CA1066164A - Backflow prevention apparatus - Google Patents
Backflow prevention apparatusInfo
- Publication number
- CA1066164A CA1066164A CA212,300A CA212300A CA1066164A CA 1066164 A CA1066164 A CA 1066164A CA 212300 A CA212300 A CA 212300A CA 1066164 A CA1066164 A CA 1066164A
- Authority
- CA
- Canada
- Prior art keywords
- valve
- pressure
- chamber
- poppet
- check valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E03—WATER SUPPLY; SEWERAGE
- E03C—DOMESTIC PLUMBING INSTALLATIONS FOR FRESH WATER OR WASTE WATER; SINKS
- E03C1/00—Domestic plumbing installations for fresh water or waste water; Sinks
- E03C1/02—Plumbing installations for fresh water
- E03C1/10—Devices for preventing contamination of drinking-water pipes, e.g. means for aerating self-closing flushing valves
- E03C1/106—Devices for preventing contamination of drinking-water pipes, e.g. means for aerating self-closing flushing valves using two or more check valves
-
- E—FIXED CONSTRUCTIONS
- E03—WATER SUPPLY; SEWERAGE
- E03C—DOMESTIC PLUMBING INSTALLATIONS FOR FRESH WATER OR WASTE WATER; SINKS
- E03C1/00—Domestic plumbing installations for fresh water or waste water; Sinks
- E03C1/02—Plumbing installations for fresh water
- E03C1/10—Devices for preventing contamination of drinking-water pipes, e.g. means for aerating self-closing flushing valves
- E03C1/108—Devices for preventing contamination of drinking-water pipes, e.g. means for aerating self-closing flushing valves having an aerating valve
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K15/00—Check valves
- F16K15/02—Check valves with guided rigid valve members
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Public Health (AREA)
- Water Supply & Treatment (AREA)
- Mechanical Engineering (AREA)
- Check Valves (AREA)
- Safety Valves (AREA)
- Fluid-Driven Valves (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A check valve having a poppet moving axially to engage a seat employs axially spaced flanges on the poppet slidably guided within a stationary barrel. The flanges define an annular groove which is ported to a closed chamber within the barrel. The force of a spring acting on the poppet to close the the valve is partially overcome by a drop in pressure of the chamber. This pressure reduction is brought about by reason of the projection of a portion of one of the flanges into the discharge passage of the check valve assembly, the pressure reduction being reflected through the groove and port of the chamber. Two identical check valve assemblies of this type are connected in series, the assemblies being perpendicular to each other, each being mounted at about a 45° angle with respect to coaxial inlet and outlet terminals. This double check valve assembly is combined with a differential control valve which acts to vent a zone between the check valves to atmosphere whenever backflow conditions are imminent, and thereby prevent reverse flow through the assembly.
A check valve having a poppet moving axially to engage a seat employs axially spaced flanges on the poppet slidably guided within a stationary barrel. The flanges define an annular groove which is ported to a closed chamber within the barrel. The force of a spring acting on the poppet to close the the valve is partially overcome by a drop in pressure of the chamber. This pressure reduction is brought about by reason of the projection of a portion of one of the flanges into the discharge passage of the check valve assembly, the pressure reduction being reflected through the groove and port of the chamber. Two identical check valve assemblies of this type are connected in series, the assemblies being perpendicular to each other, each being mounted at about a 45° angle with respect to coaxial inlet and outlet terminals. This double check valve assembly is combined with a differential control valve which acts to vent a zone between the check valves to atmosphere whenever backflow conditions are imminent, and thereby prevent reverse flow through the assembly.
Description
~066~64 This invention relates to fluid flow apparatus and is particularly directed to improvements in check valve construction and backflow prevention apparatus.
Check valves are commonly provided when it is desired to permit fluid flow in one direction but to prevent fluid flow in the other direction. A single check valve acting alone may leak slightly and, therefore, single check valves are not used when it is necessary to prevent any reverse flow, even in the smallest degree. In the latter situation, backflow prevention apparatus may take the form of two check valves connected in series with a "zone" between them. Both check valves remain open during normal flow in a forward direction, but in the event that the downstream pressure should approach the upstream pressure within a predetermined amount, for example, two pounds per square inch, the volume of the zone between the check valves is vented to atmosphere. In such devices, downstream pressure can never exceed upstream pressure, even under vacuum condi-tions with the result that reverse flow is not possible.
Backflow prevention devices of the type just described have at least two serious shortcomings. The first is that, in order to have a check valve which will close satisfactorily and more significantly, in certain cases, maintain a predetermined minimum pressure, a spring force is used, and this must be overcome during normal flow in the forward direction. Unfor-tunately, this often results in a pressure drop of serious pro-portions, particularly when two check valves in series are employed. Another difficulty is that conventional apparatus for venting the zone between the check valves is usually costly, inaccurate and difficult to maintain.
lQ66164 Accordingly, it is the principal objective of this invention to pro-vide check valves suitable for use in backflow prevention equipment and that are constructed to both provide a relatively high initial resistance to pres-sure and flow and yet as the demand for flow increases, cause the correspond-ing pressure drop to be at a minimum value.
