CA1299036C - Flame arrestor and method of manufacture - Google Patents
Flame arrestor and method of manufactureInfo
- Publication number
- CA1299036C CA1299036C CA000562354A CA562354A CA1299036C CA 1299036 C CA1299036 C CA 1299036C CA 000562354 A CA000562354 A CA 000562354A CA 562354 A CA562354 A CA 562354A CA 1299036 C CA1299036 C CA 1299036C
- Authority
- CA
- Canada
- Prior art keywords
- rod
- tube
- shim
- pieces
- flame
- 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 - Fee Related
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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
Landscapes
- Health & Medical Sciences (AREA)
- Public Health (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Gas Burners (AREA)
- Welding Or Cutting Using Electron Beams (AREA)
- Mechanical Coupling Of Light Guides (AREA)
- Laser Beam Processing (AREA)
- Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
- Thermistors And Varistors (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Filtering Materials (AREA)
Abstract
FLAME ARRESTOR AND METHOD OF MANUFACTURE
ABSTRACT
The invention teaches a method of spacing the elements of a flame arrestor and securing that spacing in a simple and economical manner. A shim is used to space the elements, the elements are welded together And the shim is removed. This leaves a controlled flow path between the elements but the spacing is such to prevent the propagation of a flame through the arrestor.
ABSTRACT
The invention teaches a method of spacing the elements of a flame arrestor and securing that spacing in a simple and economical manner. A shim is used to space the elements, the elements are welded together And the shim is removed. This leaves a controlled flow path between the elements but the spacing is such to prevent the propagation of a flame through the arrestor.
Description
FLAME ARRESTOR AND METHOD OF MANVFACTURE
TECHNICAL FIELD
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.
.
:
'~
- ~L2~9V3~i BACRGR~VND
Flame arresto rs are used in pneumatic control devices o provide a flameproof path for the pneumatics into and out of a control or instrument.
Flame arrectors provide a restricted pneumatic passage over an extended length such that a flame cannot propagate through the passage.
Several types of arrestors ~re known in the art. A sintered metal ~rrestor 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 typæs 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 ~tacked and bonded together at the un~round Aarea to-form ~ series-of-parallel flame retardant paths. This type o~ construction is quite expensive due to the grinding of the slot, and the arrestors are more bul~y 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 ~lameproof path provided between the qear teeth. ThLS type of arrestor would be quite expensive as it requires the machining of the fine gear teeth, and it would 3~ provide a restricted flow area. ~hese types of flame arrestors are expensive to make and require fine machining of the various parts.
Since the allowable gap dimensions in small flame arrestors are very small, manufacture of a small flame arrestor is particularly difficult and expensive. muS~ ~ need exists for an easy, economical method of manufacturing precision flame arrestors both small and large that would meet the ~ecessary standards here and abroad.
~Z~036 SUMMARY OF THE INVENTION
The present invention teaches a method of precisely spacing the elements of a flame arrestor and securing that spacing within the required tolerances to provide a flameproof path in pneumatic control devices. The precision ground elements of a flame arrestor are spaced by using a shim between the elements such that the shim spaces the elements within the required flameproof tolerances. The shim is gapped where necessary to allow weld gases to escape. The assembly is welded in appropriate locations to hold the elements securely together. The assembly is then heated so as to burn out or dissolve the shim leaving a controlled flow path between the elements for pneumatic flow. This provides a precision-made flame arrestor that meets the required standards.
According to one embodiment of the invention, 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.
In accordance with one aspect of the invention there is provided a method of manufacturing a flame arrestor which comprises: using a multiplicity of precision ground stock pieces, spacing the pieces with a shim that is of such a thickness that the spacing between the pieces provided by the shim 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 from between the pieces to leave a gap between the pieces such that the gap is within the tolerances necessary to provide a flameproof path through the arrestor.
C~36 4 a In accordance with another aspect of the invention there is provided a flame arrestor construction comprising: a multiplicity of flame arrestor piecesi a removable shim placed between adjoining pieces, said shim being of a thickness so as to create a gap between the pieces that will allow air flow between the pieces when the shim is removed but such gap is within the tolerances needed to prevent the propagation of a flame through the gap; and adjoining pieces being welded together at at least one point, said weld securely holding the pieces together.
