U.S. patent number RE36,912 [Application Number 09/083,667] was granted by the patent office on 2000-10-17 for method and apparatus for containing and suppressing explosive detonations.
This patent grant is currently assigned to ABC-Naco Inc.. Invention is credited to John L. Donovan.
United States Patent |
RE36,912 |
Donovan |
October 17, 2000 |
Method and apparatus for containing and suppressing explosive
detonations
Abstract
.[.A method and apparatus for enclosing, controlling and
suppressing the detonation of explosives in an explosion chamber is
disclosed. The device comprises an elongate double-walled steel
explosion chamber anchored to a concrete foundation, and having a
double-walled access door for charging new workpieces, and a
double-walled vent door for discharging the products of the
explosion. The double walls of the chamber, access door and vent
door are filled with granular shock damping material such as silica
sand, and the floor of the chamber is covered with granular
shock-damping bed such as pea gravel. Along the outside of the
chamber are steel manifolds from which a linear array of vent pipes
penetrates the double walls of the chamber, with each pipe
terminating in a hardened steel orifice through which the explosion
combustion products pass. Within the chamber, plastic polymer film
bags containing water are suspended from steel wires over the
explosive material, and at each end of the chamber..]. .Iadd.A
method and apparatus for containing and suppressing the detonation
of explosives utilizing a sealable double-walled chamber having a
floor, an access door and a vent door. The chamber walls are
filled, and the floor is covered, with granular shock-damping
material. Orificed vent pipes penetrate the chamber walls to vent
explosion products into one or more exhaust manifolds. Water-filled
bags are positioned around the explosive to absorb energy from the
detonation. .Iaddend.
Inventors: |
Donovan; John L. (Danvers,
IL) |
Assignee: |
ABC-Naco Inc. (Downers Grove,
IL)
|
Family
ID: |
24311843 |
Appl.
No.: |
09/083,667 |
Filed: |
May 22, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
578200 |
Dec 29, 1995 |
05613453 |
Mar 25, 1997 |
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Current U.S.
Class: |
110/237; 110/346;
72/56; 86/50 |
Current CPC
Class: |
F42B
33/06 (20130101); F42D 5/045 (20130101) |
Current International
Class: |
F23G
7/00 (20060101); F23G 007/00 () |
Field of
Search: |
;110/173B,173C,193,237,346 ;588/202 ;109/26,27,29 ;72/54,56,706
;29/421.2 ;86/50 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Palamarchuk et al., "Shock Waves and Their Suppression by Foam in
Explosive Treatment of Welded Joints", Avtom Svarka 1 (Dialog
search abstract only), Jan. 1995..
|
Primary Examiner: Lazarus; Ira S.
Assistant Examiner: Ciric; Ljiljana V.
Attorney, Agent or Firm: Bullwinkel Partners, Ltd.
Claims
I claim:
1. An apparatus for containing and suppressing .[.explosions.].
.Iadd.a detonation of an explosive, said apparatus .Iaddend.having
a chamber, at least one sealable door, and ignition means for
detonating .[.an.]. .Iadd.the .Iaddend.explosive .[.charge.].
within the chamber, and characterized by a plurality of plastic
film containers filled with water and suspended in a spaced array
within the chamber above the explosive to be detonated.
2. An apparatus for containing and suppressing .[.the explosions.].
.Iadd.a detonation of an explosive .Iaddend.comprising:
a closed elongated metal inner casing having a ceiling, a floor,
side walls and ends, and a closed elongated metal outer casing
spaced from the inner casing, surrounding the inner casing to form
an elongated axially symmetrical double-wall chamber having a
central axis.[.,.]..Iadd.; .Iaddend.
spacer means for connecting the outer casing to the inner casing in
rigid spaced relationship, with the space between the inner and
outer casings being filled with granular shock-damping
material.[.,.]..Iadd.; .Iaddend.
an openable access door at one end and an openable vent door at the
other end, said access and vent doors each being of double-walled
metal construction and having sealing means for causing said doors
to seal tighter with increasing differential pressure within the
chamber.[.,.]..Iadd.; .Iaddend.
additional granular shock-damping material covering the floor of
said chamber to an even depth forming a support surface for
.[.an.]. .Iadd.said .Iaddend.explosive to be detonated, and
ignition means for detonating said explosive.[., and.]..Iadd.;
.Iaddend.
shock suppression means including a plurality of vent pipes
connecting the .[.inside wall of the chamber.]. .Iadd.inner casing
side walls .Iaddend.with an elongated metal manifold .[.means.].
for receiving and directing explosion products from the vent pipes,
said manifold .[.means.]. terminating at an external discharge
point.[.,.]..Iadd.; .Iaddend.and
a plurality of liquid-filled energy absorption modules suspended in
a spaced array substantially along the central axis of the chamber
above .[.the.]. .Iadd.said .Iaddend.explosive to be detonated.
3. The apparatus of claim 2 in which the energy absorption modules
comprise plastic film containers filled with water, with the mass
of water being substantially equal to the explosive to be
detonated.
4. The apparatus of claim 3 in which the containers are individual
bags made of polyethylene sheet material, and the chamber ceiling
has a plurality of depending wire supports from which the bags are
hung.
5. The apparatus of claim 3 in which an additional water-filled bag
is disposed along the central axis of the chamber near each
end.
6. The apparatus of claim 4 in which the wire supports are made of
9 gauge steel cable.
7. The apparatus of claim 4 in which the bags are commercially
available self-locking sandwich bags of about 8.0 ounce liquid
capacity.
8. The apparatus of claim 2 in which the ignition means includes
electrical igniter wires entering the chamber through a steel hood
having .[.an.]. .Iadd.a .Iaddend.downward-facing access opening
positioned below the .[.surface of the granular bed.].
.Iadd.support surface of the granular shock-absorbing
material.Iaddend., through which the leads of an electric blasting
cap may be attached.
9. The apparatus of claim 2 in which the access door and vent door
have sensor means for electrically locking out the ignition means
when either door is not in a closed and sealed condition.
10. The apparatus of claim 2 including exhaust fan means for
evacuating gaseous explosion combustion products of the detonation
through the vent door, and drawing fresh air from the access door
to fill the chamber after an explosion.
11. The apparatus of claim 10 including .[.conduit.]. means for
receiving gaseous explosion .Iadd.combustion .Iaddend.products
discharging from the manifold discharge point and vent door after
an explosion, and directing them to a .[.scrubber.].
.Iadd.scrubbing .Iaddend.means for stripping said gaseous explosion
combustion products of particulate matter and noxious vapors.
12. .[.The.]. .Iadd.A .Iaddend.method for suppressing and
containing explosions within a chamber having at least one sealable
door and ignition means for detonating an explosive .[.charge.].
within the chamber, comprising the steps of.Iadd.:
.Iaddend.charging the chamber with .[.an.]. .Iadd.said
.Iaddend.explosive .[.workpiece.]. .Iadd.to be detonated.Iaddend.,
attaching ignition means to .[.the.]. .Iadd.said
.Iaddend.explosive, suspending a plurality of plastic film
containers filled with water in a spaced array within the chamber
above .[.the.]. .Iadd.said .Iaddend.explosive, closing and sealing
the chamber doors, detonating .[.the.]. .Iadd.said
.Iaddend.explosive, opening the chamber doors, and exhausting the
gaseous explosive combustion products through the door before
re-loading the chamber with a new explosive .[.workpiece.]..
13. A method for containing and suppressing .[.the.]. .Iadd.a
.Iaddend.detonation of an explosive comprising the steps of:
first, placing .[.an.]. .Iadd.said .Iaddend.explosive .[.charge.].
in an enclosed chamber, said chamber comprising:
a closed elongated metal inner casing having a ceiling, a floor,
side walls .Iadd.defining a central axis .Iaddend.and .Iadd.two
.Iaddend.ends.[., and.]..Iadd.; .Iaddend.
a closed elongated metal outer casing spaced from the inner
casing.[.,.]. .Iadd.and .Iaddend.surrounding the inner casing .[.to
form an elongated axially symmetrical double-wall chamber having a
central axis,.]..Iadd.; .Iaddend.
