U.S. patent application number 09/756915 was filed with the patent office on 2001-05-10 for method for rendering a detonation front harmless.
Invention is credited to Leinemann, Christoph.
Application Number | 20010000837 09/756915 |
Document ID | / |
Family ID | 7865800 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010000837 |
Kind Code |
A1 |
Leinemann, Christoph |
May 10, 2001 |
Method for rendering a detonation front harmless
Abstract
A detonation safety device having a flame-arresting device
positioned in a housing. A pipe extends into the housing and
proximate to the flame arresting device. In order to render a
detonation front traveling in a pipe harmless, the detonation front
is conveyed near the flame-arresting device. The flame-arresting
device includes a diameter larger than the pipe and the detonation
front such that the detonation front impinges only on a partial
surface of the flame-arresting device. The detonation front is
expanded in front of the arresting device so as to create a
deflagration, which then impinges on the outer cross-section of the
flame arresting device.
Inventors: |
Leinemann, Christoph;
(Braunschweig, DE) |
Correspondence
Address: |
McGuire Woods LLP
1750 Tysons Boulevard, Suite 1800
McLean
VA
22102
US
|
Family ID: |
7865800 |
Appl. No.: |
09/756915 |
Filed: |
January 10, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09756915 |
Jan 10, 2001 |
|
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09296405 |
Apr 23, 1999 |
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Current U.S.
Class: |
48/192 ;
220/88.1; 220/88.2; 431/346; 60/39.11 |
Current CPC
Class: |
F42D 5/045 20130101;
Y10S 55/20 20130101; A62C 4/02 20130101 |
Class at
Publication: |
48/192 ;
60/39.11; 220/88.1; 220/88.2; 431/346 |
International
Class: |
F17D 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 1998 |
DE |
198 18 572.3 |
Claims
Having thus described our invention, what we claim as new and
desire to secure by Letters Patent is as follows:
1. A method for rendering harmless a detonation front flowing in a
pipeline using a flame-arresting device having a diameter larger
than a diameter of the pipeline, the method including the steps of:
providing a pipe stub proximate to the flame-arresting device;
conveying, via the pipe stub, the detonation front to a portion of
the flame-arresting device having a diameter substantially equal to
the detonation front; permitting the detonation front to impinge on
the portion of the flame-arresting device; permitting the
detonation front to expand in front of the flame-arresting device
in such a way that a deflagration impinges on periphery portions of
the flame-arresting device.
2. The method of claim 1, further including diverting the
detonation front into an expansion space for pre-combustion.
3. The method of claim 1, wherein the detonation front is conveyed
to several portions of the flame-arresting device by separation
into part-detonation fronts.
4. The method of claim 1, further including: providing two or more
pipe stubs proximate to the flame-arresting device; and conveying
the detonation front to a portion of the flame-arresting device via
the two or more pipe stubs.
5. The method of claim 1, further including diverting a portion of
the detonation front through at least one connection openings in
the pipe stub into an expansion space for pre-combustion.
6. The method of claim 1, further including providing a distance
between an outlet of the pipe stub and the flame-arresting device
equal to or smaller than the diameter of the pipeline.
7. The method of claim 1, further including providing slots on the
flame-arresting device narrower on the impingement portion of the
flame-arresting device than on the periphery portions of the
flame-arresting device.
8. A detonation safety device installed in a container or a pipe,
the detonation system comprising: a housing; a flame-arresting
device having a diameter larger than a diameter of the container or
pipe and housed within the housing; at least one pipe stub
extending from the container or pipe and into the housing, an
outlet of the at least one pipe stub extending near the
flame-arresting device so that a detonation front impinges only on
a partial section of the flame-arresting device, the partial
section having a diameter substantially equal to the diameter of
the detonation front; and an expansion space surrounding the at
least one pipe stub for generation of a deflagration.
9. The detonation safety device of claim 8, wherein a distance
between the outlet of the pipe stub and the flame-arresting device
is less than or equal to a diameter of the pipe.
10. The detonation safety device of claim 8, wherein a distance
between the outlet of the pipe stub and the arresting device is
less than 1/3a diameter of the pipe.
11. The detonation safety device of claim 8, wherein an inner space
of the housing is cylindrical in shape and has a cross-section
corresponding approximately to a cross-section of the
flame-arresting device.
12. The detonation safety device of claim 11, wherein a length of
the inner space on a side of the pipe stub to the flame-arresting
device is equal to or greater than 0.5 times a diameter of the
pipe.
