US20140030666A1

US20140030666A1 - Flashback arrestor

Info

Publication number: US20140030666A1
Application number: US13/562,194
Authority: US
Inventors: David A. Pryor; Nhyanh Duyet Nguyen
Original assignee: Victor Equipment Co
Current assignee: Victor Equipment Co
Priority date: 2012-07-30
Filing date: 2012-07-30
Publication date: 2014-01-30
Also published as: CA2880264A1; WO2014031293A1

Abstract

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.

Description

FIELD

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.

BACKGROUND

The 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.

SUMMARY

In 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.

DRAWINGS

The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is a cross-sectional view of a prior art flashback arrestor mounted internally within a torch body;

FIG. 2 is an exploded view of a prior art flashback arrestor;

FIG. 3 is a cross-sectional view of another prior art flashback arrestor contained in a safety device external to a cutting torch;

FIG. 4 is a top view of an oxy-fuel cutting/welding torch including flashback arresters constructed in accordance with the teachings of the present disclosure;

FIG. 5 is a cross-sectional view of the oxy-fuel cutting/welding torch, taken along line 5-5 of FIG. 4;

FIG. 6 is a cross-sectional view of a flashback arrestor mounted internally within a torch body and constructed in accordance with the teachings of the present disclosure;

FIG. 7 is an exploded view of the flashback arrestor of FIG. 6;

FIG. 8 is a cross-sectional view of another form of a flashback arrestor contained in a safety device external to a cutting torch and constructed in accordance with the teachings of the present disclosure;

FIGS. 9A and 9B are perspective views of another form of the flashback arrestors having end caps and constructed in accordance with the teachings of the present disclosure;

FIG. 10 is a schematic view of detonation cells and shock wave during detonation;

FIG. 11 are graphs of relationships among oxy-acetylene cell width, critical tube diameter and initial pressure;

FIG. 12 is a graph of the relationship between the detonation cell width and the initial pressure when the oxy-acetylene (C₂H₂-O₂) mixture is under stoichiometric condition;

FIG. 13 is a graph of the relationship between the detonation cell width and the initial pressure when the equivalence ratio of the C₂H₂—O₂mixture is 2.5;

FIG. 14 is a graph of the relationship between the detonation cell width and the equivalence ratio of the C₂H₂—O₂mixture;

FIG. 15 is a graph of the relationship between the detonation velocity and the fuel volume % of the C₂H₂—O₂mixture; and

FIG. 16 is graph of the relationship between the detonation velocity and the tube diameter for different oxy-acetylene mixtures.

DETAILED DESCRIPTION

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 FIGS. 1 and 2, a pair of typical flashback arrestors 10 are installed in a torch body 12 of a cutting or welding torch (not shown). The torch body 12 defines an oxygen passageway 14 and a fuel gas passageway 16. The pair of flashback arrestors 10 each includes a porous metal portion 18, a fitting 20, and a check valve 22. The fitting 20 includes a bore 24 in fluid communication with the oxygen passageway 14 or the fuel gas passageway 16. The fitting 20 includes a proximal threaded portion 26 and a distal threaded portion 28. The check valve 22 is disposed in the bore 24 proximate the proximal threaded portion 26. The proximal threaded portion 26 has an outside diameter D1 and functions as a hose connector for connecting to an oxygen or fuel gas hose (not shown). The distal threaded portion 28 engages an inner surface of the torch body 12 to secure the flashback arrestor 10 to the torch body 12 via a threaded connection. The distal threaded portion 28 has an outside diameter D2 which is greater than the outside diameter D1 of the proximal threaded portion 26. An insertion portion 29 is provided proximate the distal threaded portion 28 and inserted into the porous body 18.
An O-ring 31 is disposed in an annular groove 32 (shown in FIG. 2) of the fitting 20. When the fitting 20 is installed in the torch body 12, the O-ring 31 prevents leakage of gas from the oxygen passageway 14 and the fuel gas passageway 16 to outside the flashback arrestors 10. A mounting assembly 36, which includes a mounting plate 38, a washer 40, and a screw 42, is used to secure the flashback arrestors 10 to the torch body 12.
Referring to FIG. 3, another form of typical flashback arrestors 50 are mounted to a pair of add-on devices, i.e., safety devices 52 separate from the cutting/welding torch. The safety devices 52 each include a housing 54 and a bore 56. The flashback arrestor 50 is inserted into the bore 56 of the housing 54 and includes a porous body 58, a bushing 60, and a check valve 62. The housing 54 includes a proximal threaded portion 64, which functions as a hose connector for engaging an oxygen or fuel gas hose. The bushing 60 includes a distal threaded portion 66 for engaging an inner surface of the housing 54 of the safety device 52. An O-ring 68 is provided between the housing 54 and the bushing 60 to prevent leakage of gas to outside the flashback arrestor 50. An adaptor 72, in the form of a hose nipple, has one end inserted into a hose fitting nut 70 and the other end inserted into the bushing 60 to mount the safety device 52 to the hose fitting nut 70. The distal threaded portion 66 of the bushing 60 has an outside diameter D4 greater than the outside diameter D3 of the proximal threaded portion 64 of the add-on device 52.
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 FIGS. 4 and 5, an oxy-fuel cutting/welding torch that includes flashback arrestors constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral 100. The cutting or welding torch 100 includes a torch head 102 and a handle portion 104. The handle portion 104 includes a torch body 106 and a barrel 108. The oxy-fuel cutting/welding torch 100 further includes a preheat fuel tube 112, a preheat oxygen tube 114, and a cutting oxygen tube 116 extending from the torch head 102 to the barrel 108 for supplying fuel gas and preheat/cutting oxygen to the torch head 102. A lever 118 is connected to the torch body 106 for controlling a gas valve 146. A pair of flashback arrestors 130 (only one is shown in FIG. 4) are removably mounted to the torch body 106.
Referring to FIG. 5, the torch head 102 includes a cutting/welding tip 132. The torch body 106 defines a fuel gas bore 134, an oxygen bore 136, a fuel gas passageway 138, and an oxygen passageway 140. The fuel gas passageway 138 is provided between the fuel gas bore 134 in the torch body 106 and the fuel gas tube 112 in the barrel 108 to provide fluid communication therebetween. The oxygen passageway 140 is disposed between the oxygen bore 136 in the torch body 106 and the preheat oxygen tube 114 (shown in FIG. 4) in the barrel 108 to provide fluid communication therebetween. The oxygen passageway 140 also provides fluid communication between the oxygen bore 136 and the cutting oxygen tube 116. A fuel gas hose 142 (which has left-hand threads) and an oxygen hose 144 are connected to the flashback arresters 130 to supply fuel gas and oxygen, respectively, to the fuel gas bore 134 and the oxygen bore 136. Fuel and oxygen valves 146 are provided at the torch body 106 to control flow of fuel or oxygen from the fuel gas bore 134 or the oxygen bore 136 to the fuel gas and oxygen passageways 138 and 140.
Referring to FIG. 6, the flashback arrestors 130 constructed in accordance with the teachings of the present disclosure each include a porous body 150, a fitting 152, and a check valve 154. The flashback arrestors 130 are inserted into the fuel gas bore 134 and the oxygen bore 136 in the torch body 106 for arresting and quenching flames when a flashback occurs.
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 FIG. 5). The distal threaded portion 158 has outer threads for engaging inner threads of the torch body 106 such that the flashback arrestors 130 are secured to the torch body 106 via threaded connection. The proximal threaded portion 156 has an outside diameter D5 and in one form is sized to fit within a bore of a standard pipe thread, which is a ¼-18 National Pipe Thread (NPT).
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 FIG. 5) or the oxygen passageway 140 (shown in FIG. 5) through the pores of the porous body 150. The pores have irregular shapes and define passageways through the porous body 150. The pores define a pore size, which is a function of a detonation cell size λ such that the pore size is increased to reduce a size of the sintered porous body. As an example, the pore size is between approximately 10 μm and approximately 16 μm. Because the pore size of the present disclosure is greater than the pore size (7 μm) in a typical flashback arrestor, the outside diameter of the porous body 150 can be made smaller than that of the porous body in a typical flashback arrester for a predetermined flow capacity. As such, the distal threaded portion 158 of the fitting 130 proximate the porous body 150 can also be made smaller than that of a fitting in a typical flashback arrestor. In the embodiment of FIG. 6, the distal threaded portion 158 has an outside diameter equal to or smaller than the outside diameter D5 of the proximal threaded portion 156. The porous body 150 of the present disclosure has a reduced outside diameter and an increased pore size.
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 FIG. 7, the flashback arrestors 130 constructed in accordance with the teachings of the present disclosure have fewer components than the typical flashback arrestors 10 of FIG. 2. As shown in FIG. 2, the typical flashback arrestors 10 require a pair of O-rings 31 and a mounting assembly 36, which includes a mounting plate 38, a washer 40 and a screw 42, to mount the flashback arrestors to the torch body 12. In contrast, as shown in FIG. 7, the flashback arrestors 130 of the present disclosure can be mounted to the torch body 12 without using O-rings and the mounting assembly.
Referring to FIG. 8, another form of a flashback arrester 200 is provided in an add-on device, i.e., a safety device 202 external to the hose fitting 206. The safety devices 202 are mounted to the hose fitting 206 by adapters 215 in the form of a hose nipple. The flashback arrestors 200 include a porous body 204, a fitting 207 and a check valve 208. The safety device 202 has a proximal portion 210, a distal portion 212 and a bore 205 therebetween. The adaptor 215 has one end inserted into the hose fitting nut 206 of the oxy-fuel cutting/welding torch and another end inserted into the bore 214 proximate the distal portion 212 of the add-on device 202 to mount the safety device 202 to the hose fitting nut 206. The fitting 207 includes a proximal threaded portion 214, a distal threaded portion 216, and an enlarged portion 218 therebetween. The proximal threaded portion 214 has an outside diameter D6. The distal threaded portion 216 may have an outside diameter equal to or smaller than the outside diameter D6 of the proximal threaded portion 214. The distal threaded portion 216 engages an inner threaded portion 220 of the safety device 202 via threaded connection such that the flashback arresters 200 are secured to the safety device 202. The flashback arrestors 200 are disposed outside the safety device 202 except the distal threaded portion 216. The porous body 204 includes a proximal end portion 230 and a distal end portion 232. The proximal end portion 230 is inserted into the bore 236 of the fitting 207 proximate the distal threaded portion 216. The distal end portion 232 is a closed end including a distal face 234. The check valve 208 is press-fitted into the bore 236 of the fittings 207.
Referring now to FIGS. 9A and 9B, the flashback arrestors 130 in another form may also be provided with end caps 172, which are secured to a distal end portion of the porous bodies 150 as shown. In this form, the porous bodies 150 have open end portions rather than closed ends as previously set forth, which allows for improved manufacturability. More specifically, the porous bodies 150 can be formed in a continuous length and subsequently cut to size according to the specific torch application. The end caps 172 are a similar or the same material as the porous bodies, namely, a sintered metal material in one form. The end caps 172 may be press fit into the porous bodies 150, or they may be bonded in another form of the present disclosure.
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 FIG. 10, as the combustion propagates during the detonation phase, detonation cells are created and continue to generate and re-establish themselves. Detonation cells represent the 3-D structure of the detonation wave, which has a detonation cell size or width λ. The detonation cell size λ is a function of the composition of the mixture, initial temperature and pressure, and the types of the fuel (such as propane, propylene, natural gas) and the oxidizer (such as oxygen). For example, the detonation cell size λ increases as the initial pressure decreases. The pore size of the porous body also depends on the oxy-fuel mixture. When the mixture of fuel and oxygen is more susceptible to detonation, the detonation cell size is relatively smaller. Therefore, the pore size should be smaller for effective arrestment of detonation for more volatile mixture.
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 FIG. 11, the pore size is determined based on the critical diameter. The critical diameter is the minimum pipe diameter below which a detonation of a specific fuel/oxidizer combination will not propagate because the detonation cell structure cannot exist. When a flame travels to a flashback arrestor having a pore size smaller than the detonation cell size of the detonation wave, the flame will be quenched and stop propagating because the detonation cell does not exist when the detonation wave travels through the pores.
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.
FIG. 11 shows the critical tube diameter (cell width/Pi) for a range of available initial pressure data when the oxy-fuel mixture has an equivalence ratio (ER) of 2.5 (˜47.5% fuel by volume). The equivalence ratio is the ratio of the fuel-to-oxidizer ratio to the stoichiometric fuel-to-oxidizer ratio (˜28.5% fuel by volume). The stoichiometric ratio is the xoy-fuel ratio necessary for complete combustion. The acetylene pressure of 22.5 psig (37.2 psia) is considered worst case based on operating pressures in Europe. Therefore, from the curve fit equation, the cell width for oxy-acetylene detonations at this initial pressure would be approximately 49 μm (0.0019 in). The critical tube diameter associated with this cell size is approximately 16 μm (0.0006 in).
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 FIG. 12, the detonation cell size is increased as the initial pressure is decreased. The oxy-acetylene mixture is at a stoichiometric ratio (28.5 volume % fuel). The C₂H₂—O₂detonation indicates that the detonation cell width ranges from ˜0.003 to ˜0.006 inches at 15-30 psia at the stoichiometric ratio (28.5 v % fuel). For example, when the pressures are 14.9 psia, 30.4 psia, and 44.3 psia, the cell widths are 0.169 mm (0.0067 in), 0.081 mm (0.0032 in) and 0.059 mm (0.0024 in), respectively.
As shown in FIG. 13, the oxy-acetylene mixture has an equivalence ratio of 2.5 (i.e., 47.5% fuel by volume). When the pressure is 14.6 psia, 30.0 psia, and 60 psia, the detonation cell width is 0.109 mm (0.0043 in), 0.059 mm (0.0029 in), and 0.031 mm (0.0012 in), respectively. It is clear from FIGS. 11 and 12 that the cell width is decreased when a richer fuel-to-oxidizer mixture is used.
FIG. 14 shows the stoichiometry effect on the determination of the detonation cell size. When the fuel-to-oxidizer is below the stoichiometric ratio, the detonation cell size increases abruptly. When the fuel-to-oxidizer is higher than the stoichiometric ratio, the detonation cell width is approximately the same when the equivalence ratio is between 1 and 2.5 and then gradually increases when the equivalence ratio is above 2.5.
FIG. 15 shows the detonation velocity increases when the oxy-fuel mixture has a higher percentage of fuel up to approximately 55% of the fuel. The detonation velocity then decreases as the ratio of fuel to oxygen is increased until the ratio of fuel to oxygen is 70%.
FIG. 16 is graph of the relationship between the detonation velocity and the tube diameter for different oxy-acetylene mixtures. A richer oxy-acetylene mixture has smaller tube diameter and thus smaller detonation width.
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

What is claimed is:

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,

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,

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