U.S. patent application number 10/116530 was filed with the patent office on 2002-08-15 for full opening bulged forward acting rupture disc having variable depth score line.
Invention is credited to Friend, Peter T., Hinrichs, James O., Warden, Lowell G..
Application Number | 20020108750 10/116530 |
Document ID | / |
Family ID | 24511013 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020108750 |
Kind Code |
A1 |
Friend, Peter T. ; et
al. |
August 15, 2002 |
Full opening bulged forward acting rupture disc having variable
depth score line
Abstract
A leak integrity testing apparatus (36) is provided which is
adapted to be inserted within a liquid-delivery line, as for
example an oil well tubing string (26), to permit in situ testing
of the line or string (26) without the need for removal or
inspection of the line. The apparatus (36) is a tubular body
preferably including an interconnected tubular inlet (38) and
outlet (40); a liquid pressure-responsive, metallic burst disc (42)
is located between the inlet (38) and outlet (40). The disc (42)
includes a peripheral flange (62) and an inner concavo-convex burst
region (64). A score line (82, 86) is located on the concave face
(66) of the burst region (64), and is of differential depth, having
a reduced-depth hinge area (84, 88) serving to prevent detachment
of the burst region (64) upon actuation of the disc (42). The score
line (82) preferably is located entirely inboard of the transition
region (76) between the flange (62) and burst region (64);
alternately, the score line (86) may have the hinge area (88)
thereof within the transition region (76). In use, liquid under
pressure less than the burst pressure of the disc directed against
the concave face (66) of the disc (42) thereby confirming the
integrity of the line or string (26). Increasing the pressure of
the liquid against the concave face of the disc to a level which
effects rupture of the disc, the central ruptured section of the
disc gives way and moves to an open position allowing substantially
unimpeded flow of liquid through the opening in the disc defined by
the ruptured section.
Inventors: |
Friend, Peter T.; (Odessa,
MO) ; Hinrichs, James O.; (Odessa, MO) ;
Warden, Lowell G.; (Oak Grove, MO) |
Correspondence
Address: |
HOVEY WILLIAMS TIMMONS & COLLINS
2405 GRAND BLVD., SUITE 400
KANSAS CITY
MO
64108
|
Family ID: |
24511013 |
Appl. No.: |
10/116530 |
Filed: |
April 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10116530 |
Apr 3, 2002 |
|
|
|
09626585 |
Jul 27, 2000 |
|
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Current U.S.
Class: |
166/205 |
Current CPC
Class: |
E21B 34/063
20130101 |
Class at
Publication: |
166/205 |
International
Class: |
E03B 003/18; E21B
043/00 |
Claims
We claim:
1. A unitary, forward buckling, rupture disc adapted to be mounted
on a tubular rupture disc holder in closing relationship to a
central fluid passage through the holder, said disc comprising: an
outer peripheral flange portion having a first annular face and an
opposed second annular face, an inner concavo-convex, generally
hemispherical bulged region presenting a concave face and an
opposed convex face, an annular, circumferentially extending,
cross-sectionally arcuate transition region integral with the
peripheral flange portion and the bulged region respectively, said
transition region having a first cross-sectionally arcuate annular
surface joining the first face of the flange portion to the convex
face of the bulged region and a second cross-sectionally arcuate
annular surface joining the second face of the flange portion to
the concave face of the bulged region, said first arcuate surface
being defined by a pair of circumferentially extending, concentric,
laterally spaced apart, inner and outer first margins integral with
the first annular face of the flange portion and with the convex
face of the bulged region respectively, said second arcuate surface
being defined by a pair of circumferentially extending, laterally
spaced apart, inner and outer second margins integral with the
second annular face of the flange portion and with the concave face
of the bulged region respectively, said first arcuate surface
having a smaller radius than the radius of the second arcuate
surface, and said bulged region being provided with a continuous,
generally circular score line formed in the concave face of the
bulged region inboard of and spaced inwardly of the transition
region, said score line defining a central rupture segment of the
bulged region having a generally circumscribing edge located in
proximal relationship to the inner second margin of the transition
region, said score line varying in depth along the length thereof
presenting a first reduced depth line portion defining a hinge
section of the score line and defining a second score line portion
of greater depth than said reduced depth score line portion, said
second score line portion being of a depth to rupture and allow the
central rupture segment of the bulged region to move to a fully
open position when a pre-determined pressure is applied to the
concave face of the rupture disc, said second score line portion of
the score line being located in sufficiently close relationship to
the inner second margin of the transition region and of a depth
such that the central rupture section of the bulged disc region
opens to said fully open position without severing of the hinge
section of the disc and with the edge of the central rupture disc
segment disposed in at least about substantially perpendicular
relationship to said flange, said central rupture segment of the
disc when moved to the fully open position thereof being located
out of the flow path of fluid through the rupture disc holder so as
to not present any substantial impediment to bi-directional flow of
fluid through said central passage of the rupture disc holder
2. A unitary, forward buckling rupture disc as set forth in claim
1, wherein said disc has a thickness of from about 0.010 in. to
about 0.060 in.
3. A unitary, forward buckling rupture disc as set forth in claim
2, wherein said disc has a thickness of from about 0.014 in. to
about 0.050 in.
4. A unitary, forward buckling rupture disc as set forth in claim
1, wherein said second line portion of the score line is from about
35% to about 70% of the thickness of the disc.
5. A unitary, forward buckling rupture disc as set forth in claim
4, wherein said second line portion of the score line is from about
40% to about 60% of the thickness of the disc.
6. A unitary, forward buckling rupture disc as set forth in claim
1, wherein the depth of said first score line portion of the score
line is from about 0.001 in. to about 0.005 in. less than the depth
of the second score line portion of the score line throughout the
extent of the first score line portion.
7. A unitary, forward buckling rupture disc as set forth in claim
1, wherein the depth of said second score line portion of the score
line is from about 0.002 in. to about 0.004 in. less than the depth
of said first score line portion of the score line.
8. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing and thereafter permitting full
bi-directional flow of liquid through the pipe string, said
apparatus comprising: a tubular rupture disc holder presenting a
central liquid passage therethrough and having opposed end
segments, one of said holder end segments being adapted for
attachment to an end of one of the pipe sections of the pipe string
and the other end segment of the holder being adapted to for
attachment to an end of an adjacent pipe section of the pipe
string, said holder being provided with a circumferentially
extending enlarged central section of greater diameter than the
diameter of each of the opposed end segments of the holder; and a
unitary, forward buckling, rupture disc mounted on the rupture disc
holder in normal closing relationship to said central liquid
passage through the holder, said disc provided with an outer
peripheral flange portion having a first annular face and an
opposed second annular face, an inner concavo-convex, generally
hemispherical bulged region presenting a concave face and an
opposed convex face, an annular, circumferentially extending,
cross-sectionally arcuate transition region integral with the
peripheral flange portion and the bulged region respectively, said
transition region having a first cross-sectionally arcuate annular
surface joining the first face of the flange portion to the convex
face of the bulged region and a second cross-sectionally arcuate
annular surface joining the second face of the flange portion to
the concave face of the bulged region, said first arcuate surface
being defined by a pair of circumferentially extending, concentric,
laterally spaced apart, inner and outer first margins integral with
the first annular face of the flange portion and with the convex
face of the bulged region respectively, said second arcuate surface
being defined by a pair of circumferentially extending, laterally
spaced apart, inner and outer second margins integral with the
second annular face of the flange portion and with the concave face
of the bulged region respectively, said first arcuate surface
having a smaller radius than the radius of the second arcuate
surface, and said bulged region being provided with a continuous,
generally circular score line formed in the concave face of the
bulged region inboard of and spaced inwardly of the transition
region, said score line defining a central rupture segment of the
bulged region having a generally circumscribing edge located in
proximal relationship to the inner second margin of the transition
region, said scored line varying in depth along the length thereof
presenting a first reduced depth line portion defining a hinge
section of the score line and defining a second score line portion
of greater depth than said reduced depth score line portion, said
second score line portion being of a depth to rupture and allow the
central rupture segment of the bulged region to move to a fully
open position when a pre-determined pressure is applied to the
concave face of the rupture disc, said second score line portion of
the score line being located in sufficiently close relationship to
the inner second margin of the transition region and of a depth
such that the central rupture section of the bulged disc region
opens to said fully open position without severing of the hinge
section of the disc and with the edge of the central rupture disc
segment disposed in at least about substantially perpendicular
relationship to said flange, said central rupture segment of the
disc when moved to the fully open position thereof being located in
the enlarged central section out of the flow path of liquid through
the rupture disc holder so as to not present any substantial
impediment to bi-directional flow of liquid through said central
passage of the rupture disc holder.
9. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 8, wherein said
disc has a thickness of from about 0.010 in. to about 0.060 in.
10. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 9, wherein said
disc has a thickness of from about 0.014 in. to about 0.050 in.
11. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 8, wherein said
second line portion of the score line is from about 35% to about
70% of the thickness of the disc.
12. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 11, wherein said
second line portion of the score line is from about 40% to about
60% of the thickness of the disc.
13. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 8, wherein the
depth of said first score line portion of the score line is from
about 0.001 in. to about 0.005 in. less than the depth of the
second score line portion of the score line throughout the extent
of the first score line portion.
14. Apparatus for testing the integrity of the connections between
end to end pipe sections of a liquid-delivery pipe string line
within an oil well casing as set forth in claim 8, wherein the
depth of said second score line portion of the score line is from
about 0.002 in. to about 0.004 in. less than the depth of said
first score line portion of the score line.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
09/626,585, filed Jul. 27,2000, entitled BULGED SINGLE HINGED
SCORED RUPTURE DISC HAVING CIRCULAR SCORE LINE OF LESSER DEPTH IN
HINGE AREA.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is broadly concerned with leak
integrity testing apparatus for use in testing liquid-conveying
conduits in various industrial and oil well applications. More
particularly, the invention pertains to such apparatus, and the
frangible rupture discs forming a part thereof, wherein the rupture
discs are of concavo-convex design and have a continuous score line
formed on the concave faces thereof; the score lines are of
differential depth in order to define a region of reduced depth
forming a hinge area for the burst region of the disc preventing
separation thereof upon disc rupture. The apparatus has particular
utility for use in testing of oil well tubing strings, but also may
be used in petroleum refining and petrochemical operations, as well
as other uses in which a liquid is conveyed under pressure through
a pipe or conduit.
[0004] 2. Description of the Prior Art
[0005] In order to place an oil well in service, an elongated,
sectionalized tubing string is lowered into the well casing, with
the tubing string housing a sucker rod and pump assembly. In deep
wells, the tubing string may extend thousands of feet from grade
down to an oil formation. Leaks in the joints between string
sections have a significant impact on pumping efficiency and oil
well production. In the past, it has sometimes been necessary to
remove the pipe string, locate joint leaks, and repair the string.
This can represent a very substantial expense both in terms of
repair costs and well downtime.
[0006] U.S. Pat. No. 5,996,696 describes a method and apparatus for
leak integrity testing of oil well tubing within the well casing,
thus eliminating the need for string removal for such testing. The
apparatus of the '696 patent includes a housing interposed between
string sections (usually adjacent the lower end thereof close to
the pump and well formation). The housing is equipped with a
metallic rupture disc in closing, flow-blocking relationship. When
it is desired to test the string, predetermined fluid pressure is
applied against the rupture disc. If the tubing string is
sufficiently leak-free, the rupture disc will burst at or about the
predetermined burst pressure. On the other hand, if substantial
leaks are present, insufficient pressure will be developed within
the string to burst the disc.
[0007] The preferred rupture disc design disclosed in the '696
patent is a metallic, concavo-convex disc having a discontinuous
score line formed in a face of the bulged rupture portion thereof.
The discontinuity in the score line serves as a hinge region for
the disc. While the apparatus and methods described in this patent
represent a significant breakthrough in the art, it has been found
that sometimes the disc design is not optimal from a performance
standpoint. As can be appreciated, a useful rupture disc in this
context must reliably burst at desired burst pressures, or
inaccurate test results maybe obtained.
SUMMARY OF THE INVENTION
[0008] The present invention overcomes the problems outlined above
and provides an improved leak testing apparatus for
liquid-conveying line applications, and especially oil well tubing
strings, giving increased testing reliability. Broadly speaking,
the apparatus of the invention includes a tubular holder adapted
for coupling to an oil well tubing string with a rupture disc
within the holder in normally closing relationship thereto. The
disc has a peripheral flange and a concavo-convex burst region
inboard of the flange. The disc also has a continuous score line
formed on the concave face of the disc (i.e., the face of the disc
subjected to liquid pressure during a testing operation) wherein
the score line is of varying depth along the length thereof to
define a region of reduced score line depth; this region serves as
a hinge area for the disc preventing detachment of the
concavo-convex burst region upon opening of the disc. It has been
found that discs of this character provide improved testing
results, as compared with prior designs.
[0009] The provision of the continuous score line on the concave
face of the disc permits reliable disc rupture and opening owing to
the fact that when rupture occurs, the adjacent interconnected
score line-defining wall surfaces of the disc separate from each
other. This is to be contrasted with the more usual situation where
the score line(s) on rupture discs are formed in the face thereof
remote from contact with the product and/or pressure. In such a
situation, the score line-defining wall surfaces of the disc move
toward each other during rupture.
[0010] In one embodiment, the continuous, variable depth score line
is closely adjacent to but not within the radiused transition
region between the flange and concavo-convex burst region of the
disc. Alternately, a hinge area of increased strength may be
provided by scoring the disc so that the hinge area extends along
the transition region with the remainder of the score line spaced
from the transition region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a fragmentary vertical sectional view illustrating
a typical oil well including a casing and internal tubing string,
the later having the integrity testing apparatus of the invention
installed therein;
[0012] FIG. 2 is a greatly expanded, fragmentary vertical sectional
view illustrating the integrity testing apparatus within the tubing
string, where the rupture disc of the apparatus is in its open,
ruptured condition;
[0013] FIG. 3 is a fragmentary vertical sectional view of an oil
well tubing string, with the testing apparatus of the invention
installed therein, and with the disc in blocking relationship to
liquid flow through the string;
[0014] FIG. 4 is a view similar to that of FIG. 3, but illustrating
the disc in its ruptured condition;
[0015] FIG. 5 is an elevational view of the preferred rupture disc
of the invention, viewing the concave face thereof;
[0016] FIG. 6 is a side elevational view of the disc shown in FIG.
5;
[0017] FIG. 7 is an elevational view of the rupture disc of FIGS.
5-6, viewing the convex face thereof;
[0018] FIG. 8 is a fragmentary, enlarged view illustrating the
position of the score line formed on the concave face of the
rupture disc;
[0019] FIG. 9 is a perspective view of a rupture disc body after
formation of the peripheral flange and continuous score line
thereon;
[0020] FIG. 10 is a perspective view similar to that of FIG. 9 but
viewing the opposite face of the disc body;
[0021] FIG. 11 is a perspective view similar to that of FIG. 9 but
illustrating the concave face of the disc after formation of the
concavo-convex burst region inboard of the peripheral flange;
[0022] FIG. 12 is a perspective view similar to that of FIG. 11 but
illustrating the convex face of the rupture disc;
[0023] FIG. 13 is a greatly enlarged, fragmentary cross sectional
view depicting the disc body after formation of the flange and
score line but prior to bulging thereof, and further illustrating
the differential depth of the score line along its length;
[0024] FIG. 14 is a view similar to that of FIG. 13, but
illustrating the disc body after bulging thereof;
[0025] FIG. 15 is a greatly enlarged, fragmentary cross sectional
view of the marginal flange portion of the rupture disc and which
is positioned between the tubular inlet and the tubular outlet of
the apparatus; and
[0026] FIG. 16 is a greatly enlarged, fragmentary cross sectional
view similar to FIG. 15 and illustrates the configuration of the
marginal flange portion of the rupture disc when the disc has been
subjected to sufficient pressure to effect opening of the central
part of the disc.
[0027] FIG. 17 is a schematic elevational view of the concave face
of another rupture disc in accordance with the invention, wherein
the hinge region of the score line is formed in the radiused
transition between the peripheral flange and burst region of the
disc; and
[0028] FIG. 18 is a greatly enlarged view of the hinge region and
portions of the remainder of the score line of the embodiment
depicted in FIG. 17.
[0029] The drawing figures do not limit the present invention to
the specific embodiments disclosed and described herein. The
drawings are not necessarily to scale, emphasis instead being
placed upon clearly illustrating the principles of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] Turning now to the drawings, and particularly FIG. 1, a
conventional oil well 20 is shown, having an upright, continuous
casing 22 extending from grade downwardly to an oil formation 24. A
tubing string 26 is located within the casing 22 and includes a
plurality of end-to-end connected sections such as the sections 28,
30, 32, and 34; it will of course be appreciated that an operating
well would have many such sections in its tubing string. A
sectionalized, conventional sucker rod 35 with a lowermost pump
assembly 35a are within the string 26 in order to effect pumping of
oil from the formation 24. The majority of the string sections are
interconnected via conventional couplers 29. However, at a selected
point along the length of the string 26 (usually near the lower end
thereof adjacent the formation 24) integrity testing apparatus 36
is inserted between a pair of tubing sections.
[0031] Referring to FIG. 2, it will be seen that the lower end of
section 32 is threaded, as is the upper end of section 34. The
apparatus 36 is threadably coupled between these tubing sections,
and includes a tubular inlet 38 and a tubular outlet 40, with a
burst disc 42 interposed between the inlet and outlet. In detail,
the inlet 38 is internally threaded as at 44 adjacent its upper
end, and is externally threaded as at 46 near its lower end.
Viewing FIGS. 15 and 16, it can be seen that the lowermost butt end
of the inlet 38 presents a stepped configuration 48 defined by an
outer annular surface 48a joined to an inner annular surface 48b
which is spaced axially of and interconnected to surface 48a by an
intermediate face 48c which is transverse to surfaces 48a and 48b.
The outlet 40 is internally threaded as at 50 adjacent its upper
end for connection to inlet threading 46; similarly, the outlet
lower end is threaded as at 52 for connection to the string section
34. The outlet 40 is also provided with uppermost surfaces defining
stepped configuration 54 presented by an outer annular surface 54a,
as well as an inner annular surface 54b which is out of the plane
of 54a and is joined to the latter by intermediately
transversely-extending face 54c.
[0032] As is most apparent from FIG. 15, when the disc 42 is placed
between inlet 38 and outlet 40 and the inlet 38 is rotated in the
direction to cause the inlet 38 to move toward the outlet 40, the
relative movement of the inlet 38 and outlet 40 is arrested when
the outer flange portion 70 of disc 42 is engaged on opposite sides
thereof by surfaces 48a and 54a, respectively, to thereby clamp the
disc 42 between the inlet 38 and the outlet 40. Surfaces 48b and
54b of inlet 38 and outlet 40, respectively, are disposed such that
upon clamping of the outermost annular flange portion 70 of disc 42
between surfaces 48a of inlet 38 and surface 54a of outlet 40, an
annular gap 51 is presented between the surface 48b of inlet 38 and
the directly opposed face of the inner flange portion 72 of disc
42. Gap 51 is generally of the order of from about 0.001 in. to
about 0.060 in., and preferably from about 0.003 in. to about 0.010
in. The underside of flange 54 presents an outwardly extending,
angular, chamfered surface 58 extending in a direction away from
inlet 38 which joins with radiused edge 60 of flange 54. It can be
seen from FIGS. 15 and 16 that the diameter of the opening defined
by flange 54 of outlet 40 is greater than the internal diameter of
the cylindrical suface 38a of inlet 38.
[0033] The burst disc 42 is best illustrated in FIGS. 5-8. The disc
broadly includes an outer peripheral flange 62 as well as an inner
concavo-convex burst region 64 presenting a concave face 66 and an
opposed convex face 68. The flange 62 is of stepped configuration
in cross section and has an outermost essentially flat flange
portion 70 and an inner essentially flat flange portion 72. These
flange portions are interconnected via a radiused transition region
74. As will be observed in FIG. 6, the outer and inner flange
portions 70, 72 are vertically offset from each other and
interconnected by an integral, intermediate, transversely extending
annular portion 73.
[0034] The burst region 64 is inboard of flange portion 72, with a
radiused transition region 76 therebetween. The transition region
76 (FIG. 8) is defined by a pair of concentric, laterally spaced
apart outer and inner margins 78, 80.
[0035] The disc 42 is also provided with a continuous score line 82
formed on the concave face 66 thereof. In the present embodiment,
the score line 82 is located entirely inwardly of the transition
region 76, i.e., it is spaced inwardly from transition region inner
margin 80. In addition, the score line 82 has a varying depth along
its length to define a hinge area 84 of reduced depth. Referring to
FIGS. 5-8, the hinge area 84 is centered about the 180.degree. mark
and extends for a length from about 5-10.degree. on either side
thereof. The purpose of hinge area 84 is to prevent detachment of
the burst region 64 from flange 62 upon bursting of the disc 42. To
this end, and as best seen in FIGS. 13-14, the score line 82 at the
0.degree. mark is formed to leave an unscored depth of metal "X"
in., whereas at the 180.degree. mark, the hinge area 84 of the
score line is of lesser depth, leaving an exemplary unscored depth
of metal of "X+Y" in., where "Y" for example is equal to about
0.003 in.
[0036] Preferably, the disc 42 is formed of a metal selected from
the group consisting of Inconel (an alloy of 76% Ni, 17% Cr and 7%
of Fe) and nickel, and has a thickness of from about 0.010-0.060
inches, more preferably from about 0.014-0.050 inches. The depth of
the score line 82 throughout its length except for the reduced
depth hinge area 84 is from about 35-70% of the thickness of the
disc, more preferably from about 40-60% of such thickness. The
depth of the score line at the reduced depth area 84 is from about
0.001-0.005 inches (more preferably from about 0.002-0.004 inches)
less than the depth of the score line 82 throughout the remainder
thereof.
[0037] During manufacture of the disc 42, the stepped peripheral
flange 62 is initially formed, prior to bulging of the central
region of the disc. The flange is formed by a conventional crimping
die under pressures sufficient to form the desired stepped
configuration. Next, the score line 82 is formed on what will later
become the concave face 66 of the disc, making use of an
appropriate, differential depth scoring anvil. Only after formation
of the flange 62 and score line 82 is the disc bulged to give the
concavo-convex burst region 64. While it would be possible to first
bulge the disc followed by scoring, from a manufacturing point of
view, it is greatly preferred to initially score, followed by
bulging. The metal along the transition region 76 is work hardened
during bulging of the disc, thereby providing a hinge region of
greater strength at the .
[0038] FIGS. 3-4 illustrate the operation of apparatus 36 when
placed within a tubing string 26. The disc 42 rests upon the flange
54 of outlet 40, with the stepped flange 62 in mating, face-to-face
contact with the complementally stepped upper face 56 of the
flange. When the inlet 38 is threaded into the upper end of outlet
40, the stepped butt end 48 of the inlet comes into contact with
the upper surface of the flange 62. In this fashion, the disc 42 is
firmly sandwiched between the butt end 48 and upper flange surface
56. When it is desired to conduct a leak test for the string 26,
pressurized well liquid is applied against the concave face 66 of
the disc 42. Assuming that the string 26 is essentially leak-free,
at predetermined liquid pressure, the disc 42 will rupture along
score line 82. However, owing to the presence of the reduced depth
hinge area 84, the burst region 64 will remain attached to the
flange 62 and not be carried downward into the pump area of the
string.
[0039] Again referring to FIG. 14, it will be observed that the
obliquely oriented score line-defining sidewalls 82a and 82b
diverge from a lower apex upwardly to the concave surface 66. When
the disc 42 ruptures, movement of the burst region 64 effects
relative separation between the walls 82a and 82b without any
compressive forces exerted against these sidewall surfaces. This is
to be contrasted with the more usual approach of providing a score
line on the convex face. In such a situation, rupture of the disc
causes the score line-defining sidewalls to move towards each
other, thereby compressing these surface together.
[0040] It is further to be observed from enlarged FIGS. 15 and 16,
that because of the gap 51 presented between surface 58b of inlet
38 and the opposed face of flange portion 72 of disc 42, during
bulging of the central portion of disc 42 under liquid pressure
thereagainst, the intermediate flange portion 73 of the disc is
deformed so that it essentially lines up with flange portion 72 and
the inner flange portion 70 of the disc as best illustrated in FIG.
16. This straightening out of the stepped flange portion of the
disc 42 causes the annular score line 82 to move inwardly a greater
distance from the edge 60 of flange 54 of outlet 40 to provide more
assured opening of the central part of the disc along score line
82.
[0041] The slightly radiused edge 60 of flange 54 of outlet 40 and
the receding chamfered surface 58 of flange 54 cooperate to
facilitate full opening of the central part of disc 42 as best
illustrated in FIG. 2 for substantially unimpeded flow of liquid
through the opening in the disc 42.
[0042] FIGS. 17-18 illustrate another type of score line 86 which
may be used in the discs of the invention. In this case, the
majority of the score line 86 is inboard of the transition region
76 between the inner margin of the flange and the burst region.
However, at the hinge area 88, the score line crosses the
transition region inner margin 80 and extends along the length of
the transition region 76.
[0043] As illustrated in FIG. 18, the hinge area 88 within the
transition region is defined by a pair of relatively short arcuate
segments 90 and 92 of relatively small diameter, and a longer
central arcuate segment 94 of relatively large diameter. The score
line 86 also has a pair of crossover regions 96 and 98 on opposite
sides of the segments 90 and 92 where the score line crosses the
inner margin 80 of the transition region 76. Placement of the hinge
area 88 within the transition region 76, with the remainder of the
score line 86 inboard of the transition region, provides a stronger
hinge than in the case of the first embodiment. That is, the metal
along the transition region 76 is work hardened during bulging of
the disc, thereby providing a region of greater strength.
[0044] Although the invention has been described with reference to
the preferred embodiment illustrated in the attached drawing
figures and particularly when used in testing the integrity of an
oil well pipe string, it is to be understood that the apparatus has
utility for testing a variety of different liquid-conveying pipes
or lines in petrochemical, petroleum refining, and other similar
industrial applications. It is also to be noted that equivalents
may be employed and substitutions made herein without departing
from the scope of the invention as recited in the claims.
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