~Z~ 6 BRIEF DESCRIPTION OF THE DR~WINGS
For a more complete understanding of the present in~ention and other advantages of it, a Detailed Description is given in conjunction with the accompanying Drawings, in which like reference characters denote like parts in all views and wherein:
FIGURE 1 is An exploded view of a rod and tube flame nrrestor 6howin~ the rod with a shim wrapped ~o circumferentially ~round the rod at each end being inserted into the tube;
FIGURE 2 shows a perspective view of a rod and tube flame arrestor;
FIGVRE 3 shows a longitudinal cross-sectional view along line 3-3 showing a rod welded inside a tube: and FIGURE 4 shows an end view of a rod and tube flame arrestor.
:LZ~C~6 DETPlLED DESCRIPTION
The present invention relates to a flame arrestor ~nd method of manufacturing the same that is economical and easy to machine and to assemble while maintaining the precise tolerances necessary ~o make the arrestor flameproof. The invention relates flame arrestors that can be used in pneumatic control devices ~o prevent ~he propagation of a flame.
Particularly, the invention relates ~o a rod and tube type fl~me arrestor, but the method of manufacturing can also be applied to other types of arrestors such ~s the parallel plate type.
One embodiment of tbe 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 ~uch that the diameter o4 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 dif~erence 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 wrspped cir~umferentially around rod 10 ~ear both ends, or alternatively in the middle, leaving gaps 14 in the shim to allow weld gases to e~cape. 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 i~ a pl~stic ' ~Z9~ 6 tape. me ~him 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 ~him ~ttached, is then inserted inside tube 20. The shim 12 is of such a thickness in relation to the diameter difference between rod 10 and t~e inside of tube 20 that when the rod with the ~him a~tached is inserted into the tube, the rod is held practically c~ncentric inside the tube by the ~him 12.
As shown in FIGURE 2, the tube 20 is then welded, pre~erably using ~n electron beam welder 22, to rod 10 at two spots 32 in the free weld zone 16 that are preferably about 180~ apart. ~Alternatively, the welding may be done in the center as illustrated ~5 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 1B0 apart.
After the welding, the shim is removed by one of several methods. The assembly may be heated in a nonoxidizing environment such ~s hydrogen, nitrogen, argon or even a vacuum to decompose the shim.
Another method of removing the shim woul~ be to immerse the assembly in a solvent includin~ organic solvents and acids. Preferably the welded assembly is heated in a hydrogen atmosphere at 1200-F for 20 minutes t9 decompose the shim 12. The assembly then may be ultrasonically cleAned to remove any residue. This leaves the rod 10 held ne~rly concentrically within tube 20 by the welds 32 such that the spacing between the rod and the tube allows for pneumatic ~low but is within the critical di~meter and radial gap tolerances necessary to meet 8 ~2~9C~
prescribed standards to provide a flameproof path.
- FIGUR~ 4 shows an end view of the assembled rvd and tube flame arrestor with a uniform circumferential air gap 34 between rod 10 and tube 20. The assembly is designed such ~ha~ gap 34 is less than the maximum ~llowable radial and diameter differences as ~nown in the art for providing a flameproof path a~ross the length of the ~rrestor.
In a flame arrestor, ~he critical fea~ure is the spacing between ~he pieces such that it ~llows ~or the flow of gas through the device but prevents the propagation of a flame. The volume flow o~ the gas and the length of the flame arrestor determine the critical spacing requirements. These standards are well known in the industry and are established by regulations in some countries. As one~example, European Standards provide that for a volume of 400 cubic centimeters and a rod and tube arrestor having ~ length grea~er than .374 inches ~9.5 mm), the diameter difference between the rod and the tu~e can -be only .00591 inches (.15 ~m) maximum, nd the radial gap cannot be greater than .00394 in~hes (.10 mm). (European Standards EN50018).
As an example of one construction of t~e invention that meets these precise requirements, a rod of length .4 inches is precision ground to a diameter of .1842 ~ .0001 inchesO The inside diameter of a tube is reamed and honed to o1898 ~
.0002 inches. m is maintains ~ diameter difference equal to or le s than .00591 inches ~s required by EN50018. The tube is cut at a length of .402 inches to ~nsure a flame path the ~ull length of the rod. A
plastic tape with a thickness of .0025 lnches and .
