CA1311409C - Flame arrester having detonation-attenuating means - Google Patents
Flame arrester having detonation-attenuating meansInfo
- Publication number
- CA1311409C CA1311409C CA000587033A CA587033A CA1311409C CA 1311409 C CA1311409 C CA 1311409C CA 000587033 A CA000587033 A CA 000587033A CA 587033 A CA587033 A CA 587033A CA 1311409 C CA1311409 C CA 1311409C
- Authority
- CA
- Canada
- Prior art keywords
- flame
- housing
- inlet
- cup
- arrester
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000005474 detonation Methods 0.000 claims abstract description 43
- 238000010791 quenching Methods 0.000 claims abstract description 28
- 230000000171 quenching effect Effects 0.000 claims abstract description 25
- 238000004200 deflagration Methods 0.000 claims description 10
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 10
- 239000011159 matrix material Substances 0.000 claims description 6
- 230000002093 peripheral effect Effects 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 5
- 230000003111 delayed effect Effects 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 16
- 101150038956 cup-4 gene Proteins 0.000 description 12
- 238000011144 upstream manufacturing Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 11
- 230000035939 shock Effects 0.000 description 10
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 6
- 238000001228 spectrum Methods 0.000 description 5
- 238000002485 combustion reaction Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000010485 coping Effects 0.000 description 3
- 230000006378 damage Effects 0.000 description 3
- 239000001294 propane Substances 0.000 description 3
- 125000006850 spacer group Chemical group 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000003628 erosive effect Effects 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 210000004124 hock Anatomy 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
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- 239000010959 steel Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62C—FIRE-FIGHTING
- A62C4/00—Flame traps allowing passage of gas but not of flame or explosion wave
- A62C4/02—Flame traps allowing passage of gas but not of flame or explosion wave in gas-pipes
Landscapes
- Health & Medical Sciences (AREA)
- Public Health (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Gas Burners (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
"FLAME ARRESTER HAVING DETONATION-ATTENUATING MEANS"
ABSTRACT OF THE DISCLOSURE
A flame arrester for a pipe line is provided comprising a detonation attenuator mounted within the arrester chamber between the quenching element and the backflash flame inlet. The attenuator is generally cup-shaped, aligned with the inlet, of greater diameter than the inlet but of lesser diameter than the arrester chamber, and is positioned close to the inlet so as to circumscribe it.
The major portion of the high pressure central portion of a detonation wave generated by a backflash is received by the cup and reflected back into the pipe. Some of the detonation wave passes around the cup and impinges on the arrester element - however it has been delayed sufficiently to ensure complete quenching of the flame front in the element.
ABSTRACT OF THE DISCLOSURE
A flame arrester for a pipe line is provided comprising a detonation attenuator mounted within the arrester chamber between the quenching element and the backflash flame inlet. The attenuator is generally cup-shaped, aligned with the inlet, of greater diameter than the inlet but of lesser diameter than the arrester chamber, and is positioned close to the inlet so as to circumscribe it.
The major portion of the high pressure central portion of a detonation wave generated by a backflash is received by the cup and reflected back into the pipe. Some of the detonation wave passes around the cup and impinges on the arrester element - however it has been delayed sufficiently to ensure complete quenching of the flame front in the element.
Description
~L31~
2 The present invention relates to a flame arrester
3 capable of arresting a flame front advancing through a pipe
4 line. The arrester comprises means for attenuating a detonation in combination with means for quenching the flame.
7 Flame arresters are commonly employed in pipe lines 8 where the possibility of a backflash exists.
g sackflash can occur where there is present a combination of three factors, namely: a flow of a flammable 11 air/hydrocarbon gas mixture; confinement of the mixture 12 within a pipe or other structure; and means for igniting the 13 gas mixture. A typical example exists in~the case of a flare 14 line extending from an oilfield storage tank. A flammable gas mixture flows from the tank head-space through the line 16 to a flare stack having an outlet to the atmosphere. The 17 mixture leaving the flare stack outlet is normally kept lit.
18 If the flow velocity at the stack is not sufficiently high, 19 the flame can "backflash" or burn upstream through the pipe line. If the flame front reaches the tank, the latter can 21 explode.
22 As stated, flame arresters have long been emplaced 23 in such lines to snuff out or quench the flame front before 24 it reaches an installation (such as the storage tank) where serious harm could be done.
26 Commonly, a flame arrester comprises a flanged 27 tubular housing which is connected into the line to form an 28 integral component thereof. An "element" is positioned 1 3 ~
1 witAin the bore or chamber of t~e ho~sing to extend 2 transversely fully across the bore diameter.
3 The element functions to quench the ~lame ront.
4 In structure, the element usually comprises a matrix haring a multiplicity of small diameter, elongate 6 channels extending therethrough in the direction of the pipe 7 axis. The matrix usually consists of metal. One typical 8 element, for example, comprises a long flat sheet of g aluminum, referred to as the "core". A second similar sheet is crimped in sawtooth fashion and the apexes of the crimps 1l are in contact with the upper surface of the core sheet. The 12 product is then spirally wound to produce a cylindrical 13 element. An element of this type is commonly referred to as 14 a "spiral wound crimped ribbon" element.
As stated, the channels of the element are minute 16 in width or diameter. Nore specifically, the channel 17 diameter is selected to be stnaller than the "quenching 18 diameter". The quenching diameter is the largest diameter at 19 which a flame within the channel would be extinguished under static flow conditions. The determination of the quenching 21 diameter is commonly carried out in the industry in 22 accordance with the practice outlined in "Progress iJl 23 Combustion Science and Technology", Potter, A.E. Jr., Volume 24 1, pages 145-181 (1960).
In principle then, a flame arrester element is 26 provided with small enough channels, established by 27 determination in accordance with standard industry practice, 28 so that sufficient heat will be removed from a flame, by ~ 3 ~
1 conductance through the matrix material, to cause the flame 2 to be extinguished.
3 Unfortunately, in practice, flame arresters do from 4 time to time fail to arrest the flame and explosions do occur as a result, even though they have been designed in 6 accordance with established ~nd industry-accepted practice.
7 The reason for failure, in applicant 19 view, is 8 that the conventional flame arresters are only capable of 9 coping with a limited part of the spectrum of flame propagation conditions to which they may be exposed, when ll used outside existing standards.
12 Flame propagation can occur in two modes, 13 deflagration and detonation.
14 Deflagration is a combustion wave that propagates by t~e transfer of heat and mass to the unburned gas ahead of 16 it. Associated flame front overpressures can range from O to 17 10 or 20 times the initial value (which is commonly 18 atmospheric pressure). Flame velocities are usually subsonic l9 for deflagrations.
Detonation is a combustion wave that propagates by 21 shock compression~induced ignition. Detonations travel 22 supersonically, with Mach numbers of 5 to 10. Detonation 23 overpressures typically reach 15 to 50 times the initial 24 value.
Under a suitable and complex combination of 26 circumstances (including gas composition, length of run from 27 the ignition source, and flame front turbulence-creating 28 factors such as bends and the likeJ, an advancing flame front 29 can accelerate and change from the deflagration mode to the 1 detonation mode. Detonation is evidenced by a rapid and sharp 2 escalation in the pressure accompanying the flame front, said 3 peak pressurewave being in spaced relationship in front of 4 the flame front. A typical pressure/distance plo-t based on a burn invol~ing detonation in a pipe is set forth in Figure 2, 6 following below, and shows the spectrum of pressure change 7 that occurs as a flame front transition takes place between modes.
9 When flame propagation incurs detonation, two undesirable results can occur, namely:
11 _ combustion may be initiated on the protected 12 or upstream side of a conventionally designed 13 element; and 14 - the element may be structurally damaged and thereafter lose some of its arresting 16 capability.
