CN105370924A - Side valve type decompression backflow preventer - Google Patents

Side valve type decompression backflow preventer Download PDF

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Publication number
CN105370924A
CN105370924A CN201510710124.3A CN201510710124A CN105370924A CN 105370924 A CN105370924 A CN 105370924A CN 201510710124 A CN201510710124 A CN 201510710124A CN 105370924 A CN105370924 A CN 105370924A
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CN
China
Prior art keywords
valve
backflow preventer
ring seals
downstream
guide holder
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Application number
CN201510710124.3A
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Chinese (zh)
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CN105370924B (en
Inventor
柴为民
陈永新
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杭州春江阀门有限公司
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Priority to CN201510710124.3A priority Critical patent/CN105370924B/en
Publication of CN105370924A publication Critical patent/CN105370924A/en
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Publication of CN105370924B publication Critical patent/CN105370924B/en

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16KVALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K11/00Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves
    • F16K11/10Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with two or more closure members not moving as a unit
    • F16K11/20Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with two or more closure members not moving as a unit operated by separate actuating members

Abstract

The invention discloses a side valve type decompression backflow preventer which is provided with a valve body. An inlet check valve, an outlet check valve and a drainage valve are arranged in the valve body. The preventer is characterized in that the valve body is a right-angle three-way valve composed of a horizontal pipeline and a perpendicular pipeline; a first partition with holes is arranged in the middle of the horizontal pipeline and divides the horizontal pipeline into an upstream pipeline and a downstream pipeline; the inlet check valve composed of a slide valve and the like is arranged in the upstream pipeline, a cylindrical wall of the outer circle of the slide valve is provided with a through hole, an O-shaped sealing ring is arranged on the outer circle, and the inner hole wall of the pipeline matched with the outer circle of the slide valve is provided with an annular groove and an O-shaped sealing ring; the outlet check valve is arranged in the downstream pipeline; and the drainage valve composed of a slide valve, a drainage hole and the like is arranged at the joint of the horizontal pipeline and the perpendicular pipeline. By the adoption of the slide valves and other quite simple structures, the various functions of a decompression backflow preventer are achieved; and the side valve type decompression backflow preventer has the beneficial effects of being simple in structure, small in size, small in flow resistance, reliable in work and the like.

Description

Sliding valve style pressure reduction type backflow preventer
Technical field
The present invention relates to a kind of backflow preventer, particularly relate to a kind of pressure reduction type backflow preventer adopting slide-valve structure.
Background technique
In order to conscientiously ensure people's health, national strict regulations, in chemical plant, printing and dyeing mill, hospital, brewery, fire hydrant, tall building etc. all likely the place that excessive risk pollutes is produced to potable water system, must backflow preventer be set.
The backflow preventer supplied in the market can be divided into two kinds of patterns substantially: pressure-reducing and double check valve type.The former typical construction is as shown in Chinese patent 2442057Y, and by water inlet safety check, go out Water Check Valve and form with the drain valve of its bypass, drain valve is arranged on into water safety check and goes out between Water Check Valve.When import hydraulic pressure is less than setting value higher than intermediate cavity hydraulic pressure, drain valve just starts draining, therefore anti-back flow performance is good, its main deficiency is complex structure, volume is large, cost is high, fault many (especially elastomer diaphragm is more fragile), require that miantainers' technical merit is higher, therefore makes popularization be restricted.The typical construction of the latter is as shown in Chinese patent 2010201114967 and 2004200145854, this kind of backflow preventer is by be threaded connection and the valve body one be communicated with and valve body two form, described valve body one is built with valve plate one and valve plate two assembly, during open valve, valve plate one, two rectilinear movement to the right under pressure medium effect drives seal ring on valve plate to leave sealing surface, ensure medium normal through; During cut-off valve valve plate one, two respectively under the effect of spring one, two left rectilinear movement band dynamic seal ring be close to sealing surface, ensure reflux medium not by.Although the simple cost of the latter's structure is low, when the sealing of two safety check was all lost efficacy, will refluence be produced, therefore can only be used in low-risk polluted place.
Summary of the invention
The present invention mainly solves the deficiency existing for prior art, thus the simple structure of a kind of employing of exploitation, make it have the sliding valve style backflow preventer of the various functions of pressure reduction type backflow preventer.
Above-mentioned technical problem of the present invention is mainly solved by following technical proposals: a kind of sliding valve style pressure reduction type backflow preventer, has valve body, has inlet check valve, outlet non-return valve and drain valve, it is characterized in that in valve body:
The right-angle tee that described valve body is made up of a horizontal pipe and vertical pipe, be provided with partition wall one with holes in the middle of horizontal pipe, partition wall one is separated into upstream line and downstream line horizontal pipe;
Be provided with the inlet check valve be made up of guiding valve etc. in described upstream line, the appropriate location that the barrel of described guiding valve is provided with some through hole , Wai Round is provided with some O-ring seals;
The appropriate location of the inner bore of pipeline wall coordinated with guiding valve Wai Round is provided with O-ring seals and some annular grooves;
Outlet non-return valve is provided with in described downstream line;
Described horizontal pipe and vertical pipe joint are provided with partition wall two, and partition wall two is provided with weep hole, coordinate form drain valve with the annular groove adapted and guiding valve etc.
Technological scheme of the present invention can also be perfect further:
As preferably, described guiding valve be a cup-shaped have round-ended cylinder, slidingly to fit in the endoporus of upstream line, and located by limited ring, the appropriate location of cylindrical is provided with O-ring seals and several uniform rectangular through holes; Be provided with spring one in described guiding valve endoporus, described spring one is arranged between the bulge loop in the middle part of the end face of partition wall one and guiding valve, has certain pretightening force after installation.
As preferably, on described upstream line inner hole wall, annular groove is provided with two, is provided with annular groove one near appropriate location, downstream, and be provided with annular groove two near appropriate location, upstream, each annular groove both sides are respectively provided with the chamfering of 30-45 degree.
As preferably, O-ring seals on described guiding valve cylindrical is provided with two, and upstream extremity is provided with O-ring seals two, and downstream is provided with O-ring seals three, described seal ring is arranged in groove, and the groove of described O-ring seals two is the dovetail groove that upper base is less than O-ring seals diameter.
As preferably, described outlet non-return valve comprises the annular sword limit of sealing gasket, gasket base, spring two, valve rod, guide holder and partition wall one central communication hole downstream side outer rim;
On the diameter of axle that described gasket base and sealing gasket are fixed on valve rod front end and the shaft shoulder, valve rod is sliding to be fitted in the center hole of guide holder, and after installing, sealing gasket, valve rod freely can move along the center line of guide holder;
The outer shroud of guide holder is connected by straight muscle with inner ring, and three forms the flange of guide holder, and the fan shaped borehole between muscle is water port;
Spring two is enclosed within the cylindrical of guide holder sleeve, and between guide holder flange and the end face of gasket base, has certain pretightening force after installation, and therefore, when not supplying water, sealing gasket is pressed on the annular sword limit of hole outer rim all the time.
As preferably, described drain valve is cooperatively interacted by the weep hole on partition wall two, annular groove one, the O-ring seals three of guiding valve cylindrical downstream, the downstream of guiding valve and spring one and forms drain valve.When guiding valve moves, control the opening and closing of drain valve valve port.
As preferably, two ends and the middle part of horizontal pipe are respectively provided with screw, in order to measure water-inlet cavity hydraulic pressure, intermediate cavity hydraulic pressure and water chamber hydraulic pressure respectively by ball valve.
Beneficial effect of the present invention is:
Adopt the foolproof structures such as guiding valve, make it have the various functions of pressure reduction type backflow preventer.Therefore have the advantages such as structure is simple, flow resistance is little, volume is little, fault is few, cost is low, function admirable, reliable operation, the design for pressure reduction type backflow preventer creates a kind of new method.
Accompanying drawing explanation
Accompanying drawing 1 is a kind of structural representation of the present invention (in non-water supply situation in valve each part position);
Accompanying drawing 2 is Fig. 1 each part position figure in valve in normal water supply situation;
Accompanying drawing 3 is that Fig. 1 guiding valve upstream direction in normal water supply situation moves, and the O-ring seals two of inlet check valve updrift side is about to each part position figure in valve when opening; Or guiding valve is when returning, each part position figure in valve during O-ring seals two just sealing.
Description of reference numerals: 1, valve body, 2, limited ring, 4, spring one, 5,0 shape seal ring one, 6, guiding valve, 7, nut, 8, pressing plate, 9, sealing gasket, 10, gasket base, 11, spring two, 12, valve rod, 13, jump ring one, 14, guide holder, 15, jump ring two;
A, annular groove one, b, annular groove two, d, intercommunicating pore, n, water port, m, through hole;
A, 0 shape seal ring two, B, 0 shape seal ring three, P1, snout cavity hydraulic pressure, P2, intermediate cavity hydraulic pressure, P3, outlet plenum hydraulic pressure, V1, inlet check valve valve port, V2, outlet non-return valve valve port, V3, drain valve valve port, H1, water-inlet cavity, H2, intermediate cavity, H3, water chamber, W1, partition wall one, W2, partition wall two, L, weep hole.
Embodiment
Below by embodiment, and by reference to the accompanying drawings, technological scheme of the present invention is described in further detail.
Embodiment 1:
In, in bigbore situation, sliding valve style pressure reduction type backflow preventer as shown in the figure, is made up of parts such as valve body 1, limited ring 2, spring one 4,0 shape seal ring 1, guiding valve 6, nut 7, pressing plate 8, sealing gasket 9, gasket base 10, spring 2 11, valve rod 12, jump ring 1, guide holder 14 and jump rings 2 15.
Valve body 1 is a right-angle tee, is made up of horizontal pipe and vertical pipe, and partition wall one W1 is provided with intercommunicating pore d, and horizontal pipe is separated into upstream line and downstream line, and the end of upstream line is provided with flange, is connected with bolt with the flange of intake pipe; Be provided with annular groove one a at inner hole wall near appropriate location, downstream, inner hole wall is provided with annular groove two b near appropriate location, upstream, is provided with O-ring seals 1 between two grooves; The both sides of two grooves are equipped with chamfering, and the side that O-ring seals often passes in and out is 30 degree, and opposite side is 45 degree.
Guiding valve 6 be a cup-shaped have round-ended cylinder, slide and fit in the endoporus of upstream line and located by limited ring 2, the appropriate location of cylindrical is provided with O-ring seals two A, O-ring seals three B and three uniform rectangular through hole m, their position and annular groove one a, there is strict relationship the position of annular groove two b and O-ring seals 1, in order to when guiding valve 6 moves, control the opening and closing of inlet check valve valve port V1 and drain valve valve port V3, because the side chamfering of groove one a and groove two b is 30 degree, therefore when O-ring seals two A or O-ring seals three B by time can not be cut, in addition, in order to prevent O-ring seals two A from being swept away by current when supplying water, its mounting groove is trapezoidal, and upper base is less than O-ring seals diameter, spring 1 is arranged between the bulge loop in the middle part of the end face of partition wall one W1 and guiding valve 6 endoporus, has certain pretightening force, therefore on guiding valve 6, act on the thrust of upstream direction all the time after installation, even if the power that inlet check valve is closed, even if the also power opened of drain valve.
The upstream extremity of annular groove two b, guiding valve 6 and rectangular through hole m, O-ring seals two A and spring 1 composition inlet check valve thereof.
Outlet non-return valve is made up of the annular sword limit etc. of sealing gasket 9, packing seat 10, spring 2 11, valve rod 12, guide holder 14 and partition wall one intercommunicating pore d outer rim, is arranged in the endoporus of downstream line; On diameter of axle sealing gasket 9, gasket base 10 being fixed on valve rod 12 front end by nut 7, pressing plate 8 and the shaft shoulder, valve rod 12 is sliding to be fitted in the center hole of guide holder 14, and made it to become an assembly by jump ring 2 15, after installing, sealing gasket 9, valve rod 12 etc. freely can move along the center line of guide holder 14; The outer shroud of guide holder 14 is connected by three straight muscle with inner ring, and three forms the flange of guide holder, and the fan shaped borehole between muscle is water port n; Spring 2 11 is enclosed within the cylindrical of guide holder 14 sleeve, and between guide holder flange and the end face of gasket base 10, has certain pretightening force after installation, and therefore when not supplying water, sealing gasket is pressed on the annular sword limit of intercommunicating pore d outer rim all the time; The end of downstream line is provided with flange, with the Flange joint of outlet conduit.
The upstream cavity of inlet check valve is water-inlet cavity H1, and the cavity imported and exported between safety check is intermediate cavity H2, and the downstream cavity of outlet non-return valve is water chamber H3.Center line that is laggard, outlet non-return valve is installed consistent with the center line of horizontal pipe.The two ends of horizontal pipe and middle part are respectively provided with screw I, II, III, in order to be measured water-inlet cavity hydraulic pressure P1, intermediate cavity hydraulic pressure P2 and water chamber hydraulic pressure P3 respectively by ball valve.
The partition wall W2 of horizontal pipe and vertical pipe connection part is provided with weep hole L, and weep hole L is rectangular, and width is S, and length is the diameter of hole D.The downstream of weep hole L, annular groove one a, O-ring seals three B, guiding valve 6 and spring 1 form drain valve.The interior bore ends of vertical pipe is provided with internal thread, is connected with sluice pipe.
The position relationship of inlet check valve valve port V1 and drain valve valve port V3 is: during start, and only have when after drain valve valve port V3 Close All, inlet check valve valve port V1 just can open; When refluence occurs in other words, only have after inlet check valve valve port V1 closes, drain valve valve port V3 just can open (see figure 3).
Spring 1 and spring 2 11 are designs like this: as mentioned above, during start, only have after drain valve valve port V3 closes, inlet check valve valve port V1 just can open, and the closing forces of valve port V3 is directly connected to valve port V3 when occurring of flowing backwards opens pressure, for making anti-back flow reliable in function, wish that this power is larger, but this power also should not be too large, otherwise flow resistance loss is just comparatively large, is unfavorable for energy saving.The factor of comprehensive these two aspects, national Specification, the closedown hydraulic pressure >=0.0.014MPa of drain valve, during hydraulic pressure >=0.02MPa when inlet check valve valve port V1 all opens, therefore, as the differential water pressures >=0.014MPa of the hydraulic pressure of snout cavity H1 and intermediate cavity H2, drain valve just can open draining.As long as outlet non-return valve ensures that sealing is reliable, therefore thrust is less, national Specification, and hydraulic pressure >=0.007MPa opened by outlet non-return valve.
Working principle
Fig. 1 to indicate in non-water supply situation each part position in valve, now, inlet/outlet closure of check ring, drain valve is opened, and intermediate cavity H2 communicates with weep hole L; After supplying water, water enters water-inlet cavity H1, in water-inlet cavity, hydraulic pressure raises gradually, after reaching setting pressure, overcome the thrust of spring 1, promote guiding valve 6 downstream and move, after moving a certain distance, drain valve valve port V3 closes, intermediate cavity H2 and weep hole L cuts off, and now imports and exports safety check and also not yet opens (as shown in Figure 3), if hydraulic pressure is now P1 "; After this hydraulic pressure continues to raise, and guiding valve 6 continues to vacillate dynamic downwards, and till its left side contacts with the right side of partition wall one W1, now inlet check valve V1 all opens, if hydraulic pressure is now P1 '; Then the valve port V2 of outlet non-return valve also opens (as shown in Figure 2), and water is by fan-shaped water port n between the rectangular through hole m → intermediate cavity H2 → intercommunicating pore d → outlet non-return valve valve port V2 on water-inlet cavity H1 → inlet check valve valve port V1 → guiding valve 6 barrel → water chamber H3 → guide holder 14 muscle → to downstream water supply.
Working condition under the various operating mode of lower surface analysis
1, during normal water supply, due to P1 ' ﹥ 1.3P1 " (such as 0.02MPa > 1.3 × 0.014MPa), therefore when intake pressure P1 fluctuates downwards within the specific limits, (such as < 20 ﹪) drain valve can not be opened;
2, when pipeline no user after valve, water is static, as long as intake pressure is constant, as long as namely the differential water pressures of water-inlet cavity H1 and intermediate cavity H2 is not less than setting value, drain shut valve, does not sluice;
3, when for a certain reason, cause import hydraulic pressure P1 significantly to reduce, or even during negative value, now outlet non-return valve is closed, guiding valve 6 is under the promotion of spring 1 simultaneously, quick upstream direction moves, and is closed by inlet check valve, if now each sealing place good seal in valve, so drain valve is also be in closed condition, guiding valve will stop at this position, (as shown in Figure 3), waits for and continues to supply water after P1 raises; If now inlet/outlet safety check wherein slightly leak by one or two sealings, so continuation upstream direction moves by guiding valve 6, until drain valve is opened, water in intermediate cavity H2 is discharged from weep hole L, P2 decreases, when (P1-P2) returns to setting value, and drain shut valve, and then inlet check valve is opened, recover normal water supply; If now outlet non-return valve seal failure or blocked by foreign material, so drain valve is opened, and refluence water is discharged from weep hole L, therefore can not flow backwards.
4, when causing outlet hydraulic pressure P3 significantly to raise for a certain reason, if outlet non-return valve good seal, so can not flow backwards; If seal failure, so high pressure water can flow into intermediate cavity H2, and the pressure of intermediate cavity raises, when △ P=P1-P2 is less than setting value, so guiding valve 6 upstream direction under the thrust of spring 1 moves, until drain valve is all opened, refluence water is discharged from drain valve, therefore can not flow backwards; If now inlet check valve sealing was lost efficacy simultaneously, because air has entered in intermediate cavity H2, form air partition, therefore refluence water also can not enter water-inlet cavity H1.
From the above analysis, under the present invention's why not sharp operating mode in office, even if the sealing of two safety check was all lost efficacy, can effectively prevent refluence water pollutions from cleaning the danger at water source.
Embodiment 2
In small-bore situation, internal structure of the present invention with in, bigbore substantially identical, the main distinction is, small-bore two ends and inlet and outlet pipe lines are with being threaded, and the two ends Flange joint of Large diameter.

Claims (7)

1. a sliding valve style pressure reduction type backflow preventer, has valve body, has inlet check valve, outlet non-return valve and drain valve, it is characterized in that in valve body:
The right-angle tee that described valve body (1) is made up of a horizontal pipe and vertical pipe, be provided with the partition wall one (W1) of (d) with holes in the middle of horizontal pipe, partition wall one is separated into upstream line and downstream line horizontal pipe;
Be provided with the inlet check valve be made up of guiding valve (6) in described upstream line, the barrel of described guiding valve is provided with some through holes (m), and cylindrical is provided with some O-ring seals;
The appropriate location of the inner bore of pipeline wall coordinated with guiding valve is provided with some annular grooves and O-ring seals;
Outlet non-return valve is provided with in described downstream line;
Described horizontal pipe and vertical pipe joint are provided with partition wall two (W2), and partition wall two is provided with weep hole (L), forms drain valve with guiding valve.
2. sliding valve style pressure reduction type backflow preventer according to claim 1, is characterized in that:
Described guiding valve (6) be a cup-shaped have round-ended cylinder, sliding fits in the endoporus of upstream line, and located by limited ring (2), the appropriate location of cylindrical is provided with some O-ring seals and several uniform rectangular through holes (m); Be provided with spring one (4) in described guiding valve endoporus, described spring one is arranged between the bulge loop in the middle part of the end face of partition wall one (W1) and guiding valve, has certain pretightening force after installation.
3. sliding valve style pressure reduction type backflow preventer according to claim 1 and 2, it is characterized in that: the annular groove on upstream line inner hole wall is provided with two, annular groove one (a) is provided with near appropriate location, downstream, be provided with annular groove two (b) near appropriate location, upstream, each annular groove both sides are respectively provided with the chamfering of 30-45 degree.
4. sliding valve style pressure reduction type backflow preventer according to claim 1 and 2, it is characterized in that: the O-ring seals on guiding valve cylindrical is provided with two, upstream extremity is provided with O-ring seals two (A), downstream is provided with O-ring seals three (B), described seal ring is arranged in groove, and the groove of described O-ring seals two (A) is the dovetail groove that upper base is less than O-ring seals diameter.
5. sliding valve style pressure reduction type backflow preventer according to claim 1 and 2, is characterized in that: described outlet non-return valve comprises the annular sword limit of sealing gasket (9), gasket base (10), spring two (11), valve rod (12), guide holder (14) and downstream side, hole (d) outer rim;
On the diameter of axle that described gasket base (10) and sealing gasket (9) are fixed on valve rod (12) front end and the shaft shoulder, valve rod (12) is sliding to be fitted in the center hole of guide holder (14), and after installing, sealing gasket (9), gasket base (10), valve rod (12) freely can move along the center line of guide holder (14);
The outer shroud of guide holder (14) is connected by straight muscle with inner ring, and three forms the flange of guide holder (14), and the fan shaped borehole between muscle is water port (n);
Spring two (11) is enclosed within the cylindrical of guide holder (14) sleeve, and between the end face being positioned at guide holder (14) flange and gasket base (10), certain pretightening force is had after installation, when not supplying water, sealing gasket (9) is pressed on the annular sword limit of hole (d) outer rim all the time.
6. sliding valve style pressure reduction type backflow preventer according to claim 2, it is characterized in that: described drain valve is by the weep hole (L) on partition wall two, annular groove one (a), the O-ring seals three (B) of guiding valve (6) cylindrical downstream, the downstream of guiding valve (6) and spring one (4) form.
7. sliding valve style pressure reduction type backflow preventer according to claim 1 and 2, it is characterized in that: the two ends of horizontal pipe and middle part are respectively provided with screw (I, II, III), in order to be measured water-inlet cavity hydraulic pressure (P1), intermediate cavity hydraulic pressure (P2) and water chamber hydraulic pressure (P3) respectively by ball valve.
CN201510710124.3A 2015-10-28 2015-10-28 Side valve type pressure reduction type backflow preventer CN105370924B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201510710124.3A CN105370924B (en) 2015-10-28 2015-10-28 Side valve type pressure reduction type backflow preventer

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Application Number Priority Date Filing Date Title
CN201510710124.3A CN105370924B (en) 2015-10-28 2015-10-28 Side valve type pressure reduction type backflow preventer

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CN105370924A true CN105370924A (en) 2016-03-02
CN105370924B CN105370924B (en) 2017-08-01

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
DE20218121U1 (en) * 2002-11-22 2003-03-27 Vollmer Rudolf Backflow
CN101852302A (en) * 2010-05-24 2010-10-06 杭州春江阀门有限公司 Low-resistance self-discharge backflow preventer
CN101936412A (en) * 2010-07-26 2011-01-05 杭州春江阀门有限公司 Right-angle backflow preventer
CN202012642U (en) * 2011-05-10 2011-10-19 杭州春江阀门有限公司 Novel backflow preventer
CN102865389A (en) * 2012-08-30 2013-01-09 杭州春江阀门有限公司 Water hammer resistant backflow preventer
CN205155256U (en) * 2015-10-28 2016-04-13 杭州春江阀门有限公司 Guiding valve formula decompression type backflow preventer

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
DE20218121U1 (en) * 2002-11-22 2003-03-27 Vollmer Rudolf Backflow
CN101852302A (en) * 2010-05-24 2010-10-06 杭州春江阀门有限公司 Low-resistance self-discharge backflow preventer
CN101936412A (en) * 2010-07-26 2011-01-05 杭州春江阀门有限公司 Right-angle backflow preventer
CN202012642U (en) * 2011-05-10 2011-10-19 杭州春江阀门有限公司 Novel backflow preventer
CN102865389A (en) * 2012-08-30 2013-01-09 杭州春江阀门有限公司 Water hammer resistant backflow preventer
CN205155256U (en) * 2015-10-28 2016-04-13 杭州春江阀门有限公司 Guiding valve formula decompression type backflow preventer

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