03~j width of .080 inches serves as the ~him and is wrapped circumferen~ially around the rod near both ends of the rod leaving a gap of .04 inches in the wrap to allow weld gases to escape. A shim of this thickness will hold the rod practically concentric within the tube as ~ diameter gap of only ~0009 exists between ~he tube, the shim and ~he rod. With a radial gap standard of .003~4 inches, the tolerance in the concentricity of the rod with~n the tube is .001 inches. The selected shim, therefore, adequately ~paces the rod within the tube. ~olding the rod to this degree of concentrici~y 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. In the construction just mentioned, the radial gap between the rod and tube is .0028 + .0002 inches if the rod was held perfectly concentric within the tube. A
diameter gap of .00091 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 maximum radial gap allowed by the European Standards. To complete the construction, the tube is electron beam welded to the rod at two spots in the center of the tube, or al~ernatively at the ends, approY.imately 180~ apart. The assembly is then heated to a temperature sufficient to dissolve the plastic shim.
Since the llowable gap dimensions are very 3~ small, manufacture of such a small flame ~rrestor usin~ previously known methods is difficult. The present method of manufacture allows for the precise manufacture of even small fl~ame arrestors. As the 10 ~Z~
size of the flame ~rrestor increases, a shim with the appropriate ~hickness ~ay be selected. The inser~ion of a removable shim provides an inexpensive means to temporarily fix ~nd hold the pieces of the flame arrestor to the required precise gap dimensions.
Welding ~he pieces together then penmanently fixes the precise dimensions, and the weld resul~s in only a ~mall area that interferes wi~h the flow ~hrough the arrestor.
1o The u~e of a removable shim in the method of manufacture just described pro~des an economical means of holding ~he rod concentrically within the tube to the required degree of tolerance. The present invention may be used to construct a nonconcentric rod and ~ube flame arrestor, but a concentric construction is preferred as ~he 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 requirementO A larger rod provides less flow area between the rod and the tube requirin~ a greater pressure to achieve the same flow rate as a con~entric configuration allows. Using the same : dimensions and requirements as illustrated above, the flow rate for the concentric construction is more than three times greater than the flow rate for the nonconcentri~arrestor with the larger rod for the ~ame pressure drop acroRs the arrestors~ The present ~nvention, therefore,~provides ~ means for positioning the rod within the tube that allows for a ' .
1 1 12~9~336 smaller di~meter rod to be used thereby allowing a greater gas flow rate through the flame arrestor.
This method of manufacture can also be used ~o construct various types and sizes of flame arrestors. For example, to construct ~ parallel plate type of flame arrestor, precision ground plates are alternatively stacked with sheets of the shim material. Spaces may be lef~ in the shim ~o provide a weld zone. The pl~tes may be welded together as e~ch successive plate i8 stac~ed on the underlying plate, or the plates may be welded nt the ends after all the plates have been stacked together. ~he assembly then may be heated to remove the Yhim.
Again, the shim must not have a thlcknes3 greater 1~ than that allowed gap for ~ 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.
As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing ~rom the teachings of the present invention.
TECHNICAL FIELD
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.
.
:
'~
- ~L2~9V3~i BACRGR~VND
Flame arresto rs are used in pneumatic control devices o provide a flameproof path for the pneumatics into and out of a control or instrument.
Flame arrectors provide a restricted pneumatic passage over an extended length such that a flame cannot propagate through the passage.
Several types of arrestors ~re known in the art. A sintered metal ~rrestor 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 typæs 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 ~tacked and bonded together at the un~round Aarea to-form ~ series-of-parallel flame retardant paths. This type o~ construction is quite expensive due to the grinding of the slot, and the arrestors are more bul~y 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 ~lameproof path provided between the qear teeth. ThLS type of arrestor would be quite expensive as it requires the machining of the fine gear teeth, and it would 3~ provide a restricted flow area. ~hese types of flame arrestors are expensive to make and require fine machining of the various parts.
Since the allowable gap dimensions in small flame arrestors are very small, manufacture of a small flame arrestor is particularly difficult and expensive. muS~ ~ need exists for an easy, economical method of manufacturing precision flame arrestors both small and large that would meet the ~ecessary standards here and abroad.