17 These problems associated with detonation have been 18 acknowledged in the prior art literature.
19 In reviewing the literature, applicant noted two different theories of interest given to explain the failure 21 of arresters when exposed to detonation. One theory 22 suggested that the high pressure of detonation would propPl 23 hot gas through the channels at such high velocity that the 24 conventionally designed element would be incapable of cooling the gas sufficiently. On reaching the upstream end of the 26 element, the still-hot gas would combine with the unburned 27 gas and heat it so that spontaneous ignition would occur. The 28 other theory suggested that the high pressure would densify 29 the flammable gas mixture in the channels so that flame :~ 3 ~
1 advancing through the channels would create so much heat that 2 the matrix heat sink would be incapa~le of preventing the 3 flame from reaching the upstream end of the channels.
4 Two modifications of an arrester element readily suggest themselves from these theories, as a means for coping 6 with the high pressure failures. More particularly, one 7 could:
8 - reduce the width of the channels; or 9 - further elongate the channels;
lo to thereby increase the heat-removal capability of the 11 element.
12 Reducing the channel width or diarneter is a 13 solution of only limited applicability or practicality. As 14 the channel diameter is reduced, the pressure drop across the element increases. Choking a vent line in this fashion is 1~ undesirable. So that leaves elongation of the channels as an 7 avenue to explore.
3 Applicant constructed and tested an element having 19 a channel length 16 times that of a commercially available element designed in accordance with conventional practice.
21 When subjected to detonation conditions, this extended 22 element still failed over a significant portion of the flame 23 propagation spectrum. Thus channel elongation does not 24 appear to solve the problem of failure at high pressure, at least in a practical and feasible fashion.
26 Another possible modification for the element has 27 been suggested in the prior art, to improve quenching 28 capability. This involves providing channels which are 29 tortuous in configuration and have alternating sections of ~ 3 ~
1 expanded and reduced diameter. Channels of this design cause 2 the flame front to move turbulently.
3 Applicant tested elements having such turbulence-4 creating channels and found that they do provide improved quenching. However, when subjected to the high pressures 6 approaching or accompanying detonation conditions, the 7 elements still failed with some regularity.
8 So there is still a need for a flame arrester which 9 is improved with respect to handling the full spectrum or range of flame propagation conditions, including detonation.
12 In accordance with the invention, a detonation 13 attenuator is provided within the housing of a flame 4 arrester. ~he attenuator is positioned in front of the quenching element, to receive and reflect part of the centra7 16 portion of the detonation wave back into the pipe. Only a 17 portion of the detonation wave passes around the attenuator 18 and accompanies the flame to the element. By incorporating 19 an attenuator of successful deslgn , an arrester is prorided which has heen tested and shown to be much improved in coping 21 with a full spectrum of flame propagation conditions~.
22 The modified flame arrester involves, in 23 combination:
24 - A housing whose internal chamber has a greater cross-sectional area than that of the pipe 26 line~ so there is expansion of the shock 27 wave/flame front as it enters the chamber; and ~ 3 ~
1 - A generally cup-shaped attenuator or member, 2 positioned in line with and adjacent to the 3 housing flame front inlet, for receiving and 4 reflecting part of the detonation wave back down the pipe. The attenuator side wall is 6 inwardly spaced from tAe lonqitudinal wall of 7 the housing to thereby form an annular 8 passage connecting the flame front inlet with g the quenching element. The peripheral portion of the shock wave/flame front train passes 11 through this passage to the element, wherein 12 the flame is quenched.
13 The combination has the following advantages:
14 - The element lS protected by the attenuator from structural damage from detonation, to a 16 much improved extent. In test runs without an 17 attenuator, the element was rendered 18 ineffective after as few as 3 detonations.
19 When tested with the attenuator in place, the same type of element was able to ~ithstand as 21 many as 25 detonations without significant 22 damage;
23 _ The combined components performed to quench 24 detonations. ~hen tested under similar conditions against several commercially 26 available flame arresters, the new arrester 27 was successful in ~uenching on every run while 28 the other units failed on some runs, as shown 29 later in this specificatlon. Stated otherwise, ~L 3 ~
1 the present arrester performed successfully over 2 the full spsatrum of wava propagation a-t the test 3 conditions; and 4 - In applications where the flame arrester is used in situations where the flow and the potential 6 flame ~ront approach from the same dirsction, the 7 attenuator can serve to protect the element from 8 velocity erosion or degradation ~rom collision by 9 solid objects in the line. VeloGity erosion oacurs when fine particles carried in a high 11 velocity gas ~low strike the element~
12 Broadly stated, the invention is a flame arrester for 13 arresting the advance of a flame front through a pipe line, 14 comprising: a generally tubular housing, said housing being adapted to be connected with the pipe line, whereby the hous:ing forms an integral component thereof, said housing forminy an 17 inlet for a flame front advancing through the pipe line and an 18 outlet, said housing thus forming an open-ended chamber; element 19 means, positioned in the chamber at its outlet end and extending transversely across the chamber, for quenching the flame 21 attempting to pass therethrough; and a generally cup-shaped 22 member, positioned in the chamber in line with and adjacent to 23 but spaced from the inlet, said cup-shaped member being 24 positioned between the inlet and the element means, said member having a solid end wall extending transversely across the inlet 26 and a side wall, said side wall being spaoed inwardly from the 27 longitudinally extending wall of the housing, to ~orm an annular 28 passage therewith, said cup-shaped member having its mouth 29 directed toward the inlet, said cup-shaped member being operative to reaeive the central portion of a detonation wave sntering the 31 chamber and to reflect part of it back into the pipe line.
~ 3 ~
DESCRIPTION OF THE DRAWINGS
2 Figure 1 is a schematic side view showing a pair of 3 flame arresters in use in a typical application, namely in 4 the flare and air lines of an oil storage tank;
Figure 2 is a plot of pressure versus run-up 6 distance for a typical pressure profile generated in a burn 7 down a pipe line in accordance with Figure 13, said burn 8 involving both deflagration and detonation modes;
9 Figure 3 is a partly broken away side Yiew of one form of the arrester;
11 Figures 4 and 5 are end views of the arrester of 12 Figure 3;
13 Figure 6 is a fully sectional plan view of the 14 arrester of Figure 3, taken along the line A--A;
Figure 7 is a perspective partly-broken-away view 16 of the attenuator or cup-shaped member of Figures 3 and 6;
Figure 8 is a perspective view of a crimped ribbon quenching element, partly broken away to illustrate the 19 quenching channels;
Figure ~ is a sectional side Yiew of an arrester 21 having a preferred form of element consisting o~ a stack of 22 expanded metal sheets;
23 Figure 10 is a perspective Yiew of the element 24 stack of P'igure 9;
Figure 11 is a perspective view showing the element 26 stack of Figure 10 in a partly exploded form;
27 Figure 12 shows a fragment of two superimposed 28 sheets of e~panded metal stacked in alternating orientation, 29 showing the 90 rotation of the diamond-shaped openings;
~31~
1 Figure 13 is a schematic of the test circuit used to 2 develop the data set forth in the Examples;
3 Figures 14a to 14d are fanciful simplified 4 representations of the arrester and the process of detonation arrestment believed to occur in it;
6 Figures 15 and 16 show schematically the identical 7 arresters, one with attenuator and one without, used to develop 8 the data of Example 1;
9 Figure 17 shows schematically a preferred arrester having an attenuator formed with a bent back side wall;
11 Figure 18 shows schematically an arrester, having a 12 single element segment and provided with a flat plate attenuator, 13 used to develop the data of Example II;
14 Figure 19 shows another alternative form of arrester;
and 16 Figure 20 shows schematically an arrester identical to 17 that of Figure 17 except that the attenuator does not have the 18 bent back side wall, said arresters of Figures 17 and 20 being 19 used to develop the data of rrable V.
