Title: Borehole conduit cutting apparatus and process
Abstract: The apparatus is used for cutting an opening through the wall of a conduit located in a borehole traversing the subsurface formations. The apparatus includes a body adapted to be lowered into the conduit to a desired level. The body is formed by a cylindrical wall defining an elongated chamber having a combustible charge receiving portion and an ignition portion located close to the combustible charge receiving portion. A plurality of spaced apart apertures are formed through the wall defining a given pattern which may be at least one elongated row of apertures generally parallel with the axis of the cylindrical wall or a line which encloses a given configuration on one side of the axis. A combustible charge is located in the combustible charge receiving portion of the chamber, and an ignition device is located in the ignition portion of the chamber for igniting the combustible charge for creating a flame and hot combustion products for passage through the apertures for cutting the wall of the conduit to form an opening through the wall of the conduit. In the preferred embodiment, the combustible charge is located in the chamber above, at the level and below the apertures.
Patent Number: 6,971,449 Issued on 12/06/2005 to Robertson
| Inventors:
|
Robertson; Michael C. (Burleson, TX)
|
| Assignee:
|
Weatherford/Lamb, Inc. (Houston, TX)
|
| Appl. No.:
|
304653 |
| Filed:
|
May 4, 1999 |
| Current U.S. Class: |
166/297; 166/55; 166/63 |
| Intern'l Class: |
E21B 043/11.7 |
| Field of Search: |
166/55,552,63,72,297,298
|
References Cited [Referenced By]
U.S. Patent Documents
| 2506799 | May., 1950 | Livingston.
| |
| 2535964 | Dec., 1950 | Stanton.
| |
| 2587244 | Feb., 1952 | Sweetman.
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| 2758543 | Aug., 1956 | Grandin.
| |
| 4298063 | Nov., 1981 | Regalbuting et al.
| |
| 352397 | Oct., 1982 | Christopher.
| |
| 4598769 | Jul., 1986 | Robertson.
| |
| 4798244 | Jan., 1989 | Trost.
| |
| 4799829 | Jan., 1989 | Kenny.
| |
| 4905759 | Mar., 1990 | Wesson et al.
| |
| 4960171 | Oct., 1990 | Parrott et al.
| |
| 5135050 | Aug., 1992 | Tailby.
| |
| 5435394 | Jul., 1995 | Robertson.
| |
| 5636692 | Jun., 1997 | Haugen.
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| 5690171 | Nov., 1997 | Winch et al.
| |
| 5709265 | Jan., 1998 | Haugen et al.
| |
| 5791417 | Aug., 1998 | Haugen et al.
| |
| 5813465 | Sep., 1998 | Terrell et al.
| |
| 5862862 | Jan., 1999 | Terrell.
| |
| 6016753 | Jan., 2000 | Glenn et al.
| |
| 6024169 | Feb., 2000 | Haugen.
| |
| 6035935 | Mar., 2000 | Regalbuto.
| |
| 6135206 | Oct., 2000 | Gano et al.
| |
| 6202752 | Mar., 2001 | Kuck et al.
| |
| Foreign Patent Documents |
| 0 819 827 | Jan., 1998 | EP.
| |
| 0 846 838 | Jun., 1998 | EP.
| |
| 2177740 | Jan., 1987 | GB.
| |
| 2346633 | Aug., 2000 | GB.
| |
| WO 97/2190/3 | Jun., 1997 | WO.
| |
| WO 99/6471/5 | Dec., 1999 | WO.
| |
| WO 00/5072/7 | Aug., 2000 | WO.
| |
| WO 00/6687/6 | Nov., 2000 | WO.
| |
Primary Examiner: Bagnell; David
Assistant Examiner: Walker; Zakiya
Attorney, Agent or Firm: Moser, Patterson & Sheridan, L.L.P.