~Z~036 SUMMARY OF THE INVENTION
The present invention teaches a method of precisely spacing the elements of a flame arrestor and securing that spacing within the required tolerances to provide a flameproof path in pneumatic control devices. The precision ground elements of a flame arrestor are spaced by using a shim between the elements such that the shim spaces the elements within the required flameproof tolerances. The shim is gapped where necessary to allow weld gases to escape. The assembly is welded in appropriate locations to hold the elements securely together. The assembly is then heated so as to burn out or dissolve the shim leaving a controlled flow path between the elements for pneumatic flow. This provides a precision-made flame arrestor that meets the required standards.
According to one embodiment of the invention, 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.
In accordance with one aspect of the invention there is provided a method of manufacturing a flame arrestor which comprises: using a multiplicity of precision ground stock pieces, spacing the pieces with a shim that is of such a thickness that the spacing between the pieces provided by the shim 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 from between the pieces to leave a gap between the pieces such that the gap is within the tolerances necessary to provide a flameproof path through the arrestor.
C~36 4 a In accordance with another aspect of the invention there is provided a flame arrestor construction comprising: a multiplicity of flame arrestor piecesi a removable shim placed between adjoining pieces, said shim being of a thickness so as to create a gap between the pieces that will allow air flow between the pieces when the shim is removed but such gap is within the tolerances needed to prevent the propagation of a flame through the gap; and adjoining pieces being welded together at at least one point, said weld securely holding the pieces together.
~Z~ 6 BRIEF DESCRIPTION OF THE DR~WINGS
For a more complete understanding of the present in~ention and other advantages of it, a Detailed Description is given in conjunction with the accompanying Drawings, in which like reference characters denote like parts in all views and wherein:
FIGURE 1 is An exploded view of a rod and tube flame nrrestor 6howin~ the rod with a shim wrapped ~o circumferentially ~round the rod at each end being inserted into the tube;
FIGURE 2 shows a perspective view of a rod and tube flame arrestor;
FIGVRE 3 shows a longitudinal cross-sectional view along line 3-3 showing a rod welded inside a tube: and FIGURE 4 shows an end view of a rod and tube flame arrestor.
:LZ~C~6 DETPlLED DESCRIPTION
The present invention relates to a flame arrestor ~nd method of manufacturing the same that is economical and easy to machine and to assemble while maintaining the precise tolerances necessary ~o make the arrestor flameproof. The invention relates flame arrestors that can be used in pneumatic control devices ~o prevent ~he propagation of a flame.
Particularly, the invention relates ~o a rod and tube type fl~me arrestor, but the method of manufacturing can also be applied to other types of arrestors such ~s the parallel plate type.
One embodiment of tbe 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 ~uch that the diameter o4 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 dif~erence 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 wrspped cir~umferentially around rod 10 ~ear both ends, or alternatively in the middle, leaving gaps 14 in the shim to allow weld gases to e~cape. 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 i~ a pl~stic ' ~Z9~ 6 tape. me ~him 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 ~him ~ttached, is then inserted inside tube 20. The shim 12 is of such a thickness in relation to the diameter difference between rod 10 and t~e inside of tube 20 that when the rod with the ~him a~tached is inserted into the tube, the rod is held practically c~ncentric inside the tube by the ~him 12.
As shown in FIGURE 2, the tube 20 is then welded, pre~erably using ~n electron beam welder 22, to rod 10 at two spots 32 in the free weld zone 16 that are preferably about 180~ apart. ~Alternatively, the welding may be done in the center as illustrated ~5 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 1B0 apart.
After the welding, the shim is removed by one of several methods. The assembly may be heated in a nonoxidizing environment such ~s hydrogen, nitrogen, argon or even a vacuum to decompose the shim.
Another method of removing the shim woul~ be to immerse the assembly in a solvent includin~ organic solvents and acids. Preferably the welded assembly is heated in a hydrogen atmosphere at 1200-F for 20 minutes t9 decompose the shim 12. The assembly then may be ultrasonically cleAned to remove any residue. This leaves the rod 10 held ne~rly concentrically within tube 20 by the welds 32 such that the spacing between the rod and the tube allows for pneumatic ~low but is within the critical di~meter and radial gap tolerances necessary to meet 8 ~2~9C~
prescribed standards to provide a flameproof path.