DESCRIPTION OF T~IE PREFERRED EMBODIMENT
21 In General 22 The flame arrester 1 comprises a generally tubular housing 23 2, a quenching element 3, and a cup-shaped member or cup 4, rrhe 24 housing 2 is adapted to be connected into a pipe llne 5 to form a flow component thereof. The element 3 and cup 4 are positioned 26 within the housing 2.
~ 3 ~
1 The ~ouslng 2 The housing 2 is a multi-component assembly which 3 consists of a flanged upstream end member 6, a tubular middle 4 member 7 (made up of rings), and a downstream flange member 8. ("upstream" and lldownstream" refer to the direction of 6 flow of the gas passing through the line 5.) 7 ~he upstream end member 6 forms a central bore or 8 passage g for communication with the bore of the upstream end g of the pipe line 5. It will be noted that the member 6 is outwardly flared, so that the diameter of the bore 9 is 11 greater than that of the pipe line 5~ ~he member 6 also 12 forms suitable openings around its periphery for receiving 13 threaded tie rods lO which, in cooperation with nuts ll, hold 14 the members 6, 7, 8 together.
The downstream flange member 8 also forms 16 peripheral openings for receiving the tie rcds lO. ~he 17 member 8 forms a central threaded bore or flame inlet 12 18 which enables the member to be screwed onto the threaded 19 downstream end of the pipe line 5. This bore 12 forms the flame front inlet for the arrester l.
21 When the three members 6, 7 , 8 are assembled using 22 the tie rods lO and nuts ll, the housing 2 forms an open-23 ended internal chamber 13, which provides a gas flow passage 24 through the unit when it is connected into the pipe line 5.
The diameter of this chamber 13 is greater than or expanded 26 relative to the diameter of the pipe line bore.
~ 3 ~
1The Quenchin~ Element 2The quenching element 3 is positioned in the 3upstream end of the housing chamber 13.
4In the embodiment shown in Figure 6, the element 3 5comprises upstream and downstream rings 14 and crossbars 15 6holding four discrete element segments 16 and spacers 17 7positioned between them in end-to-end format.ion. Each 8element segment 16 has a conventional spiral-wound crimped 9ribbon 18 wound around a core 19 and contained within a ring 10~0 which is part of the housing middle member 7. The solid 1lmaterial for "matrix"~ of the rib~on 18 forms a multiplicity 12of small width, elongate, discrete channels 21. ~he channels 1321 extend in the direction of the longitudinal axis of the 14housing chamber 13. The width or diameter of these channels 1521 is selected to ~e smaller than the quenching diameter, 16when determined in accordance with standard industry practice 17for the conditions involved.
18It will be noted that the spacers 17 maintain a 19slight gap 22 between each element segment 16. These gaps 22 20provide expansion zones for gas in the channels 21 and lead 21to turbulent flow of that gas.
22A preferred form of quenching element is shown in 23Figures 9 - 1~. This element comprises a stack 30 of sheets 2431 of expanded metal forming a multiplicity of diamond-25`shaped channels 32. ~he sheets 31 are oriented in 26alternating fashion so that the major dimension of the 27channels 32 of one sheet 31 is crosswise to th`e majvr 28dimension of the channels of the next sheet. Stated 29otherwise, each sheet 31 is rotated 90 relative to the next i 3 ~
1 sheet in alternating fashion. This is particularly shown in 2 Figure 12.
3 Ring-like end plates 33 are provided at each end of the 4 stack 30. Nut and bolt assemblies 34 sxtend through the e~d plates 33 and sheets 31 and hold the stack 30 to~ether. The tie 6 rods 10 also extend through the assembly and clamp it against the 7 inner shoulder 35 of the upstream end member 6.
8 l'he Attenuator 9 The attenuator comprises a cup-shaped member or cup 4 having a solid end wall 41 and a tubular side wall 42. The cup 11 4 is fixed in place in line with and adjacent to the flame inlet 12 12. More particularly, threaded rods 43 extend through the cup 13 end wall 41 and flange member 8. Spacers 44 cooperate with the 14 wall 41 and member 8 to fix the cup 4 in place.
As shown, the side wall 42 of the cup 4 is inwardly 16 spaced from the longitudinal wall of the housing middle member 17 7. There is thus formed an annular passage 45 therebetween. The 18 mouth 4a of the cup 4 is directed toward the ~lame front inlet 19 12. It will also be noted that the rim 46 of the cup 4 is spaced a short distance (the "stand-off") from the downstream flange 21 member 8. The annular passage 45 communicates with the stand-22 off space 47 to form an L-shaped path past the cup 4. It will 23 further be noted that the diameter of the bore 48 of the cup 4 24 is greater than the diameter of the flame inlet 12. Stated otherwise, the cup 4 encircles the flame inlet 12.
26 Before describing the observed operation of the present 27 arrester, it is useful to describe the nature of a 1 3 ~
1 de~onation wave. To applicant's understanding, it comprises 2 three diferent zones or segments. These are: a shock wave, a 3 following induction zone, and then a reaction zone. These ~ones 4 are fancifully illustrated in Figures l~a - d. The shock wave is responsible or the compression and heating of the unburned 6 gas. The induction zone represents the region extending back to 7 the point at which exothermic release begins in the hot, 8 pressurized gas. And the reaction or flame zone represents the 9 region wherein exothermic reaction is initiated and completed.
Applicant's understanding o the process proceeding in 11 the present arrester is as follows:
12 When there is a detonation, the detonation wave 13 advances through the pipe line 5. On entering the chamber 13, 14 the wave expands radially. The strong central portion of the wave proceeds into the bore 48 of the cup 4 and a significant 16 portion is reflected by the cup 4 back down the pipe line. Only 17 the weaker peripheral portion of the shock wave accompanies the 18 flame through the L-shaped passage 47, 45 to the element 3, 19 where the flame is quenched.
The pressure associated with the peripheral portion o~
21 the shock wave that bypasses the attenuator is consiaerably lower 22 than that associated with the central portion. The annular or 23 peripheral portion no longer appears to propagate as a 24 detonation.
Applicants' tests have indicated:
26 - That in the absence of the attenuator, a flame 27 ront in the detonation mode will usually 28 penetrate through the conventionally designed ~31~
1 quenching element and ign.ite gas upstream 2 thereof;
3 - That, when using the same element and test 4 conditions but with the attenuator in place in the arrester , the flame front does not 6 penetrate beyond the arrester and ignite the 7 upstream gas;
8 - That, in the absence of the attenuator, the g element becomes damaged in the course of a few detonation tests; and 11 - That, with the attenuator in place, the same 12 element under the same test conditions, is not 13 damaged.
14 The invention is supported and illustrated by the following examples:
16 Example 1 17 This example shows that a flame arrester having an 18 attenuator and a conventional quenching element, in 19 accordance with the invention, succes~fully arrested an air/propane flame front at both deflagration and detonation 21 conditions. The burn runs were carried out in the test 22 assembly shown in Figure 13.
23 Test Conditions:
24 quenching element: aluminum crimped metal ribbon, 0.050 inch crimp 26 height, round spiral 27 wound, 8 inch path 28 length;
~31~
1 do~nstream (burn straight run, 35 feet, 3"
2 end) piping: schedule 80 steel p~pe, 3 threaded to 4 arrester, lO ignition location points tapped 6 into pipe, for use with a 7 spark plug ignitor;
8 housing detail: chamber 7" long with 9 8" diameter;
gas mixture: 4.6% propane-11 air;
12 The test procedure was as follows:
13 ~ _ The propane and air were metered into the 14 down-stream pipe;
- The mixture composition was monitored with a 16 gas chromatograph to ensure propane concentration accuracy;
18 The pipe system was purged with the 19 mixture and ignited. Different runs were ignited at different distances from the 21 arrester. (Ignition location was important to 22 all of these tests. The explosion pressures 23 experienced by the flame arrester tended to 24 increase as the burn distance was increased.