According to one aspect of the invention there is provided in a check valve, the combination of means forming an inlet passage terminating in a stationary inclined annular valve seat, an inclined stationary barrel posi-tioned coaxially of the valve seat, the barrel having a cylindrical wall, a valve poppet movable toward and away from said valve seat, a spring acting to move said valve poppet into sealing contact with said valve seat, said spring acting to create a pressure drop when said valve poppet is initially moved away from said seat by fluid pressure in the inlet passage, said valve poppet having axially spaced flanges slidably guided within said wall of said barrel, means cooperating with said barrel and said valve poppet to define a chamber remote from said valve seat, means forming a discharge passage, a portion of said wall and one of said flanges projecting into said discharge passage to create a zone of relatively rapid flow and consequent reduced pressure, and means establishing communication between said zone and said chamber, whereby forward flow of fluid through the check valve causes a reduction in pressure in the chamber to oppose the action of said spring.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in whi~h:
Figure 1 is a sectional elevation showing a preferred embodiment of the check valve of this invention, the inlet and outlet terminals being coaxial and the axis of motion of the check valve poppet being positioned at a 45 angle.
Figure 2 is a sectional view of a similar check valve, the inlet and outlet terminals being positioned at 90 and the axis of movement of the check valve poppet being coaxial with the inlet axis.
Figure 3 is a sectional view of a similar check valve, the inlet and outlet terminals being coaxial and the axis of movement of the check valve 6~ .
~,' -poppet being at right angles thereto.
Figure 4 is a sectional view of a similar check valve, the inlet and outlet terminals and axis of movement of the check valve poppet all being co-axial.
Figure 5 is a sectional elevation showing a preferred form of double check valve assembly, both check valves being shown in closed position.
. ,, - 2a -~066164 Figure 6 is a graph showing pressure loss plotted against flow rate in a commercial form of the double check valve assembly shown in Figure 5.
One curve of the graph relates to a device of three-quarter inch nominal size and the other curve relates to a device of one inch nominal size.
Figure 7 is a side elevation showing a complete back-flow preventer assembly embodying this invention.
Figure 8 is an end elevation of the device shown in Figure 7.
Figure 9 is a schematic diagram in sectional elevation showing a double check valve assembly and its connections to a differential control valve assembly, the parts being shown in position for full flow in the normal direction.
Figure 10, on the same sheet as Figures 7 and 8, is a graph showing pressure loss plotted against flow rate for the backflow preventer device shown in Figures 7-9. One curve of the graph relates to a device of three-quarter inch nominal size and the other curve relates to the one inch nominal size.
Figure 11 is a sectional view showing a modified form of differential pressure control valve, the parts being positioned for normal forward flow.
Figure 12 is a view similar to Figure 10, the parts being in position corresponding to backflow conditions.
Referring to the drawings, the check valve assembly generally designated 10 is shown in its various embodiments in Figures 1, 2, 3 and 4.
The check valve assembly 10 includes a poppet 11 slidably mounted within a stationary barrel 12. An annular resilient ring 13 serves as a valve face and is held in place on the poppe 11 by means of a retaining washer 14 and a threaded fastening 15.
106616~
A coil compression spring 17 acts on the poppet 11 to bring the resilient ring 13 into sealing engagement with the station-ary annular seat 18 provided at the end of the inlet passage 19.
The poppet 11 has a first flange 20 and a second flange 21 both slidably mounted within the stationary barrel 12.
An annular groove 22 is defined between the flanges 20 and 21 and one or more ports 23 establish communication between the groove 22 and the spring chamber 24. In Figure 1, the inlet terminal 26 and the outlet terminal 27 are coaxial, and the axis of movement of the poppet 11 is positioned at about 45 with respect thereto. In Figure 2, the inlet teTminal 26a and the outlet teTminal 27a are at right angles, and the axis of movement of the poppet 11 is coaxial with the inlet terminal 26a. In Figure 3, the inlet terminal 26b and the outlet terminal 27b are coaxial, and the axis of movement of the poppet 11 is at right angles thereto. In Figure 4, the inlet terminal 27c and the outlet terminal 27c are coaxial, and the movement of the poppet 11 is along the same axis.
The check valve assembly 10 is in open position as shown in Figures 1, 2, 3 and 4. Fluid in the inlet 19 passes between the annular seat 18 and the resilient ring 13 into the outlet passage 28. Inlet pressure is then present in chamber -29 acting upon the total pressure area of flange 20 to overcome the force of spring 17. Thus, flange 20 effectively SeTVeS as a seal between the pressure area 29 and pressure area 22. In Figure 4, stationary housing 30 encircles the barTel 12 and axial passageways 31 are provided to carry fluid from the chamber 29 to the outlet terminal 27c.
In each case the outer diameters of the poppet flanges 20 and 21 are substantially larger than the effective diameter 1066~6~
of the stationary seat 18, so that when the check valve is in closed position with the resilient ring 13 engaging the seat 18, the pressure in the inlet passage 19 acts over a substantially smaller area than the pressure in the spring chamber 24. When the pressure in the inlet passage 19 applied across area of seat 18 is sufficient to overcome the force of the spring 17 and the pressure in the spring chamber 24, both the static and the dynamic head are subsequently applied to the larger effective area of the flange 20. Thus, the increase in effective area when the valve first opens results in a substantial force to overcome the spring force, and the valve moves advantageously toward the open position.
When the check valve parts are in open position corre-sponding to forward flow operation, as shown in Figures 1-4, the flow of the fluid creates a low pressure region around the poppet ll in the groove 22. This occurs because a portion of the flange 20 and a portion of the groove 22 extend into the outlet passage 28. This reduced pressure is transmitted to the spring chamber 24 through the groove 22 and through the port or ports 23, as well as through the clearance between the flange 21 and the barrel 12.
Consequently, as the velocity of forward flow increases, the unit pressure in the chamber 17 decreases over the effective area defined by the diameter of flange 20.
