EP0283690B1 - Piège à flammes et procédé pour sa fabrication - Google Patents

Piège à flammes et procédé pour sa fabrication Download PDF

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Publication number
EP0283690B1
EP0283690B1 EP19880101880 EP88101880A EP0283690B1 EP 0283690 B1 EP0283690 B1 EP 0283690B1 EP 19880101880 EP19880101880 EP 19880101880 EP 88101880 A EP88101880 A EP 88101880A EP 0283690 B1 EP0283690 B1 EP 0283690B1
Authority
EP
European Patent Office
Prior art keywords
pieces
rod
tube
shim
arrestor
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
Application number
EP19880101880
Other languages
German (de)
English (en)
Other versions
EP0283690A3 (en
EP0283690A2 (fr
Inventor
Alan R. Gaul
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dresser Industries Inc
Original Assignee
Dresser Industries Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Dresser Industries Inc filed Critical Dresser Industries Inc
Publication of EP0283690A2 publication Critical patent/EP0283690A2/fr
Publication of EP0283690A3 publication Critical patent/EP0283690A3/en
Application granted granted Critical
Publication of EP0283690B1 publication Critical patent/EP0283690B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • This invention relates to a precisely manufactured flame arrestor and to a simple, economical method of manufacture that achieves the precise tolerances required in an arrestor to provide a flameproof path.
  • Flame arrestors are used in pneumatic control devices to provide a flameproof path for the pneumatics into and out of a control or instrument. Flame arrestors provide a restricted pneumatic passage over an extended length such that a flame cannot propagate through the passage.
  • a sintered metal arrestor has been commonly used; however, recently adopted European standards no longer permit the use of this type of flame arrestor.
  • Another type is a Lisk arrestor which is comprised of layers of crimped and flat sheet metal that are wrapped together and held in a case by a rivet.
  • Other types include the parallel plate types that usually consist of flat plates with a slot ground into the plate to a depth equal to the maximum gap allowed for the length of the flame path. The plates are then stacked and bonded together at the unground area to form a series of parallel flame retardant paths.
  • This type of construction is quite expensive due to the grinding of the slot, and the arrestors are more bulky due to the solid area that supports the gap and forms the bond area.
  • Another type of flame arrestor would be a gear shaped rod that is pressed into a tube with the flameproof path provided between the gear teeth. This type of arrestor would be quite expensive as it requires the machining of the fine gear teeth, and it would provide a restricted flow area. These types of flame arrestors are expensive to make and required fine machining of the various parts.
  • the present invention provides a method of manufacturing a flame arrestor wherein the spacing and tolerances are critical.
  • the present invention teaches a method of manufacturing a flame arrestor comprising the steps of: using a multiplicity of precision ground stock pieces (10,20), spacing the pieces (10,20) with a shim (12) that is of such a thickness that the spacing between the pieces (10,20) provided by the shim (12) is within the necessary tolerances to provide a barrier to the propagation of a flame through the arrestor, welding the pieces together, and removing the shim (12) from between the pieces (10,20) to leave a gap (14) between the pieces (10,20) such that the gap (14) is within the tolerances necessary to provide a flameproof path through the arrestor.
  • the method taught by the present invention is used to construct a rod and tube type flame arrestor.
  • a precision ground rod and tube are used such that the rod will fit inside the tube, and when held concentrically by the shim, it provides a radial gap within the required tolerances for a flameproof path.
  • the rod is welded to the tube and the assembly is heated to dissolve the shim.
  • the method taught by the present invention may be used to produce various types and sizes of flame arrestors.
  • the invention also relates to a flame arrestor which comprises: a multiplicity of precision ground stock pieces (10,20) a removable shim (12) used to space the pieces generally concentrically to create a gap (14) that allows air flow between the pieces (10,20) when the shim (12) is removed but such spacing is within tolerances to create a flame barrier through the arrestor; and the pieces (10,20) being welded at such points as to hold the pieces (10,20) securely together when the shim (12) is removed.
  • the present invention relates to a flame arrestor and method of manufacturing the same that is economical and easy to machine and to assemble while maintaining the precise tolerances necessary to make the arrestor flameproof.
  • the invention relates to flame arrestors that can be used in pneumatic control devices to prevent the propagation of a flame.
  • the invention relates to a rod and tube type flame arrestor, but the method of manufacturing can also be applied to other types of arrestors such as the parallel plate type.
  • One embodiment of the present invention is a method for making a rod and tube type flame arrestor.
  • the dimensions of the rod and tube to be used in the invention must be such that the diameter of the rod is less than the inner diameter of the tube, and the difference between the diameter of the rod and the inner diameter of the tube is within the required tolerances for a flameproof path. This difference includes both the diameter difference and radial difference when the rod is held almost concentrical within the tube.
  • Precision ground stock is used for the rod and tube with the rod being precision ground on the outer surface and the tube being precision ground on the inner surface.
  • the rod 10 is prepared as shown in FIGURE 1 with a shim 12 wrapped circumferentially around rod 10 near both ends, or alternatively in the middle, leaving gaps 14 in the shim to allow weld gases to escape.
  • the shim is preferably of a material that will decompose when heated in a nonoxidizing environment or dissolve in a solvent. Most preferably, the shim is a plastic tape.
  • the shim 12 is wrapped around rod 10 in such a manner as to leave a free weld zone 16 in the center of the surface of rod 10. Rod 10, with the shim attached, is then inserted inside tube 20.
