CN103291979B - The backflow preventer of low cracking pressure, low flow resistance, reliable non-return - Google Patents
The backflow preventer of low cracking pressure, low flow resistance, reliable non-return Download PDFInfo
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- CN103291979B CN103291979B CN201210047674.8A CN201210047674A CN103291979B CN 103291979 B CN103291979 B CN 103291979B CN 201210047674 A CN201210047674 A CN 201210047674A CN 103291979 B CN103291979 B CN 103291979B
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Abstract
The invention discloses the backflow preventer of a kind of low cracking pressure, low flow resistance, reliable non-return, comprise into water safety check, go out Water Check Valve and drain valve, described water inlet safety check and go out Water Check Valve backflow preventer is divided into water-inlet cavity, intermediate cavity and water chamber, first elastomer diaphragm covers the first valve port between water-inlet cavity and intermediate cavity by the activity of water inlet spring, isolation water-inlet cavity and intermediate cavity; The area S1 of described first elastomer diaphragm in the first valve port outer ring water-inlet cavity is multiplied by the directed force F 1 produced into water pressure P1, be greater than under the state of the directed force F 3 of water spring on the first elastomer diaphragm, first elastomer diaphragm is away from the first valve port, water-inlet cavity and intermediate cavity UNICOM, water inlet safety check valve port is opened.The present invention has the feature of low cracking pressure, low flow resistance, reliable non-return, minimum to terminal use's use water influence of hydraulic pressure, meet the Outdoor Fire Hydrant outlet hydraulic pressure of regulation, and it is convenient to change easily damaged parts.
Description
Technical field
The present invention relates to control fluid in pipeline can only the Waterpower control device of one-way flow, particularly relate to the backflow preventer of low cracking pressure used on a kind of tap water pipeline, low flow resistance, reliable non-return.
Background technique
Must install backflow preventer with waterpipe to terminal use abroad, the water in strict restriction conduit can only one-way flow, and prevent pipeline backflow pollution, China city is also performing successively.Backflow preventer belongs to the special purpose device of protection tap water main pipeline water supply quality, is arranged on tap water pipeline before terminal use, if when terminal use's hydraulic pressure occurs higher than water feeding pressure, can prevents the aqueous reflux of terminal use from returning main pipeline.
Backflow preventer divides two kinds: pressure-reducing and low-drag type.Pressure-reducing: prevent refluence effective, but loss of head is comparatively large, terminal use's use water is had a strong impact on; Low-drag type: almost the same with pressure-reducing, just lowers spring rate, and such initial opening pressure reduces, and current standard is 7KPa.These two kinds of backflow preventers are all adopt two conventional one-way valves, and its maximum defect is the center that flap is placed in pipeline fluid, has spring after flap, and flap unlatching displacement is larger, and acting force of the spring is larger, and flap and spring are the obstacles of fluid flowing.Therefore current backflow preventer flow resistance both domestic and external is relatively large, if do not change original structure, it is almost impossible for lowering flow resistance.
The water inlet safety check of backflow preventer at present used both at home and abroad and to go out Water Check Valve are all conventional one-way valves is mounted valves in pipeline, pipeline internal medium do not flow or upstream pressure lower than under authorized pressure time, utilize pressing force of the spring to make valve closing.Open or large discharge under, this spring has become the obstacle of normal water supply with valve.How to reduce the problem that backflow preventer hydraulic losses is bigger than normal, be global problem so far always.
Summary of the invention
The present invention is exactly the backflow preventer providing a kind of low cracking pressure, low flow resistance, reliable non-return in order to solve the problem that flow resistance is relatively large, hydraulic losses is bigger than normal that above-mentioned existing backflow preventer exists.
Object of the present invention is achieved through the following technical solutions:
The backflow preventer of a kind of low cracking pressure, low flow resistance, reliable non-return, comprise into water safety check, go out Water Check Valve and drain valve, described water inlet safety check and go out Water Check Valve backflow preventer is divided into water-inlet cavity, intermediate cavity and water chamber, first elastomer diaphragm covers the first valve port between water-inlet cavity and intermediate cavity by the activity of water inlet spring, isolation water-inlet cavity and intermediate cavity; The area S1 of described first elastomer diaphragm in the first valve port outer ring water-inlet cavity is multiplied by the directed force F 1 produced into water pressure P1, be greater than under the state of the directed force F 3 of water spring on the first elastomer diaphragm, first elastomer diaphragm is away from the first valve port, water-inlet cavity and intermediate cavity UNICOM, water inlet safety check valve port is opened.