When the pressure in the outlet passage 28 falls below a predetermined value, as compared to the pressure in the inlet passage l9, the portion of the poppet 11 which protrudes into the outlet passage 28, Figures 1-3, and the entire poppet in Figure 4, receives the full static and dynamic force of the fluid in reverse flow, the force as thus developed acts over the full effective area of the spring chamber 24, which combined with the force of the spring 17 acts to close the valve promptly.
It will be observed that, in the construction just de-scribed, as the velocity of forward flow increases, the velocity head produces a positive opening force on the poppet 11 on the side containing the resilient ring 13 together with a lowering of unit pressure in the chamber 24, both effects serving to overcome the force of the spring 17. Moreover the lowering of pressure in the spring chamber is developed due to the portion of the poppet flange 20 protruding into the outlet passage 28 and creating a restriction 77 in which the momentum of fluid flow acting upon the static fluid in groove 22 results in the lowering of pressure in groove 22 and transmitted to the spring chamber through the communicating port 23. Consequently, as the demand for flow increases, the resulting momentum increase results in an ever decreasing pressure in the spring chamber.
Concurrently, as the rate of flow increases, the velocity head acting upon the full effective area of flange 20 (on the side with the resilient seal) increases. With both effects thus combined, a substantial pressure differential is created across the flange 20 to create an increasing force to overcome the force of the spring. Furthermore, even with the introduction of restriction 77 and a consequent "induced" pressure drop at that point, the net result is an advantageous pressure differ-ential across the poppet and a reduction in the total pressure drop across the valve. Moreover, the spaced flanges 20 and 21 guide the poppet in its movements within the baTrel 12 with adequate clearances to avoid mechanical frictional losses to minimize mechanical malfunctions. The absence of guide pins, toggle levers, etc., also assists in the reduction of mechanical friction.
The double check valve assembly generally designated 33, shown in FiguTe 5, employs two duplicate check valve assem-blies lOa and lOb which are substantially the same as the checkvalve 10 described in detail above. These check valve assemblies are arranged at right angles, the check valve lOa assembly being 1~)6616~
positioned at 45 to the axis of the inlet terminal 34 and the check valve assembly lOb being at 45 to the axis of the outlet terminal 35. The construction and operation of each of these check valve assemblies lOa and 10_ is the same as that of the check valve assembly 10 described above. Moreover, the geometric relationship of the assemblies lOa and 10_ as shown in Figure 5 produces a uniform flow pattern by minimizing the extent o-E the changes in direction of flow and the extent of obstructions to forward flow, thus minimizing fluid pressure losses.
The chart of Figure 6 shows the pressure loss through the double check ~alve assembly of Figure 5, for both the nominal size of three-quarter inch and the nominal size of one inch. It will be observed that the pressure loss through the assemblies lOa and 10 actually falls off as the flow rate increases, up to about 15 gallons per minute for the three-quarter inch size and up to about 18 gallons per minute for the one inch size.
It will be observed that the moving parts of each check valve assembly lOa and 10_ may be installed and removed independ-ently without any need to disconnect the entire assembly from the line. Moreover, each check valve assembly is so arranged as to utilize the full impact of the dynamic pressure in the support line when in forward flow operation, for effectively mini-mizing hydraulic pressure losses. Furthermore, each check valve assembly is so arranged as to have portions of the poppet thereof protruding into its respective discharge passage, or in communi-cation with its discharge passage, so as to be responsive to the slightest reverse flow action, closing spontaneously to prevent backflow.
The backflow preventer assembly shown in Figures 7, 8, and 9 include a double check valve assembly 33 having its inlet terminal 34 connected to a supply pipe 36 through a shutoff valve 37 and a union coupling 38. The outlet terminal 35 of the double ~06~ 4 check valve assembly 33 is connected through union coupling 39 and shutoff valve 40 to the service pipe 41.
A control valve assembly 43 is connected to the double check valve assembly 33 by means of discharge pipe 44 and pressure-sensing lines 45 and 46. The discharge pipe 44 forms a portion of the stationary housing 47 which contains a removable valve seat 48. A valve stem 49 carries a valve head 50 at its lower end and a resilient disk 51 on the valve head closes against the seat 48. When the parts are in position as shown in Figure 9, the valve is closed and therefore discharge of fluid from the port 52 in the double check valve assembly 33 through discharge pipe 44 is prevented. The port 52 is located downstream from the check valve lOa.and upstream from the check valve lOb.
Means are provided for moving the stem 49 to open or close the valve 48, 50, and as shown in the drawings this means includes flexible diaphragm 54 having its outer periphery clamped between the flange 55 on the housing 47 and the flange 56 on the cover 57. The inner portion of the diaphragm 54 is clamped to the stem 49 between the plates 58 and 59. A seal ring 60 on the stem 49 slides within the housing bore 61, and a seal ring 62 on the annular piston 63 of the stem 49 slides within the housing bore 64.
A chamber 65 is formed within the housing 47 below the diaphragm 54 and a chamber 66 is formed above the diaphragm within the cover 57. The chamber 65 communicates through passage 46 and port 67 with the inlet passage 68 of the check valve assembly lOa.
The chamber 66 is connected through cover port 69, passage 45 and port 70 with the inlet passage 71 for the check valve assembly lOb. From this description it will be understood that the differ-ential pressure across the diaphragm 54 is the same as the differ-ential pressure between the inlet passage 68 and the inlet passage 71.