- FIGUR~ 4 shows an end view of the assembled rvd and tube flame arrestor with a uniform circumferential air gap 34 between rod 10 and tube 20. The assembly is designed such ~ha~ gap 34 is less than the maximum ~llowable radial and diameter differences as ~nown in the art for providing a flameproof path a~ross the length of the ~rrestor.
In a flame arrestor, ~he critical fea~ure is the spacing between ~he pieces such that it ~llows ~or the flow of gas through the device but prevents the propagation of a flame. The volume flow o~ the gas and the length of the flame arrestor determine the critical spacing requirements. These standards are well known in the industry and are established by regulations in some countries. As one~example, European Standards provide that for a volume of 400 cubic centimeters and a rod and tube arrestor having ~ length grea~er than .374 inches ~9.5 mm), the diameter difference between the rod and the tu~e can -be only .00591 inches (.15 ~m) maximum, nd the radial gap cannot be greater than .00394 in~hes (.10 mm). (European Standards EN50018).
As an example of one construction of t~e invention that meets these precise requirements, a rod of length .4 inches is precision ground to a diameter of .1842 ~ .0001 inchesO The inside diameter of a tube is reamed and honed to o1898 ~
.0002 inches. m is maintains ~ diameter difference equal to or le s than .00591 inches ~s required by EN50018. The tube is cut at a length of .402 inches to ~nsure a flame path the ~ull length of the rod. A
plastic tape with a thickness of .0025 lnches and .
03~j width of .080 inches serves as the ~him and is wrapped circumferen~ially around the rod near both ends of the rod leaving a gap of .04 inches in the wrap to allow weld gases to escape. A shim of this thickness will hold the rod practically concentric within the tube as ~ diameter gap of only ~0009 exists between ~he tube, the shim and ~he rod. With a radial gap standard of .003~4 inches, the tolerance in the concentricity of the rod with~n the tube is .001 inches. The selected shim, therefore, adequately ~paces the rod within the tube. ~olding the rod to this degree of concentrici~y 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. In the construction just mentioned, the radial gap between the rod and tube is .0028 + .0002 inches if the rod was held perfectly concentric within the tube. A
diameter gap of .00091 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 maximum radial gap allowed by the European Standards. To complete the construction, the tube is electron beam welded to the rod at two spots in the center of the tube, or al~ernatively at the ends, approY.imately 180~ apart. The assembly is then heated to a temperature sufficient to dissolve the plastic shim.
Since the llowable gap dimensions are very 3~ small, manufacture of such a small flame ~rrestor usin~ previously known methods is difficult. The present method of manufacture allows for the precise manufacture of even small fl~ame arrestors. As the 10 ~Z~
size of the flame ~rrestor increases, a shim with the appropriate ~hickness ~ay be selected. The inser~ion of a removable shim provides an inexpensive means to temporarily fix ~nd hold the pieces of the flame arrestor to the required precise gap dimensions.
Welding ~he pieces together then penmanently fixes the precise dimensions, and the weld resul~s in only a ~mall area that interferes wi~h the flow ~hrough the arrestor.
1o The u~e of a removable shim in the method of manufacture just described pro~des an economical means of holding ~he rod concentrically within the tube to the required degree of tolerance. The present invention may be used to construct a nonconcentric rod and ~ube flame arrestor, but a concentric construction is preferred as ~he 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 requirementO A larger rod provides less flow area between the rod and the tube requirin~ a greater pressure to achieve the same flow rate as a con~entric configuration allows. Using the same : dimensions and requirements as illustrated above, the flow rate for the concentric construction is more than three times greater than the flow rate for the nonconcentri~arrestor with the larger rod for the ~ame pressure drop acroRs the arrestors~ The present ~nvention, therefore,~provides ~ means for positioning the rod within the tube that allows for a ' .
1 1 12~9~336 smaller di~meter rod to be used thereby allowing a greater gas flow rate through the flame arrestor.