Preferably, under described state of opening at water inlet safety check valve port, influent pressure pretend be used in described first elastomer diaphragm gross area on, the active force now produced is far longer than the active force all opened into water spring, and described water inlet safety check is all opened.
Preferably, the area S1 of described first elastomer diaphragm in the first valve port outer ring water-inlet cavity is 2 times of the area S3 in the first valve port inner ring intermediate cavity, and the seal pressure produced is 5 times into water pressure P1.
Preferably, described water inlet safety check comprises the first valve body, the first valve gap, the first elastomer diaphragm, the first guide and limit bar and water inlet spring; Described first valve body is connected with the first valve gap by bolt, press between first valve body and the first valve gap and put the first elastomer diaphragm, first elastomer diaphragm is connected to the first valve gap by water inlet spring, establish the first guide and limit bar constraint water inlet spring in first valve gap, the other end of the first guide and limit bar is connected with the first elastomer diaphragm.
Preferably, the runner of described water inlet safety check first valve body inlet to the first valve port is set to ramp structure.
Preferably, described water inlet safety check first valve body and sprue are intake, water outlet direction exists tilt angle, the angle ranging from 30-60 degree.
Preferably, separate with one second elastomer diaphragm between described intermediate cavity and water chamber, described second elastomer diaphragm covers the second valve port between intermediate cavity and water chamber by the activity of water outlet spring, the area S2 of the second elastomer diaphragm in the second valve port outer ring intermediate cavity is multiplied by the directed force F 2 that fluid pressure P2 produces, under the state being greater than the directed force F 4 of water outlet spring on the second elastomer diaphragm, second elastomer diaphragm is away from the second valve port, intermediate cavity and water chamber UNICOM, go out Water Check Valve valve port and open.
Preferably, the area S2 of described second elastomer diaphragm in the second valve port outer ring intermediate cavity is 1.2 times of the area S4 in the second valve port inner ring water chamber, and the seal pressure produced is 5 times of fluid pressure P2.
Preferably, the runner that described water inlet safety check is exported to out Water Check Valve second valve port is set to ramp structure.
Preferably, go out Water Check Valve described in and comprise the second valve body, the second valve gap, the second elastomer diaphragm, the second guide and limit bar and water outlet spring; Described second valve body is connected with the second valve gap by bolt, press between second valve body and the second valve gap and put the second elastomer diaphragm, second elastomer diaphragm is connected to the second valve gap by water outlet spring, establish the second guide and limit bar constraint water outlet spring in second valve gap, the other end of the second guide and limit bar is connected with the second elastomer diaphragm.
Compared with prior art, the present invention has following beneficial effect:
The present invention has the feature of low cracking pressure, low flow resistance, reliable non-return, minimum to terminal use's use water influence of hydraulic pressure, meet the Outdoor Fire Hydrant outlet hydraulic pressure of regulation, and it is convenient to change easily damaged parts.
Accompanying drawing explanation
Fig. 1 is the structural representation of backflow preventer closed condition;
Fig. 2 is the structural representation of backflow preventer opening state.
Embodiment
The present invention is described in detail below in conjunction with accompanying drawing.
See Fig. 1, Fig. 2, the backflow preventer of low cracking pressure of the present invention, low flow resistance, reliable non-return at least comprises into water safety check, goes out Water Check Valve and drain valve, but change into water safety check, the structure going out Water Check Valve, working method and mounting point, and flap is not on runner.