13. The detonation safety device of claim 11, wherein the length of
the inner space on the side of the pipe stub to the flame-arresting
device is less than or equal to twice a diameter of the pipe.
14. The detonation safety device of claim 8, wherein the partial
section of the flame-arresting device is different than a
peripheral section of the flame-arresting device surrounding the
partial section.
15. The detonation safety device of claim 14, wherein the partial
section of the flame-arresting device includes narrower slots than
slots on the peripheral section of the flame-arresting device.
16. The detonation safety device of claim 14, wherein a slot length
of the slots of the flame-arresting device is equal throughout the
flame-arresting device.
17. The detonation safety device of claim 8, wherein the at least
one pipe stub includes openings to the expansion space adjacent to
the at least one pipe stub.
18. The detonation safety device of claim 8, wherein the at least
one pipe stub includes two pipe stubs positioned on opposing sides
of the flame-arresting device.
19. The detonation safety device of claim 8, wherein the at least
one pipe stub includes at least two pipe stubs installed in front
of the flame-arresting device.
20. The detonation safety device of claim 19, wherein the at least
two pipe stubs are positioned symmetrically about a central axis of
the flame-arresting device.
21. The detonation safety device of claim 19, wherein a diameter of
the at least two pipe stubs is less than a diameter of the pipe.
Description
BACKGROUND OF THE INVENTION
1. 1. Field of the Invention
2. The present invention generally relates to a method and
apparatus for rendering harmless a detonation front traveling in a
pipeline and, more particularly, to a detonation safety device
having a flame-arresting device that hinders the transmission of
the detonation flame.
3. 2. Background Description
4. The propagation of an explosion in a flammable gas mixture in a
container and/or pipeline system can occur as detonation or as
deflagration. In the case of detonation, the flame front and the
shock front created by the pressure wave of the explosion are
superimposed such that flame propagation velocities may reach
several thousand meters/second (m/s) and combustion pressures in
the shock direction may reach upwards of 100 bars. In the case of
deflagration, the shock waves precede the flame front such that
flame propagation velocities of deflagration are in the order of
several hundred m/s and the combustion pressures in the shock
direction are upwards of 10 bars (with an original pressure of the
mixture of one bar).
5. Several methods are known to avoid the destructive effects of
detonations. These methods attempt to weaken and/or end the
detonation, preferably by transforming the detonation into a
deflagration prior to arrival at a flame-arresting device. In many
instances, the flame-arresting device is combined with "detonation
brakes" and/or "detonation shock catchers" (e.g., detonation
absorbers), and farther includes a number of long and narrow slots.
These long and narrow slots attempt to cool the flame until the
flame becomes extinct.
6. By way of example, DE-PS 1192 980 (German patent) describes a
detonation safety device consisting of a detonation brake and a
flame arresting device. In this device, a detonation front
propagating in a pipeline is split by a convex outer surface of a
cylindrical wall and reaches an expansion space that has a volume
comparatively greater than the pipeline. A second semicircular
cylindrical wall of a smaller diameter than the cylindrical wall is
provided such that two facing free wall parts of the cylindrical
wall and the second semicircular cylindrical wall are overlapped,
thereby forming a labyrinth of various turns. In order to
extinguish the detonation, the split detonation front travels
through the labyrinth until it reaches the flame-arresting device.
The flame-arresting device is placed in an exit housing and angled
at 90 degrees to the pipeline in which the detonation initially
propagated.
7. However, in these known devices as described with reference to
DE-PS 1192 980, the split detonation fronts create a secondary
detonation, especially under unfavorable mixture composition
conditions. It is thus necessary to size the flame-arresting device
in such a way that it performs the flame extinguishing function
even in the secondary detonation case. In order to accomplish the
flame extinguishing function, the flame extinguishing slots of the
arresting device must be adequately long and narrow so as to
realize a relatively high pressure loss during normal pipeline
operation. However, these long and narrow slots require high
maintenance which can be costly and time consuming.
8. By way of further example, DE 195 36 292 C2 teaches a split of
the detonation front into a main front and a secondary front. In
the case of DE 195 36 292 C2, the main front is conducted into the
expansion space with a longer transit time so that upon entry into
the expansion space the main front contains combustion gases of the
secondary front. It is noted, however, that the splitting of the
detonation into main and secondary fronts such that the main front
needs a longer transit time to reach the expansion space also
requires many turns which thus results in a minimum volume for the
detonation safety device. Thus, there is a need to use a
pre-installed shock buffer for at least the main front. It is
noted, however, that the use of the shock buffer results in a
relatively high fabrication cost especially when the detonation
safety device is impacted by detonation fronts from both sides in
which case the shock buffers must be installed on both sides of the
flame-arresting device.