More particularly, starting from the ignition 26 point closest to the flame arrester, the 27 deflagration pressure increased with 28 increasing distance from the flame arrester 29 flame inlet. After a certain point (ignition 1 3 ~
1 location #7), a flame front passed through the 2 deflagration/detonation transition zone with 3 only detonations occurring when longer run-up 4 distan~es were thereafter used.) - Flame arrester failure ti.e. flame propagation 6 on the protected sideJ was determined by flam~
7 ionisation sensor5, as shown in Figure 13.
8 The test results were as follows.
9 Having reference to Figure 1~, there is shown a schematic of an arrester A in accordance with the invention, 1l having a cup-shaped attenuator. The arrester A was 12 repeatedly tested as set forth in Table I on the test circuit 13 of Figure 13 and the flame was quenched on every test.
14 ~ABLE I
Ignition Locations 1 2 3 4 5 6 7 a 9 1 o Number of 16 Ignitions lO lO lO lO lO lO lO 30 lO lO
Number of 17 Failures O O O O O O O I O O O
18 zone of zone of 19 deflagration detonation Having reference to Figure 16, there is shown a 21 schematic of an arrester B otherwise identical to arrester A
22 but absent the attenuator. It was only tested for 23 detonations and failed as shown in Table II.
1 3 ~
1 T~sLE II
2 Ignition location ~8 8 3 Number of ignitions 3 5 4 Number of failures two separate tests 6 The attenuation of impingin~ shock waves was 7 verified u~ing quick response pressure transducers located as 8 sho~n on Figure 13. The ~trength of the inlet shock was 9 determined by pressure measurement Pl on the inlet pipe immediately prior to entry into the flame arrester. The 11 atten~ated pressure P2 was measured just before the quenching 12 elementO Typical results were as follows:
13 ~ABLE III
Ignition LocationPl(psigJ P2 (p9ig) #10 410 18 16 #8 710 350 17 Example II
18 This example compares burn test xun results when an 19 arrester havin~ a flat disc, in accordance with Fiyure 1~, was u~ed. With the flat disc in place as the attcnu~tor~ the 21 results were a~ follows:
23 Ignition location:#10 24 Number of ignition~: 5 Number of failures: 5 ~9 ~3~l~a~
I Alternative Embodimen~s 2 An improved embodiment of the attenuator is 3 illustrated in Figure 17. In this embodiment, the sidewal.l 4 60 of the cup 61 i3 partly turned back to create an annular confined zone 62 for trapping a periphe~al portion of tAe 6 ~hock ~ave. The arrester of ~gure l7 corresponded wlth 7 that of Figure 20, except for tha shape of the attenuator.
8 ~he modi~ied entrance or mouth of this c1'p i~proves 9 quenching of detonations. This was ~1emonstrated by severe condition runs initiated from the ignition location (#lO) 11 most distant from the arrester and having a flame accelerator 12 in the line. The results of testing two arresters, shown in 13 Figures l7 and 20, were as follows:
ArresterIgnftion Number of Number of Desiqn~ocation ~qnitions Failures 16 Figure 17 #lO lO 0 17 Figure 20 #lO 5 3 18 Figure lg shows another al~ernative form of 1~ arrester.
More particularly, Figure l9 shows an arrester 70 21 having a tubular housing 71 closed at its upper end by a wall 22 72. A cylindrical element 73 i~ created by wrapping coiled 23 expanded metal 7~ around a support spool 75-. The spool 75 24 ha~ structural support bars 76 that run parallel to its axis.
The expanded metal diamonds are all oriented in the same 26 direction throughout the depth of the element 73. The cup 77 27 is situ~ted in the space 78 formed by the hollo~ spool 7~.
28 The mouth 79 of the cup 77 is open towaxd the flame inlet 80.
1 311 ~~r~
l In this configuration, the cup 77 act~ to reduce ~ the amount of pressure piling that results from the 3 reflection of the incoming shock wave from the hou~ing end 4 wall 72.
7 Flame arresters are commonly employed in pipe lines 8 where the possibility of a backflash exists.
g sackflash can occur where there is present a combination of three factors, namely: a flow of a flammable 11 air/hydrocarbon gas mixture; confinement of the mixture 12 within a pipe or other structure; and means for igniting the 13 gas mixture. A typical example exists in~the case of a flare 14 line extending from an oilfield storage tank. A flammable gas mixture flows from the tank head-space through the line 16 to a flare stack having an outlet to the atmosphere. The 17 mixture leaving the flare stack outlet is normally kept lit.
18 If the flow velocity at the stack is not sufficiently high, 19 the flame can "backflash" or burn upstream through the pipe line. If the flame front reaches the tank, the latter can 21 explode.
22 As stated, flame arresters have long been emplaced 23 in such lines to snuff out or quench the flame front before 24 it reaches an installation (such as the storage tank) where serious harm could be done.
26 Commonly, a flame arrester comprises a flanged 27 tubular housing which is connected into the line to form an 28 integral component thereof. An "element" is positioned 1 3 ~
1 witAin the bore or chamber of t~e ho~sing to extend 2 transversely fully across the bore diameter.
3 The element functions to quench the ~lame ront.
4 In structure, the element usually comprises a matrix haring a multiplicity of small diameter, elongate 6 channels extending therethrough in the direction of the pipe 7 axis. The matrix usually consists of metal. One typical 8 element, for example, comprises a long flat sheet of g aluminum, referred to as the "core". A second similar sheet is crimped in sawtooth fashion and the apexes of the crimps 1l are in contact with the upper surface of the core sheet. The 12 product is then spirally wound to produce a cylindrical 13 element. An element of this type is commonly referred to as 14 a "spiral wound crimped ribbon" element.
As stated, the channels of the element are minute 16 in width or diameter. Nore specifically, the channel 17 diameter is selected to be stnaller than the "quenching 18 diameter". The quenching diameter is the largest diameter at 19 which a flame within the channel would be extinguished under static flow conditions. The determination of the quenching 21 diameter is commonly carried out in the industry in 22 accordance with the practice outlined in "Progress iJl 23 Combustion Science and Technology", Potter, A.E. Jr., Volume 24 1, pages 145-181 (1960).
In principle then, a flame arrester element is 26 provided with small enough channels, established by 27 determination in accordance with standard industry practice, 28 so that sufficient heat will be removed from a flame, by ~ 3 ~
1 conductance through the matrix material, to cause the flame 2 to be extinguished.
3 Unfortunately, in practice, flame arresters do from 4 time to time fail to arrest the flame and explosions do occur as a result, even though they have been designed in 6 accordance with established ~nd industry-accepted practice.
7 The reason for failure, in applicant 19 view, is 8 that the conventional flame arresters are only capable of 9 coping with a limited part of the spectrum of flame propagation conditions to which they may be exposed, when ll used outside existing standards.
12 Flame propagation can occur in two modes, 13 deflagration and detonation.
14 Deflagration is a combustion wave that propagates by t~e transfer of heat and mass to the unburned gas ahead of 16 it. Associated flame front overpressures can range from O to 17 10 or 20 times the initial value (which is commonly 18 atmospheric pressure). Flame velocities are usually subsonic l9 for deflagrations.