This method of manufacture can also be used ~o construct various types and sizes of flame arrestors. For example, to construct ~ parallel plate type of flame arrestor, precision ground plates are alternatively stacked with sheets of the shim material. Spaces may be lef~ in the shim ~o provide a weld zone. The pl~tes may be welded together as e~ch successive plate i8 stac~ed on the underlying plate, or the plates may be welded nt the ends after all the plates have been stacked together. ~he assembly then may be heated to remove the Yhim.
Again, the shim must not have a thlcknes3 greater 1~ than that allowed gap for ~ 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.
As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing ~rom the teachings of the present invention.
Claims (19)
1. A method of manufacturing a flame arrestor which comprises:
using a multiplicity of precision ground stock pieces, spacing the pieces with a shim that is of such a thickness that the spacing between the pieces provided by the shim is within the necessary tolerances to provide a barrier to the propagation of flame through the arrestor, welding the pieces together, and removing the shim from between the pieces to leave a gap between the pieces such that the gap is within the tolerances necessary to provide a flameproof path through the arrestor.
using a multiplicity of precision ground stock pieces, spacing the pieces with a shim that is of such a thickness that the spacing between the pieces provided by the shim is within the necessary tolerances to provide a barrier to the propagation of flame through the arrestor, welding the pieces together, and removing the shim from between the pieces to leave a gap between the pieces such that the gap is within the tolerances necessary to provide a flameproof path through the arrestor.
2. The method of Claim 1 wherein the multiplicity of precision ground pieces includes a rod and a tube, said rod and tube being dimensioned such that the rod can be inserted inside the tube and the diameter difference between the rod and the inner diameter of the tube is less than the maximum diameter difference that would provide a flameproof path through the rod and tube.
3. The method of Claim 1 wherein the multiplicity of precision ground pieces includes parallel plates.
4. The method of Claim 1 wherein the welding of pieces is done by using an electron beam welder.
5. The method of Claim 1 wherein the shim is removed by decomposing it in a nonoxidizing environment.
6. The method of Claim 1 wherein the shim is removed by dissolving it with a solvent.
7. A method of manufacturing a rod and tube type flame arrestor which comprises:
using a rod with a precision ground outer surface;
using a tube with a precision ground inner surface such that the inner diameter of the tube is greater than the diameter of the rod but the difference between the inner diameter of the tube and the diameter of the rod is less than the maximum tolerances required to provide a flame barrier;
wrapping the rod circumferentially with a removable shim and leaving a free weld zone, said shim being of such a thickness to allow the rod to be inserted and held almost concentrically inside the tube;
inserting the rod inside the tube;
welding the tube to the rod at two points nearly 180°
apart; and removing the shim.
using a rod with a precision ground outer surface;
using a tube with a precision ground inner surface such that the inner diameter of the tube is greater than the diameter of the rod but the difference between the inner diameter of the tube and the diameter of the rod is less than the maximum tolerances required to provide a flame barrier;
wrapping the rod circumferentially with a removable shim and leaving a free weld zone, said shim being of such a thickness to allow the rod to be inserted and held almost concentrically inside the tube;
inserting the rod inside the tube;
welding the tube to the rod at two points nearly 180°
apart; and removing the shim.
8. The method of Claim 7 wherein the welding is performed near the center of the tube, and wherein the shim is wrapped at both ends of the rod.
9. The method of Claim 7 wherein the welding is performed near the ends of the tube.
10. The method of Claim 7 wherein the shim is removed by heating the assembly in a nonoxidizing environment..
11. The method of Claim 7 wherein the shim is removed by dissolving it in a solvent.
12. The method of Claim 7 wherein the shim is a plastic tape.
13. A flame arrestor construction comprising:
a multiplicity of flame arrestor pieces;
a removable shim placed between adjoining pieces, said shim being of a thickness so as to create a gap between the pieces that will allow air flow between the pieces when the shim is removed but such gap is within the tolerances needed to prevent the propagation of a flame through the gap; and adjoining pieces being welded together at at least one point, said weld securely holding the pieces together.
a multiplicity of flame arrestor pieces;
a removable shim placed between adjoining pieces, said shim being of a thickness so as to create a gap between the pieces that will allow air flow between the pieces when the shim is removed but such gap is within the tolerances needed to prevent the propagation of a flame through the gap; and adjoining pieces being welded together at at least one point, said weld securely holding the pieces together.
