FLASHBACK ARRESTOR
A flashback arrestor for use in gas cutting or welding equipment includes a porous body which defines a proximal end portion and a distal end portion and which has a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
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The present disclosure relates to oxy-fuel cutting or welding equipment and more specifically to flashback arrestors for the oxy-fuel cutting or welding equipment.
BACKGROUNDThe statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Oxy-fuel cutting or welding torches generally employ oxygen and a fuel gas, such as acetylene or propane, by way of example, to cut or weld a workpiece. The oxy-fuel torch is generally connected to an oxygen hose that supplies preheat and cutting oxygen, and a fuel gas hose that supplies fuel, to the cutting or welding torch. Preheat oxygen and the fuel gas are mixed in the cutting or welding torch and ignited to provide heat to the workpiece. Cutting oxygen may be added to react with the heated workpiece to initiate a cutting process.
While the oxy-fuel cutting or welding torches have proven to be relatively safe if operated properly, an inherent hazard, known as “flashback”, is present in the process. Flashback can occur when oxygen enters the fuel side of the system or vice versa due to a reverse flow. The mixed gases, if ignited, can cause a flame to retreat into the torch handle or even the gas hoses and can cause an explosion at any point in the system.
One solution to this problem is to install a check valve in each of the oxygen and fuel passageways to allow the oxygen and the fuel to flow in one direction to prevent the reverse flow. Check valves, however, are mechanical devices and may become unreliable when contaminated with dirt or debris, which can cause the check valve to leak. Moreover, the check valves cannot prevent flashback flame from propagating upstream once flashback occurs.
Another solution to this problem is to use a flashback arrestor (FBA). FBAs do not prevent flashback from occurring, but can stop the flashback flame from further propagating beyond the FBA and into the oxygen/fuel hoses or other components in the oxy-fuel cutting or welding system. The FBA generally includes a stainless steel filter that removes heat and free radicals from a flame at a rate that is fast enough to quench the flame and to prevent re-ignition of the hot gas.
The FBAs, however, have the disadvantage of being easily clogged with debris. The stainless steel filter used in a typical FBA is a porous body generally having a pore size of approximately 7 μm (0.000276 inches in diameter), which is about 1/14 the size of a human hair (0.004 inches in diameter). Due to such fine pore size of the filter, FBAs can be easily clogged with debris. Moreover, the FBAs are installed in the oxygen and fuel gas passageways in the torch and can restrict flow of the oxygen and fuel gases due to the fine pore size. Therefore, the torch performance is adversely affected.
SUMMARYIn one form of the present disclosure, a flashback arrestor for use in gas cutting or welding equipment includes a porous body defining a proximal end portion and a distal end portion and having a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
In another form of the present disclosure, a flashback arrestor for use in gas cutting or welding equipment includes a body defining a proximal end portion and a distal end portion and having a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
In still another form of the present disclosure, a device for arresting a flame includes a body having a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
In still another form of the present disclosure, a flashback arrestor for use in gas cutting or welding equipment includes a sintered body and a fitting. The sintered body defines a proximal end portion and a distal end portion and having a plurality of pores. Each of the pores defines a pore size. The fitting is disposed at the proximal end portion. The fitting is sized to fit within a bore of a standard pipe thread. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
In still another form of the present disclosure, an oxy-fuel cutting/welding torch includes a torch body defining a proximal end portion and a distal end portion, an oxygen passageway having an inlet at the proximal end portion, a fuel passageway having an inlet at the proximal end portion, a first flashback arrestor disposed within the oxygen passageway at the proximal end portion, and a second flashback arrestor disposed within the fuel passageway at the proximal end portion. Each of the first and second flashback arrestors defines a body having a proximal end portion and a distal end portion and includes a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
In another form, a device for arresting a flame is provided that comprises a body having a plurality of pores, each of the pores defining a target pore size, wherein the pore size is a function of an initial pressure of a gas mixture and an equivalence ratio of the gas mixture such that the pore size is increased to reduce a size of the body.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. It should also be understood that various cross-hatching patterns used in the drawings are not intended to limit the specific materials that may be employed with the present disclosure. The cross-hatching patterns are merely exemplary of preferable materials or are used to distinguish between adjacent or mating components illustrated within the drawings for purposes of clarity.
Referring to
An O-ring 31 is disposed in an annular groove 32 (shown in
Referring to
In the typical flashback arrestors 10 and 50, the porous bodies 18 and 58 have a pore size of approximately 7 μm. This pore size is based on the indicated pores size from ISO 4003 bubble point testing. Bubble point testing indicates the pore size is based on “capillary theory” and cylindrical capillary tube data. The indicated pore size is related to the bubble point pressure based on Poiseuille's law which incorporates an empirical constant that is a function of the filter material, form, etc. This constant is essentially a capillary shape factor. Therefore, the bubble point testing is typically only a relative comparison for a given element or medium. In various forms, the true pore size is likely 2 to 5 times smaller than that indicated by bubble point test results.
Referring to
Referring to
Referring to
The fittings 152 each include a proximal threaded portion 156, a distal threaded portion 158 and an enlarged portion 160 therebetween. The proximal threaded portion 156 has outer threads for engaging the fuel hose 142 or the oxygen hose 144 (shown in
The check valve 154 is press-fitted inside the bore 168 of the fitting 152 proximate the proximal threaded portion 156 and allows oxygen or fuel gas to flow in one direction, i.e., from the oxygen/fuel gas hoses, through the fittings 152 to the porous bodies 150.
The porous body 150 of the flashback arrestor 130 is, in one form, a cylindrical body and is formed by a sintering process. In one form, the material for the porous body 150 is a stainless steel grade 316. However, it should be understood that a variety of materials having a high thermal conductivity may be employed, including other metallic materials such as nickel, brass, bronze, and alloys thereof, among others.
The porous body 150 defines a proximal end portion 162 and a distal end portion 164 and a bore 166 extending therebetween. The bore 166 of the porous body 150 is in fluid communication with the bore 168 of the fitting 152. The porous body 150, in one form, is press-fit into the distal threaded portion 158 of the fitting 152.
As further shown, the proximal end portion 162 of the porous body 150 has an open end, whereas the distal end portion 164 of the porous body 150 has a closed end with a distal face 168. The porous body 150 defines a plurality of pores. The bore 166 of the porous body 150 is in fluid communication with the fuel gas passageway 138 (shown in
The flashback arrestor 130 may further include a check valve 170 disposed within the fitting 152. The fitting 152 is used to secure the check valve 154 to the torch body 106. Therefore, no O-ring or additional mounting assembly is needed to mount the flashback arrestors 130 to the torch body 106.
Referring to
Referring to
Referring now to
The pores of the porous body of the flashback arrestors 130 and 200 constructed in accordance with the teachings of the present disclosure can be used to arrest both deflagrations and detonations. The pore size of the pores is a function of a detonation cell size λ.
Flashback in an oxy-fuel system is the propagation of combustion that travels in a reverse direction of the normal gas flow. The propagation of combustion undergoes two phases: a deflagration phase and a detonation phase. During the deflagration phase, the flame first enters the torch and progressively increases in velocity. The velocity of the flame during the deflagration phase is at a rate below mach 1 (i.e., subsonic velocity); however, the velocity of the flame continues to increase until it reaches mach 1 (sonic velocity). Once the velocity reaches sonic speed, a deflagration-to-detonation transition (DDT) can occur with associated abnormally high velocities and pressures.
The detonation phase ensues and continues to increase in velocity beyond mach 1 (supersonic velocity). The distance the flame travels during the phase change from deflagration to detonation is known as the induction length. Testing reveals that the induction length is very short and occurs approximately 0.5″ to 0.7″ from the tip end of the torch.
When a detonation phase is reached, a large amount of energy is released and the propagation rate of the combustion process becomes supersonic. Testing reveals that the propagation rate of a detonation can reach 3,000 meters/second.
Referring to
The pore size of the porous body 150 in accordance with the teachings of the present disclosure is determined based on the detonation cell width λ, which is a function of the composition of the mixture, initial temperature and pressure, and the types of the fuel and the oxidizer. The pore size of the porous body 150 can effectively disrupt regeneration of detonation cells to thereby extinguish the flame propagation.
Referring to
Therefore, the target pore size in accordance with the teachings of the present disclosure is based on critical tube diameter data, which is calculated from cell width data for oxy-acetylene worst case initial pressure and stoichiometry conditions. Acetylene (C2H2) is used as the fuel gas in determining the desired pore size of the flashback arrestors because acetylene is the most volatile and has the highest burning velocity. As long as the determined pore size of the flashback arrestors can stop generation of the oxy-acetylene detonation cell, the determined pore size can also stop generation of the detonation cell by a mixture of oxygen and other fuel gases.
Curve fits of these data allow specifying a target cell width or critical tube diameter for a given pressure. The curve fit equation for cell width (A) for oxy-acetylene mixtures with an ER of 2.5 is:
λ=1309.2×(P)−0.907
where: λ=cell width (microns)
-
- P=initial mixture pressure (psia)
The geometry of sintered metal pores is not circular and thus application of the critical tube diameter for a given stoichiometry and initial pressure would not necessarily directly apply. The critical dimension would likely be between the values of cell width (typically applicable to square or rectangular geometries) and cell width divided by Pi (typically applicable to circular geometries). Based on this logic, the critical dimensions (true pore size) for arresting an oxy-acetylene detonation (Equivalence Ratio=2.5) is estimated to be between 16 μm to 49 μm.
The maximum acetylene pressure that is recommended for use in North America is 29.7 psia, whereas Europe and other parts of the world allow acetylene pressure to be used at 37.2 psia. With these parameters, the research and testing result in a determined detonation cell width size of 0.0019″. By dividing the detonation cell width by pi, the critical diameter of 0.0006047″ (or 15.4 μm) is achieved.
As shown in
As shown in
To provide a degree of safety and allow for variances in the manufacture of sintered filters, a pore size in the range of 10-14 μm can be viably used. The lower limit of this range is greater than the pore size of 7 μm in a typical flashback arrestor. The increased pore size of the flashback arrestors of the present disclosure increases flow capacity of the sintered porous body. Due to the increased flow capacity, the physical size of the porous body can be reduced. The reduced size of the porous body allows the distal threaded portion of the fittings, which is used to secure the flashback arrester to the torch body or an add-on safety device, to have a size adapted for a bore of a ¼-18 NPT pipe thread, which is a standard thread in most oxy-fuel torches as a means to join a hose connection to the torch body. As such, the flashback arrestor of the present disclosure can be relatively easily mounted to the bores of most oxy-fuel torches.
Moreover, by installing the filter directly into the bore of the fitting proximate to the proximal threaded portion, the flashback arrestors of the present disclosure can achieve the advantage of material reduction. In addition, the flashback arrestors of the present disclosure are smaller than the typical flashback arrestors and have a simpler design with fewer components. Therefore, the flashback arrestors can reduce manufacturing costs.
The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.
Claims
1. A flashback arrestor for use in gas cutting or welding equipment comprising:
- a porous body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size,
- wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
2. The flashback arrestor according to claim 1, wherein the pore size is between approximately 10 and approximately 16 microns.
3. The flashback arrestor according to claim 1 further comprising a fitting disposed at the proximal end portion, the fitting being adapted to secure the flashback arrestor to the gas cutting or welding equipment.
4. The flashback arrestor according to claim 3, wherein the fitting is sized to fit within a bore of a standard pipe thread.
5. The flashback arrestor according to claim 4, wherein the standard pipe thread is a ¼-18 National Pipe Thread (NPT).
6. The flashback arrestor according to claim 3 further comprising a filter disposed within the fitting.
7. The flashback arrestor according to claim 1, further comprising an end cap secured to a distal end portion of the porous body.
8. The flashback arrestor according to claim 1, wherein the porous body is formed with a sintering process.
9. The flashback arrestor according to claim 1, wherein the pores define passageways through the porous body having irregular shapes.
10. The flashback arrestor according to 1, wherein the sintered body defines a cylindrical geometry.
11. A flashback arrestor for use in gas cutting or welding equipment comprising:
- a body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size,
- wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
12. The flashback arrestor according to claim 11, wherein the body is sintered.
13. The flashback arrestor according to claim 11 further comprising a fitting disposed at the proximal end portion, the fitting being adapted to secure the flashback arrestor to the gas cutting or welding equipment.
14. The flashback arrestor according to claim 13, wherein the fitting is sized to fit within a bore of a standard pipe thread.
15. The flashback arrestor according to claim 13 further comprising a filter disposed within the fitting.
16. The flashback arrestor according to claim 11, wherein the pore size is between approximately 10 and approximately 16 microns.
17. The flashback arrestor according to claim 11, wherein the pore size is a function of an initial pressure of a gas mixture and an equivalence ratio of the gas mixture.
18. The flashback arrestor according to claim 17, wherein the pore size λ is defined by the equation:
- λ=1309.2×(P)−0.907
- wherein P is the initial pressure of a mixture of oxygen and acetylene having an equivalence ratio of about 2.5.
19. A device for arresting a flame comprising:
- a body having a plurality of pores, each of the pores defining a pore size,
- wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
20. The device according to claim 19, wherein the body is sintered.
21. A flashback arrestor for use in gas cutting or welding equipment comprising:
- a sintered body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size;
- a fitting disposed at the proximal end portion, the fitting being sized to fit within a bore of a standard pipe thread,
- wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
22. The flashback arrestor according to claim 21 further comprising a filter disposed within the fitting.
23. The flashback arrestor according to claim 21, wherein the pore size is between approximately 10 and approximately 16 microns.
24. An oxy-fuel cutting/welding torch comprising:
- a torch body defining a proximal end portion and a distal end portion;
- an oxygen passageway having an inlet at the proximal end portion;
- a fuel passageway having an inlet at the proximal end portion;
- a first flashback arrestor disposed within the oxygen passageway at the proximal end portion; and
- a second flashback arrestor disposed within the fuel passageway at the proximal end portion,
- wherein each of the first and second flashback arrestors define a body having a proximal end portion and a distal end portion and comprise a plurality of pores, each of the pores defining a pore size, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
25. The oxy-fuel cutting/welding torch according to claim 24, wherein the bodies of the flashback arrestors are sintered.
26. The oxy-fuel cutting/welding torch according to claim 24 further comprising:
- a first fitting disposed at the proximal end portion of the first flashback arrestor; and
- a second fitting disposed at the proximal end portion of the second flashback arrestor,
- the fittings being adapted to secure the flashback arrestors within the passageways of the oxy-fuel cutting/welding torch.
27. The oxy-fuel cutting/welding torch according to claim 26, wherein the fittings are sized to fit within a bore of a standard pipe thread
28. The oxy-fuel cutting/welding torch according to claim 28 further comprising:
- a first filter disposed within the first fitting; and
- a second filter disposed within the second fitting.
29. The flashback arrestor according to claim 24, wherein the pore size is between approximately 10 and approximately 16 microns.
30. A device for arresting a flame comprising:
- a body having a plurality of pores, each of the pores defining a target pore size,
- wherein the pore size is a function of an initial pressure of a gas mixture and an equivalence ratio of the gas mixture such that the pore size is increased to reduce a size of the body.
31. The device according to claim 30, wherein the target pore size λ is defined by the equation:
- λ=1309.2×(P)−0.907
- wherein P is the initial pressure of a mixture of oxygen and acetylene having an equivalence ratio of about 2.5.
Type: Application
Filed: Jul 30, 2012
Publication Date: Jan 30, 2014
Applicant: Victor Equipment Company (Denton, TX)
Inventors: David A. Pryor (Denton, TX), Nhyanh Duyet Nguyen (Frisco, TX)
Application Number: 13/562,194
International Classification: F23D 14/82 (20060101); F23D 14/54 (20060101);