Detonation is a combustion wave that propagates by 21 shock compression~induced ignition. Detonations travel 22 supersonically, with Mach numbers of 5 to 10. Detonation 23 overpressures typically reach 15 to 50 times the initial 24 value.
Under a suitable and complex combination of 26 circumstances (including gas composition, length of run from 27 the ignition source, and flame front turbulence-creating 28 factors such as bends and the likeJ, an advancing flame front 29 can accelerate and change from the deflagration mode to the 1 detonation mode. Detonation is evidenced by a rapid and sharp 2 escalation in the pressure accompanying the flame front, said 3 peak pressurewave being in spaced relationship in front of 4 the flame front. A typical pressure/distance plo-t based on a burn invol~ing detonation in a pipe is set forth in Figure 2, 6 following below, and shows the spectrum of pressure change 7 that occurs as a flame front transition takes place between modes.
9 When flame propagation incurs detonation, two undesirable results can occur, namely:
11 _ combustion may be initiated on the protected 12 or upstream side of a conventionally designed 13 element; and 14 - the element may be structurally damaged and thereafter lose some of its arresting 16 capability.
17 These problems associated with detonation have been 18 acknowledged in the prior art literature.
19 In reviewing the literature, applicant noted two different theories of interest given to explain the failure 21 of arresters when exposed to detonation. One theory 22 suggested that the high pressure of detonation would propPl 23 hot gas through the channels at such high velocity that the 24 conventionally designed element would be incapable of cooling the gas sufficiently. On reaching the upstream end of the 26 element, the still-hot gas would combine with the unburned 27 gas and heat it so that spontaneous ignition would occur. The 28 other theory suggested that the high pressure would densify 29 the flammable gas mixture in the channels so that flame :~ 3 ~
1 advancing through the channels would create so much heat that 2 the matrix heat sink would be incapa~le of preventing the 3 flame from reaching the upstream end of the channels.
4 Two modifications of an arrester element readily suggest themselves from these theories, as a means for coping 6 with the high pressure failures. More particularly, one 7 could:
8 - reduce the width of the channels; or 9 - further elongate the channels;
lo to thereby increase the heat-removal capability of the 11 element.
12 Reducing the channel width or diarneter is a 13 solution of only limited applicability or practicality. As 14 the channel diameter is reduced, the pressure drop across the element increases. Choking a vent line in this fashion is 1~ undesirable. So that leaves elongation of the channels as an 7 avenue to explore.
3 Applicant constructed and tested an element having 19 a channel length 16 times that of a commercially available element designed in accordance with conventional practice.
21 When subjected to detonation conditions, this extended 22 element still failed over a significant portion of the flame 23 propagation spectrum. Thus channel elongation does not 24 appear to solve the problem of failure at high pressure, at least in a practical and feasible fashion.
26 Another possible modification for the element has 27 been suggested in the prior art, to improve quenching 28 capability. This involves providing channels which are 29 tortuous in configuration and have alternating sections of ~ 3 ~
1 expanded and reduced diameter. Channels of this design cause 2 the flame front to move turbulently.
3 Applicant tested elements having such turbulence-4 creating channels and found that they do provide improved quenching. However, when subjected to the high pressures 6 approaching or accompanying detonation conditions, the 7 elements still failed with some regularity.
8 So there is still a need for a flame arrester which 9 is improved with respect to handling the full spectrum or range of flame propagation conditions, including detonation.
12 In accordance with the invention, a detonation 13 attenuator is provided within the housing of a flame 4 arrester. ~he attenuator is positioned in front of the quenching element, to receive and reflect part of the centra7 16 portion of the detonation wave back into the pipe. Only a 17 portion of the detonation wave passes around the attenuator 18 and accompanies the flame to the element. By incorporating 19 an attenuator of successful deslgn , an arrester is prorided which has heen tested and shown to be much improved in coping 21 with a full spectrum of flame propagation conditions~.
22 The modified flame arrester involves, in 23 combination:
24 - A housing whose internal chamber has a greater cross-sectional area than that of the pipe 26 line~ so there is expansion of the shock 27 wave/flame front as it enters the chamber; and ~ 3 ~
1 - A generally cup-shaped attenuator or member, 2 positioned in line with and adjacent to the 3 housing flame front inlet, for receiving and 4 reflecting part of the detonation wave back down the pipe. The attenuator side wall is 6 inwardly spaced from tAe lonqitudinal wall of 7 the housing to thereby form an annular 8 passage connecting the flame front inlet with g the quenching element. The peripheral portion of the shock wave/flame front train passes 11 through this passage to the element, wherein 12 the flame is quenched.
13 The combination has the following advantages:
14 - The element lS protected by the attenuator from structural damage from detonation, to a 16 much improved extent. In test runs without an 17 attenuator, the element was rendered 18 ineffective after as few as 3 detonations.
19 When tested with the attenuator in place, the same type of element was able to ~ithstand as 21 many as 25 detonations without significant 22 damage;
23 _ The combined components performed to quench 24 detonations. ~hen tested under similar conditions against several commercially 26 available flame arresters, the new arrester 27 was successful in ~uenching on every run while 28 the other units failed on some runs, as shown 29 later in this specificatlon. Stated otherwise, ~L 3 ~
1 the present arrester performed successfully over 2 the full spsatrum of wava propagation a-t the test 3 conditions; and 4 - In applications where the flame arrester is used in situations where the flow and the potential 6 flame ~ront approach from the same dirsction, the 7 attenuator can serve to protect the element from 8 velocity erosion or degradation ~rom collision by 9 solid objects in the line. VeloGity erosion oacurs when fine particles carried in a high 11 velocity gas ~low strike the element~
12 Broadly stated, the invention is a flame arrester for 13 arresting the advance of a flame front through a pipe line, 14 comprising: a generally tubular housing, said housing being adapted to be connected with the pipe line, whereby the hous:ing forms an integral component thereof, said housing forminy an 17 inlet for a flame front advancing through the pipe line and an 18 outlet, said housing thus forming an open-ended chamber; element 19 means, positioned in the chamber at its outlet end and extending transversely across the chamber, for quenching the flame 21 attempting to pass therethrough; and a generally cup-shaped 22 member, positioned in the chamber in line with and adjacent to 23 but spaced from the inlet, said cup-shaped member being 24 positioned between the inlet and the element means, said member having a solid end wall extending transversely across the inlet 26 and a side wall, said side wall being spaoed inwardly from the 27 longitudinally extending wall of the housing, to ~orm an annular 28 passage therewith, said cup-shaped member having its mouth 29 directed toward the inlet, said cup-shaped member being operative to reaeive the central portion of a detonation wave sntering the 31 chamber and to reflect part of it back into the pipe line.