14. The flame arrestor construction of Claim 13 wherein the multiplicity of pieces includes a precision ground rod and a tube with a precision ground inner surface, said rod having a diameter less than the inner diameter of the tube but the diameter difference between the rod and the tube being less than the maximum difference allowed for the length of said .
tube to achieve a flameproof path.
tube to achieve a flameproof path.
15. The flame arrestor of Claim 13 wherein the shim is composed of a material that will decompose when heated in a non-oxidizing environment.
16. A rod and tube type flame arrestor construction comprising:
a precision ground rod;
a tube that is precision honed on the inner surface and having an inner diameter such that the differences between the diameter of the rod and the inner diameter of the tube are less than the maximum differences allowed to provide a flameproof path over the length of said tube and still allow pneumatic flow between the rod and the tube when the rod is inserted in the tube;
a removable shim being wrapped around at least one portion of said rod;
the rod being inserted inside the tube and centered nearly concentrically;
the rod and tube being welded together in at least one point and the weld being sufficient to hold said rod in relation to said tube when the shim is removed.
a precision ground rod;
a tube that is precision honed on the inner surface and having an inner diameter such that the differences between the diameter of the rod and the inner diameter of the tube are less than the maximum differences allowed to provide a flameproof path over the length of said tube and still allow pneumatic flow between the rod and the tube when the rod is inserted in the tube;
a removable shim being wrapped around at least one portion of said rod;
the rod being inserted inside the tube and centered nearly concentrically;
the rod and tube being welded together in at least one point and the weld being sufficient to hold said rod in relation to said tube when the shim is removed.
17. The flame arrestor construction of claim 16 wherein the shim is a plastic tape.
18. The flame arrestor construction of claim 16 wherein the shim is wrapped circumferentially around the rod at each end and being gapped in at least one place.
19. The flame arrestor construction of claim 16 wherein the rod and tube are welded together at two points near the longitudinal center of the tube with the points being about 180° apart.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2991687A | 1987-03-25 | 1987-03-25 | |
| US029,916 | 1987-03-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1299036C true CA1299036C (en) | 1992-04-21 |
Family
ID=21851559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000562354A Expired - Fee Related CA1299036C (en) | 1987-03-25 | 1988-03-24 | Flame arrestor and method of manufacture |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0283690B1 (en) |
| JP (1) | JPS6458273A (en) |
| AU (1) | AU607741B2 (en) |
| BR (1) | BR8801239A (en) |
| CA (1) | CA1299036C (en) |
| DE (1) | DE3873796T2 (en) |
| ES (1) | ES2033949T3 (en) |
| MX (1) | MX172293B (en) |
Families Citing this family (1)
| 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)
| 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 (en) * | 1955-11-07 | 1957-05-16 | Panergon | Fire protection device |
-
1988
- 1988-02-09 ES ES88101880T patent/ES2033949T3/en not_active Expired - Lifetime
- 1988-02-09 EP EP19880101880 patent/EP0283690B1/en not_active Expired - Lifetime
- 1988-02-09 DE DE19883873796 patent/DE3873796T2/en not_active Expired - Fee Related
- 1988-02-29 AU AU12384/88A patent/AU607741B2/en not_active Ceased
- 1988-03-18 BR BR8801239A patent/BR8801239A/en not_active IP Right Cessation
- 1988-03-24 JP JP6834288A patent/JPS6458273A/en active Pending
- 1988-03-24 CA CA000562354A patent/CA1299036C/en not_active Expired - Fee Related
- 1988-03-25 MX MX1089688A patent/MX172293B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6458273A (en) | 1989-03-06 |
| MX172293B (en) | 1993-12-13 |
| EP0283690A3 (en) | 1989-08-23 |
| BR8801239A (en) | 1988-10-25 |
| EP0283690A2 (en) | 1988-09-28 |
| ES2033949T3 (en) | 1993-04-01 |
| DE3873796T2 (en) | 1993-02-04 |
| AU1238488A (en) | 1988-09-29 |
| AU607741B2 (en) | 1991-03-14 |
| EP0283690B1 (en) | 1992-08-19 |
| DE3873796D1 (en) | 1992-09-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |