Check valve assembly and method for mounting and installing check valves within a housing

A check valve assembly, including a check valve and an associated check valve mounting flange. Additionally, a backflow preventer is shown, which uses a pair of check valve assemblies transversely positioned within a tubular housing. Also disclosed is a method for installing a downstream check valve to a mounting flange, located within a remote, outlet chamber of the backflow preventer housing. The check valve has an elongated base plate, generally elongated in shape. The mounting flange is provided with an elongated hole, sized and configured to pass a properly oriented downstream check valve during installation and removal procedures. The location and design of the downstream check valve assembly ensures that during backflow conditions, the check valve compresses against the mounting flange in sealing engagement.

FIELD OF THE INVENTION 
The invention relates generally to the field of backflow preventers 
installed in water lines to prevent pollution of the water supply system 
during reverse siphoning, or backflow conditions. More specifically, the 
invention pertains to a check valve assembly installed within backflow 
preventers, exhibiting improved sealing characteristics during backflow 
conditions. The invention also pertains to a method for installing a check 
valve in a remote, outlet chamber of a backflow preventer housing, through 
a single access port in an intermediate chamber of the housing. 
BACKGROUND OF THE INVENTION 
Backflow prevention devices are installed in the main water supply lines 
leading to industrial and commercial water users, as well as apartment 
dwellers. These devices arrest any reverse flow of liquid pollutants from 
those facilities into the main water supply system, in the event of a 
catastrophic loss or drop in hydraulic pressure in the supply system. 
A backflow preventer typically includes a pair of check valves, arranged 
serially within a valve housing. The housing includes an inlet port for 
connection to the water system supply line, and an outlet port for 
connection to the user's incoming water line. When a predetermined water 
pressure differential exists across the inlet and outlet ports, the force 
is sufficient to urge the clappers of both check valves into an open 
position, allowing water to flow freely therethrough. If an insufficient 
pressure differential exists, the clappers of both check valves are biased 
into a closed position. Providing the clappers of the closed check valves 
seal properly, a backflow of liquid, from the outlet port to the inlet 
port is prevented. A pair of check valves is commonly used for redundancy, 
in the event one of the valves fails. 
There are two primary considerations in the installation and operation of 
these devices: (1) the need to install, service, and replace the check 
valves quickly and with relative ease; and, (2) the necessity for the 
check valves effectively to withstand the considerable pressure which may 
develop during backflow conditions. 
This latter consideration is of particular concern, for example, in systems 
providing water to chemical or manufacturing plants, where a backflow of 
toxic liquid into the water supply system could pose a dangerous health 
hazard. 
When water is flowing forwardly through a backflow preventer, the force 
acting upon the check valve mechanisms in the downstream direction is 
approximately two percent of the force applied to the valve in the reverse 
direction, under a backflow condition. Under forward flow conditions, the 
check valves are easily held or retained in place by conventional 
fasteners, such as nuts, bolts, screws, or threads. However, under 
backflow conditions and the much higher attendant forces, these fasteners 
may allow leakage around the check valve seal, or they may fail entirely. 
Since even minor leakage of toxins or pollutants could have serious 
consequences, the need exists for a mounting system which eliminates the 
possibility of seal compromise. 
In prior art backflow preventers employing two check valves, the first, 
upstream check valve is normally adequately secured by conventional 
fasteners. This is the case because the base of the first check valve is 
typically mounted to an attachment structure, such as a flange, a fitting, 
or a tube, upstream from the base. Forward flow produces only small 
forces, insufficient to separate the check valve from the upstream 
attachment structure. And, under backflow conditions, the components which 
form the seal between the base of the check valve and the attachment 
structure experience higher compression, thus increasing the reliability 
of the seal and the integrity of the attachment. 
However, a different consideration exists for the second, downstream check 
valve. In prior art backflow preventers having a line diameter of no 
greater than 21/2", the base of the second check valve is mounted to an 
attachment structure, downstream from the base. As would be expected, this 
arrangement works well during normal, forward flow through the backflow 
preventer, as the sealing and mechanical attachment components are 
subjected to compressive forces. However, under the extreme forces cause 
by backflow pressure, the seal between the second check valve and its 
downstream attachment structure is challenged. An increase in back 
pressure applied against the second check valve tends to separate the base 
of the check valve from the attachment structure. Thus, for backflow 
preventers in relatively small lines, backflow conditions have exactly the 
opposite effect upon the integrity of the hydraulic seals between the 
upstream and downstream check valves and their respective attachment 
structures. 
This potential for leakage increases with larger diameter lines and the 
greater forces attendant with such lines. Accordingly, prior art backflow 
preventers for supply lines larger than 21/2" in diameter, employ two 
inspection ports in the backflow preventer housing. The second inspection 
port allows the downstream check valve to be mounted to an attachment 
structure upstream from the base of the valve. This arrangement provides 
the same enhanced seal reliability for the downstream check, as enjoyed by 
the upstream check valve during backflow conditions. 
Unfortunately, the inclusion of a second inspection port is expensive, 
increases service time, makes the unit physically longer and provides an 
additional location where leaks can occur. It would therefore be 
beneficial to eliminate the need for this second inspection or access 
port, but retain the sealing advantage afforded by mounting the check 
valve to an attachment structure upstream from the base of the valve. 
Accordingly, it is an object of the present invention to provide an 
improved backflow prevention device, which effectively resists backflow 
pressures exerted against it. 
It is a further object of the present invention to provide a backflow 
prevention device having a single access port, permitting quick and easy 
installation and servicing of both check valves. 
It is yet a further object of the present invention to provide a backflow 
preventer employing upstream and downstream check valve assemblies which 
are mounted to their attachment structures in the same relation, with 
respect to the direction of water flow. 
It is another object of the present invention to provide check valves 
assemblies having retaining, sealing, and check valve mechanisms which are 
structurally and functionally compatible and interchangeable. 
It is yet another object of the present invention to provide a method for 
installing a check valve in a remote, outlet chamber of a backflow 
preventer housing, through a single access port in an intermediate chamber 
of the housing. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an apparatus and a method are 
provided for effectively preventing the backflow of liquids through a 
fluid conduit. The apparatus herein includes an elongated backflow 
preventer housing, preferably containing two check valve assemblies 
arranged serially therein. The housing is essentially a tubular conduit, 
having inlet and outlet ports at either end for incoming and outgoing 
passage of a liquid through the conduit. A single access port is included 
within the sidewall of the housing between the inlet and outlet ports, 
providing selective entry within the interior of the housing. This single 
port is provided for installing, servicing, and replacing components of 
the two check valve assemblies. 
Each check valve assembly includes a circular mounting flange, a check 
valve, and fasteners for interconnecting the valve to the flange. The 
mounting flanges are transversely disposed within the housing, on either 
side of the access port. Each flange includes a non-circular hole 
therethrough for the passage of liquid through the housing. The hole in 
the downstream flange also provides for the occasional passage of a 
downstream check valve during its installation and servicing. 
The check valve employed herein includes a special base plate, having an 
elongated, planar configuration and a centrally positioned aperture for 
the passage of liquid. The base plate disclosed herein is substantially 
elliptical in elevation, although other configurations having an major 
elongated dimension and a lesser transverse dimension will work as well. A 
valve clapper is pivotally attached to one side of the base plate to form 
a hinged cover over the aperture. The upstream side of the clapper may 
include a keeper disc and a resilient ring seal. When the clapper is in a 
closed position, this seal seats within the aperture, engaging the face of 
the aperture and sealing the aperture against backflow. 
In the preferred embodiment, an elongated, arcuate cam arm is also 
provided. The cam arm is pivotally attached on a side of the check valve 
mounting plate, opposite the pivot attachment of the clapper. The cam arm 
is spring biased toward the base plate, urging the underlying clapper into 
a closed position over the aperture. When a sufficient pressure 
differential exists across the check valve, the upstream force overcomes 
the spring bias, and the check valve is urged into an open position. 
A particularly significant feature of the present invention is the 
elongated, or non-circular configuration of the check valve base plate. 
Another significant feature is the non-circular hole provided in the 
flange plate, through which the downstream check valve can be passed both 
for initial assembly, and for later servicing. These unique, non-symmetric 
configurations facilitate installation of the downstream check valve on a 
remote, downstream side of the mounting flange. This construction and 
method of assembly affords a tight seal during a backflow condition, when 
the base plate is compressed against the mounting flange. 
Yet another feature of the disclosed check valve assembly, is a universal 
check valve construction which can be used both in upstream and downstream 
applications, when mounted to respective upstream and downstream mounting 
flanges. This feature simplifies both assembly and servicing, and reduces 
the number of replacement parts which must be kept on hand.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings, FIGS. 1 through 3 show a universal check valve 
11, including an elongated, planar base plate 12, a circular clapper 13, 
and an arcuate cam arm 14. The clapper and clapper biasing mechanisms of 
the check valves for use herein may be of conventional design, such as a 
spring-biased poppet clapper, or a pivotally mounted clapper, spring or 
gravity biased to a closed position. However, applicant prefers using the 
differential loading fluid check valve construction shown in U.S. Pat. No. 
5,046,525, having a common assignee herewith. The disclosure and subject 
matter of U.S. Pat. No. 5,046,525 are hereby incorporated by reference 
into the present application. 
Check valve base 12 is generally elliptical in front elevation, having a 
major longitudinal dimension and a minor transverse dimension. The 
specific configuration is not critical as long as the base is elongated, 
having a transverse dimension which is less than the longitudinal 
dimension. This important characteristic allows the check valve to be 
oriented and manipulated into and out from an installed position in a 
manner which provides unique advantages and utility, to be described more 
fully herein. 
Base 12 includes a circular aperture 16 for the passage of liquid through 
the check valve 11. Clapper 13 is pivotally mounted on one side of 
aperture 16 by a pair of base brackets 17 and a pair of clapper brackets 
18, interconnected by a rod 19. A proximate end 20 of cam arm 14 is 
pivotally mounted on a shaft 21, supported by a pair of cam brackets 22 
located on the other side of aperture 16. A spring 23, encircling shaft 21 
and having portions on either side of cam arm 14, biases a remote end 26 
of the cam arm toward base 12. 
A roller 24 is rotatably mounted on an outer edge of clapper 13, effective 
to engage an inner surface of cam arm 14. As shown in FIG. 2, when the 
remote end 26 of cam arm 14 is adjacent base 12, arm 14 impinges upon 
roller 24 and maintains clapper 13 in a closed position over aperture 16. 
As shown most clearly in FIG. 7, clapper 13 includes a base disc 27, an 
annular seal 28, and a seal keeper 29. Threads 30 are provided in 
contingent, circular wall portions of disc 27 and keeper 29, to secure the 
clapper assembly together and allow replacement of seal 28. Disc 27 and 
keeper 29 are preferably manufactured from a hard plastic material, 
whereas seal 28 is manufactured from a resilient rubber material, or the 
like. With clapper 13 urged into a closed position by arm 14, seal 28 is 
maintained in tight sealing relation over aperture 16. 
An O-ring 31 is provided in the front face of base plate 12 for sealing 
engagement with a mounting flange, to be discussed below. Four upstream 
mounting holes 32 are arranged around the periphery of base 12. Mounting 
holes 32 pass entirely through plate 12. Four downstream mounting holes 33 
are located radially inwardly from respective holes 32, just inside the 
boundary defined by O-ring 31. Mounting holes 33 are tapped, but do not 
pass entirely through plate 12. A gripping bar 34, secured by bolts 36, 
may optionally be mounted across the forward face of plate 12, to assist 
in handling check valve 11. 
The check valve 11 of the present invention is advantageously used in 
conjunction with a special mounting flange, the combination herein being 
termed a check valve assembly. Typically, one or more of the check valve 
assemblies is transversely mounted within a tubular housing, allowing 
passage of water therethrough in a forward direction only. This device, 
termed a backflow preventer in the industry, is serially interconnected 
within a main water supply line leading to commercial or industrial users 
of water. 
Turning now to FIG. 7, it will be noted that an upstream check valve 
assembly 39 and a downstream check valve assembly 41, are serially 
positioned within a backflow preventer 37. Backflow preventer 37 includes 
an elongated, tubular housing 38, either manufactured as a single, unitary 
casting, or comprised of several components, specially formed and welded 
together. As shown herein, housing 38 is manufactured entirely from pieces 
of stainless steel material, owing to its high strength, low weight, and 
resistance to corrosive effects. 
Housing 38 includes an inlet port 42, an outlet port 43, an inlet flange 
44, and an outlet flange 46. Flanges 44 and 46 facilitate attachment of 
backflow preventer 37 to corresponding flanges on a main water supply 
line. Housing 38 also includes an inlet chamber 47, an intermediate 
chamber 48, and an outlet chamber 49, together defining a forward liquid 
flow path therethrough, indicated by numeral 51. 
A service port 52 is provided within the sidewall of housing 38, between 
inlet port 42 and outlet port 43. A domed cover 53 is secured in place 
over port 52, by a split ring 54. Only one half of the split ring is 
evident in FIG. 7. A pair of bolts (not shown), compresses each half of 
the split ring against a circular, resilient gasket 56. Removal of ring 54 
and cover 53 allows selective access to intermediate chamber 48, for 
assembly and servicing of backflow preventer 37. 
During initial assembly of preventer 37, downstream check valve assembly 41 
is first installed, followed by upstream check valve assembly 39. For 
later servicing, assembly 39 may be removed and reinstalled independently 
from assembly 41. However, as will explained more fully below, servicing 
of assembly 41 will require first that assembly 39 be removed. 
Upstream check valve assembly 39 includes an upstream mounting flange 57 
and an upstream check valve 58 (see FIG. 15). Flange 57 is mounted 
transversely within housing 38, defining a wall boundary between inlet 
chamber 47 and intermediate chamber 48. Flange 57 is provided with an 
elongated hole 59 for passage of the liquid flow path 51, through the 
flange. Four mounting bolts 61 are welded to flange 57, and are arranged 
in spaced relation around hole 59. 
Upstream check valve 58 is constructed in essentially the same manner as 
previously described check valve 11, shown particularly in FIGS. 1-3. The 
only feature of valve 11 which is unnecessary for valve 58 is gripping bar 
34. Making reference to FIGS. 7 and 15, it will be appreciated that by 
grasping cam arm 14, check valve 58 can be lowered through service port 52 
into intermediate chamber 48, and installed flush against mounting flange 
57. Bolts 61 pass through holes 32, leaving a threaded portion extending 
through base plate 12. Nuts 62 are then threaded onto bolts 61, securely 
fastening check valve 58 to mounting flange 57. O-Ring 31 is thereby 
compressed into sealing engagement with mounting flange 57, completing the 
installation of check valve 58. 
Downstream check valve assembly 41 includes a downstream mounting flange 63 
and a downstream check valve 64 (see FIG. 14). Flange 63 lacks mounting 
bolts 61, but is otherwise identical in size and configuration to flange 
57. As shown in FIG. 7, flange 63 is also mounted transversely within 
housing 38, and defines a wall boundary between intermediate chamber 48 
and outlet chamber 49. Flange 63 is provided with an elongated hole 66, 
identical in size and configuration to hole 59, but having an important 
additional function in the practice of the present invention. 
Hole 66 is dimensioned and shaped to pass a properly oriented downstream 
check valve 64, both for purposes of initial assembly of backflow 
preventer 37, and for later servicing of check valve 64. Making particular 
reference to FIG. 6, it will be noted that hole 66 has a generally 
rectangular shape, modified by arcuate sidewall cutouts 67. The elongated 
dimension of hole 66 is sufficient to accommodate the transverse dimension 
of base plate 12 of check valve 64. And, the transverse dimension of hole 
66, including cutouts 67, is sufficient to accommodate the distance 
between the mounting face of base plate 12 and the outer edge of cam arm 
14. Thus, with the elongated axis of check valve 64 coincident with the 
center of hole 66, and cam arm 14 oriented as shown in FIG. 6, check valve 
64 may be passed completely through hole 66. 
With this as background, an initial assembly or subsequent service 
procedure for downstream check valve 64 will now be explained in detail. 
FIGS. 8 through 12 show the various steps which are undertaken in handling 
and manipulating the check valve 64 into an installed position. Removal of 
the valve 64 is carried out by simply reversing the order of the 
installation steps. 
In FIG. 8, the split ring and dome cover over service port 52 have been 
removed, allowing check valve 64 to be lowered, along the direction of its 
longitudinal axis, into intermediate chamber 48. The orientation of valve 
64 is such, that cam brackets 22 and spring 23 are located on the upper 
end of the valve. The next step, shown in FIG. 9, involves a reorientation 
of the valve, within intermediate chamber 48. The valve is rotated in 
counter-clockwise fashion, about the axis of clapper 13, so that the cam 
brackets 22 are directed upstream and the base brackets are directed 
downstream. The resultant position of valve 64 is illustrated in FIGS. 6 
and 10. 
The valve is then passed through elongated hole 66, with sidewall cutout 67 
accommodating the arcuate profile of cam arm 14. By grasping gripping bar 
34, the installer is able to reorient valve 64, so that its longitudinal 
axis is vertical, with cam brackets 22 now located on the lower end of the 
valve. Concurrently, base plate 12 of the valve is oriented upstream, in 
adjacent, parallel relation to downstream mounting flange 63 (see, FIG. 
12). Again relying upon the gripping bar, the installer draws valve 64 
upstream into contingent relation with flange 63, and maintains it in that 
position so that flange holes 68 are aligned with downstream mounting 
holes 33 (see FIG. 14). Four bolts 69 are then passed through holes 68 and 
screwed into holes 33 to fasten valve 64 securely to plate 63. O-ring 31 
is thereby compressed against plate 63, forming a hydraulic seal 
therewith. 
After the downstream check valve is installed, the upstream check valve may 
be installed in the manner described above. It should also be noted that 
while the upstream check valve can independently be serviced without 
disturbing the downstream check valve, the reverse is not the case. If the 
downstream check valve is to be serviced, the upstream check valve must 
first be removed, so that sufficient clearance exists for the removal and 
reinstallation of the downstream check valve. 
It is generally preferable to have the upstream and downstream check valves 
oriented with their longitudinal axes vertical, and the respective pivot 
rods 19 located on the upper end of each valve. This is the check valve 
orientation shown in FIG. 7. The reason for this preference is that it 
allows any incoming debris or foreign matter to pass more easily through 
the check valves, instead of lodging between the clapper and the base 
plate, and possibly defeating the reverse flow protection of the check 
valves. 
However, the specific orientation of the check valves is not critical to 
successful practice of the present invention. The longitudinal axes of 
either the upstream or the downstream check valves, or both, may be 
horizontal, for example. FIG. 13 shows such an alternative orientation for 
the downstream check valve assembly 41. An identical, horizontal 
orientation may also be used advantageously for the upstream check valve 
assembly 39. 
If, for example, a backflow preventer is provided with an external pressure 
relief valve operating on the "reduced pressure" principle, it may be 
desirable to orient assembly 39 so that its longitudinal axis is 
horizontal. Such an external pressure relief valve is shown in FIG. 10 of 
U.S. Pat. No. 5,046,525, previously incorporated by reference. It has been 
determined that under very high flow rates, the turbulence created by 
water flowing downstream from the upstream check valve may cause a 
pressure relief valve to open without a fault condition existing. To 
alleviate this problem, the upstream check valve may be reoriented, so 
that the longitudinal axis of the valve is horizontal. In this way, the 
bulk of the turbulence is directed toward the median sidewall of the 
housing 38, rather than downwardly toward the sensor line of the pressure 
relief valve. 
Housing 38 may also be provided with additional valves, fittings, and 
accessories. For example, FIG. 7 shows an upstream test cock 71, an 
intermediate test cock 72, and a downstream test cock 73. These test cocks 
are temporarily interconnected to pressure gauges for reading static 
and/or dynamic fluid pressures within the various chambers of the housing 
38. In this way, proper operation and the integrity of the check valve 
seals can be confirmed. Plugs 74 are also included within the sidewall of 
housing 38, closing off respective threaded ports in communication with 
inlet chamber 47 and intermediate chamber 48. Removal of these plugs will 
allow connection to exterior lines and valves, such as the pressure relief 
valve, operating on the "reduced pressure" principle, discussed above. 
In normal operation, a fluid flow path 51 passes freely through the 
backflow preventer of the present invention, by urging both upstream and 
downstream check valves into an open position (see, FIG. 7). If a 
catastrophic loss of incoming pressure occurs, the pressure differential 
across the check valves will not be sufficient to overcome the load or 
bias, imposed by cam arm 14, and the valves will close. In the event that 
reverse flow, or backflow pressures develop, the hydraulic forces imposed 
upon the downstream side of the clappers 13 will urge the check valves 
into a tightly closed position. These forces will further be transmitted 
through base 12, to compress each sealing O-ring against a respective 
mounting flange. Thus, greater backflow pressures effect a more positive 
and effective seal for both check valves 58 and 64, ensuring that no 
pollution of the water supply will occur. 
It will be appreciated then, that I have disclosed a check valve assembly 
and a backflow preventer which enjoy improved reliability over prior art 
devices, and which allow easy access for assembly, servicing, and 
replacement of internal components.