Water inlet safety check 100 comprises the first valve body 11, first valve gap 12, first elastomer diaphragm 13, first guide and limit bar 14 and water inlet spring 15; First valve body 11 is connected with the first valve gap 12 by bolt, press between first valve body 11 and the first valve gap 12 and put the first elastomer diaphragm 13, first elastomer diaphragm 13 is connected to the first valve gap 12 by water inlet spring 15, the other end establishing the first guide and limit bar 14 to retrain water inlet spring 15, first guide and limit bar 14 in first valve gap 12 is connected with the first elastomer diaphragm 13.Go out Water Check Valve 200 and comprise the second valve body 21, second valve gap 22, second elastomer diaphragm 23, second guide and limit bar 24 and water outlet spring 25; Second valve body 21 is connected with the second valve gap 22 by bolt, press between second valve body 21 and the second valve gap 22 and put the second elastomer diaphragm 23, second elastomer diaphragm 23 is connected to the second valve gap 22 by water outlet spring 25, the other end establishing the second guide and limit bar 24 to retrain water outlet spring 25, second guide and limit bar 24 in second valve gap 22 is connected with the second elastomer diaphragm 23.Filter screen does not represent at this.
Water inlet safety check 100 and go out Water Check Valve 200 and be connected in series UNICOM, backflow preventer is divided into water-inlet cavity, intermediate cavity and water chamber, first elastomer diaphragm 13 covers on the first valve port A1 between water-inlet cavity and intermediate cavity by the activity of water inlet spring 15, isolation water-inlet cavity and intermediate cavity; Second elastomer diaphragm 23 covers on the second valve port A2 between intermediate cavity and water chamber by water outlet spring 25 activity, separates intermediate cavity and water chamber.
The area S1 of the first elastomer diaphragm 13 in the first valve port A1 outer ring water-inlet cavity is multiplied by the directed force F 1 that the water inlet pressure P1 in water-inlet cavity produces, be greater than under the state of the directed force F 3 of water spring 15 on the first elastomer diaphragm 13, first elastomer diaphragm 13 is away from the first valve port A1, water-inlet cavity and intermediate cavity UNICOM, water inlet safety check valve port is opened.
Under the state that water inlet safety check valve port is opened, influent pressure pretend be used in the first elastomer diaphragm 13 gross area on, the active force now produced is far longer than the active force all opened into water spring 15, and water inlet safety check is all opened.
Go out Water Check Valve working principle equivalent water inlet safety check, the area S2 of the second elastomer diaphragm 23 in the second valve port A2 outer ring intermediate cavity is multiplied by the directed force F 2 that fluid pressure P2 produces, under the state being greater than the directed force F 4 of water outlet spring 25 on the second elastomer diaphragm 23, second elastomer diaphragm 23 is away from the second valve port A2, intermediate cavity and water chamber UNICOM, go out Water Check Valve valve port and open.Because the open water going out Water Check Valve forces down the unlatching hydraulic pressure in water inlet safety check, therefore the rigidity of water outlet spring 25 is lower than water inlet spring 15.
The effect of elastomer diaphragm of the present invention has three, and one is the isolation diaphragm into water and water outlet, and two is the sensing elements into water and water outlet two hydraulic pressure, and three is valve sealing elements of safety check.For obtaining good effect, the runner of water inlet safety check first valve body 11 entrance to the first valve port A1, water inlet safety check is exported to out the runner of Water Check Valve second valve port A2, all be set to ramp structure, to utilize in inclined-plane a1, a2(Fig. 1,2 shown in dotted line) guide fluid flowing, reduce the flow resistance that fluid produces because of eddy current in valve body.Water inlet safety check first valve body 11, go out that Water Check Valve second valve body 21 is intake with sprue, water outlet direction exists tilt angle, the angle ranging from 30-60 degree, preferably 45 degree.
The specific works process of this backflow preventer is described in detail as follows:
The flap of water inlet safety check is the first elastomer diaphragm 13, and fluid is directed on the first elastomer diaphragm of water safety check first valve port A1 outer ring by inclined-plane, the outer ring a1 of safety check first valve body 11 of intaking by the direction of arrow shown in Fig. 1.
When water feeding pressure lower than water inlet safety check design load time, due to water inlet spring action, the first elastomer diaphragm 13 and the first valve port A1 keep sealing, intake closure of check ring.When water feeding pressure is greater than the design load into water safety check, water feeding pressure P1 acts on the first elastomer diaphragm 13 of the first valve port A1 outer ring, its directed force F 1 produced is greater than the directed force F 3 into water spring 15, first elastomer diaphragm 13 overcomes its initial sealing force, away from the first valve port A1, the valve port of water inlet safety check is opened.Fluid enters inner ring by the outer ring of safety check first valve body of intaking, and fluid pressure is herein P2.Once open, water feeding pressure acts on the gross area of the first elastomer diaphragm, as long as hydraulic pressure P1 and P2 acting on the first elastomer diaphragm two sides has micro-pressure reduction, the active force that its pressure reduction produces overcomes the full open power into water spring completely, water inlet safety check standard-sized sheet.