.[.spacer.]. .Iadd.spacing .Iaddend.means for connecting the outer
casing to the inner casing in rigid spaced relationship, .[.with.].
.Iadd.said outer and inner casing defining a space therebetween,
.Iaddend.the space between the inner and outer casings being filled
with granular shock-damping material.[.,.]..Iadd.; .Iaddend.
an openable access door at one end .Iadd.of the inner casing
.Iaddend.and an openable vent door at the other end, said access
and vent doors each being of double-walled metal construction and
having sealing means for causing said doors to seal tighter with
increasing differential pressure within the chamber.[.;.]..Iadd.;
.Iaddend.
additional granular shock-damping material covering the floor of
said .[.chamber.]. .Iadd.inner casing .Iaddend.to an even depth
forming a support surface for .[.an.]. .Iadd.said
.Iaddend.explosive to be detonated.[., and.]..Iadd.; .Iaddend.
ignition means for detonating said explosive.[.,.]..Iadd.;
.Iaddend.and
shock suppression means including a plurality of vent pipes
connecting the .[.inside wall of the chamber.]. .Iadd.inner casing
side walls .Iaddend.with an elongated metal manifold .[.means.].
for receiving and directing explosion products from the vent pipes,
said manifold .[.means.]. terminating at an external discharge
point.[.,.]..Iadd.; .Iaddend.
second, placing a plurality of liquid-filled energy absorption
modules suspended in a spaced array substantially along the central
axis .[.of the chamber.]. above .[.the.]. .Iadd.said
.Iaddend.explosive to be detonated.[.,.]..Iadd.; .Iaddend.
third, closing and sealing the access and vent doors.[.,.]..Iadd.;
.Iaddend.and
fourth, detonating said explosive.
14. The method of claim 13 including the further steps of opening
said vent door and access door and evacuating .[.the.]. gaseous
explosion combustion products of the detonation through the vent
door, while allowing fresh air to fill the chamber from the access
door.
15. The method of claim 13 including the further steps of directing
.[.the.]. gaseous explosion combustion products from the manifold
.[.means.]. and from the access door into a .[.scrubber.].
.Iadd.scrubbing .Iaddend.means for stripping said gaseous explosion
combustion products of particulate matter and noxious vapors.
16. The method of claim 13 in which the energy absorption modules
comprise plastic film containers filled with water, with the mass
of water being substantially equal to the explosive to be
detonated.
17. The method of claim 16 in which the containers are individual
bags made of polyethylene sheet material, and the .[.chamber.].
.Iadd.inner casing .Iaddend.ceiling has a plurality of depending
wire supports from which the bags are hung.
18. The method of claim 17 in which the wire supports are made of 9
gauge steel cable.
19. The method of claim 17 in which the bags are commercially
available self-locking sandwich bags of about 8.0 ounce liquid
capacity.
20. The method of claim 17 in which an additional water-filled bag
is disposed along the central axis .[.of the chamber.]. near each
end of the .[.container.]. .Iadd.inner casing.Iaddend..
21. The method of claim 13 in which the ignition means includes
electrical igniter wires entering the chamber through a steel hood
having an downward-facing access opening positioned below the
.[.surface of the granular bed.]. .Iadd.support surface of the
granular shock-damping material.Iaddend., through which .[.the.].
leads of an electric blasting cap may be attached.
22. The method of claim 13 including the step of sensing the
position of the access door and vent door, and electrically locking
out the ignition means when either door is not in a closed and
sealed condition. .Iadd.
23. An apparatus for containing and suppressing a detonation of an
explosive, said apparatus having a chamber, at least one sealable
door, and ignition means for detonating an explosive within the
chamber, and characterized by a plurality of modules containing an
energy absorbing substance, said modules positioned a spaced array,
within the chamber, around the explosive to be detonated.
.Iaddend..Iadd.24. A method for suppressing and containing a
detonation of an explosive within a chamber having at least one
sealable door and ignition means for detonating an explosive within
the chamber, comprising the steps of charging the chamber with the
explosive to be detonated, attaching ignition means to the
explosive, positioning a plurality of modules containing an energy
absorbing substance said modules positioned in a spaced array,
within the chamber, around said explosive, closing and sealing said
at least one door, detonation, said explosive, opening said at
least one door, and exhausting the gaseous explosive combustion
products through said at least one door before re-loading the
chamber with a new explosive. .Iaddend.
Description
FIELD OF THE INVENTION
This invention relates to a method and apparatus for containing,
controlling and suppressing the detonation of explosives,
particularly for the explosion working of metals, and for the
disposal of unwanted explosive and toxic materials.
BACKGROUND OF THE INVENTION
Explosives have many useful industrial applications including
surface hardening of austenitic manganese alloy steels, surface
deposition coating, welding of metallic components, compression
molding of components from powders and granular media, and disposal
of unwanted explosive or toxic materials.
The prior art reflects many attempts to contain the explosion
process for the suppression of noise, shock and noxious polluting
explosion products.
Hampel U.S. Pat. No. 5,419,862 discloses a large explosion chamber
in which an explosive work piece is introduced in through an air
lock into a vacuum chamber where it is detonated, and after
detonation the explosion products are allowed to escape into the
atmosphere. The chamber is mechanically secured by anchor rods to a
foundation.
Gambarov, et al. U.S. Pat. No. 4,100,783 discloses a cylindrical
containment vessel, split along its diameter for separation, and
openable for the insertion of large work pieces such as railway
frogs, stone crusher wear parts and the like. After insertion of a
work piece and explosive charge, the chamber is closed and locked
and the explosive detonated by a built-in detonating device. The
explosion combustion products are allowed to exhaust to the
atmosphere through an air valve.
Deribas U.S. Pat. No. 4,085,883 and Minin U.S. Pat. No. 4,081,982
disclose spherical containment vessels with a bottom opening
through which a work piece incorporating an explosive is introduced
through an elevator means, and continuous feed wire electrodes are
used to make contact with an electrically initiated detonator when
the work piece is in place. The latter patent also discloses means
for introducing an internal liquid spray after the explosion for
the purpose of neutralizing toxic by-products of the explosion.
Smirnov, et al. U.S. Pat. No. 4,079,612 discloses a roughly
hemispherical containment vessel mounted on a concrete foundation
with a shock-absorbing work table for supporting the work piece and
explosive material, which are detonated through electric ignition
wires leading through openings in the containment vessel to the
outside.
A different approach is disclosed by Paton, et al. U.S. Pat. No.
3,910,084 in which multiple closed-end pipes are disposed radially
around a central column in which the explosion is initiated, with
the shock waves dampened by internal baffles within the tubes.
Access is gained to the chamber through a removable top cover
plate.
Klein, et al. U.S. Pat. No. 3,611,766 discloses a vertical
explosion chamber incorporating a cushioned work table for
supporting the work piece and explosive charge, and an internal
shock-mounted mechanical dampening means consisting of a steel
grate for absorbing the explosive pressure waves. Klein U.S. Pat.
No. 3,464,249 discloses a similar containment vessel, in this case
spherical, with a bottom covering of loose granular material such
as sand which supports the work piece and explosive charge. The
explosion products are discharged through a vertical pipe
containing a noise silencer, and the entire assembly is supported
by shock absorbing means in a reinforced brick or concrete pit for
the further suppression of shock and noise.
All of the above prior art devices represent improvements over the
methods first used for explosion hardening of manganese steel rail
components which involved placing the explosive-covered work piece
in an open field, or at the bottom of an open pit such an abandoned
gravel pit, and setting off the explosion in the open air with
resultant noise, dust, disturbance and contamination of the
environment. In addition, the uncontrolled use of explosives
required great amounts of space, posed substantial danger to
equipment and personnel, and had the undesirable effect of
demolishing the ignition leads, the work piece support surface, and
everything else within the immediate vicinity of the explosion.
It is therefore the principal object of the present invention to
provide an improved method and apparatus for containing,
controlling and suppressing the effects of explosive detonations
used for industrial purposes. The purpose of the invention is to
provide a containment device which can contain and suppress each
explosion so that it poses no hazard to surrounding plant and
equipment, or to the environment.
A further object is to provide such a method and apparatus which
permits rapid and convenient charging and removal of work pieces,
thereby achieving much higher rates of production than have been
possible using prior art devices and techniques. A related object
is to provide an explosive containment vessel which can be
constructed inexpensively of common materials using conventional
welding techniques but which is sturdy enough to withstand months
and years of continuous use without deterioration. A related object
is to provide such a device in which inexpensive consumable
materials, such as silica sand and pea gravel, are used as damping
and shock absorbing agents, rather than complex and expensive
internal springs, metal grates, and the like.
Another object is to provide an explosion containment chamber which
is readily opened from one end to allow charging and removal of
work pieces by conventional means such as a forklift truck, and to
allow easy entrance and exit by maintenance personnel. A further
object is to provide quick and efficient removal of gaseous
explosion by-products after detonation so that maintenance
personnel can immediately enter the chamber to remove the treated
work piece and put another in place for the next operation.
Still another object is to provide an internal ignition system in
which the electrical leads for the detonation initiation system are
protected from blast effect and are reusable for a great number of
explosion cycles, rather than being destroyed and having to be
replaced after each cycle.
Another principal object of the invention is to provide a means of
quickly removing and treating the gaseous explosion by-products by
passing them through a scrubber system, so that operating personnel
can re-enter the chamber immediately while the scrubber continues
to process the products of the previous explosion as a new work
piece and explosive charge are being readied. Also, it is an object
of the scrubber system to further dampen and suppress shock and
noise from each detonation by virtue of the extended travel path of
the explosion products as they pass through the scrubber.
Finally, a particularly important object of the invention is to
provide a simple and inexpensive means for absorbing the unused
energy of the explosion, for instantaneously reducing temperatures
and pressures within the chamber, while at the same time
suppressing dust and particulate matter in the explosion
by-products.
SUMMARY OF THE INVENTION
The improved explosion chamber of the invention comprises an
elongate double-walled steel explosion chamber anchored to a
concrete foundation, and having a double-walled access door for
charging new work pieces, and a double-walled vent door for
discharging the products of the explosion. The double walls of the
chamber, access door and vent door are filled with granular shock
damping material such as silica sand, and the floor of the chamber
is covered with granular shock-damping bed such as pea gravel.
Along the outside of the chamber are steel manifolds from which a
linear array of vent pipes penetrates the double walls of the
chamber, with each pipe terminating in a hardened steel orifice
through which the explosion combustion products pass.
Within the chamber, plastic polymer film bags containing water are
suspended from steel wires over the explosive material, and at each
end of the chamber. Electrical igniter lead wires enter the chamber
through a steel hood having a downward-facing access opening
positioned in a protected location below the surface of the
granular bed, but accessible by an operator for quickly attaching
an electrical blasting cap.
The access and vent door are interlocked with the electrical
igniter to block ignition unless both doors are positively shut.
When the doors are opened after a detonation, a vent fan is
positioned to exhaust explosion combustion products from the
chamber and to draw fresh air in through the access door. The
manifolds and vent door discharge into a scrubber for further
cooling and environmental treatment of the gaseous combustion
products.
The method of operation of the invention comprises the steps of
placing an explosive work piece through the access door and onto
the granular bed, suspending plastic bags containing an amount of
water approximating the weight of explosive, attaching an
electrical blasting cap to the igniter lead wires, closing the
access and vent door, electrically detonating the explosive,
immediately opening both access and vent door, and using fan means
for exhausting the combustion products of the detonation from the
chamber in preparation for inserting the next explosive work
piece.
The gaseous combustion products exiting the manifolds and vent
discharge are then cooled and environmentally treated in a scrubber
before being released to the atmosphere.
A BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIG. 1 is a cut-away perspective view of .[.access door 6 end of.].
the improved explosion containment chamber of the present
invention;
FIG. 2 is a cut-away partial perspective view of the opposite end
of the chamber of FIG. 1, including a scrubber for cleaning the
gaseous explosion products before venting them to the
atmosphere;
FIG. 3 is a partial sectional plan view of the explosion chamber of
the preceding figures;
FIG. 4 is a partial sectional side elevation of the explosion
chamber of the preceding figures;
FIG. 5 is a reduced-scale sectional plan view of the full length of
the explosion chamber of the preceding figures showing a railroad
track work piece in place for explosion hardening treatment;
FIG. 6 is a sectional end elevation showing the access door 6 end
of the explosion chamber of the preceding figures;
FIG. 7 is a sectional end elevation showing the vent door 7 end of
the explosion chamber of the preceding figures, with a piece of
rail trackwork in place for treatment; and
FIG. 8 is an enlarged partial sectional end elevation of the
ignition wire entry point into the explosion chamber of the
preceding figures.
DETAILED DESCRIPTION OF THE INVENTION
Turning to the drawings, FIG. 1 is a sectional perspective of the
improved explosion chamber of the present invention. The chamber
comprises an inner casing 1 having a ceiling, floor, side walls and
ends, being fabricated of sheet steel using conventional welding
techniques. Surrounding the inner casing 1 are a plurality of
spaced circumstantial flanges or ribs 2 over which a welded sheet
steel outer casing 3 is constructed so that the ribs 2 cause the
outer casing 3 to be spaced from the inner casing 1 and leaving a
gap which is then filled with a granular shock-damping material
.Iadd.4.Iaddend.. In the preferred embodiment, the inner and outer
metal casings are constructed of three-quarter inch thick sheet
steel separated by circumferential steel I-beam ribs 2 spaced every
two feet. All seams are continuous-welded. According to the
invention, the space between the inner and outer casing 3 is filled
with a firm, granular shock-absorbing material, preferably silica
sand.
The explosion chamber is anchored by bolts or other suitable means
(not shown) to a reinforced concrete foundation 5. In the preferred
embodiment shown, the inside dimensions of the explosion chamber
are: eight feet high, six feet wide, and fifty feet long. The
reinforced concrete foundation 5 is preferably at least four feet
thick.
As one of the major advantages of the invention, the internal
dimensions of the chamber allow an operator to enter, stand up and
work easily, and its length permits long pre-welded sections of
railroad trackwork to be inserted and explosion-hardened, which was
not possible in prior art explosion chambers.
The chamber is provided with two doors, an access door 6, and a
vent door 7. Both doors are constructed of double-walled welded
steel similar to the chamber walls, and each is hinged to open in
an inward direction. The door jambs are constructed so that each
door fits in a sealing relationship so that increased pressure
within the chamber causes the door to seal tighter against its
frame. The volume within the double-walled doors is also filled
with shock-damping material, preferably silica sand.
The floor of the chamber is preferably covered with a bed 8 of
granular shock-damping material, preferably pea gravel, to a
uniform depth of about one foot, thereby forming a support surface
for the work piece and explosive to be detonated.
To initiate ignition of the explosive, electrical wire firing leads
9 penetrate the chamber through a pressure-sealed opening 10 and
emerge through a welded sheet steel shield box or hood 11 having a
downward-facing opening positioned below the surface of the
granular shock-damping material. To prepare the work piece and
charge for detonation, a suitable electric detonator cap 12 is
inserted into the explosive charge and the ends of its wire leads
13 are routed over to the firing wire hood 11. The pea gravel is
scooped away to expose the ends of the firing wire leads 9, the
leads are twisted together to complete the firing circuit, and then
the pea gravel is swept back over the detonator cap leads 13 to
again surround and enclose the open end of the hood 11. While the
detonator cap leads 13 are substantially disintegrated by the
explosion, the firing wire leads 9 remain protected under the hood
11 and may be re-used repeatedly.
As a principal feature of the invention, shock suppression means
are provided for the chamber in the form of a plurality of vent
pipes disposed along the centerline of each interior side wall of
the chamber, with each vent pipe communicating through the chamber
double wall into an elongated steel manifold 15 means extending
alongside the chamber on each side and terminating in a discharge
outlet 16. In the preferred embodiment each manifold 15 is ten
inches square and is fabricated by continuous-seam welding from
one-half 2 inch steel plate. The ribs 2 consist of eighteen-inch
I-beam sections spaced at two foot intervals. The vent pipes 14 are
of two inch diameter steel tubing, and like the ribs 2 are spaced
at two foot intervals. Where it connects to the inner wall of the
chamber, each vent pipe is fitted .[.at.]. with a hardened steel
orifice 17 three-quarters of an inch in diameter. In the preferred
embodiment, the
fifty-foot chamber has twenty-four vent pipes 14 and orifice 17 per
side, for a total of forty-eight vent pipes 14 and orifice 17 in
all.
Within the chamber, square corners are avoided because of the
tendency of explosives to exert unusually high pressures at such
critical points. Therefore, a fillet piece 18 is welded into each
corner to break the 90.degree. square corner into two 45.degree.,
which has the effect of rounding the corner and eliminating
stress-raising corners or pockets which would otherwise impose
undesirable destructive forces on the corner welds.
In the preferred embodiment of the invention, additional sound
suppression is obtained by coating the exterior surfaces of the
outer chamber and manifold 15 with a polyurethane rigid foam
coating 20 of known composition to a depth of at least four inches.
The entire foam-covered structure is further enclosed in an
enclosure such as a sturdy wooden shed (not shown) having screened
ventilating slots to permit free circulation of air.
To open and close the access and vent door 7, double-acting
hydraulic cylinders 19 are provided. As a further feature of the
invention, important safety objectives are realized by providing
each door with sensor means 21 as part of an electrical interlock
(not shown) between the access door 6, vent door 7 and ignition
means, whereby the access door 6 must both be in a closed and
sealed position before the ignition means can be energized. In this
way it is impossible to inadvertently detonate an explosive charge
prematurely before the doors are fully closed, the result of which
would be substantial destruction and damage to equipment such as
the vent fan 22, not to mention the risk of bodily injury to
operating personnel in the vicinity of the access door 6.
In the preferred embodiment the chamber ceiling is fitted with a
welded I-beam for use as a trolley to insert and remove
particularly long lengths of steel trackwork or other work pieces
of a similar shape.
Another principal feature of the invention is the provision for
each explosion of .[.a.]. liquid-filled energy absorption modules
disposed roughly along the interior centerline of the chamber.
These devices serve to cool the gaseous explosion products, and to
suppress dust and debris in the chamber after each explosion.
In the preferred embodiment, the energy absorption devices are
simple self-sealing polyethylene bags filled with water and hung on
hanger wires 25 approximately along the center line of the chamber
above and around the work piece and explosive charge. It has been
discovered that commercially available "Zip-Lock" brand sandwich
bags, six by eight inches in dimension and 0.002 inches (two mils)
thick are satisfactory for this purpose. While water is preferable,
any suitable energy-absorbing vaporizable material can also be
used.
According to the invention, the volume of water placed in the
chamber for each explosion is selected to be approximately equal in
weight to the amount of explosive to be detonated. This volume of
water is distributed among several bags which are then hung in a
staggered array approximately along the center line of the chamber
in the vicinity of the explosive. Preferably, the water bags 24 are
hung on the hooked ends of nine-gauge steel rods .[.are.]. welded
to the ceiling of the chamber.
By using the water-filled energy absorption means, it has been
found that the instantaneous theoretical pressure of the explosion
is reduced by more than half, and the introduction of moisture into
the chamber at the moment of detonation and thereafter has a
beneficial effect of suppressing dust and cooling the explosion
products instantly. In contrast to explosions without the use of
the water-filled bags, the perceived impact and noise of the
explosion is substantially reduced, and operating personnel are
.[.enabled.]. .Iadd.able .Iaddend.to enter the chamber immediately
after each detonation to remove one work piece and replace it with
the next.
It has also been found in practice that the beneficial effects of
the water bags 24 are enhanced if an additional water bag 26 is
placed at each end of the chamber, away from the work piece,
approximately four feet from the access door 6, and twelve feet
from the vent door 7, although other spacings are satisfactory
also.
In practice, using the water bags 24 in the manner of the invention
results in the complete vaporization of both the water and the
polyethylene bags, serving to absorb and suppress the undesired
shock of the explosion, while leaving behind virtually no debris or
residue. After each explosion, the access door 6 can be opened
immediately, and all that can be seen are wisps of water vapor
which are swept out the vent door 7 in the manner described further
herein.
According to another important feature of the invention, all
gaseous explosion by-products are quickly exhausted from the
chamber in a controlled manner. After each explosion, the vent door
7 and access door 6 are simultaneously opened, the vent fan 22 is
energized, and the gaseous explosion products from the chamber are
drawn through the vent door 7 opening while the atmosphere in the
chamber is replaced with fresh air drawn through the open access
door 6. In practice, using the method and apparatus describe, it
has been found that the access and vent door 7 may be immediately
opened after each explosion, thereby permitting operating personnel
to enter the chamber immediately after each explosion to remove the
treated work piece and replace it with the next.
Another major feature of the present invention is that all gaseous
explosion products are controllably discharged and directed into a
suitable environmental treatment means such as a scrubber 27. In
the illustrated embodiment, a water-spray scrubber 27 of
conventional construction is used to receive the discharge from
both side-mounted manifold 15, and from the vent fan 22 as well, so
that no gaseous explosion products escape to the atmosphere
untreated. In addition, the tortuous path offered by the scrubber
27 creates a further level of advantageous shock and noise
suppression.
To permit the refilling of gaps in the chamber walls caused by
settling of the shock damping silica sand, a bin or hopper 28 is
provided above the chamber with spaced openings 29 through which
sand may move to replace lost volume as the sand in the walls
settles or compacts with each detonation. It has been found that
despite such compaction, the use of silica sand (as opposed to
masonry sand) does not result in any diminishing of the
shock-damping effect.
Despite the immense destructive forces of each explosive
detonation, the chamber of the present invention, with its vent
pipes 14 and energy absorbing liquid modules, has been found in
practice to diminish the surplus destructive energy of each
explosion to a point where the trolley beam 23 is virtually
unaffected. Similarly, the depending wires for hanging the energy
absorption water bags 24 are virtually unaffected after each blast.
This allows the chamber to be used continuously, with a productive
output of as many as 10 or 12 explosions per hour, which is an
order of magnitude greater than permitted by any of the explosion
chambers of the prior art, or by conventional open-pit explosive
techniques.
In practice, with the preferred embodiment described, the method
and apparatus of the present invention has been successfully
utilized to safely detonate explosive charges in a wide range of
sizes, ranging from two to fifteen pounds of C2 plastic explosive
(also know as PETN), with minimal amounts of shock, noise and
adverse effect on the environment. Surprisingly, it has been found
that business office operations in an adjoining office building
only two hundred feet away from the explosion chamber can be
conducted in a completely normal manner, with the explosions being
indistinguishable from the ordinary background noise of the office
environment.
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