1~6~64 The coil compression spring 73 in the chamber 66 acts on the diaphragm plate 58 to move the stem 49 in a direction to open the discharge valve 48, 50. The force of the spring is assisted by the unit pressure in the chamber 66 and is opposed by the unit pressure in the chamber 65. This opposition force is increased by the fluid pressure acting against the underside of the annular piston 64. The annular space above the piston 64 and within the housing 47 is vented to atmosphere through vent port 74.
In operation, the differential control valve 43 serves to vent the zone between the check valve assemblies lOa and lOb through the discharge port 52 whenever the downstream pressure approaches the upstream pressure within a predetermined amount.
Thus for example, the parts may be designed and adjusted so that when the pressure in the inlet terminal 34 is less than two PSI
greater than the pressure in the outlet terminal 35, the differ-ential control valve 43 will open to permit fluid to flow from the zone port 52 through the pipe 44 and through the open valve 48, 50 to atmosphere. The several forces applied to the stem 49 in addition to gravity are the opposing forces developed by inlet pressure reflected in chamber 65, outlet pressure reflec-ted in chamber 66, zone pressure at port 52 reflected against piston 63, as well as on discharge valve 50, and the force of spring 73.
It will be observed that the effective area of the diaphragm 54 is much greater than that of the valve seat 48.
Also, the ports 67 and 70 are angularly positioned to reflect both static and dynamic pressures in their respective passages. Accordingly, the differential control valve 43 causes fluid to be vented out through zone port 52 whenever the outlet passage pressure from check valve assembly lOa (reflected through line 45) plus the force of the spring 76, plus the effect of ~066~6~
~.~r~vity, exceeds the inlet pressure from passage 68 (reflected through line 46) acting in chamber 65. The balance piston 63 has the same effective area as that of the seat 48, plus that of the communicating stem 49, so that the pressure exertedon the valve head 50 and the sliding stem 49 is balanced out by the pressure exerted on the piston 63. In similar fashion, the differential control valve 43 remains closed to prevent loss of fluid through the zone port 52 so long as the total force generated by inlet pressure in the chamber 65 exceeds the sum of the force generated by outlet pressure in chamber 66 supplemented by the force of the spring 73 and by the effect of gravity.
The chart of Figure 10 shows the pressure loss through the backflow preventer assembly shown in Figures 7 and 8, for both the nominal size of three-quarter inch and the nominal size of one inch, when normal flow occurs in the forward direction.
It will be observed that the pressure loss through the entire backflow preventer assembly actually falls off as the flow rate increases up to about 20 gallons per minute for the three-quarter inch size, and up to about 32 gallons per minute for the one inch size.
In the modified form of differential control valve shown in Figures 11 and 12, an axial passage 75 in the stem 49a replaces the cover port 69. This passage 75 and its side outlet port 76 establishes communication between the cover chamber 66 and the dis-charge pipe 44. Only one sensing line 46 is used, and it connects the chamber 65 through line 46 to the inlet passage 68, as de-scribed above. The sensing line 45 and port 70 are not used.
Figure 11 shows the parts of the diaphragm control valve in closed position corresponding to normal forward flow operation, and Figure 12 shows the same parts in position to discharge fluid from the zone port 52 to atmosphere when backflow conditions are present or imminent. In other respects, the construction and operation of the modified form of the diaphragm control valve shown in Figures 11 and 12 are the same as that previously described.
-- lo --- - -1066~
Havin~ fully described our in~ention, it is to be understood that we are not to be limited by the details herein set forth but that our in~ention is of the full scope of the appended claims.
Check valves are commonly provided when it is desired to permit fluid flow in one direction but to prevent fluid flow in the other direction. A single check valve acting alone may leak slightly and, therefore, single check valves are not used when it is necessary to prevent any reverse flow, even in the smallest degree. In the latter situation, backflow prevention apparatus may take the form of two check valves connected in series with a "zone" between them. Both check valves remain open during normal flow in a forward direction, but in the event that the downstream pressure should approach the upstream pressure within a predetermined amount, for example, two pounds per square inch, the volume of the zone between the check valves is vented to atmosphere. In such devices, downstream pressure can never exceed upstream pressure, even under vacuum condi-tions with the result that reverse flow is not possible.
Backflow prevention devices of the type just described have at least two serious shortcomings. The first is that, in order to have a check valve which will close satisfactorily and more significantly, in certain cases, maintain a predetermined minimum pressure, a spring force is used, and this must be overcome during normal flow in the forward direction. Unfor-tunately, this often results in a pressure drop of serious pro-portions, particularly when two check valves in series are employed. Another difficulty is that conventional apparatus for venting the zone between the check valves is usually costly, inaccurate and difficult to maintain.
lQ66164 Accordingly, it is the principal objective of this invention to pro-vide check valves suitable for use in backflow prevention equipment and that are constructed to both provide a relatively high initial resistance to pres-sure and flow and yet as the demand for flow increases, cause the correspond-ing pressure drop to be at a minimum value.
According to one aspect of the invention there is provided in a check valve, the combination of means forming an inlet passage terminating in a stationary inclined annular valve seat, an inclined stationary barrel posi-tioned coaxially of the valve seat, the barrel having a cylindrical wall, a valve poppet movable toward and away from said valve seat, a spring acting to move said valve poppet into sealing contact with said valve seat, said spring acting to create a pressure drop when said valve poppet is initially moved away from said seat by fluid pressure in the inlet passage, said valve poppet having axially spaced flanges slidably guided within said wall of said barrel, means cooperating with said barrel and said valve poppet to define a chamber remote from said valve seat, means forming a discharge passage, a portion of said wall and one of said flanges projecting into said discharge passage to create a zone of relatively rapid flow and consequent reduced pressure, and means establishing communication between said zone and said chamber, whereby forward flow of fluid through the check valve causes a reduction in pressure in the chamber to oppose the action of said spring.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in whi~h:
Figure 1 is a sectional elevation showing a preferred embodiment of the check valve of this invention, the inlet and outlet terminals being coaxial and the axis of motion of the check valve poppet being positioned at a 45 angle.
Figure 2 is a sectional view of a similar check valve, the inlet and outlet terminals being positioned at 90 and the axis of movement of the check valve poppet being coaxial with the inlet axis.
Figure 3 is a sectional view of a similar check valve, the inlet and outlet terminals being coaxial and the axis of movement of the check valve 6~ .
~,' -poppet being at right angles thereto.
Figure 4 is a sectional view of a similar check valve, the inlet and outlet terminals and axis of movement of the check valve poppet all being co-axial.
Figure 5 is a sectional elevation showing a preferred form of double check valve assembly, both check valves being shown in closed position.
. ,, - 2a -~066164 Figure 6 is a graph showing pressure loss plotted against flow rate in a commercial form of the double check valve assembly shown in Figure 5.
One curve of the graph relates to a device of three-quarter inch nominal size and the other curve relates to a device of one inch nominal size.
Figure 7 is a side elevation showing a complete back-flow preventer assembly embodying this invention.
Figure 8 is an end elevation of the device shown in Figure 7.
Figure 9 is a schematic diagram in sectional elevation showing a double check valve assembly and its connections to a differential control valve assembly, the parts being shown in position for full flow in the normal direction.
Figure 10, on the same sheet as Figures 7 and 8, is a graph showing pressure loss plotted against flow rate for the backflow preventer device shown in Figures 7-9. One curve of the graph relates to a device of three-quarter inch nominal size and the other curve relates to the one inch nominal size.
Figure 11 is a sectional view showing a modified form of differential pressure control valve, the parts being positioned for normal forward flow.
Figure 12 is a view similar to Figure 10, the parts being in position corresponding to backflow conditions.
Referring to the drawings, the check valve assembly generally designated 10 is shown in its various embodiments in Figures 1, 2, 3 and 4.
The check valve assembly 10 includes a poppet 11 slidably mounted within a stationary barrel 12. An annular resilient ring 13 serves as a valve face and is held in place on the poppe 11 by means of a retaining washer 14 and a threaded fastening 15.
106616~
A coil compression spring 17 acts on the poppet 11 to bring the resilient ring 13 into sealing engagement with the station-ary annular seat 18 provided at the end of the inlet passage 19.
The poppet 11 has a first flange 20 and a second flange 21 both slidably mounted within the stationary barrel 12.
An annular groove 22 is defined between the flanges 20 and 21 and one or more ports 23 establish communication between the groove 22 and the spring chamber 24. In Figure 1, the inlet terminal 26 and the outlet terminal 27 are coaxial, and the axis of movement of the poppet 11 is positioned at about 45 with respect thereto. In Figure 2, the inlet teTminal 26a and the outlet teTminal 27a are at right angles, and the axis of movement of the poppet 11 is coaxial with the inlet terminal 26a. In Figure 3, the inlet terminal 26b and the outlet terminal 27b are coaxial, and the axis of movement of the poppet 11 is at right angles thereto. In Figure 4, the inlet terminal 27c and the outlet terminal 27c are coaxial, and the movement of the poppet 11 is along the same axis.
The check valve assembly 10 is in open position as shown in Figures 1, 2, 3 and 4. Fluid in the inlet 19 passes between the annular seat 18 and the resilient ring 13 into the outlet passage 28. Inlet pressure is then present in chamber -29 acting upon the total pressure area of flange 20 to overcome the force of spring 17. Thus, flange 20 effectively SeTVeS as a seal between the pressure area 29 and pressure area 22. In Figure 4, stationary housing 30 encircles the barTel 12 and axial passageways 31 are provided to carry fluid from the chamber 29 to the outlet terminal 27c.
In each case the outer diameters of the poppet flanges 20 and 21 are substantially larger than the effective diameter 1066~6~
of the stationary seat 18, so that when the check valve is in closed position with the resilient ring 13 engaging the seat 18, the pressure in the inlet passage 19 acts over a substantially smaller area than the pressure in the spring chamber 24. When the pressure in the inlet passage 19 applied across area of seat 18 is sufficient to overcome the force of the spring 17 and the pressure in the spring chamber 24, both the static and the dynamic head are subsequently applied to the larger effective area of the flange 20. Thus, the increase in effective area when the valve first opens results in a substantial force to overcome the spring force, and the valve moves advantageously toward the open position.
When the check valve parts are in open position corre-sponding to forward flow operation, as shown in Figures 1-4, the flow of the fluid creates a low pressure region around the poppet ll in the groove 22. This occurs because a portion of the flange 20 and a portion of the groove 22 extend into the outlet passage 28. This reduced pressure is transmitted to the spring chamber 24 through the groove 22 and through the port or ports 23, as well as through the clearance between the flange 21 and the barrel 12.
Consequently, as the velocity of forward flow increases, the unit pressure in the chamber 17 decreases over the effective area defined by the diameter of flange 20.
When the pressure in the outlet passage 28 falls below a predetermined value, as compared to the pressure in the inlet passage l9, the portion of the poppet 11 which protrudes into the outlet passage 28, Figures 1-3, and the entire poppet in Figure 4, receives the full static and dynamic force of the fluid in reverse flow, the force as thus developed acts over the full effective area of the spring chamber 24, which combined with the force of the spring 17 acts to close the valve promptly.
It will be observed that, in the construction just de-scribed, as the velocity of forward flow increases, the velocity head produces a positive opening force on the poppet 11 on the side containing the resilient ring 13 together with a lowering of unit pressure in the chamber 24, both effects serving to overcome the force of the spring 17. Moreover the lowering of pressure in the spring chamber is developed due to the portion of the poppet flange 20 protruding into the outlet passage 28 and creating a restriction 77 in which the momentum of fluid flow acting upon the static fluid in groove 22 results in the lowering of pressure in groove 22 and transmitted to the spring chamber through the communicating port 23. Consequently, as the demand for flow increases, the resulting momentum increase results in an ever decreasing pressure in the spring chamber.
Concurrently, as the rate of flow increases, the velocity head acting upon the full effective area of flange 20 (on the side with the resilient seal) increases. With both effects thus combined, a substantial pressure differential is created across the flange 20 to create an increasing force to overcome the force of the spring. Furthermore, even with the introduction of restriction 77 and a consequent "induced" pressure drop at that point, the net result is an advantageous pressure differ-ential across the poppet and a reduction in the total pressure drop across the valve. Moreover, the spaced flanges 20 and 21 guide the poppet in its movements within the baTrel 12 with adequate clearances to avoid mechanical frictional losses to minimize mechanical malfunctions. The absence of guide pins, toggle levers, etc., also assists in the reduction of mechanical friction.
The double check valve assembly generally designated 33, shown in FiguTe 5, employs two duplicate check valve assem-blies lOa and lOb which are substantially the same as the checkvalve 10 described in detail above. These check valve assemblies are arranged at right angles, the check valve lOa assembly being 1~)6616~
positioned at 45 to the axis of the inlet terminal 34 and the check valve assembly lOb being at 45 to the axis of the outlet terminal 35. The construction and operation of each of these check valve assemblies lOa and 10_ is the same as that of the check valve assembly 10 described above. Moreover, the geometric relationship of the assemblies lOa and 10_ as shown in Figure 5 produces a uniform flow pattern by minimizing the extent o-E the changes in direction of flow and the extent of obstructions to forward flow, thus minimizing fluid pressure losses.
The chart of Figure 6 shows the pressure loss through the double check ~alve assembly of Figure 5, for both the nominal size of three-quarter inch and the nominal size of one inch. It will be observed that the pressure loss through the assemblies lOa and 10 actually falls off as the flow rate increases, up to about 15 gallons per minute for the three-quarter inch size and up to about 18 gallons per minute for the one inch size.
It will be observed that the moving parts of each check valve assembly lOa and 10_ may be installed and removed independ-ently without any need to disconnect the entire assembly from the line. Moreover, each check valve assembly is so arranged as to utilize the full impact of the dynamic pressure in the support line when in forward flow operation, for effectively mini-mizing hydraulic pressure losses. Furthermore, each check valve assembly is so arranged as to have portions of the poppet thereof protruding into its respective discharge passage, or in communi-cation with its discharge passage, so as to be responsive to the slightest reverse flow action, closing spontaneously to prevent backflow.
The backflow preventer assembly shown in Figures 7, 8, and 9 include a double check valve assembly 33 having its inlet terminal 34 connected to a supply pipe 36 through a shutoff valve 37 and a union coupling 38. The outlet terminal 35 of the double ~06~ 4 check valve assembly 33 is connected through union coupling 39 and shutoff valve 40 to the service pipe 41.
A control valve assembly 43 is connected to the double check valve assembly 33 by means of discharge pipe 44 and pressure-sensing lines 45 and 46. The discharge pipe 44 forms a portion of the stationary housing 47 which contains a removable valve seat 48. A valve stem 49 carries a valve head 50 at its lower end and a resilient disk 51 on the valve head closes against the seat 48. When the parts are in position as shown in Figure 9, the valve is closed and therefore discharge of fluid from the port 52 in the double check valve assembly 33 through discharge pipe 44 is prevented. The port 52 is located downstream from the check valve lOa.and upstream from the check valve lOb.
Means are provided for moving the stem 49 to open or close the valve 48, 50, and as shown in the drawings this means includes flexible diaphragm 54 having its outer periphery clamped between the flange 55 on the housing 47 and the flange 56 on the cover 57. The inner portion of the diaphragm 54 is clamped to the stem 49 between the plates 58 and 59. A seal ring 60 on the stem 49 slides within the housing bore 61, and a seal ring 62 on the annular piston 63 of the stem 49 slides within the housing bore 64.
A chamber 65 is formed within the housing 47 below the diaphragm 54 and a chamber 66 is formed above the diaphragm within the cover 57. The chamber 65 communicates through passage 46 and port 67 with the inlet passage 68 of the check valve assembly lOa.
The chamber 66 is connected through cover port 69, passage 45 and port 70 with the inlet passage 71 for the check valve assembly lOb. From this description it will be understood that the differ-ential pressure across the diaphragm 54 is the same as the differ-ential pressure between the inlet passage 68 and the inlet passage 71.
1~6~64 The coil compression spring 73 in the chamber 66 acts on the diaphragm plate 58 to move the stem 49 in a direction to open the discharge valve 48, 50. The force of the spring is assisted by the unit pressure in the chamber 66 and is opposed by the unit pressure in the chamber 65. This opposition force is increased by the fluid pressure acting against the underside of the annular piston 64. The annular space above the piston 64 and within the housing 47 is vented to atmosphere through vent port 74.
In operation, the differential control valve 43 serves to vent the zone between the check valve assemblies lOa and lOb through the discharge port 52 whenever the downstream pressure approaches the upstream pressure within a predetermined amount.
Thus for example, the parts may be designed and adjusted so that when the pressure in the inlet terminal 34 is less than two PSI
greater than the pressure in the outlet terminal 35, the differ-ential control valve 43 will open to permit fluid to flow from the zone port 52 through the pipe 44 and through the open valve 48, 50 to atmosphere. The several forces applied to the stem 49 in addition to gravity are the opposing forces developed by inlet pressure reflected in chamber 65, outlet pressure reflec-ted in chamber 66, zone pressure at port 52 reflected against piston 63, as well as on discharge valve 50, and the force of spring 73.
It will be observed that the effective area of the diaphragm 54 is much greater than that of the valve seat 48.
Also, the ports 67 and 70 are angularly positioned to reflect both static and dynamic pressures in their respective passages. Accordingly, the differential control valve 43 causes fluid to be vented out through zone port 52 whenever the outlet passage pressure from check valve assembly lOa (reflected through line 45) plus the force of the spring 76, plus the effect of ~066~6~
~.~r~vity, exceeds the inlet pressure from passage 68 (reflected through line 46) acting in chamber 65. The balance piston 63 has the same effective area as that of the seat 48, plus that of the communicating stem 49, so that the pressure exertedon the valve head 50 and the sliding stem 49 is balanced out by the pressure exerted on the piston 63. In similar fashion, the differential control valve 43 remains closed to prevent loss of fluid through the zone port 52 so long as the total force generated by inlet pressure in the chamber 65 exceeds the sum of the force generated by outlet pressure in chamber 66 supplemented by the force of the spring 73 and by the effect of gravity.
The chart of Figure 10 shows the pressure loss through the backflow preventer assembly shown in Figures 7 and 8, for both the nominal size of three-quarter inch and the nominal size of one inch, when normal flow occurs in the forward direction.
It will be observed that the pressure loss through the entire backflow preventer assembly actually falls off as the flow rate increases up to about 20 gallons per minute for the three-quarter inch size, and up to about 32 gallons per minute for the one inch size.
In the modified form of differential control valve shown in Figures 11 and 12, an axial passage 75 in the stem 49a replaces the cover port 69. This passage 75 and its side outlet port 76 establishes communication between the cover chamber 66 and the dis-charge pipe 44. Only one sensing line 46 is used, and it connects the chamber 65 through line 46 to the inlet passage 68, as de-scribed above. The sensing line 45 and port 70 are not used.
Figure 11 shows the parts of the diaphragm control valve in closed position corresponding to normal forward flow operation, and Figure 12 shows the same parts in position to discharge fluid from the zone port 52 to atmosphere when backflow conditions are present or imminent. In other respects, the construction and operation of the modified form of the diaphragm control valve shown in Figures 11 and 12 are the same as that previously described.
-- lo --- - -1066~
Havin~ fully described our in~ention, it is to be understood that we are not to be limited by the details herein set forth but that our in~ention is of the full scope of the appended claims.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a check valve, the combination of: means forming an inlet passage terminating in a stationary inclined annular valve seat, an inclined stationary barrel positioned coaxially of the valve seat, the barrel having a cylindrical wall, a valve poppet movable toward and away from said valve seat, a spring acting to move said valve poppet into sealing contact with said valve seat, said spring acting to create a pressure drop when said valve poppet is initially moved away from said seat by fluid pressure in the inlet passage, said valve poppet having axially spaced flanges slidably guided within said wall of said barrel, means cooperating with said barrel and said valve poppet to define a chamber remote from said valve seat, means forming a discharge passage, a portion of said wall and at least one of said flanges projecting into said discharge passage to create a zone of relatively rapid flow and consequent reduced pressure, means establishing communication between said zone and said chamber, whereby forward flow of fluid through the check valve causes a reduction in pressure in the chamber to oppose the action of said spring.
2. The combination set forth in claim 1 in which said barrel is coaxial with but larger than said valve seat.
3. The combination set forth in claim 1 in which the spring comprises a coil compression spring mounted within said chamber.
4. The combination set forth in claim 1 in which the inlet passage is provided with an inlet terminal and the outlet passage is provided with an outlet terminal.
5. The combination set forth in claim 4 in which said terminals are axially aligned.
6. The combination set forth in claim 4 in which said terminals are axially aligned and the axis of movement of said valve poppet is inclined at an angle with respect thereto.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA327,334A CA1090675A (en) | 1973-10-26 | 1979-05-10 | Backflow prevention apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41017373A | 1973-10-26 | 1973-10-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1066164A true CA1066164A (en) | 1979-11-13 |
Family
ID=23623549
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA212,300A Expired CA1066164A (en) | 1973-10-26 | 1974-10-25 | Backflow prevention apparatus |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5083819A (en) |
| BR (1) | BR7408966D0 (en) |
| CA (1) | CA1066164A (en) |
| DE (1) | DE2450465A1 (en) |
| FR (2) | FR2250939B1 (en) |
| GB (1) | GB1490553A (en) |
| IL (1) | IL45802A (en) |
| ZA (1) | ZA746432B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8037899B2 (en) | 2008-05-08 | 2011-10-18 | Shinshu University | Backflow preventer |
| US8381764B2 (en) | 2008-04-07 | 2013-02-26 | Shinshu University | Check valve |
| CN103697198A (en) * | 2013-12-24 | 2014-04-02 | 泉州市沪航阀门制造有限公司 | Double-chamber control mechanism of pressure difference principle backflow preventer |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3996962A (en) * | 1976-03-19 | 1976-12-14 | Rockwell International Corporation | Backflow preventer and relief valve assembly |
| US4185656A (en) * | 1977-12-13 | 1980-01-29 | Braukmann Armaturen Ag | Dual check valve structure |
| US4232704A (en) * | 1978-03-28 | 1980-11-11 | Amtrol Inc. | In line back flow preventer |
| US4241752A (en) * | 1978-05-30 | 1980-12-30 | Watts Regulator Company | Backflow preventer |
| US4231387A (en) * | 1979-01-11 | 1980-11-04 | Chas. M. Bailey Co., Inc. | Backflow preventing valve |
| DE3322771A1 (en) * | 1983-06-24 | 1985-01-03 | Alfred Teves Gmbh, 6000 Frankfurt | VALVE ARRANGEMENT TO LIMIT THE PRESSURE IN A PRINTING SYSTEM |
| DE3742207A1 (en) * | 1987-12-12 | 1989-06-22 | Lang Apparatebau Gmbh | BACKFLOW PREVENTORS, ESPECIALLY FOR INSTALLATION IN DRINKING WATER PIPES |
| DE3936962A1 (en) * | 1989-11-07 | 1991-05-08 | Waletzko Armaturen Gmbh | BACKFLOW PREVENTORS, ESPECIALLY FOR INSTALLATION IN DRINKING WATER PIPES |
| US5226441A (en) * | 1989-11-13 | 1993-07-13 | Cmb Industries | Backflow preventor with adjustable outflow direction |
| US5107888A (en) * | 1989-11-13 | 1992-04-28 | Cmb Industries, Inc. | N-shaped backflow preventor |
| US5046525A (en) * | 1990-06-15 | 1991-09-10 | Ames Company, Inc. | Differential loading fluid check valve |
| DE4309085C1 (en) * | 1993-03-20 | 1995-01-05 | Schubert & Salzer Ag | System separator |
| JP3016993U (en) * | 1995-04-14 | 1995-10-17 | 株式会社タブチ | Compound non-return type universal joint |
| DE29605420U1 (en) * | 1996-03-23 | 1996-06-13 | Festo Kg, 73734 Esslingen | Quick exhaust valve for pneumatic applications |
| DE10201626A1 (en) | 2002-01-16 | 2003-07-31 | Wildfang Dieter Gmbh | check valve |
| DE202004016530U1 (en) * | 2004-10-25 | 2006-03-02 | Gebr. Kemper Gmbh & Co. Kg Metallwerke | Pipe aerator and shut-off valve of a water installation with pipe aerator |
| CN103742390B (en) * | 2013-11-28 | 2015-10-28 | 成都欧浦特控制阀门有限公司 | A kind of air pump being provided with coil tension spring |
| KR102393812B1 (en) * | 2018-03-12 | 2022-05-03 | 가부시키가이샤 이시자키 | Reciprocating bodies for check valves and check valves |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1710635A (en) * | 1924-08-06 | 1929-04-23 | Mortimer C Rosenfeld | Valve |
| US3283772A (en) * | 1964-02-04 | 1966-11-08 | Donald G Griswold | Backflow prevention device with improved pressure sensing means |
-
1974
- 1974-10-07 IL IL45802A patent/IL45802A/en unknown
- 1974-10-09 ZA ZA00746432A patent/ZA746432B/en unknown
- 1974-10-24 DE DE19742450465 patent/DE2450465A1/en not_active Ceased
- 1974-10-25 GB GB46301/74A patent/GB1490553A/en not_active Expired
- 1974-10-25 CA CA212,300A patent/CA1066164A/en not_active Expired
- 1974-10-25 BR BR8966/74A patent/BR7408966D0/en unknown
- 1974-10-25 FR FR7435902A patent/FR2250939B1/fr not_active Expired
- 1974-10-26 JP JP49123862A patent/JPS5083819A/ja active Pending
-
1975
- 1975-04-22 FR FR7512553A patent/FR2257834B1/fr not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8381764B2 (en) | 2008-04-07 | 2013-02-26 | Shinshu University | Check valve |
| US8037899B2 (en) | 2008-05-08 | 2011-10-18 | Shinshu University | Backflow preventer |
| CN103697198A (en) * | 2013-12-24 | 2014-04-02 | 泉州市沪航阀门制造有限公司 | Double-chamber control mechanism of pressure difference principle backflow preventer |
Also Published As
| Publication number | Publication date |
|---|---|
| IL45802A (en) | 1977-05-31 |
| GB1490553A (en) | 1977-11-02 |
| IL45802A0 (en) | 1975-03-13 |
| JPS5083819A (en) | 1975-07-07 |
| FR2250939B1 (en) | 1978-08-11 |
| ZA746432B (en) | 1976-06-30 |
| FR2257834B1 (en) | 1979-10-05 |
| FR2257834A1 (en) | 1975-08-08 |
| FR2250939A1 (en) | 1975-06-06 |
| AU7418174A (en) | 1976-04-15 |
| DE2450465A1 (en) | 1975-04-30 |
| BR7408966D0 (en) | 1975-09-23 |
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