The flap going out Water Check Valve is the second elastomer diaphragm 23, and the fluid of inner ring is directed to out on the elastomer diaphragm of Water Check Valve second valve port A2 outer ring by inclined-plane, the outer ring a2 going out Water Check Valve.
In like manner, the requirement of Water Check Valve opened by pressure is gone out according to standard, P2 acts on out on the second elastomer diaphragm 23 of Water Check Valve second valve port A2 outer ring, its directed force F 2 produced is greater than the directed force F 4 of water outlet spring 25, second elastomer diaphragm 23 overcomes the initial sealing force of water outlet spring 25, separates with the second valve port A2 going out Water Check Valve.Fluid enters inner ring by the outer ring going out Water Check Valve second valve body, and fluid pressure is herein P3.Once the second elastomer diaphragm with go out Water Check Valve second valve port A2 and separate, fluid pressure acts on the gross area of the second elastomer diaphragm, as long as hydraulic pressure P2 and P3 acting on the second elastomer diaphragm two sides has micro-pressure reduction, the active force that its pressure reduction produces overcomes the full open power of water outlet spring completely, goes out Water Check Valve standard-sized sheet.Fig. 2 is the structural representation of backflow preventer full open state.
When the downstream water demand of backflow preventer is few, flow is low, or water feeding pressure P1 is equal with water outlet hydraulic pressure P3, due to the effect of water inlet spring (or water outlet spring), first valve port A1(of first (or second) elastomer diaphragm and water inlet safety check or go out the second valve port A2 of Water Check Valve) gluing, sealing, water inlet safety check and water outlet closure of check ring.When backflow preventer downstream pressure is higher than upstream pressure, water outlet hydraulic pressure is greater than water feeding pressure, and the sealing force acted on elastomer diaphragm strengthens, and the sealing at this place is more reliable.Destroy elastomer diaphragm to prevent sealing force excessive, the first/the second guide and limit bar limits the excessive deformation of the first/the second elastomer diaphragm, plays a protective role.
Water inlet safety check and the design going out Water Check Valve:
Water inlet safety check, go out Water Check Valve can open reliably under the hydraulic pressure of regulation, fluid pressure acts on elastomer diaphragm, elastomer diaphragm is not by the restriction of physical dimension, can the area of alter pressure action on elastomer diaphragm according to unlatching requirement, the micro-initial sealing power be greater than into water spring (or water outlet spring) of the active force making it produce, elastomer diaphragm is opened, once open, the area that fluid pressure acts on elastomer diaphragm changes into gross area by original local area, fluid pressure is now on the contrary lower than initial fluid pressure as calculated, elastomer diaphragm just can be made to be in full open state.To design the backflow preventer of 100 internal diameters, water inlet safety check: cracking pressure 8KPa, full open pressure reduction 6KPa; Go out Water Check Valve: cracking pressure 4KPa, full open pressure reduction 2.5KPa.
Therefore as requested, the area of the first elastomer diaphragm and the second elastomer diaphragm initially can be any given in design, not by the restriction of Flow diameter.In like manner, cracking pressure initially can be any given in design.
Fluid enters inner ring by (water inlet safety check, go out Water Check Valve) valve body outer ring by the first valve port A1 or the second valve port A2, and the area of outer ring can change according to demand, inner ring area be import and export needed for area, also can require adjustment according to flow resistance.After the rea adjusting of inner ring and outer ring, designing and calculating its water inlet spring or water outlet spring, just can reach design objective requirement.Preferably, the area S1 of the first elastomer diaphragm in the first valve port outer ring water-inlet cavity is 2 times of the area S3 in the first valve port inner ring intermediate cavity, and the seal pressure produced is 5 times into water pressure P1.The area S2 of the second elastomer diaphragm in the second valve port outer ring intermediate cavity is 1.2 times of the area S4 in the second valve port inner ring water chamber, and the seal pressure produced is 5 times of fluid pressure P2.
Water inlet spring (or water outlet spring) on elastomer diaphragm is given as requested, due to structural feature, can Redundancy Design, and improve seal pressure, therefore can improve the up-to-standard rate of batch production.Water inlet safety check and the sprue going out Water Check Valve mounting point and water are separated, and overcome the problem on obstacle that the flap of conventional check valve and spring are water flow passage completely.
Be only several specific embodiments of the application above, but the application is not limited thereto, the changes that any person skilled in the art can think of, all should drops in the protection domain of the application.
Claims (10)
1. the backflow preventer of a low cracking pressure, low flow resistance, reliable non-return, comprise into water safety check, go out Water Check Valve and drain valve, it is characterized in that, described water inlet safety check and go out Water Check Valve backflow preventer is divided into water-inlet cavity, intermediate cavity and water chamber, first elastomer diaphragm covers the first valve port between water-inlet cavity and intermediate cavity by the activity of water inlet spring, isolation water-inlet cavity and intermediate cavity; The area S1 of described first elastomer diaphragm in the first valve port outer ring water-inlet cavity is multiplied by the directed force F 1 produced into water pressure P1, be greater than under the state of the directed force F 3 of water spring on the first elastomer diaphragm, first elastomer diaphragm is away from the first valve port, water-inlet cavity and intermediate cavity UNICOM, water inlet safety check valve port is opened.
2. the backflow preventer of low cracking pressure as claimed in claim 1, low flow resistance, reliable non-return, it is characterized in that, described under the state of water inlet safety check valve port unlatching, influent pressure pretend be used in described first elastomer diaphragm gross area on, the active force now produced is far longer than the active force all opened into water spring, and described water inlet safety check is all opened.
3. the backflow preventer of low cracking pressure as claimed in claim 1, low flow resistance, reliable non-return, it is characterized in that, the area S1 of described first elastomer diaphragm in the first valve port outer ring water-inlet cavity is 2 times of the area S3 in the first valve port inner ring intermediate cavity, and the seal pressure produced is 5 times into water pressure P1.
4. the backflow preventer of low cracking pressure as claimed in claim 1, low flow resistance, reliable non-return, is characterized in that, described water inlet safety check comprises the first valve body, the first valve gap, the first elastomer diaphragm, the first guide and limit bar and water inlet spring; Described first valve body is connected with the first valve gap by bolt, press between first valve body and the first valve gap and put the first elastomer diaphragm, first elastomer diaphragm is connected to the first valve gap by water inlet spring, establish the first guide and limit bar constraint water inlet spring in first valve gap, the other end of the first guide and limit bar is connected with the first elastomer diaphragm.
5. the backflow preventer of low cracking pressure as claimed in claim 4, low flow resistance, reliable non-return, it is characterized in that, the runner of described water inlet safety check first valve body inlet to the first valve port is set to ramp structure.
6. the backflow preventer of low cracking pressure as claimed in claim 4, low flow resistance, reliable non-return, it is characterized in that, described water inlet safety check first valve body and sprue are intake, water outlet direction exists tilt angle, the angle of inclination is 30-60 degree.
7. low cracking pressure as claimed in claim 1, low flow resistance, the backflow preventer of reliable non-return, it is characterized in that, separate with one second elastomer diaphragm between described intermediate cavity and water chamber, described second elastomer diaphragm covers the second valve port between intermediate cavity and water chamber by the activity of water outlet spring, the area S2 of the second elastomer diaphragm in the second valve port outer ring intermediate cavity is multiplied by the directed force F 2 that fluid pressure P2 produces, under the state being greater than the directed force F 4 of water outlet spring on the second elastomer diaphragm, second elastomer diaphragm is away from the second valve port, intermediate cavity and water chamber UNICOM, go out Water Check Valve valve port to open.
8. the backflow preventer of low cracking pressure as claimed in claim 7, low flow resistance, reliable non-return, it is characterized in that, the area S2 of described second elastomer diaphragm in the second valve port outer ring intermediate cavity is 1.2 times of the area S4 in the second valve port inner ring water chamber, and the seal pressure produced is 5 times of fluid pressure P2.
9. the backflow preventer of low cracking pressure as claimed in claim 7, low flow resistance, reliable non-return, it is characterized in that, the runner that described water inlet safety check is exported to out Water Check Valve second valve port is set to ramp structure.
10. the backflow preventer of the low cracking pressure as described in claim 1 or 7, low flow resistance, reliable non-return, is characterized in that, described in go out Water Check Valve and comprise the second valve body, the second valve gap, the second elastomer diaphragm, the second guide and limit bar and water outlet spring; Described second valve body is connected with the second valve gap by bolt, press between second valve body and the second valve gap and put the second elastomer diaphragm, second elastomer diaphragm is connected to the second valve gap by water outlet spring, establish the second guide and limit bar constraint water outlet spring in second valve gap, the other end of the second guide and limit bar is connected with the second elastomer diaphragm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210047674.8A CN103291979B (en) | 2012-02-28 | 2012-02-28 | The backflow preventer of low cracking pressure, low flow resistance, reliable non-return |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210047674.8A CN103291979B (en) | 2012-02-28 | 2012-02-28 | The backflow preventer of low cracking pressure, low flow resistance, reliable non-return |
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| Publication Number | Publication Date |
|---|---|
| CN103291979A CN103291979A (en) | 2013-09-11 |
| CN103291979B true CN103291979B (en) | 2016-04-20 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201210047674.8A Active CN103291979B (en) | 2012-02-28 | 2012-02-28 | The backflow preventer of low cracking pressure, low flow resistance, reliable non-return |
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Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106015630B (en) * | 2016-07-05 | 2018-06-26 | 武汉长光电源有限公司 | Modified lead valve |
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| EP0235766A2 (en) * | 1986-03-03 | 1987-09-09 | AWECO Kunststofftechnik Gerätebau GmbH & Co. KG | Safety valve for household appliances |
| JP2832575B2 (en) * | 1994-02-10 | 1998-12-09 | 株式会社東京暖冷器製作所 | Gate valve |
| DE29904815U1 (en) * | 1999-03-16 | 1999-05-12 | Huang Chun Cheng | Construction with an electromagnetic diaphragm valve with two sealing valves |
| CN2442057Y (en) * | 2000-09-05 | 2001-08-08 | 南海市九江永兴阀门制造有限公司 | Counter flow stop device |
| HK1033687A1 (en) * | 1999-06-29 | 2001-09-14 | Kane Kougyou Co Ltd | Reverse flow prevention apparatus. |
| JP2002213629A (en) * | 2001-01-19 | 2002-07-31 | Nippo Valve Co Ltd | Pressure-reducing type backflow prevention device |
| CN101097024A (en) * | 2006-06-28 | 2008-01-02 | 上海上龙阀门厂 | Process for manufacturing precise induction totally separating type anti-soil draining equipment |
| CN202056363U (en) * | 2011-05-17 | 2011-11-30 | 天津市国威给排水设备制造有限公司 | Dual-diaphragm micro-resistance ultrashort backflow preventer |
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2012
- 2012-02-28 CN CN201210047674.8A patent/CN103291979B/en active Active
Patent Citations (8)
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|---|---|---|---|---|
| EP0235766A2 (en) * | 1986-03-03 | 1987-09-09 | AWECO Kunststofftechnik Gerätebau GmbH & Co. KG | Safety valve for household appliances |
| JP2832575B2 (en) * | 1994-02-10 | 1998-12-09 | 株式会社東京暖冷器製作所 | Gate valve |
| DE29904815U1 (en) * | 1999-03-16 | 1999-05-12 | Huang Chun Cheng | Construction with an electromagnetic diaphragm valve with two sealing valves |
| HK1033687A1 (en) * | 1999-06-29 | 2001-09-14 | Kane Kougyou Co Ltd | Reverse flow prevention apparatus. |
| CN2442057Y (en) * | 2000-09-05 | 2001-08-08 | 南海市九江永兴阀门制造有限公司 | Counter flow stop device |
| JP2002213629A (en) * | 2001-01-19 | 2002-07-31 | Nippo Valve Co Ltd | Pressure-reducing type backflow prevention device |
| CN101097024A (en) * | 2006-06-28 | 2008-01-02 | 上海上龙阀门厂 | Process for manufacturing precise induction totally separating type anti-soil draining equipment |
| CN202056363U (en) * | 2011-05-17 | 2011-11-30 | 天津市国威给排水设备制造有限公司 | Dual-diaphragm micro-resistance ultrashort backflow preventer |
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| CN103291979A (en) | 2013-09-11 |
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