  • the shim 12 is of such a thickness in relation to the diameter difference between rod 10 and the inside of tube 20 that when the rod with the shim attached is inserted into the tube, the rod is held practically concentric inside the tube by the shim 12.
  • the tube 20 is then welded, preferably using an electron beam welder 22, to rod 10 at two spots 32 in the free weld zone 16 that are preferably about 180° apart.
  • the welding may be done in the center as illustrated in Figure 2 or at the ends of the rod and tube.
  • a cross-sectional view along the line 3-3 as shown in FIGURE 3 shows the two welds 32 in the middle section of the assembly about 180° apart.
  • the shim is removed by one of several methods.
  • the assembly may be heated in a nonoxidizing environment such as hydrogen, nitrogen, argon or even a vacuum to decompose the shim.
  • Another method of removing the shim would be to immerse the assembly in a solvent including organic solvents and acids.
  • the welded assembly is heated in a hydrogen atmosphere at 1200°F for 20 minutes to decompose the shim 12.
  • the assembly then may be ultrasonically cleaned to remove any residue. This leaves the rod 10 held nearly concentrically within tube 20 by the welds 32 such that the spacing between the rod and the tube allows for pneumatic flow but is within the critical diameter and radial gap tolerances necessary to meet prescribed standards to provide a flameproof path.
  • FIGURE 4 shows an end view of the assembled rod and tube flame arrestor with a uniform circumferential air gap 34 between rod 10 and tube 20.
  • the assembly is designed such that gap 34 is less than the maximum allowable radial and diameter differences as known in the art for providing a flameproof path across the length of the arrestor.
  • the critical feature is the spacing between the pieces such that it allows for the flow of gas through the device but prevents the propagation of a flame.
  • the volume flow of the gas and the length of the flame arrestor determine the critical spacing requirements.
  • European Standards provide that for a volume of 400 cubic centimeters and a rod and tube arrestor having a length greater than .374 inches (9.5 mm), the diameter difference between the rod and the tube can be only .00591 inches (.15 mm) maximum, and the radial gap cannot be greater than .00394 inches (.10 mm). (European Standards EN50018).
  • a rod of length .4 inches is precision ground to a diameter of .1842 ⁇ .0001 inches (4,679 ⁇ 0,003 mm).
  • the inside diameter of a tube is reamed and honed to .1898 ⁇ .0002 inches (4,679 ⁇ 0,003 mm). This maintains a diameter difference equal to or less than .00591 inches (0,150 mm) as required by EN50018.
  • the tube is cut at a length of .402 inches (10,211 mm) to insure a flame path the full length of the rod.
  • a plastic tape with a thickness of .0025 inches (0,0635 mm) and width of .080 inches (2,032 mm) serves as the shim and is wrapped circumferentially around the rod near both ends of the rod leaving a gap of .04 inches (1,016 mm) in the wrap to allow weld gases to escape.
  • a shim of this thickness will hold the rod practically concentric within the tube as a diameter gap of only .0009 inches (0,0223 mm) exists between the tube, the shim and the rod.
  • With a radial gap standard of .00394 inches (0.10 mm) the tolerance in the concentricity of the rod within the tube is .001 inches (0,0254 mm).
  • the selected shim therefore, adequately spaces the rod within the tube. Holding the rod to this degree of concentricity within the tube is critical in order to provide the maximum amount of flow area between the rod and tube while still meeting the radial gap requirements.
  • the radial gap between the rod and tube is .0028 ⁇ .0002 inches (0,071 ⁇ 0,005 mm) if the rod was held perfectly concentric within the tube.
  • a diameter gap of .00091 inches (0,0231 mm) with the shim inserted allows the rod to be held within the tube such that the maximum radial gap that could occur is less than the .00394 inches (0,10 mm) maximum radial gap allowed by the European Standards.
  • the tube is electron beam welded to the rod at two spots in the center of the tube, or alternatively at the ends, approximately 180° apart. The assembly is then heated to a temperature sufficient to dissolve the plastic shim.
  • the use of a removable shim in the method of manufacture just described provides an economical means of holding the rod concentrically within the tube to the required degree of tolerance.
  • the present invention may be used to construct a nonconcentric rod and tube flame arrestor, but a concentric construction is preferred as the concentric configuration provides a greater flow area for the same radial gap requirement. If a nonconcentric configuration in which the rod contacted one side of the tube was used, the diameter of the rod would have to be increased from the concentric rod diameter in order to meet the radial gap requirement. A larger rod provides less flow area between the rod and the tube requiring a greater pressure to achieve the same flow rate as a concentric configuration allows.
  • the flow rate for the concentric construction is more than three times greater than the flow rate for the nonconcentric arrestor with the larger rod for the same pressure drop across the arrestors.
  • the present invention therefore, provides a means for positioning the rod within the tube that allows for a smaller diameter rod to be used thereby allowing a greater gas flow rate through the flame arrestor.
  • This method of manufacture can also be used to construct various types and sizes of flame arrestors.
  • precision ground plates are alternatively stacked with sheets of the shim material. Spaces may be left in the shim to provide a weld zone.
  • the plates may be welded together as each successive plate is stacked on the underlying plate, or the plates may be welded at the ends after all the plates have been stacked together.
  • the assembly then may be heated to remove the shim. Again, the shim must not have a thickness greater than that allowed gap for a flameproof path through a parallel plate arrestor.
  • the method of inserting a shim, welding the pieces together and removing the shim allows for precision manufacture of flame arrestors.
  • the method of manufacturing taught by the present invention achieves these tolerances in an economical and simple manner without requiring the fine machining of many parts.

Landscapes

  • Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Mechanical Coupling Of Light Guides (AREA)
  • Gas Burners (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Laser Beam Processing (AREA)
  • Welding Or Cutting Using Electron Beams (AREA)
  • Thermistors And Varistors (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Filtering Materials (AREA)

Claims (18)

  1. Procédé de fabrication d'un organe d'arrêt de flamme, comprenant les étapes suivantes :
       l'utilisation de plusieurs pièces initiales usinées avec précision (10, 20),
       l'espacement des pièces (10, 20) avec une épaisseur telle que la distance comprise entre les pièces (10, 20) correspond aux tolérances nécessaires à la formation d'une barrière s'opposant à la propagation d'une flamme dans l'organe d'arrêt,
       le soudage des pièces les unes aux autres,
    caractérisé par l'utilisation d'une cale (12) pour l'espacement des pièces (10, 20) avant le soudage, et
       la suppression de la cale (12) de l'espace formé entre les pièces (10, 20) afin qu'il reste entre les pièces (10, 20) un espace (14) tel qu'il correspond aux tolérances nécessaires à la réalisation d'un trajet empêchant la propagation des flammes dans l'organe d'arrêt.
  2. Procédé selon la revendication 1, dans lequel les pièces initiales usinées avec précision comportent une tige (10) et un tube (20), la tige (10) et le tube (20) ayant des dimensions telles que la tige (10) peut être introduite dans le tube (20) et la différence entre le diamètre de la tige (10) et le diamètre interne du tube (20) est inférieure à la différence maximale de diamètre qui permet la formation d'un trajet empêchant la propagation des flammes dans la tige (10) et le tube (20).
  3. Procédé selon la revendication 2, dans lequel l'espacement des pièces (10, 20) par la cale (12) est réalisé par enveloppement de la tige (20) circonférentiellement d'une cale amovible (12) avec conservation d'une zone libre (16) de soudage, la cale amovible (12) ayant une épaisseur telle qu'elle permet l'introduction de la tige (10) et son maintien presque concentriquement dans le tube (20).
  4. Procédé selon la revendication 3, dans lequel la cale amovible (12) comprend deux pièces de calage (12), une pièce étant enroulée circonférentiellement autour de la tige (10) à chacune des extrémités, les deux pièces de calage enroulées (12) laissant un espace à un emplacement au moins.
  5. Procédé selon la revendication 1, dans lequel le soudage des pièces (10, 20) est réalisé à l'aide d'un appareil de soudage à faisceau d'électrons.
  6. Procédé selon la revendication 1, dans lequel le soudage des pièces est réalisé en deux points qui sont séparés de 180° de façon générale.
  7. Procédé selon la revendication 1, dans lequel le soudage des pièces est réalisé près du milieu du tube (20).
  8. Procédé selon la revendication 1, dans lequel le soudage des pièces est réalisé près des extrémités du tube (20).
  9. Procédé selon la revendication 1, dans lequel la cale (12) est éliminée par chauffage de la tige (10) et du tube (20) en atmosphère non oxydante.
  10. Procédé selon la revendication 1, dans lequel la cale (12) est éliminée par dissolution dans un solvant.
  11. Procédé selon la revendication 1, dans lequel la cale (12) est un ruban de matière plastique.
  12. Organe d'arrêt de flamme comprenant :
       plusieurs pièces initiales usinées de précision (10, 20),
       ces pièces (10, 20) étant maintenues à distance afin qu'il reste un espace (14) permettant la circulation d'air entre les pièces (10, 20), cet espace formé entre les pièces correspondant aux tolérances permettant la création d'une barrière s'opposant à la propagation des flammes dans l'organe d'arrêt,
       les pièces (10, 20) étant soudées en des points assurant le maintien ferme des pièces (10, 20) en coopération l'une avec l'autre, caractérisé en ce qu'une cale amovible est utilisée pour l'espacement des pièces avant le soudage.
  13. Organe d'arrêt de flamme selon la revendication 12, dans lequel les pièces (10, 20) comprennent une tige (10) usinée avec précision et un tube (20) ayant une surface interne usinée avec précision, la tige (10) ayant un diamètre inférieur au diamètre interne du tube (20), mais la différence de diamètre entre la tige (10) et le tube (20) est inférieure à la différence maximale permise pour la formation d'un trajet empêchant la propagation des flammes le long du tube (20) tout en permettant une circulation pneumatique entre la tige (10) et le tube (20) lorsque la tige (10) est introduite dans le tube (20).
  14. Organe d'arrêt de flamme selon la revendication 12, dans lequel la cale (12) est enroulée circonférentiellement autour de la tige (10) à chaque extrémité de la tige (10) et délimite un espace à un emplacement au moins.
  15. Organe d'arrêt de flamme selon la revendication 12, dans lequel la cale (12) est un ruban de matière plastique.
  16. Organe d'arrêt de flamme selon la revendication 12, dans lequel la cale (12) peut être éliminée de l'organe d'arrêt de flamme par chauffage de la cale (12) en atmosphère non oxydante.
  17. Organe d'arrêt de flamme selon la revendication 12, dans lequel la cale (12) peut être éliminée de l'organe d'arrêt de flamme par dissolution de la cale dans un solvant.
  18. Organe d'arrêt de flamme selon la revendication 13, dans lequel la tige (10) et le tube (20) sont soudés en deux points proches du milieu longitudinal du tube (20), les deux points étant séparés de 180° environ.
EP19880101880 1987-03-25 1988-02-09 Piège à flammes et procédé pour sa fabrication Expired - Lifetime EP0283690B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US2991687A 1987-03-25 1987-03-25
US29916 2001-12-31

Publications (3)

Publication Number Publication Date
EP0283690A2 EP0283690A2 (fr) 1988-09-28
EP0283690A3 EP0283690A3 (en) 1989-08-23
EP0283690B1 true EP0283690B1 (fr) 1992-08-19

Family

ID=21851559

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880101880 Expired - Lifetime EP0283690B1 (fr) 1987-03-25 1988-02-09 Piège à flammes et procédé pour sa fabrication

Country Status (8)

Country Link
EP (1) EP0283690B1 (fr)
JP (1) JPS6458273A (fr)
AU (1) AU607741B2 (fr)
BR (1) BR8801239A (fr)
CA (1) CA1299036C (fr)
DE (1) DE3873796T2 (fr)
ES (1) ES2033949T3 (fr)
MX (1) MX172293B (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5752812A (en) * 1996-02-28 1998-05-19 Delaware Capital Formation, Inc. Vapor recovery pump

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB363628A (en) * 1930-09-12 1931-12-14 Arthur Stephenson A device for the prevention of back fires in gas apparatus
FR1136632A (fr) * 1955-11-07 1957-05-16 Panergon Dispositif de protection contre l'incendie

Also Published As

Publication number Publication date
ES2033949T3 (es) 1993-04-01
CA1299036C (fr) 1992-04-21
AU607741B2 (en) 1991-03-14
BR8801239A (pt) 1988-10-25
JPS6458273A (en) 1989-03-06
EP0283690A3 (en) 1989-08-23
AU1238488A (en) 1988-09-29
DE3873796T2 (de) 1993-02-04
DE3873796D1 (de) 1992-09-24
EP0283690A2 (fr) 1988-09-28
MX172293B (es) 1993-12-13

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