Claims
1. An apparatus for cutting an opening through the wall of a metal conduit located
in a borehole traversing the subsurface formations, comprising:
a body adapted to be lowered into the metal conduit,
said body comprising a surrounding wall defining an elongated chamber,
a plurality of spaced apart outer apertures formed through said surrounding wall
along a length thereof,
said surrounding wall having an inner side and a central axis,
a heat shield wall located next to said inner side of said surrounding wall along
said length and surrounding an inner zone,
a plurality of spaced apart inner apertures formed through said heat shield wall
in alignment with said plurality of spaced apart outer apertures, wherein said
inner and outer apertures are located in at least one elongated row which extends
generally parallel to said axis,
a combustible charge located in said inner zone, and
an ignition means located in said chamber close to said inner zone for igniting
said combustible charge for creating hot combustion products for passage through
said inner and outer apertures for forming the opening through the wall of the
metal conduit.
2. The apparatus of claim 1, wherein:
said combustible charge is located in said inner zone at positions above, at
the level of, and below said apertures.
3. The apparatus of claim 1, wherein:
the at least one elongated row comprises a plurality of elongated spaced apart
rows on one side of said surrounding wall and said heat shield wall and generally
parallel to said axis.
4. The apparatus of claim 3, wherein:
said combustible charge is located in said inner zone at positions above, at
the level of, and below said apertures.
5. The apparatus of claim 1, wherein:
said surrounding wall of said body has a central axis,
said inner and outer apertures define a pattern which encloses a given configuration
on one side of said surrounding wall and said heat shield wall.
6. The apparatus of claim 5, wherein:
said combustible charge is located in said inner zone at positions above, at
the level of, and below said apertures.
7. The apparatus of claim 1, wherein:
said surrounding wall has an outer side,
a thin outer wall located next to said outer side of said surrounding wall and
surrounding said outer apertures,
said outer wall having an upper end and a lower end located above and below said
outer apertures respectively,
means for forming seals between said upper and lower ends of said outer wall
and said outer side of said surrounding wall to prevent liquid in the borehole
from entering said apertures,
said flame and combustion products being capable of passing through said outer
wall for forming an opening through the wall of the metal conduit.
8. The apparatus of claim 7, wherein:
said outer side of said surrounding wall is cylindrical in shape having a smaller
outside diameter, in the vicinity of said outer apertures, than at the positions
of said seals such that a space exists between said smaller diameter portion and
said outer wall.
9. The apparatus of claim 1 wherein:
said surrounding wall is formed of metal,
said heat shield wall is formed of a non-metallic material.
10. The apparatus of claim 9, wherein:
said heat shield wall is formed of carbon.
11. A method of cutting an opening through the wall of a metal conduit located
in a borehole traversing the subsurface formations of the earth, comprising the
steps of:
lowering into said metal conduit an apparatus comprising a surrounding wall defining
a chamber having a central axis and a heat shield wall dispose proximate an interior
surface of the surrounding wall,
said chamber of said apparatus having a plurality of stacked combustible charges
located therein and a plurality of spaced apart apertures formed through said wall
of said apparatus along a line which encloses a given configuration with said charges
being located in said chamber above, at the level of, and below said apertures,
and
igniting said combustible charges to create a flame and hot combustion products
for passage through said apertures for forming an opening through the wall of the
metal conduit corresponding to said given configuration.
12. A method of cutting an elongated opening through the wall of a metal conduit
located in a borehole traversing the subsurface formations of the earth, comprising
the steps of:
lowering into said metal conduit an apparatus comprising a surrounding wall defining
a chamber having a central axis,
said chamber of said apparatus having a plurality of stacked combustible charges
located therein and a plurality of spaced apart apertures formed through said wall
of said apparatus along a generally straight line generally parallel to the axis
of said wall of said apparatus, with said charges being located in said chamber
above, at the level of, and below said apertures, and
igniting said combustible charges above, at the level of, and below said apertures
to create a flame and hot combustion products for passage through said apertures
for forming an opening through the wall of the metal conduit along the line defined
by said apertures.
13. An apparatus for forming an opening through a wall of a metal conduit disposed
in a borehole, comprising:
a body adapted to be lowered into the metal conduit, the body comprising a surrounding
wall defining a chamber and having a central axis;
a plurality of apertures formed through a portion of the surrounding wall along
a generally straight line generally parallel to the axis of the surrounding wall;
a heat shield wall located next to an interior surface of the surrounding wall;
a plurality of apertures formed through the heat shield wall and aligned with
the plurality of apertures of the surrounding wall;
one or more combustible charges disposed within the chamber; and
an ignition member for igniting the one or more combustible charges, whereby
hot combustion products are formed for passage through the plurality of apertures
of the heat shield wall and the surrounding wall, thereby forming the opening through
the wall of the metal conduit.
14. The apparatus of claim 13, wherein the one or more combustible charges are
disposed at positions above, at the level of, and below the plurality of apertures
of the surrounding wall.
15. The apparatus of claim 13, wherein the plurality of apertures of the surrounding
wall are formed on one side of the surrounding wall.
16. The apparatus of claim 15, wherein the one or more combustible charges are
disposed at positions above, at the level of, and below the plurality of apertures
of the surrounding wall.
17. The apparatus of claim 13, further comprising:
an outer wall disposed next to an exterior surface of the surrounding wall and
surrounding the plurality of apertures of the surrounding wall; and
a plurality of seal members disposed between the outer wall and the surrounding
wall to prevent liquid in the borehole from entering the plurality of apertures
of the surrounding wall, wherein the combustion products are capable of passing
through the outer wall for forming the opening through the wall of the metal conduit.
18. The apparatus of claim 17, wherein the plurality of apertures of the surrounding
wall are in fluid in communication with an annular space formed between the surrounding
wall and the outer wall.
19. The apparatus of claim 13, wherein the surrounding wall comprises a metal
and the heat shield wall comprises a non-metallic material.
20. The apparatus of claim 19, wherein the heat shield wall comprises carbon.
21. An apparatus for cutting an opening through a wall of a metal conduit located
in a borehole traversing the subsurface formations, comprising:
a body adapted to be lowered into the metal conduit,
said body comprising a surrounding wall along a length thereof,
said surrounding wall having an inner side and a central axis,
a heat shield wall located next to said inner side of said surrounding wall along
said length and surrounding an inner zone,
a plurality of spaced apart inner apertures formed through said heat shield wall
in alignment with said plurality of spaced apart outer apertures,
a combustible charge located in said inner zone at positions above , at the level
of, and below said apertures, and
an ignition means located in said chamber close to said inner zone for igniting
said combustible charge for creating hot combustion products for passage through
said inner and outer apertures for forming the opening through the wall of the
metal conduit.
22. An appartus for cutting an opening through a wall of a metal conduit located
in a borehole traversing the subsurface formation, comprising:
a body adapted to be lowered into the metal conduit,
said body comprising a surrounding wall defining an elongated chamber,
a plurality of spaced apart outer apertures formed through said surrounding wall
along a length thereof,
said surrounding wall having an inner side and a central axis,
a heat shield wall located next to said inner side of said surrounding wall along
said length and surrounding an inner zone,
a plurality of spaced apart inner apertures formed through said heat shield wall
in alignment with said plurality of space apart outer apertures, wherein said inner
and outer apertures are located in a plurality of elongated spaced apart rows on
one side of said surrounding wall and said heat shield wall and generally parallel
to said axis,
a combustible charge located in said inner zone, and
an ignition means located in said chamber close to said inner zone for igniting
said combustible charge for creating hot combustion products for passage through
said inner and outer apertures for forming the opening through the wall of the
metal conduit.
23. The apparatus of claim 22, wherein said combustible charge is located in
said inner zone at positions above, at the level of, and below said apertures.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus and process for forming an opening through
conduit located in a borehole formed in the earth.
2. Description of the Prior Art
U.S. Pat. Nos. 4,298,063, 4,598,769, and 5,435,394 disclose apparatus for cutting
conduit located in a borehole formed in the earth. U.S. Pat. Nos. 4,598,769 and
5,435,394 are incorporated into this application by reference.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a new and useful apparatus and process
for cutting an opening in a conduit located in a borehole formed in the earth.
The apparatus of the invention comprises a body adapted to be lowered into the
casing located in the borehole. The body comprises a surrounding wall defining
an elongated chamber having a combustible charge receiving portion and an ignition
means portion located close to the combustible charge receiving portion. A portion
of the wall surrounding the combustible charge receiving portion has a plurality
of spaced apart apertures formed therethrough in a given pattern. A combustible
charge is located in the combustible charge receiving portion of the chamber. An
ignition means is located in the ignition means portion of the chamber for igniting
the combustible charge for creating a flame and hot combustion products for passage
through the apertures for cutting an opening in the surrounding conduit.
The opening may be formed by burning an enlarged area through the conduit or
by burning a slot through the conduit around a conduit wall portion which wall
portion then is removed.
In the preferred embodiment, the combustible charges are located above, at the
level of and below the apertures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B are an exploded cross-sectional view of the apparatus of the
invention. The symbol B indicates that the lower end of the member on the right
side of FIG. 1A is connected to the upper end of the member on the left side of
FIG. 1B.
FIG. 2 is a cross-sectional view of FIG. 1B taken along lines 2—2 thereof.
FIG. 3 is an isometric view of a portion of apparatus of FIGS. 1A and 1B.
FIG. 4 is an isometric view of a portion of a borehole casing having a window
cut through one side of its wall.
FIG. 5 is a schematic view of the apparatus of FIGS. 1A and 1B in a cased borehole.
FIG. 6 is an isometric view of a portion of the apparatus of FIGS. 1A and 1B
showing nozzle apertures located in a given pattern.
FIG. 7 is an isometric view of a portion of a borehole casing showing a window
cut through one side of its wall with the resulting metal plug still in place.
FIGS. 8 and 9 illustrate a different process of forming a window in the casing.
FIG. 10 is a schematic view of a borehole tool for removing the loose plug of
FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIGS. 1A and 1B, the apparatus of the invention is identified
at
421. It comprises an anchor subassembly
16, an ignition means
subassembly
30 comprising members
32 and
34, an upper combustible
charge holding subassembly
431, a nozzle and intermediate combustible charge
holding subassembly
433 and a lower combustible charge holding subassembly
435. Members
32,
34,
431,
433, and
435
are formed of suitable metal.
The anchor
16, and subassemblies
30,
431,
433,
435
are assembled as shown in FIG.
5 and lowered to a desired level into a borehole
601 that has been cased with metal casing
603 and operated to form
an elongated window
605 or opening through the casing
603 as shown
in FIG. 4 to allow access to the formation from the existing borehole for example
to allow recovery of petroleum in the formations through the opening
605.
The length of the opening
605 may be generally parallel to the central axis
of the casing
603. Its length and width can vary.
The anchor subassembly
16 and the ignition subassembly
30 are similar
to those disclosed in U.S. Pat. No. 4,598,769. The anchor subassembly
16
has a wireline cable
18 coupled to its upper end and has its lower end coupled
to the ignition means subassembly
30. The ignition subassembly comprise
metal members
32 and
34 screwed together with an electrode plug
46
coupled to member
32. The electrode
46 has a prong
48 which
engages an electrical conductor
50 supported by the lower end of member
32. A metal spring
52 is disposed between the conductor
50
and an electrically actuated ignition means or squib
44 which is located
in a small aperture
383 extending through the lower end
34E of member
34. Members
37A,
37B, and
37C are O-ring seals. The
members
46,
48,
50 and
52 are electrically insulated
to prevent a short. This ignition system may be defined as an electric line firing system.
Member
431 has annular wall
432 with an enlarged opening
435
at its upper end
436 with threads
437 leading to a smaller opening
439. The lower end
441 of member
431 has exterior threads
443 and O-ring seals
445.
The nozzle subassembly
433 comprises an annular wall
447 with a
cylindrical opening
451 formed therethrough with interior threads
453
and
455 at its upper and lower ends
457 and
459. The wall
447 comprises a wall section
471 having a smaller outside diameter
than the ends
447 and
459. A plurality of rows of apertures
473
extend through the wall section
471 on one side thereof as shown in FIGS.
3,
6, and
8. In FIG. 3 there is shown three spaced apart rows A,
B, C of apertures
473 with each row comprising a plurality of spaced apart
apertures
473 and with each row being generally parallel to the axis
475
of the member
433. In FIG. 2, there is shown nine rows A-I of apertures
473. The number of rows and the length of the rows of apertures depend on
the width and length of the window
605 to be formed in the casing
603
of the borehole
601.
Located on the inside of the wall section
471 is a hollow cylindrical
shield
481 having apertures
483 formed therethrough which are aligned
with the apertures
473. A thin metal sleeve
485 is secured around
the outer wall
447 to prevent water from entering the apertures
473
and
483. Members
487 and
489 are O-ring seals.
The lower subassembly
435 comprises an annular wall
501 having
an upper end
503 with O-ring seals
505 and exterior threads
507.
A cylindrical aperture
509 extends into the member
435 to a larger
diameter opening
511 having interior threads
513. A metal plug
515
with O-ring seals
517 and exterior threads
519 is inserted into the
opening
511 and screwed into the lower end
521 of the member
435.
Also provided are a plurality of combustible pyrotechnic charges
578
made of conventional material which is compressed into donut shaped pellets. Each
of the charges has a cylindrical outer surface and a central aperture
578A
extending therethrough. The charges
578 are stacked on top of each other
within the annular inside chamber portions
431C,
433C (inside of
the carbon sleeve
481) and
435C with their apertures
578A
in alignment. Loosely packed combustible material
580 preferably of the
same material used in forming the charges
578 is disposed with the apertures
578A of the charges
578 such that each charge
578 is ignited
from the loosely packed combustible material upon ignition by the ignition means
44.
In assembling the components
30,
431,
433, and
435,
the threads
507 of end
501 of member
435 are screwed into
threads
455 of the open end
459 of member
433; the threads
443 of end
441 of member
431 are screwed to the threads
453
of the open end
457 of member
433. During the assembly process, the
charges
578 are stacked into the chamber portions
435C,
433C,
and
431C of members
435,
433, and
431. The threads
34T of end
34E of assembled member
30 are screwed to the threads
437 of the open end
436 of the member
431. During the assembly
process the charges
578 are stacked on each other from the top end
515T
of the plug
515 and the material
580 placed in their apertures
578A.
The apparatus then is lowered into the borehole
601 and into the casing
603 by way of the cable
18 and uphole equipment illustrated at
611
in FIG.
5. The equipment
611 includes a reel around which the cable
18 is wound and unwound to raise and lower the apparatus
421. The
cable
18 includes an electrically insulated electrical lead
615 which
is coupled to the ignition means
44 by way of members
46,
48,
50 and
52 and an electrically insulated ground or return lead
617
coupled to the ignition means
44. An electrical power source
621
and a switch
623 are provided for applying electrical power to the ignition
means
44 when the switch
623 is closed. The ignition means
44
includes an electrical resistor which generates heat when electrical current is
applied thereto. Thus when switch
623 is closed, current is applied to the
resistor of the ignition means
44, which generates enough heat to ignite
the material
580 and hence the charges
578 to generate a very high
temperature flame with other hot combustion products which pass through the heat
shield apertures
483 and the nozzle apertures
473 and through the
thin sleeve
485 to cut or burn a window or opening
605 through the
casing
603. After the window is formed, the apparatus
421 is removed
from the borehole
601 and casing
603 by winding the cable
18
around the reel of uphole equipment
611.
Instead of forming the window
605 by burning through the wall of casing
603 in all areas within the window
605, the window
605 may
be formed by forming the nozzle apertures
473 and
483 in a rectangular
pattern to define the window as shown in FIGS. 8 and 9. In this embodiment, the
nozzle apertures
473 and
483 will be located along two spaced apart
vertical lines
673A and
673B and along two spaced apart horizontal
lines
673C and
673D on one side of the axis
475. If the length
of the window
605 to be formed is long, the nozzle apertures also
473
and
483 may be located along spaced apart intermediate horizontal lines
673E-
673H as shown in FIG.
8. Referring to FIGS. 8 and 9,
upon firing of the charges, slits or grooves will be formed through the wall of
the casing
603 along lines
603A-
603D surrounding a loose casing
plug
603P or a plurality of plugs
603P if the nozzle apertures
673E-
673H
are used which then is/are removed by removing the apparatus
421 from the
borehole and lowering a tool down the borehole with a junk basket or an electromagnet.
Referring to FIG. 10, a tool
731 having an electro-magnet
733 coupled
to the uphole electrical source
621 is lowered in the borehole
601
to the level of the window
605. The switch
623 is closed to energize
the electromagnet
733 to attach and pull the plug
603P or plugs
603P
from the window
605 and which is/are removed from the borehole by removing
the tool
731.
Instead of forming a rectangular window
605, the nozzle apertures
473 and
483 may be arranged for example in a circle to form a circular
window
605.
As mentioned above, the window
605 may be formed through the wall of the
casing
603 to provide access to the formation from the borehole
601
for the recovery of petroleum through the window
605.
The apparatus of the invention also may be used to cut a window through metal
production tubing, coiled metal tubing or metal drill pipe in a borehole.
The invention may be used as a window cutter for casing or casing liner where
the initial cement job was poorly performed such that little or no cement exists
between the casing outside diameter and the formation wall. A poor cement job allows
for migration of well fluids in the annular cavity behind the casing. The invention
allows for the formulation of a large defined opening in the casing wall for transport
of cement through the window and into the annular cavity filling the void.
The invention also may be used as a window cutter for drill pipe/drill collars
to form a large window so that fluid circulation may be established above the drill
bit and at or below a stuck point. The large window will allow the operator to
pump a high volume of fluid through the window and up the annular side of the drill
pipe flushing the annulus between the drill pipe and the formation wall. Once circulation
is established, the drill pipe can be freed and removed from the well, thus eliminating
an expensive fishing job.
In another embodiment, a slickline battery firing system may be employed in lieu
of the electric line firing system to energize the ignition means
44. This
system comprises a slickline cable connection for supporting the modified apparatus
421 and which is connected to a pressure firing head. The pressure firing
head comprises a metal piston having a larger diameter head with a smaller diameter
metal rod extending downward from the bottom of the larger diameter head. The piston
is slidably located in a hollow cylinder. A spring surrounding the rod is employed
to provide upward pressure against the under side of the larger diameter head.
The spring is adjustable to allow for hydrostatic compensation of well fluids so
that the system does not fire at bottom hole pressure. When the piston is moved
downward the lower end of the rod will make contact with an electrical lead from
the battery pack and an electrical lead coupled to one side of the ignition means
(the minus terminal of the battery pack and the other side of the ignition means
44 are grounded) to discharge current to the ignition means to ignite the
material
580 and fire the combustible charges
578. Fluid ports extend
through the wall of the cylinder above the larger diameter piston head. When the
borehole apparatus is in place in the borehole ready to cut the metal conduit to
form an opening therethrough, a pump at the surface increases the fluid pressure
in the conduit and moves the piston downward against the pressure of the spring
to allow the rod to make electrical contact with the leads to fire the combustible
charges
578.
In still another embodiment, a slickline percussion firing system may be employed
in lieu of the electric line firing system to ignite the charges
578. This
system comprises a slickline cable head connection connected for supporting the
modified apparatus
421 and which is connected is to a pressure firing subassembly.
The pressure firing subassembly comprises a cylinder having the piston and spring
described in connection with the battery firing system. Ports are formed through
the cylinder wall above the piston. Fluid pressure is increased to force the piston
rod (firing pin) against a lower percussion firing cap which ignites upon impact
to ignite the charges
578.
Also a coiled tubing percussion firing system may be employed in lieu of the
electric line firing system to ignite the charges
578. This system comprises
coiled tubing for supporting the modified apparatus
421 connected to a connector
subassembly which connects to a pressure firing head which comprises a hollow cylinder
which supports an interior piston by shear pins. The coiled tubing is coupled to
the interior of the cylinder at its upper end. The piston has a central flow path
extending axially downward from it supper end and then radially outward through
the cylinder wall. A firing pin extends from the lower end of the piston. The flow
path allows the coiled tubing to fill with water as the assembly is lowered in
a downhole and also allows for circulation of fluid in running of the assembly.
When the apparatus is at the desired cutting depth, a ball is dropped into the
coiled tubing which passes to the piston, plugging the flow path allowing an increase
in fluid pressure to be achieved in the coiled tubing and cylinder which shears
the shear pins driving the firing pin into a percussion cap to ignite the charges
578.
Preferably the charges
578 are located above the nozzle apertures
473; at the level of the nozzle apertures
473; and below the nozzle
apertures
473 to provide a balanced force when the charges
578 are
ignited. This arrangement also provides more heat and force for forming a wide
and long window
605 in the casing
603.
In the event that the window
605 to be formed is relatively narrow and
short, the charges
578 may be located, above the apertures
473 only,
above and at the level of the apertures
473 only, at the level of the apertures
473 only, at the level of and below the apertures
473 only, or below
the apertures
473 only. For forming a narrow window, only one or two rows
A or A plus B of apertures
473 and
483 may be formed through the
wall
471 of the nozzle subassembly
433 and through the heat shield
481. The charges
578 may be located above the apertures
473
only by forming an annular shoulder on the inside wall
432 of the member
431 at its lower end
411 and stacking the charges upward from the
shoulder to the ignition means
44. The charges
580 may be located
above and at the level of the apertures
473 only by forming an annular shoulder
on the inside of the wall
471 just below the apertures
473 and stacking
the charges
578 upward from the shoulder to the ignition means
44.
The charges
578 may be located at the level of the apertures
473
only by forming an annular shoulder on the inside of the wall
471 below
the apertures
473 and dispensing with the use of the member
431;
stacking the charges
578 from the shoulder to the upper level of the apertures
473; and screwing the end
34E of the member
34 into the upper
open end of the member
433. The charges
578 may be located at the
level of and below the level of the apertures
473 only by dispensing with
the use of the member
431; stacking the charges from the top
515T
of the plug
515 up to the upper level of the apertures
473; and screwing
the end
34E of the member
34 into the upper open end of member
433.
When the electric line firing system is used, the charges may be located below
the apertures
473 only by dispensing with the use of the member
431;
stacking the charges upward from the top
515T of the plug
515 to
the lower level of the apertures
473; and locating the ignition system
46,
48,
50,
42,
44 at the bottom of the chamber
435
and with the ignition means
44 facing upward next to the lower end of the
charges
578; and coupling the anchor subassembly
16 to the upper
end of member
433. The leads
615 and
617 will extend through
the apertures
578A of the charges
578 to the ignition means
44.
In one embodiment, the member
431,
433, and
435 each may
have an outside diameter of 3½ inches. The nozzle apertures
473 and
483 each may have a diameter of ¼ inches. For the embodiment of FIG.
2, for nine rows A-I, adjacent apertures
473 in each row may be spaced apart
0.400 of an inch and adjacent rows spaced apart 15° (0.400 of an inch). The
length of the rows A-I may be 8 feet. It is to be understood that these specifications
may vary. The apertures
473 each may have a diameter of 0.200".
For the embodiment of FIGS. 8 and 9, the two rows
673A and
673B
of apertures
473 forming the long side of the rectangle may be spaced apart 8".
*
