducing portion by a throttling portion 4a, and a by-pass 4b communicating with the throttling portion 4a is installed on the downstream side of the branch point with the sub-line 2 in the main line 1, and moreover, both by-pass means 3b and 4b communicate with each other.

TECHNICAL FIELD 
The present invention relates to a piping system, and particularly relates 
to a piping system in which the fluid inside the upstream side pipe and 
inside the valve does not stagnate when the valve is open or when the 
valve is closed. 
BACKGROUND ART 
In a pipe line in the conventional semiconductor manufacturing process and 
so forth, a sub-line 32 is installed as necessary and a valve 33 is 
provided for the adjusting or opening and closing control of the fluid 
being supplied to said sub-line 32, as shown in FIG. 6. If the valve 33 is 
closed, the fluid in the line 35 from a branch point 34 to the valve 33 
remains stagnant as a necessary consequence. If this stagnant state is 
continued for a long period of time, microorganisms and the like develop 
in the fluid and the purity of the water deteriorates. As one of the means 
for solving these problems, a method that includes minimizing the volume 
of line 35, which is the stagnant portion, for instance, using a branch 
valve as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 
62-151676 in the branch point 34 can be considered. 
However, because the valve 33 must be positioned close to a main line 31 
according to said conventional method, its mount position is restricted, 
thereby creating serious problems in such a complex piping system as that 
inside the unit. Further, when using said branch valve as the valve 33, 
the valve is not only subjected to the aforesaid restriction but also if 
the caliber difference between the main line 31 and the sub-line 32 is 
substantial, the fabrication of the branch valve itself may be difficult 
and it is impossible to completely eliminate this stagnant portion, in 
view of its structure, because, if a ball valve is used as a branch valve, 
the fluid sealed between the valve chest space sealed by two seat rings 
inside the ball valve remains stagnant when the ball is in a closed 
position. What in more important is that the entire line 37 from said 
valve 33 to a use-point 36 becomes a stagnant portion if the valve 33 is 
closed. 
DISCLOSURE OF THE INVENTION 
The present invention has been conceived so as to solve the problems of 
said conventional technique and the purpose of this invention is to 
provide a non-stagnant piping system having the special features stated in 
the following items a to c: 
a. Even when the valve is closed, the fluid in the line from the branch 
point to the point where the valve is substantially sealed does not remain 
stagnant. 
b. No restriction exists as to the mount position of the valve. That is to 
say, the valve can be mounted anywhere in the sub-line as necessary. 
c. Even if the ball valve is used as the valve, the line and the valve 
chest inside the valve will not become the fluid stagnant portions when 
closed. 
Additionally, if the ball valve is used as the valve, the fluid will not 
remain stagnant in the space inside the valve chest even when opened, 
which has been the fluid stagnant portion in the past. In short, a fluid 
stagnant portion does not exist regardless of whether the valve is open or 
closed. 
The constitution of the non-stagnant piping system of this invention for 
solving said problems is characterized in that, in a pipe line for the 
purpose of fluid transportation, a valve unit provided with a by-pass 
means for transporting fluid to the outside on the upstream side of a 
valve portion having a perfect fluid closing function that ensures a 
substantial sealing of the fluid, and a pressure reducing unit having a 
pressure reducing portion by a throttling means in the interior and 
provided with a by-pass means for communicating said pressure reducing 
portion with the exterior are installed; said by-pass means of said valve 
unit communicating with said by-pass means of said pressure reducing 
portion, as well as said pressure reducing unit is installed at a location 
where it is possible to suck the fluid on the upstream side of the valve 
portion when said valve unit is closed. 
In a preferred embodiment of this invention, said valve unit is a ball 
valve comprising a ball provided with a communicating port for 
communicating the upstream side flow channel with a valve chamber when the 
valve is closed. 
Also, in a preferred embodiment of this invention, said pressure reducing 
unit is a diaphragm valve provided with a by-pass means at the valve seat 
thereof. 
Further, the material of the non-stagnant piping system according to this 
invention may be either metal or plastic, and will not be restricted. 
When the fluid flows into the piping line of this invention, the fluid 
flows into the valve unit and the pressure reducing portion, and when the 
valve unit is closed, the upstream side fluid of the valve unit flows into 
the pressure reducing portion through the communicating channel between 
the by-pass means of the valve unit and the by-pass means of the pressure 
reducing portion by the pressure differential because the upstream side 
fluid pressure of the valve unit is higher than the fluid pressure of the 
pressure reducing portion. Therefore, the upstream side fluid of the valve 
unit always flows to the pressure reducing portion and does not remain 
stagnant even if the valve unit is closed. Even if the valve unit is open, 
the mode of operation similar to the above description can be obtained and 
fluid stagnancy can be avoided by designing the opening area of the 
pressure reducing portion such that the fluid pressure of the pressure 
reducing portion may become lower than the upstream side fluid pressure of 
the valve unit. 
According to this invention, the following effects are obtained. 
a. Even if the valve mounted in the sub-line should be in a closed state, 
the fluid can be kept extremely clean because the fluid in the line from 
the branch point in the main line up to the valve portion, which ensures 
an effective sealing of the fluid, will not remain stagnant. 
b. The mount position of the valve in the sub-line is not at all 
restricted. In short, because the valve can be mounted anywhere as 
necessary in the sub-line, the distance of the fluid stagnant line from 
the valve to the use-point can freely be adjusted to the necessary minimum 
value, which was impossible in the past. In addition, there is no obstacle 
to the construction of the piping system even in a complex unit. 
c. Even if a ball valve is mounted in the sub-line, the fluid stagnant 
portion of the sub-line up to the valve portion from the branch point with 
the main line can be eliminated almost completely because the fluid always 
flows to the valve chest, whereas the fluid remained stagnant in the past 
when said valve was closed. Further, because the fluid inside the valve 
chest that was conventionally a stagnant portion is sucked by the pressure 
reducing unit, the fluid does not remain stagnant there even when the 
valve is opened. Namely, because the ball valve performs the same function 
as the diaphragm valve in the system according to this invention, it is 
economical. 
d. This system not only contributes greatly to energy saving measures 
because no other motive power source is required for operating the system, 
but also none of the undesirable particles that normally occur in the 
production process of super LSIs are generated from the system of this 
invention because the pressure reducing means has no mechanically driven 
section. 
In addition to the effects as described in said items a to d, the present 
invention is capable of structuring the system into an extremely simple 
and compact design.

BEST MODE FOR CARRYING OUT THE INVENTION 
Hereunder, some preferred embodiments according to this invention are 
described on the basis of the drawings. FIG. 1 is a vertical sectional 
view showing the first embodiment of this invention. In this figure, 
numeral 1 denotes a main line and numeral 2 a sub-line branched from the 
main line. Numeral 3 is a diaphragm valve (hereinafter to be described 
"valve"), that is used as a valve unit for adjusting and stopping the flow 
rate of the fluid supplied to a use-point 8, and a valve portion 3a for 
effectively stopping the fluid is installed in its interior. Further, a 
by-pass means 3b in a tube state for communicating the flow channel inside 
the body of the valve 3 with the outside is installed integrally with the 
body of the valve 3 just before the upstream side of said valve portion 
3a. Numeral 4 is a venturi tube type pressure reducing unit having a 
throttling portion 4a in its interior, and a tubular by-pass means 4b 
communicating said throttling portion 4a with the outside is also 
installed integrally in the pressure reducing unit body. Here, in this 
embodiment, the throttling portion 4a of the pressure reducing unit 4 has 
a venturi tube type structure but is not limited to this type alone; the 
pressure reducing unit of the type shown in FIG. 4 and FIG. 5 can also be 
favorably used. That is to say, the pressure reducing unit 21 in FIG. 4 
has a weir 22 in its interior, and a by-pass means 23 is installed 
immediately after said weir 22. An extremely compact pressure reducing 
unit can be fabricated by adopting this type of structure. Moreover, a 
pressure reducing unit 24 in FIG. 5 is formed by remodelling a 
commercially available diaphragm valve. As is widely known, a valve seat 
portion 27 as shown in the figure is installed in this type of valve, but 
an orifice being structured by this valve seat portion 27 is adopted as a 
throttling portion 26. Numeral 25 is a by-pass means installed in the 
valve seat portion 27. Adoption of this type of structure is very 
convenient since the opening area of the throttling portion 26 can be 
changed as necessary. The absence of a restriction in the flow direction 
is also one of the merits. 
Numeral 5 is a coupling means, and in this embodiments, a tube made of PFA, 
which is a fluorocarbon resin, is used. One end of said coupling means 5 
is fused and connected to the by-pass means 3b of the valve 3 and the 
other end of said means is connected to the by-pass means 4b of the 
pressure reducing unit 4 respectively, thus said coupling means connects 
the by-pass means 3b and 4b to each other. The valve 3, the by-pass means 
3b, the pressure reducing unit 4, the by-pass means 4b and the coupling 
means 5 are fabricated by PFA respectively in the present embodiment, but 
are not restricted to this type of material and may be fabricated from 
other plastic and metallic material. In addition, the by-pass means 3b and 
4b need not be formed into a unified body, respectively, and may be formed 
by fitting and fixing the commercially available couplings, etc. 
Numeral 6 denotes a branch point between the main line 1 and the sub-line 
2; numeral 7 denotes a water storage tank and numeral 8 denotes a 
use-point. 
The non-stagnant piping system of this embodiment consisting of said 
components operates as follows. 
When the fluid flows to the main line 1 in FIG. 1, said fluid flows to the 
water storage tank 7 via the branch point 6 and the pressure reducing unit 
4, but its branch stream from the branch point 6 flows out to the sub-line 
2. Said branch stream is supplied to the use-point 8 via the valve unit 3. 
In this situation, supposing the static pressure of fluid (hereinafter to 
be described "fluid pressure") on the upstream side of the throttling 
portion 4a of the pressure reducing unit 4 in the main line 1 is P.sub.1, 
the fluid pressure of said throttling portion 4a is P.sub.2, the down 
stream side fluid pressure is P.sub.3, and moreover the fluid pressure on 
the upstream side of the valve portion 3a of the valve unit 3 in the 
sub-line 2 is P.sub.4, and the fluid pressure on the downstream side is 
P.sub.5, then the relative relation of fluid pressure in the respective 
sections concurs with the below mentioned formulae by the hydro-mechanical 
action because the fluid flowing through the main line 1 is contracted by 
the throttling portion 4a of the pressure reducing unit 4. 
EQU P.sub.1 &gt;P.sub.3 &gt;P.sub.2 (1) 
On the other hand, because the fluid flowing through the sub-line 2 
generates fluid resistance by the action of the valve portion 3a of the 
valve 3, the relative relation between P.sub.4 and P.sub.5 concurs with 
the below mentioned formula. 
EQU P.sub.4 &gt;P.sub.5 (2) 
However, if a ball valve and the like scarecely generating fluid resistance 
are used as the valve 3, formula (2) is expressed by the following 
formula. 
EQU P.sub.4 .apprxeq.P.sub.5 (2)' 
Since this piping system has the purpose of supplying the fluid to the 
use-point 8, the following formula must be constituted. 
EQU P.sub.1 .gtoreq.P.sub.4 (3) 
(However, the equal sign is constituted only when the valve is closed.) 
In the case that the valve unit 3 is closed, the following formula can be 
constituted from said formulae (1), (2) and (3). 
EQU P.sub.4 &gt;P.sub.2 (4) 
Now, if the valve unit 3 is closed, a pressure differential (P.sub.4 
-P.sub.2) (hereinafter to be described ".DELTA.P") is generated between 
the fluid pressure P.sub.4 immediately before the valve portion 3a and the 
fluid pressure P.sub.2 of the throttling portion 4a from Formula (4). 
Because the by-pass means 3b of the valve unit 3 communicates with the 
by-pass means 4b of the pressure reducing unit 4 by the coupling means 5, 
the fluid on the upstream side of the valve portion 3a passes through the 
coupling means 5 and the by-pass means 4b from the by-pass means 3b and is 
sucked out to the flow channel inside the pressure reducing unit 4. 
Therefore, the fluid on the upstream side of the valve portion 3a will not 
remain stagnant even if the valve unit 3 is closed. The mode of operation 
similar to the said description can be obtained by designing the opening 
area of the throttling portion of the pressure reducing unit 4 such that 
said formula (4 ) may be constituted even if the valve unit is open. 
In this way, so long as said pressure differential .DELTA.P is generated, 
the fluid on the upstream side of the valve portion 3 is sucked out to the 
flow channel inside the pressure reducing unit 4 irrespective of the 
opened or closed state of the valve unit 3. 
Further, this mode of operation remains unchanged whether the line 9 on the 
upstream side of the valve unit 3 is short or long. However, said pressure 
reducing unit 4 must be mounted at a position where said pressure 
differential .DELTA.P is to be generated. 
In addition, because a diaphragm valve is used as the valve 3 in this 
embodiment, no stagnant area is generated even if said valve 3 is open. 
Needless to say, for maintaining the foregoing pressure differential 
.DELTA.P, the fluid must always flow to the pressure reducing unit 4 even 
if the valve 3 is closed. In order to eliminate the stagnant area further, 
it is possible to structure a method that minimizes the distance from the 
valve 3 to the use-point is possible, but in this case, the distance from 
the by-pass means 3b to the by-pass means 4b becomes considerably longer, 
and the resistance of the fluid passing through the coupling means 5 
becomes greater as a necessary consequence. That is to say, said pressure 
differential becomes smaller. However, in this type of case, said pressure 
differential .DELTA.P becomes the required value by decreasing, as 
necessary, the opening area of the throttling portion 4a of the pressure 
reducing unit 4. In short, no restriction exists regarding the mount 
position of the valve 3. 
FIG. 2 and FIG. 3 are vertical section views of the main portion showing 
the second embodiment of this invention, in particular, showing an example 
using, as the valve 3 in FIG. 1, a ball valve with a small hole bored in 
the ball, which is used favorably in the super LSI manufacturing process, 
etc. Explanations of structural components other than said valve 3 are 
omitted because they are identical to those of the first embodiment shown 
in FIG. 1. 
FIG. 2 shows the valve in an open state, while FIG. 3 shows the valve in a 
closed state. 
Numeral 11 in FIG. 2 denotes a ball, and the valve is opened and closed by 
turning said ball 90.degree.. Numeral 12 is a valve portion, and a 
substantially sealing action is achieved when the valve is closed. Numeral 
13 is a communicating port provided in the ball 11 that communicates a 
flow channel 17 with a valve chest 14 in the valve opened state and also 
communicates the valve chest 14 with the flow channel 17 even when the 
valve is closed. Numeral 15, 16 and 19 represent a by-pass means, a 
coupling means and a pressure reducing unit, respectively. 
This embodiment consisting of the above structural components operates as 
follows. 
When the fluid flows in the arrow direction, almost all of the fluid flows 
out to the flow channel 18, but a part of the fluid flows out to the valve 
chest 14 through the communicating port 13. Now supposing the upstream 
side fluid pressure of the valve portion 12 is P.sub.6, the fluid pressure 
inside the valve chest 14 is P.sub.7, and the pressure of the fluid 
passing through the throttling portion of the pressure reducing unit 19 is 
P.sub.8, then the following formula will be constituted because the valve 
chest 14 communicates with the flow channel 17 by the communicating port 
13. 
EQU P.sub.6 .apprxeq.P.sub.7 (5) 
The relation between P.sub.7 and P.sub.8 can be expressed by the following 
formula as explained in the mode of operation in the preceding article. 
EQU P.sub.7 &gt;P.sub.8 (6) 
The following formula can be constituted from formulae (5) and (6). 
EQU P.sub.6 &gt;P.sub.8 (7) 
Therefore, a part of said fluid is sucked into the flow channel inside the 
pressure reducing unit 19 via the valve chest 14, the by-pass means 15 and 
the coupling means 16 from the flow channel 17. That is to say, the fluid 
always flows in the valve chest, which has conventionally been a fluid 
stagnant area in the valve opened state. 
Also, because the valve chest 14 communicates with the flow channel 17 via 
the communicating port 13 when the ball 11 is closed as illustrated in 
FIG. 3, said Formula (7) is constituted, and the fluid in the valve chest 
14 and the flow channel 17 upstream of the valve portion 12 is sucked to 
the flow channel inside the pressure reducing unit 19. 
According to the constitution of this embodiment, even if a ball valve is 
used, an almost ideal non-stagnant piping system can be provided 
irrespective of the opened or closed state of the valve, and thus its 
effect is considerable. 
CAPABILITY OF EXPLOITATION IN INDUSTRY 
The present invention can be effectively utilized in an ultra pure water 
line and a chemical liquid line in the semi-conductor industry and in the 
field of biochemistry, etc. fields in which fluids inside piping systems 
are required to remain pure.