9. In principle, it would be possible to use a flame-arresting
device without a shock buffer. However, the slots of the arresting
device must be quite long and narrow in order to achieve adequate
safety, resulting in high pressure losses across the arresting
device. If flame arresting devices with low pressure drop are used,
the flame front entering the arresting device can push lighter
non-combusted mixtures through the arresting device which would
thus result in higher stream velocities and the creation of
turbulence in the flame extinguishing slots in the flame front
travel direction. The higher stream velocities would thus increase
the combustion velocity and reduce the extinction capability and
the flame arresting safety of the device. It is further known that
if the arresting devices with high damming capability created by
long and narrow slots are used to provide high flame arresting
safety, significant operational drawbacks of high pressure losses
will result in the arresting devices.
SUMMARY OF THE INVENTION
10. It is therefore an object of the present invention to provide a
detonation safety device which is built with simple and inexpensive
components.
11. It is a further object of the present invention to provide a
detonation safety device which does not have large pressure
drops.
12. It is still a further object of the present invention to
provide a detonation safety device which provides a high degree of
flame arresting safety.
13. It is another object of the present invention to provide a
detonation safety device which does not use a shock buffer.
14. According to the invention, there is provided a detonation
safety device which renders harmless a detonation front traveling
in a pipeline by the use of a flame-arresting device. The
detonation safety device includes a housing built into a pipeline
and/or container system having a specific diameter. The
flame-arresting device is housed in the housing and hinders the
detonation of the flame of the detonation front.
15. The diameter of the flame-arresting device is significantly
larger than the pipe diameter thus providing a desired low pressure
drop. Since the diameter of the flame-arresting device is larger
that the pipeline diameter, it is appropriate to convey the
detonation front as several part-fronts to various parts of the
flame arresting device. This arrangement also allows an even
distribution of flowing gases over the comparatively large surface
area of the arresting device during normal operations.
16. A pipe stub extends from the pipe and into the housing. The
outlet of the pipe stub is proximate to the flame-arresting device
and creates an open space so that a detonation front traveling
through the pipe stub impinges only on a portion of the
flame-arresting device. The pipe stub is placed near the
flame-arresting device such that the portion being impinged by the
front is essentially equal to the pipeline diameter. The
flame-extinguishing operating mode becomes more effective as the
end of the pipe stub is placed closer to the flame-arresting
device.
17. The pipe stub may also include small (relative to the pipe
diameter) connection openings between the pipe stub and the
surrounding open space which causes pre-combustion of the
detonation front in the expansion space. The pre-combusted gases
avoid the tendency of a renewed detonation front in the expansion
space, especially one caused by a reflection off the end wall of
the expansion space furthest away from the arresting device. In
this way, the length of the expansion space can be reduced. In
still further embodiments of the present invention, several pipe
stubs are provided, where each of the pipe stubs have a smaller
diameter than the diameter of the pipeline.
18. Preferably, the flame-arresting device has a total diameter of
at least double the front impingement diameter so that low pressure
drops are achieved during normal operations. A lower limit for the
reduction of the gap between the end of the pipe stub and the
flame-arresting device results from the need that, during normal
operations, the total cross-section of the flame-arresting device
be uniformly impinged at the usual, normally relatively low, flow
velocities. Within the limits of these boundary conditions, the
distance between the outlet of the pipe stub and the
flame-arresting device is equal to or larger than one third of the
pipe diameter and equal to or smaller than the pipe diameter.
19. The detonation front is expanded before reaching the
flame-arresting device in such a manner that a deflagration ensues
and impinges on the outer cross-section of the flame-arresting
device. In the embodiments of the present invention, a small
portion of the detonation front is diverted to an expansion space
for pre-burning so that pre-combusted gases can prevent a renewed
formation of a detonation front in the expansion space.
20. By using the configuration of the present invention, the
detonation safety device of the present invention may be used
without a shock buffer.
BRIEF DESCRIPTION OF THE DRAWINGS
21. The foregoing and other objects, aspects and advantages will be
better understood from the following detailed description of a
preferred embodiment of the invention with reference to the
drawings, in which:
22. FIG. 1 shows a flame-arresting device of the present
invention;
23. FIG. 2 shows an expansion of a deflagration front initiated by
secondary ignition by the detonation front;
24. FIG. 3 shows the flame-arresting device of the present
invention under normal operating conditions;
25. FIG. 4 shows the flame-arresting device of the present
invention with detonation fronts in both flow directions;
26. FIG. 5 shows the flame-arresting device of FIG. 1 with narrow
slots;
27. FIG. 6 shows the flame-arresting device of FIG. 1 with openings
on a pipe;
28. FIG. 7 shows the flame-arresting device of FIG. 1 with several
pipe stubs of smaller diameter;
29. FIG. 8 shows the flame-arresting device of the present
invention under normal operating conditions according to FIG.
7;
30. FIG. 9 shows the flame-arresting device of FIG. 1 with two pipe
stubs of smaller diameter; and
31. FIG. 10 shows the flame-arresting device of the present
invention under normal operating conditions according to FIG.
9.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
32. Referring now to the drawings, and more particularly to FIG. 1,
there is shown a detonation safety device of the present invention.
The detonation safety device includes a housing 2 which is inserted
into a pipeline 1. The housing 2 is flanged at both ends to the
pipeline 1 thereby creating an inner space 3 of the housing 2. The
preferred shape of the housing 2 is cylindrical with a
cross-section approximately equal to that of the flame-arresting
device 5.
33. A pipe stub 4 extends from one end of the pipeline 1 into the
inner space 3, and extends to a flame-arresting device 5 mounted
concentrically with the housing 2. In the preferred embodiment, the
flame-arresting device 5 is mounted between two halves 6 of the
housing 2 and is secured by flange connections 7.
34. FIG. 1 further shows a detonation front 8 traveling through the
pipe stub 4 and impinging upon a portion 9 of the flame arresting
device 5. The flame-arresting device 5 includes a diameter larger
than the pipe and the detonation front such that the detonation
front impinges only on a partial surface (e.g., portion 9) of the
flame-arresting device 5. Preferably, the flame-arresting device 5
has a total diameter of at least double the front impingement
diameter so that low pressure drops are achieved during normal
operations.
35. FIG. 2 shows an expansion of a deflagration front initiated by
secondary ignition by the detonation front. Specifically, the
detonation front impinges on the partial surface of the
flame-arresting device 5 and then expands in front of the arresting
device 5 so as to create a deflagration. The deflagration then
impinges on the outer cross-section of the flame arresting
device.
36. FIG. 2 also shows that the pipe stub 4 includes a diameter D,
and that the detonation front 8 impinges only on a portion 9 of the
flame arresting device 5 (substantially equal to the diameter D of
the pipeline 1). The diameter of the portion 9 of the flame
arresting device 5 is approximately equal to the diameter D of the
pipeline 1. The detonation front which impinges upon only the
portion 9 of the flame-arresting device 5 is subject to high flow
resistance. This can be further reinforced by constructing the
flame-arresting device 5 so that the impingement section (e.g.,
portion 9) is different from the peripheral sections of the
flame-arresting device 5.
37. As seen further in FIG. 2, the shock wave of detonation front 8
encounters a relatively high flow resistance at the flame arresting
device 5 due to the small diameter D. Thus, the detonation front 8
is partially reflected by the flame-arresting device 5 and is
brought to extinction upon entering the portion 9 of the
flame-arresting device 5. The detonation front 8 also creates a
secondary ignition in the expansion space 13 of the housing 6
located in the open area between the end of the pipe stub 4 and the
flame-arresting device 5. The expansion space 13 extends for a
distance L1 between the outlet of the pipe stub 4 to an end wall 10
of the housing 6.
38. The secondary ignition of FIG. 2 creates a deflagration in the
expansion space 13. This deflagration further impinges on the outer
periphery portions of the flame-arresting device 5 which
significantly lowers the flame propagation velocity and combustion
pressure. The deflagration reflections from the walls of the
expansion space 13, especially the end wall 10 surrounding the pipe
stub 4, could again initiate a detonation front. However, by using
an adequate minimum length L1, the detonation front is eliminated
since the reflected deflagration front transformed into a
detonation front encounters an already combusted gas mixture in
front of the flame-arresting device 5. Thus, the detonation front
is rendered harmless.
39. In the preferred embodiment, length L1 is larger or equal to
0.5 D and smaller or equal to 2 D and more preferably equal to 0.6
D of the pipeline 1; however, other appropriate lengths may equally
be used depending on the pressure drop across the arresting device
5. It is noted that when pre-combustion occurs, the length L1 may
be reduced to one half of the pipeline diameter D.
40. The detonation front is allowed to impinge only on a portion of
the flame-arresting device 5 by conducting the detonation front
very close to the flame-arresting device 5 by use of the pipe stub
4. Thus, an expansion space is created on the inlet side of the
flame-arresting device 5 which permits the detonation front to
generate a deflagration, by secondary combustion. Since the
flame-arresting device 5 is impinged by the detonation front only
on a part of the flame-arresting device 5 surface it offers very
high flow resistance. The free cross-section surface of the whole
flame-arresting device 5 is preferably equal or greater than the
pipe diameter D of the pipeline 1.
41. Referring now to FIG. 3, the cross-section of the
flame-arresting device 5 is either equal to or larger than the
cross-section area of pipe stub 4 (diameter D) so that normal gas
flow 11, rather than the detonation front 8, does not cause any
significant pressure loss across the flame-arresting device 5. FIG.
3 further shows the open distance L2 between the outlet end of the
pipe stub 4 and the flame-arresting device 5 surface. The distance
L2 is chosen such that under normal operation conditions the
flame-arresting device 5 is uniformly impinged by the flowing
medium over the entire surface area of the flame-arresting device
5. This takes place when L2 is larger or equal to one third of
diameter D and smaller or equal to than diameter D. However, it is
further understood that the distance L2 may obtain an optimal
length depending on the pressure drop across the arresting device
5.
42. FIG. 4 shows the flame-arresting device 5 of the present
invention with detonation fronts in both flow directions.
Specifically, FIG. 4 shows the pipe stub 4 provided on both sides
of flame arresting device 5. Thus, the detonation safety device of
FIG. 4 may be used for detonation fronts 8 traveling in either
direction.
43. FIG. 5 shows the flame-arresting device 5 with narrow slots 9'
about the center thereof and substantially directly in the path of
the detonation front. The narrow slots 9' of the flame-arresting
device 5 provides a higher flow resistance to the detonation front
8 as compared to the slots of FIG. 1. It is advantageous for the
slots 9' in the impingement area to be narrower, while for reason
of manufacturing the slot lengths of all of the slots are uniform
over the whole flame-arresting device 5 cross-section.
44. Referring now to FIG. 6, the pipe stub 4 is provided with small
connection openings 12 that divert a portion of the entering
detonation front 8 immediately after the beginning of housing 2.
The connection openings 12 transfer the detonation front 8 directly
into the expansion space 13 which causes pre-combustion of the
detonation front in the expansion space 13. The burnt gases in the
expansion space 13 hinder the generation of a secondary detonation
by reflection of a deflagration off the end wail 10 of the housing
2 which results in a reduction in the length L1.
45. FIG. 7 shows several pipe stubs 4' each having a smaller
diameters than diameter D (as shown in FIG. 1) of the pipeline 1.
The arrangement of the pipe stubs 4' shown in FIG. 7 includes a
central stub 4' aligned with the pipeline 1 but having a slightly
smaller diameter D than that of the pipeline 1. Four additional
pipe stubs 4' are placed radially from the central stub 4' at equal
distances from each other. As seen in FIG. 7, the flame-arresting
device 5 is extremely large in relation to the diameter of the pipe
stubs 4' which allows the flame-arresting device 5 to obtain a very
low pressure loss through during normal operation. It is further
noted that the effective gap length L2 is maintained and that a
uniform distribution of the flowing medium on the flame-arresting
device 5 during normal operation is obtain when the several pipe
stubs 4' are installed opposite the cross-section of the
flame-arresting device 5.
46. Still referring to FIG. 7, the detonation front 8 traveling
through the pipeline 1 is split into several partial detonation
fronts 8' that impinge on the corresponding portions 9" of the
flame-arresting device 5. Also, the back end-wall 10', limiting the
length L1 of the expansion space 13, is formed by wall pieces that
create a distribution space 14 in the flow direction in front of
the flame-arresting device 5. This expansion space 13 spreads from
the diameter D of the pipeline 1 to the effective diameter of the
flame-arresting device 5, and further includes the pipe stubs 4'.
FIG. 8 shows the normal operation of the flame-arresting device 5
such that normal part-streams 11' pass through the stubs 4' and are
distributed uniformly on the cross-section surface of the arresting
device 5.
47. FIG. 9 shows two pipe stubs 4' which are placed equidistant
from the center axis of the housing 2 and/or the flame-arresting
device 5. This arrangement also leads to partial detonation fronts
8' of FIG. 9 and/or normal part-flows as shown in FIG. 10.
48. While the invention has been described in terms of a single
preferred embodiment, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the appended claims.
* * * * *