~ 3 ~
DESCRIPTION OF THE DRAWINGS
2 Figure 1 is a schematic side view showing a pair of 3 flame arresters in use in a typical application, namely in 4 the flare and air lines of an oil storage tank;
Figure 2 is a plot of pressure versus run-up 6 distance for a typical pressure profile generated in a burn 7 down a pipe line in accordance with Figure 13, said burn 8 involving both deflagration and detonation modes;
9 Figure 3 is a partly broken away side Yiew of one form of the arrester;
11 Figures 4 and 5 are end views of the arrester of 12 Figure 3;
13 Figure 6 is a fully sectional plan view of the 14 arrester of Figure 3, taken along the line A--A;
Figure 7 is a perspective partly-broken-away view 16 of the attenuator or cup-shaped member of Figures 3 and 6;
Figure 8 is a perspective view of a crimped ribbon quenching element, partly broken away to illustrate the 19 quenching channels;
Figure ~ is a sectional side Yiew of an arrester 21 having a preferred form of element consisting o~ a stack of 22 expanded metal sheets;
23 Figure 10 is a perspective Yiew of the element 24 stack of P'igure 9;
Figure 11 is a perspective view showing the element 26 stack of Figure 10 in a partly exploded form;
27 Figure 12 shows a fragment of two superimposed 28 sheets of e~panded metal stacked in alternating orientation, 29 showing the 90 rotation of the diamond-shaped openings;
~31~
1 Figure 13 is a schematic of the test circuit used to 2 develop the data set forth in the Examples;
3 Figures 14a to 14d are fanciful simplified 4 representations of the arrester and the process of detonation arrestment believed to occur in it;
6 Figures 15 and 16 show schematically the identical 7 arresters, one with attenuator and one without, used to develop 8 the data of Example 1;
9 Figure 17 shows schematically a preferred arrester having an attenuator formed with a bent back side wall;
11 Figure 18 shows schematically an arrester, having a 12 single element segment and provided with a flat plate attenuator, 13 used to develop the data of Example II;
14 Figure 19 shows another alternative form of arrester;
and 16 Figure 20 shows schematically an arrester identical to 17 that of Figure 17 except that the attenuator does not have the 18 bent back side wall, said arresters of Figures 17 and 20 being 19 used to develop the data of rrable V.
DESCRIPTION OF T~IE PREFERRED EMBODIMENT
21 In General 22 The flame arrester 1 comprises a generally tubular housing 23 2, a quenching element 3, and a cup-shaped member or cup 4, rrhe 24 housing 2 is adapted to be connected into a pipe llne 5 to form a flow component thereof. The element 3 and cup 4 are positioned 26 within the housing 2.
~ 3 ~
1 The ~ouslng 2 The housing 2 is a multi-component assembly which 3 consists of a flanged upstream end member 6, a tubular middle 4 member 7 (made up of rings), and a downstream flange member 8. ("upstream" and lldownstream" refer to the direction of 6 flow of the gas passing through the line 5.) 7 ~he upstream end member 6 forms a central bore or 8 passage g for communication with the bore of the upstream end g of the pipe line 5. It will be noted that the member 6 is outwardly flared, so that the diameter of the bore 9 is 11 greater than that of the pipe line 5~ ~he member 6 also 12 forms suitable openings around its periphery for receiving 13 threaded tie rods lO which, in cooperation with nuts ll, hold 14 the members 6, 7, 8 together.
The downstream flange member 8 also forms 16 peripheral openings for receiving the tie rcds lO. ~he 17 member 8 forms a central threaded bore or flame inlet 12 18 which enables the member to be screwed onto the threaded 19 downstream end of the pipe line 5. This bore 12 forms the flame front inlet for the arrester l.
21 When the three members 6, 7 , 8 are assembled using 22 the tie rods lO and nuts ll, the housing 2 forms an open-23 ended internal chamber 13, which provides a gas flow passage 24 through the unit when it is connected into the pipe line 5.
The diameter of this chamber 13 is greater than or expanded 26 relative to the diameter of the pipe line bore.
~ 3 ~
1The Quenchin~ Element 2The quenching element 3 is positioned in the 3upstream end of the housing chamber 13.
4In the embodiment shown in Figure 6, the element 3 5comprises upstream and downstream rings 14 and crossbars 15 6holding four discrete element segments 16 and spacers 17 7positioned between them in end-to-end format.ion. Each 8element segment 16 has a conventional spiral-wound crimped 9ribbon 18 wound around a core 19 and contained within a ring 10~0 which is part of the housing middle member 7. The solid 1lmaterial for "matrix"~ of the rib~on 18 forms a multiplicity 12of small width, elongate, discrete channels 21. ~he channels 1321 extend in the direction of the longitudinal axis of the 14housing chamber 13. The width or diameter of these channels 1521 is selected to ~e smaller than the quenching diameter, 16when determined in accordance with standard industry practice 17for the conditions involved.
18It will be noted that the spacers 17 maintain a 19slight gap 22 between each element segment 16. These gaps 22 20provide expansion zones for gas in the channels 21 and lead 21to turbulent flow of that gas.
22A preferred form of quenching element is shown in 23Figures 9 - 1~. This element comprises a stack 30 of sheets 2431 of expanded metal forming a multiplicity of diamond-25`shaped channels 32. ~he sheets 31 are oriented in 26alternating fashion so that the major dimension of the 27channels 32 of one sheet 31 is crosswise to th`e majvr 28dimension of the channels of the next sheet. Stated 29otherwise, each sheet 31 is rotated 90 relative to the next i 3 ~
1 sheet in alternating fashion. This is particularly shown in 2 Figure 12.
3 Ring-like end plates 33 are provided at each end of the 4 stack 30. Nut and bolt assemblies 34 sxtend through the e~d plates 33 and sheets 31 and hold the stack 30 to~ether. The tie 6 rods 10 also extend through the assembly and clamp it against the 7 inner shoulder 35 of the upstream end member 6.
8 l'he Attenuator 9 The attenuator comprises a cup-shaped member or cup 4 having a solid end wall 41 and a tubular side wall 42. The cup 11 4 is fixed in place in line with and adjacent to the flame inlet 12 12. More particularly, threaded rods 43 extend through the cup 13 end wall 41 and flange member 8. Spacers 44 cooperate with the 14 wall 41 and member 8 to fix the cup 4 in place.
As shown, the side wall 42 of the cup 4 is inwardly 16 spaced from the longitudinal wall of the housing middle member 17 7. There is thus formed an annular passage 45 therebetween. The 18 mouth 4a of the cup 4 is directed toward the ~lame front inlet 19 12. It will also be noted that the rim 46 of the cup 4 is spaced a short distance (the "stand-off") from the downstream flange 21 member 8. The annular passage 45 communicates with the stand-22 off space 47 to form an L-shaped path past the cup 4. It will 23 further be noted that the diameter of the bore 48 of the cup 4 24 is greater than the diameter of the flame inlet 12. Stated otherwise, the cup 4 encircles the flame inlet 12.
26 Before describing the observed operation of the present 27 arrester, it is useful to describe the nature of a 1 3 ~
1 de~onation wave. To applicant's understanding, it comprises 2 three diferent zones or segments. These are: a shock wave, a 3 following induction zone, and then a reaction zone. These ~ones 4 are fancifully illustrated in Figures l~a - d. The shock wave is responsible or the compression and heating of the unburned 6 gas. The induction zone represents the region extending back to 7 the point at which exothermic release begins in the hot, 8 pressurized gas. And the reaction or flame zone represents the 9 region wherein exothermic reaction is initiated and completed.
Applicant's understanding o the process proceeding in 11 the present arrester is as follows:
12 When there is a detonation, the detonation wave 13 advances through the pipe line 5. On entering the chamber 13, 14 the wave expands radially. The strong central portion of the wave proceeds into the bore 48 of the cup 4 and a significant 16 portion is reflected by the cup 4 back down the pipe line. Only 17 the weaker peripheral portion of the shock wave accompanies the 18 flame through the L-shaped passage 47, 45 to the element 3, 19 where the flame is quenched.
The pressure associated with the peripheral portion o~
21 the shock wave that bypasses the attenuator is consiaerably lower 22 than that associated with the central portion. The annular or 23 peripheral portion no longer appears to propagate as a 24 detonation.
Applicants' tests have indicated:
26 - That in the absence of the attenuator, a flame 27 ront in the detonation mode will usually 28 penetrate through the conventionally designed ~31~
1 quenching element and ign.ite gas upstream 2 thereof;
3 - That, when using the same element and test 4 conditions but with the attenuator in place in the arrester , the flame front does not 6 penetrate beyond the arrester and ignite the 7 upstream gas;
8 - That, in the absence of the attenuator, the g element becomes damaged in the course of a few detonation tests; and 11 - That, with the attenuator in place, the same 12 element under the same test conditions, is not 13 damaged.
14 The invention is supported and illustrated by the following examples:
16 Example 1 17 This example shows that a flame arrester having an 18 attenuator and a conventional quenching element, in 19 accordance with the invention, succes~fully arrested an air/propane flame front at both deflagration and detonation 21 conditions. The burn runs were carried out in the test 22 assembly shown in Figure 13.
23 Test Conditions:
24 quenching element: aluminum crimped metal ribbon, 0.050 inch crimp 26 height, round spiral 27 wound, 8 inch path 28 length;
~31~
1 do~nstream (burn straight run, 35 feet, 3"
2 end) piping: schedule 80 steel p~pe, 3 threaded to 4 arrester, lO ignition location points tapped 6 into pipe, for use with a 7 spark plug ignitor;
8 housing detail: chamber 7" long with 9 8" diameter;
gas mixture: 4.6% propane-11 air;
12 The test procedure was as follows:
13 ~ _ The propane and air were metered into the 14 down-stream pipe;
- The mixture composition was monitored with a 16 gas chromatograph to ensure propane concentration accuracy;
18 The pipe system was purged with the 19 mixture and ignited. Different runs were ignited at different distances from the 21 arrester. (Ignition location was important to 22 all of these tests. The explosion pressures 23 experienced by the flame arrester tended to 24 increase as the burn distance was increased.
More particularly, starting from the ignition 26 point closest to the flame arrester, the 27 deflagration pressure increased with 28 increasing distance from the flame arrester 29 flame inlet. After a certain point (ignition 1 3 ~
1 location #7), a flame front passed through the 2 deflagration/detonation transition zone with 3 only detonations occurring when longer run-up 4 distan~es were thereafter used.) - Flame arrester failure ti.e. flame propagation 6 on the protected sideJ was determined by flam~
7 ionisation sensor5, as shown in Figure 13.
8 The test results were as follows.
9 Having reference to Figure 1~, there is shown a schematic of an arrester A in accordance with the invention, 1l having a cup-shaped attenuator. The arrester A was 12 repeatedly tested as set forth in Table I on the test circuit 13 of Figure 13 and the flame was quenched on every test.
14 ~ABLE I
Ignition Locations 1 2 3 4 5 6 7 a 9 1 o Number of 16 Ignitions lO lO lO lO lO lO lO 30 lO lO
Number of 17 Failures O O O O O O O I O O O
18 zone of zone of 19 deflagration detonation Having reference to Figure 16, there is shown a 21 schematic of an arrester B otherwise identical to arrester A
22 but absent the attenuator. It was only tested for 23 detonations and failed as shown in Table II.
1 3 ~
1 T~sLE II
2 Ignition location ~8 8 3 Number of ignitions 3 5 4 Number of failures two separate tests 6 The attenuation of impingin~ shock waves was 7 verified u~ing quick response pressure transducers located as 8 sho~n on Figure 13. The ~trength of the inlet shock was 9 determined by pressure measurement Pl on the inlet pipe immediately prior to entry into the flame arrester. The 11 atten~ated pressure P2 was measured just before the quenching 12 elementO Typical results were as follows:
13 ~ABLE III
Ignition LocationPl(psigJ P2 (p9ig) #10 410 18 16 #8 710 350 17 Example II
18 This example compares burn test xun results when an 19 arrester havin~ a flat disc, in accordance with Fiyure 1~, was u~ed. With the flat disc in place as the attcnu~tor~ the 21 results were a~ follows:
23 Ignition location:#10 24 Number of ignition~: 5 Number of failures: 5 ~9 ~3~l~a~
I Alternative Embodimen~s 2 An improved embodiment of the attenuator is 3 illustrated in Figure 17. In this embodiment, the sidewal.l 4 60 of the cup 61 i3 partly turned back to create an annular confined zone 62 for trapping a periphe~al portion of tAe 6 ~hock ~ave. The arrester of ~gure l7 corresponded wlth 7 that of Figure 20, except for tha shape of the attenuator.
8 ~he modi~ied entrance or mouth of this c1'p i~proves 9 quenching of detonations. This was ~1emonstrated by severe condition runs initiated from the ignition location (#lO) 11 most distant from the arrester and having a flame accelerator 12 in the line. The results of testing two arresters, shown in 13 Figures l7 and 20, were as follows:
ArresterIgnftion Number of Number of Desiqn~ocation ~qnitions Failures 16 Figure 17 #lO lO 0 17 Figure 20 #lO 5 3 18 Figure lg shows another al~ernative form of 1~ arrester.
More particularly, Figure l9 shows an arrester 70 21 having a tubular housing 71 closed at its upper end by a wall 22 72. A cylindrical element 73 i~ created by wrapping coiled 23 expanded metal 7~ around a support spool 75-. The spool 75 24 ha~ structural support bars 76 that run parallel to its axis.
The expanded metal diamonds are all oriented in the same 26 direction throughout the depth of the element 73. The cup 77 27 is situ~ted in the space 78 formed by the hollo~ spool 7~.
28 The mouth 79 of the cup 77 is open towaxd the flame inlet 80.
1 311 ~~r~
l In this configuration, the cup 77 act~ to reduce ~ the amount of pressure piling that results from the 3 reflection of the incoming shock wave from the hou~ing end 4 wall 72.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A flame arrester for arresting the advance of a flame front through a pipe line, comprising:
a generally tubular housing, said housing being adapted to be connected with the pipe line, whereby the housing forms an integral component thereof, said housing forming an inlet for a flame front advancing through the pipe line and an outlet, said housing thus forming an open-ended chamber;
element means, positioned in the chamber at its outlet end and extending transversely across the chamber, for quenching the flame attempting to pass therethrough; and a generally cup-shaped member, positioned in the chamber in line with and adjacent to but spaced from the inlet, said cup-shaped member being positioned between the inlet and the element means, said member having a solid end wall extending transversely across the inlet and a side wall, said side wall being spaced inwardly from the longitudinally extending wall of the housing, to form an annular passage therewith, said cup-shaped member having its mouth directed toward the inlet, said cup-shaped member being operative to receive the central portion of a detonation wave entering the chamber and to reflect part of it back into the pipe line.
a generally tubular housing, said housing being adapted to be connected with the pipe line, whereby the housing forms an integral component thereof, said housing forming an inlet for a flame front advancing through the pipe line and an outlet, said housing thus forming an open-ended chamber;
element means, positioned in the chamber at its outlet end and extending transversely across the chamber, for quenching the flame attempting to pass therethrough; and a generally cup-shaped member, positioned in the chamber in line with and adjacent to but spaced from the inlet, said cup-shaped member being positioned between the inlet and the element means, said member having a solid end wall extending transversely across the inlet and a side wall, said side wall being spaced inwardly from the longitudinally extending wall of the housing, to form an annular passage therewith, said cup-shaped member having its mouth directed toward the inlet, said cup-shaped member being operative to receive the central portion of a detonation wave entering the chamber and to reflect part of it back into the pipe line.
2. The flame arrester as set forth in claim 1 wherein:
the width of the mouth of the cup-shaped member is greater than the width of the housing inlet, whereby the cup-shaped member encircles the inlet.
the width of the mouth of the cup-shaped member is greater than the width of the housing inlet, whereby the cup-shaped member encircles the inlet.
3. A flame arrester for arresting the advance of a flame front through a pipe line, comprising:
a generally tubular housing, said housing being adapted to be connected with the pipe line whereby the housing forms an integral component thereof, said housing forming an inlet for a flame front advancing through the pipe line, said housing further forming an open-ended chamber of expanded diameter relative to the pipe line with which it is to be used;
element means positioned in the housing at its outlet end and extending transversely fully across the housing chamber, for quenching the flame attempting to pass therethrough, said element means comprising a matrix forming a multiplicity of discrete channels extending therethrough generally in the direction of the longitudinal axis of the housing, each such channel having a width less than the diameter required for quenching a flame front in the deflagration mode; and detonation attenuating means for receiving the central portion of a detonation wave entering the chamber and reflecting it, said means being positioned in the chamber at its inlet end and comprising a generally cup-shaped member having its mouth directed toward the inlet, said cup-shaped member having its side wall inwardly spaced from the longitudinally extending wall of the housing to form an annular passage therewith, the width of the mouth of the cup-shaped member being greater than the width of the inlet whereby the cup-shaped member encircles the inlet, the first end of the cup-shaped member being spaced from the adjacent end wall of the housing, whereby a peripheral portion of the flame front may enter the annular passage and reach the element means.
a generally tubular housing, said housing being adapted to be connected with the pipe line whereby the housing forms an integral component thereof, said housing forming an inlet for a flame front advancing through the pipe line, said housing further forming an open-ended chamber of expanded diameter relative to the pipe line with which it is to be used;
element means positioned in the housing at its outlet end and extending transversely fully across the housing chamber, for quenching the flame attempting to pass therethrough, said element means comprising a matrix forming a multiplicity of discrete channels extending therethrough generally in the direction of the longitudinal axis of the housing, each such channel having a width less than the diameter required for quenching a flame front in the deflagration mode; and detonation attenuating means for receiving the central portion of a detonation wave entering the chamber and reflecting it, said means being positioned in the chamber at its inlet end and comprising a generally cup-shaped member having its mouth directed toward the inlet, said cup-shaped member having its side wall inwardly spaced from the longitudinally extending wall of the housing to form an annular passage therewith, the width of the mouth of the cup-shaped member being greater than the width of the inlet whereby the cup-shaped member encircles the inlet, the first end of the cup-shaped member being spaced from the adjacent end wall of the housing, whereby a peripheral portion of the flame front may enter the annular passage and reach the element means.
4. The flame arrester as set forth in claim 1 wherein:
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
5. The flame arrester as set forth in claim 2 wherein:
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
6. The flame arrester as set forth in claim 3 wherein:
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
the element comprises a stack of expanded metal sheets, each such sheet having a multiplicity of generally diamond-shaped openings having long and short widths, the sheets being alternately juxtapositioned so that a sheet has its opening long dimension rotated at about 90° relative to the next adjacent sheet.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000587033A CA1311409C (en) | 1988-12-23 | 1988-12-23 | Flame arrester having detonation-attenuating means |
| AU47036/89A AU622961B2 (en) | 1988-12-23 | 1989-12-20 | Flame arrester having detonation-attenuating means |
| EP89313508A EP0375455A3 (en) | 1988-12-23 | 1989-12-22 | Flame arrester |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000587033A CA1311409C (en) | 1988-12-23 | 1988-12-23 | Flame arrester having detonation-attenuating means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1311409C true CA1311409C (en) | 1992-12-15 |
Family
ID=4139368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000587033A Expired - Lifetime CA1311409C (en) | 1988-12-23 | 1988-12-23 | Flame arrester having detonation-attenuating means |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0375455A3 (en) |
| CA (1) | CA1311409C (en) |
Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5165484A (en) * | 1991-09-17 | 1992-11-24 | Chaput Victor B | Oil well fire extinguisher having oil jet dispersing screens |
| TW271407B (en) * | 1993-03-29 | 1996-03-01 | Sean Hsian Wei Cheng | |
| DE4438797C1 (en) * | 1994-10-18 | 1996-03-07 | Rmg Gaselan Regel & Mestechnik | Fitting secure against detonation for pipes |
| DE19536292C2 (en) * | 1995-09-29 | 1997-09-25 | Leinemann Gmbh & Co | Method and device for reducing a detonation in a container or piping system |
| DE19818572C1 (en) * | 1998-04-25 | 1999-11-11 | Leinemann Gmbh & Co | Process for rendering a detonation front harmless and detonation protection |
| GB9906669D0 (en) * | 1999-03-24 | 1999-05-19 | Marvac Limited Ag | Improved detonation flame arrester |
| AT408839B (en) | 1999-04-14 | 2002-03-25 | Hoerbiger Ventilwerke Gmbh | FLAME LOCK |
| DE19957836B4 (en) | 1999-11-25 | 2004-05-27 | RMG - Gaselan Regel + Meßtechnik GmbH | Method and device for damping the pressure surge on flame arresters during detonations |
| DE19957837C2 (en) * | 1999-11-25 | 2001-11-15 | Rmg Gaselan Regel & Mestechnik | Method and device for damping the pressure surge at flame arresters in the event of detonations |
| DE10112957B4 (en) | 2001-03-17 | 2005-12-22 | Leinemann Gmbh & Co. | Flame arrester arrangement |
| US6699035B2 (en) * | 2001-09-06 | 2004-03-02 | Enardo, Inc. | Detonation flame arrestor including a spiral wound wedge wire screen for gases having a low MESG |
| DE202006017508U1 (en) | 2006-11-15 | 2007-02-08 | Rembe Gmbh | Blast pressure discharge mechanism for use in container, has modular rack, which holds wall, where bars are arranged between base and cover units of rack and are inserted and detachably fixed in retainer openings |
| DE102014116149A1 (en) * | 2014-11-06 | 2016-05-12 | R. Stahl Schaltgeräte GmbH | Flame-proofing filter of a number of layer sequences as well as arrangements of flameproof filters and their use |
| US10286241B2 (en) * | 2017-03-28 | 2019-05-14 | The Boeing Company | Combustion arrester quantification systems and methods |
| US10543387B2 (en) | 2017-03-28 | 2020-01-28 | The Boeing Company | Combustion arrester test systems and methods |
| CN110013631B (en) * | 2018-01-09 | 2024-04-05 | 中国石油化工股份有限公司 | Flame arrester capable of monitoring flame retarding condition |
| DE102018116576B3 (en) * | 2018-07-09 | 2019-11-07 | Oberland Mangold Gmbh | Flame arrestor and process for its preparation |
| CN110393876B (en) * | 2019-08-05 | 2024-05-31 | 清华大学 | Fireproof device for lithium ion battery |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR26558E (en) * | 1922-03-09 | 1924-02-01 | Safety device preventing the explosion of receptacles containing flammable liquids or gases | |
| DE482406C (en) * | 1926-12-07 | 1929-09-12 | Werner Handellsgesellschaft | A breakdown fuse consisting of a gravel pot and a siphon-like liquid seal |
| GB368680A (en) * | 1929-08-30 | 1932-03-10 | Wolf Otto | Dry return shock safety device of assembled corrugated metal bodies for autogeous welding torches |
| US1960043A (en) * | 1931-04-18 | 1934-05-22 | Protectoseal Co | Attachment for combustible gas conduits |
| DE1429088A1 (en) * | 1963-06-27 | 1968-12-12 | Neumann Dr Ing Jan | Impervious capillary protection for adjusting the flame in a pipeline |
| DE2436206A1 (en) * | 1974-07-26 | 1977-08-04 | Erben Des Smetanca Vladimi Die | Explosion preventing pipe insert - has tubular shell reinforced with longitudinal partitions andremovable middle part |
-
1988
- 1988-12-23 CA CA000587033A patent/CA1311409C/en not_active Expired - Lifetime
-
1989
- 1989-12-22 EP EP89313508A patent/EP0375455A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0375455A3 (en) | 1990-08-29 |
| EP0375455A2 (en) | 1990-06-27 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |