Oxyfuel welding and cutting system and method of operating the same

Abstract

An oxyfuel system (1) for supplying a lance (7) with fuel gas stored under pressure in a container (2b), the system comprising the following components: (a) an upstream fuel gas supply line (27) located between the container (2b) and the lance (7); (b) a demand valve (4) arranged in the upstream gas supply line (27); (c) a lance (7) connected to the oxygen supply line (26). According to the invention, the lance comprises a venturi nozzle (33) adapted to generate, in operating conditions, a negative pressure Pnegate of at least-0.3 bar relative to atmospheric pressure in the upstream gas supply line (27), and the demand valve (4) is vacuum-controlled and configured to have a pressure setpoint for opening the demand valve (4), the pressure setpoint is a negative value with respect to atmospheric pressure and is equal to or more negative than Pnatural.

Description

Technical Field

[0001] The present invention relates to an oxyfuel system. In particular, the present invention relates to a system for supplying a burner with a fuel gas stored under pressure in a container, wherein a fuel gas extraction line leads from the container to the burner, in which fuel gas extraction line there is at least one gas demand valve. Background Art

[0002] As we all know, oxy-fuel welding, brazing, heating and cutting are processes that use fuel gas and oxygen.

[0003] Equipment for oxy-fuel welding, brazing, heating and cutting requires an oxygen source and a fuel gas source (usually contained in cylinders), two pressure regulators, two flexible hoses (one for each gas source), a spray gun, and, as a mandatory requirement, a flashback arrestor. This setup can also be used for brazing and brazing.

[0004] The regulator ensures that the gas pressure in the cylinder can be set in accordance with EN-ISO: 2503, and the operator then turns the needle valve on the spray gun to adjust the volume required to perform the task. Accurate flow control using a needle valve relies on a constant supply pressure from the regulator to the spray gun.

[0005] Hoses are manufactured to be compatible with the gas being used. Sometimes hoses are used in a dual hose or twin tube design, meaning the oxygen and gas hoses are joined together. However, the bead of molten metal released by the cutting process can get stuck between the hoses and burn off, releasing the pressurized gases inside, which, in the case of gas, often ignite.

[0006] Fuel gases such as acetylene are not only flammable, in some cases, they are explosive. Although its upper flammability limit in air is 81%, the explosive decomposition behavior of acetylene makes this limit irrelevant. If a detonation / deflagration wave enters an acetylene cylinder, the cylinder may be blown apart by the subsequent decomposition. Ordinary one-way / check valves that usually prevent backflow / reverse flow cannot prevent flashback because they do not contain flame extinguishing components.

[0007] Flashback arrestors and / or check valves (non-return valves) can be installed between the regulator and the hose, and ideally between the hose and the gun for both oxygen and fuel gas lines to prevent the flame or oxygen-fuel mixture from being pushed back into either regulator of the cylinder, thereby damaging the equipment or causing the cylinder to explode. A check valve only allows gas to flow in one direction. It is usually a chamber that contains a ball that is pressed on one end by a spring. One-way flow of gas pushes the ball away, and lack of flow or reverse flow causes the spring to push the ball into the inlet, thereby blocking flow.

[0008] The spray gun is the tool that the operator uses to perform the appropriate task required. It has a connection and valve for the gas, a connection cloth and valve for the oxygen, a handle for the welder to grasp, and a gas mixing device where the gas and oxygen mix with a nozzle from which the flame emerges. Two basic types of spray guns are used; (i) nozzle mix spray guns and (ii) premix-spray type spray guns.

[0009] Acetylene, LPG (liquefied petroleum gas) and other fuel gases are highly flammable and form explosive mixtures with the surrounding air and / or oxygen. A major cause of accidents with gas equipment is leaking connections or poorly maintained equipment, which can cause explosions when the highly flammable leaking gas is ignited. Even a small leak can cause a flash fire or explosion, especially when the equipment is used in poorly ventilated areas or confined spaces, such as in underground mining operations where gas can accumulate. During operation, sparks and spatter are generated, which are the main cause of fire.

[0010] To detect leaks in hoses or connections, apply a leak detection spray to all gas and oxygen connections starting at the cylinder valve, regulator (including all other connections), and ending at the spray gun nozzle. It is particularly user-unfriendly when the entire hose needs to be sprayed and inspected. Foam bubbles at the leak point will clearly indicate a leak. The user will then know that it is dangerous to ignite the gas at the nozzle and / or gas system before stopping the leak or replacing the leaking part.

[0011] This can be very dangerous as much of this gas equipment is used underground or in confined spaces, where the risk of an explosion and its effects can be devastating.

[0012] Purpose of the Invention

[0013] It is an object of the present invention to provide an oxy-fuel system which at least partially mitigates some of the above-mentioned risks.

[0014] In particular, the object of the invention is to improve known gas supply systems in terms of safety standards.

[0015] In addition, it was necessary to specify a method that would allow the spray gun to be supplied with superstoichiometric amounts of fuel gas without necessarily compromising the safety of the system. Summary of the invention

[0016] According to the present invention, there is provided an oxygen-fuel system comprising:

[0017] Gas supply device;

[0018] Vacuum controlled demand valve;

[0019] Cutting lances that create a venturi strong enough to allow flow through a vacuum controlled demand valve.

[0020] The components of the oxy-fuel system are fluidly connected in series with the fuel gas supply, vacuum-controlled demand valve, and spray gun.

[0021] In particular, the oxy-fuel system of the present invention is intended for supplying a fuel gas stored under pressure in a container to a spray gun and comprises the following components:

[0022] (a) The upstream gas supply line between the vessel and the spray gun;

[0023] (b) a demand valve arranged in the upstream gas supply line;

[0024] (c) a spray gun connected to an oxygen supply line,

[0025] The lance comprises a venturi nozzle adapted to generate, under operating conditions, a negative pressure P of at least -0.3 bar relative to atmospheric pressure in the upstream gas supply line. negative , and the demand valve is vacuum controlled and configured to have a pressure set point for opening the demand valve, the pressure set point being negative relative to atmospheric pressure and equal to P negative or P negative More negative.

[0026] Due to the Venturi effect, the oxygen flow from the ejector creates an effective negative pressure P in the upstream gas supply line. negative The decisive factor for the Venturi effect is the effective negative pressure P in the upstream gas supply line. negative .

[0027] The modified demand valve or "demand valve" matched with the modified spray gun is vacuum controlled and is configured to have a pressure set point that must be reached to open the valve, the pressure set point being negative relative to atmospheric pressure and equal to P negative or P negative More negative.

[0028] If there is a leak in the upstream gas supply line between the demand valve and the mixing nozzle inlet, the setpoint cannot be reached because the gas escapes from there, so the demand valve will not open. The same applies if there is a leak in the oxygen line so that the Venturi effect is not sufficient to set the negative pressure setpoint, or if one of the two lines mentioned above is blocked.

[0029] Effective negative pressure P negative Defined as the pressure measured in the upstream gas supply line when the gun is in operating mode. This means that a nozzle is inserted in the outlet path of the oxygen-gas mixture, e.g. a cutting, welding or heating nozzle is inserted in the gun. Regardless of the specific nozzle currently used, an effective negative pressure P must be achieved. negativeIn the idle state, which means when no nozzle is inserted in the outlet path of the gas mixture, the negative pressure must be lower than the effective negative pressure P negative More negative (relative to atmospheric pressure). negative The values ​​given are always relative to atmospheric pressure (i.e. 1 bar), regardless of whether they are preceded by a minus sign. negative A higher value means a greater difference from 1 bar, i.e. a lower absolute pressure. In this sense, for example, -0.4 bar is a "higher value" than -0.3 bar.

[0030] The invention differs fundamentally from the current state of the art for lance mixers because, on the one hand, it meets the requirements of DIN EN 5175, but in addition generates a defined negative pressure of more than -0.3 bar relative to atmospheric pressure (1 bar). This high negative pressure makes it possible to open a corresponding vacuum-controlled demand valve (e.g. a so-called SAT valve - Safety Advanced Technology) and to deliver the required amount of gas in order to optimally regulate the flame and thus also to generate a gas surplus.

[0031] To open the demand valve, its pressure setting must be equal to or less than (i.e. more negative) the effective negative pressure P generated by the central tube spray gun. negative On the other hand, the higher the negative pressure generated by the spray gun, the greater the suction effect and the more sensitive the leak detection. Therefore, the pressure setting value for opening the demand valve is preferably at least -2.5 bar relative to atmospheric pressure, preferably at least -3 bar, most preferably at least -4 bar.

[0032] The invention optimizes the injector and demand valve.

[0033] The demand valve comprises a valve body having an upper portion and a lower portion secured by a securing device, a flow path, a flow path closing member and a diaphragm for moving the closing member from a closed position to an open position when a pressure differential exists across the diaphragm.

[0034] Preferably, the demand valve is a diaphragm valve (or membrane valve), comprising:

[0035] (a) a valve body having a first port connected to the container and a second port connected to the upstream gas supply line,

[0036] (b) a diaphragm sandwiched in the valve body,

[0037] (c) a closing member coupled to a first side of the diaphragm and cooperating with a valve seat located between the valve inlet and the valve outlet, the closing member being adapted to open a passage between the valve inlet and the valve outlet when a pressure on a second side of the diaphragm is equal to or greater than (more negative relative to atmospheric pressure) the pressure set point.

[0038] This diaphragm valve has a simple and sturdy design and works reliably.

[0039] In particular, to achieve the highest possible pressure set points, the diaphragm has a diameter D M The circular cross section, where D M This is advantageous if it is greater than 50 mm, preferably greater than 52 mm, particularly preferably greater than 54 mm.

[0040] When the valve outlet opening d v The large size of the diaphragm is particularly noticeable in comparison to its small size. This is because D M / d v The higher the ratio, the greater the gas flow rate for the same suction. Or, to put it another way, with a higher ratio it is easier to set a gas surplus in the gas / oxygen mixture without reducing suction power too much.

[0041] In this regard, in a preferred embodiment, the valve seat is formed with an inner diameter d v The valve port has a diameter ratio of D M / d v Greater than 8.5, preferably greater than 8.8, and most preferably greater than 9.1.

[0042] The lance most suitable for an oxy-fuel system is preferably an injector lance comprising a lance body, a lance head connected to the lance body, and a lance end retained in the lance head, wherein the lance body has flow paths defined therein, at least one of the flow paths being a gas supply line extending from a gas inlet, and at least another of the flow paths being an oxygen path extending from an oxygen inlet, wherein at least conduit portions of the upstream gas supply line and the oxygen supply line are joined at a venturi nozzle to form a common outlet path to the lance end,

[0043] wherein the venturi nozzle comprises a pressure nozzle fluidly connected to the oxygen supply line and having a nozzle outlet,

[0044] wherein the outlet path comprises a mixing nozzle and a mixing nozzle inlet for producing an oxygen-fuel gas mixture,

[0045] Wherein the venturi nozzle and the mixing nozzle are adapted to generate a negative pressure P of at least -0.3 bar relative to atmospheric pressure in the operating mode negative .

[0046] In so-called "injector lances", the oxygen is supplied at a higher pressure than the gas. The oxygen flowing into the injector creates a negative pressure, as a result of which the gas is sucked in and entrained. The oxygen and gas mix in the mixing tube. In the case of prior art self-contained systems, this negative pressure is not defined, but only the entire system must meet the requirements of DIN EN ISO 5172 in order to obtain the corresponding approval. In order to ensure that a negative pressure is established in the injector lance, this DIN standard specifies the performance of a "suction test". The "suction test" is still considered to have been passed if the pressure measured on the gas side does not exceed 0.5 times the gas pressure specified by the manufacturer. This means that if the pressure on the gas side is above atmospheric pressure, i.e. the pressure in the gas line is greater than zero, this condition is also met, but this is not a "negative pressure" with a pressure below atmospheric pressure. Nevertheless, the inventors have measured the pressure in the gas pipes of injector lances available on the market. They found that they typically have a negative pressure of 0.05 to 0.2 bar at the gas connection (which means an absolute pressure of 0.8 to 0.95 bar).

[0047] However, on the one hand, this reduced pressure is not clearly defined and may also fluctuate into the positive pressure range as a function of process conditions or changes in the spray gun design. On the other hand, although the pressure is reduced, it may not be low enough to detect (small) pressure changes caused by (small) leaks, and thus insufficient to cause a connected demand valve to close reliably.

[0048] That is, one of the advantages of the present invention is the recognition that the "negative pressure" in the prior art systems is undefined and too low for repeatable functionality. This means that the core of the present invention is to generate a defined negative pressure to ensure the functionality of the entire system in combination with the negative pressure valve, thereby producing an absolutely leak-free and safe system. Therefore, the satisfaction conditions of ISO 51722 are also met, but do not represent the main focus.

[0049] The gun creates enough venturi effect to ensure that the demand valve in the upstream fuel line opens. In the event of a fuel line rupture, the demand valve closes, thus ensuring the safety of the gun and the connected system.

[0050] The invention also optimizes the ratio and dimensions of the injectors, primarily the pressure and mixing nozzles, so that for the first time a properly defined negative pressure difference of >0.3 bar can be generated in the gas supply line.

[0051] The suction effect at the gas connection achieved by the Venturi effect is primarily intended to provide safety protection against gas backflow into the gas line under all operating conditions of the respective gun or application.

[0052] The preferred design of the Venturi nozzle and the mixing nozzle allows an effective negative pressure P to be set in the upstream gas supply line. negativeAt least -0.4 bar relative to atmospheric pressure, preferably in the range of -0.4 to -0.8 bar, particularly preferably in the range of -0.42 to -0.6 bar.

[0053] The higher the lower limit of the selected range, the more sensitive the response of the leak detection. However, the more difficult it is to set the negative pressure set value repeatedly, and the higher the cost. Therefore, a negative pressure set point higher than -0.8 bar is technically feasible but not preferred in practice.

[0054] Multiple design and process parameters can be used to adjust the negative pressure set value. A particularly preferred design parameter is that the distance A between the nozzle outlet of the pressure nozzle and the inlet of the mixing nozzle is set between 0.2 mm and 2 mm, preferably between 0.25 mm and 1.5 mm, particularly preferably between 0.3 mm and 1.2 mm.

[0055] If the distance A is too narrow, the oxygen flow flowing out of the narrow pressure nozzle outlet will hinder the inflow of fuel gas. If the distance A is too large, the oxygen flow upstream of the mixing nozzle inlet may fan out and even mix significantly with the fuel gas before reaching the mixing nozzle inlet, and the effective negative pressure P in the upstream fuel gas supply pipeline cannot be achieved. negative of the set value.

[0056] Another preferred design measure to achieve a sufficient Venturi effect is that the diameter of the inlet of the mixing nozzle is D, the diameter of the nozzle outlet of the pressure nozzle is d, and the diameter ratio d / D is applicable to: 0.1 < d / D < 0.8, preferably 0.15 < d / D < 0.5, particularly preferably 0.2 < d / D < 0.4.

[0057] When the diameter ratio d / D is less than 0.1, the flow rate of oxygen is very low, so the gas volume and the power of the spray gun are also very low. When the diameter ratio d / D is greater than 0.8, the Venturi effect and the suction force become smaller and smaller.

[0058] If the Venturi nozzle includes at least one injector insert, a fuel gas chamber is formed therein or thereon, the fuel chamber is fluidly connected to the upstream fuel gas supply pipeline and is close to the inlet of the mixing nozzle, and the nozzle outlet of the pressure nozzle faces the inlet of the mixing nozzle.

[0059] For example, at least one injector insert is inserted into the spray gun body or the spray gun head. It includes at least one channel and / or cavity for the inflow of oxygen flow. It also includes at least one channel and / or cavity for the inflow of fuel gas, or it forms at least one channel and / or cavity for fuel gas together with the surrounding spray gun body or spray gun head.

[0060] The nozzle outlet of the pressure nozzle communicates with the fuel gas chamber, for example, adjacent to the fuel gas chamber. The oxygen flow flowing out of the pressure nozzle outlet and entering the opposite mixing nozzle inlet passes through the fuel gas chamber, and due to the Venturi effect, an effective negative pressure P is generated there.negative and brings the gas into the mixing nozzle on the opposite side.

[0061] exist Figure 7 The diagram shows the oxygen pressure at the inlet of the pressure nozzle (in bar) versus the outlet pressure (in bar) at the oxygen regulator for a spray gun without a cutting nozzle and with different cutting nozzle sizes inserted therein (the numbers in columns 4 to 9 indicate the range of metal sheet thicknesses for which the cutting nozzle is designed).

[0062] Table 1 shows Figure 7 and Figure 8 The measurement value on which the .

[0063]

[0064]

[0065] It can be seen that the pressure drop is essentially independent of the type of cutting nozzle used and that the pressure at the pressure nozzle is directly proportional to the pressure at the pressure regulator.

[0066] With regard to the method of the invention for operating the spray gun according to the invention, the above technical problem is solved by a method comprising the following method steps:

[0067] Through the upstream gas supply line at a nominal gas pressure P in the range of 0.5 to 2 bar H2 supplying gas to the spray gun,

[0068] · Through the oxygen pipeline with a nominal oxygen pressure P in the range of 2 to 10 bar O2 supplying oxygen to the lance,

[0069] The lance is provided with a Venturi nozzle which is designed such that under operating conditions an effective negative pressure P of at least -0.3 bar relative to atmospheric pressure is set in the gas supply line. negative ,

[0070] wherein the demand valve is vacuum controlled and is configured to have a pressure set point for opening the demand valve, the pressure set point being negative relative to atmospheric pressure and equal to P negative or P negative More negative.

[0071] The design of the Venturi nozzle allows a negative pressure P to be set in the upstream gas supply line. negative At least -0.3 bar relative to atmospheric pressure.

[0072] Due to the Venturi effect, the oxygen flow leaving the pressure nozzle outlet and entering the mixing nozzle inlet creates an effective negative pressure P in the upstream gas supply line.negative This runs through the gas supply line to the shut-off valve (demand valve). The demand valve is vacuum controlled and will only open if negative pressure P in the upstream gas supply line is negative Reach equal to or more negative than the effective negative pressure P negative The demand valve opens only when the pressure set point is reached.

[0073] The system of burner and demand valve is adjusted to each other so that only when enough oxygen flows through the burner to create a minimum negative pressure, the demand valve will open so that gas can also flow. Without oxygen flow, there is no gas flow.

[0074] If there is a leak in the upstream gas supply line between the demand valve and the gun, the pressure setting cannot be reached because the gas escapes there, so the demand valve will not open. The same applies if there is a leak in the oxygen line so that the Venturi effect is not sufficient to set the negative pressure setting, or if one of the two lines mentioned above is blocked.

[0075] In a particularly preferred process variant, a negative pressure P is provided in the upstream gas supply line. negative At least -0.4 bar, preferably in the range of -0.4 to -0.8 bar, preferably in the range of -0.42 to -0.6 bar relative to atmospheric pressure, and the pressure set point for opening the demand valve is at least -2.5 bar, preferably at least -3 bar, preferably at least -4 bar relative to atmospheric pressure.

[0076] The fuel gas supply in the oxy-fuel welding and cutting system is acetylene, however the invention is not limited in this respect and LPG (liquefied petroleum gas), hydrogen, MPS and MAPP gases, propylene, butane, chemalkane or any other suitable fuel gas may be used.

[0077] In a preferred embodiment, a gas-oxygen mixture at or near the stoichiometric point is used, ie, 35% acetylene and 65% oxygen or 82% oxygen and 18% LPG (liquefied petroleum gas), or other gas-oxygen mixtures close to the stoichiometric point.

[0078] The oxy-fuel system allows the operator to produce a fuel gas / oxygen mixture at or near the stoichiometric point, which is 35% acetylene and 65% oxygen, or 82% oxygen and 18% LPG (liquefied petroleum gas), or close to such other stoichiometric points, depending on the other fuels used.

[0079] In another preferred embodiment, a fuel gas-oxygen mixture is used with a superstoichiometric fuel gas, for example, the excess fuel gas is at least 5%, preferably at least 9% higher than the fuel gas in the stoichiometric mixture.

[0080] Vacuum demand valves in oxygen-fuel systems are made of lightweight materials. The valve body and all its components are preferably made of Nylon- (also known as "Polyamid-6").

[0081] The oxy-fuel system is a SAT oxy-fuel system.

[0082] These and other features of the present invention are described in greater detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which:

[0084] Figure 1 An oxy-fuel system is shown;

[0085] Figure 2 Shows the composition Figure 1 A spray gun that is part of an oxy-fuel system;

[0086] Figure 3 Shows the composition Figure 1 A valve that is part of an oxy-fuel system;

[0087] Figure 4 Shows Figure 3 The cross section of the valve in;

[0088] Figure 5 Shows Figure 3 Exploded view of the valve in;

[0089] Figure 6 Shows Figure 2 A cross section of a spray gun head of a spray gun;

[0090] Figure 7 A diagram explaining the relationship between the oxygen pressure set on the pressure regulator and the pressure applied to the pressure nozzle is shown;

[0091] Figure 8 shows a graph explaining the relationship between the oxygen pressure set on the pressure regulator and the suction pressure applied in the upstream fuel gas supply line; and

[0092] Fig. 9 A three-dimensional representation of a longitudinal injector integrated in a lance head is shown, partly in section. DETAILED DESCRIPTION

[0093] According to the drawings, an oxy-fuel system is generally indicated by the reference numeral 1 .

[0094] The oxyfuel system is a SAT oxyfuel system (SAT-Safety Advanced Technology) which uses gas instead of liquid. The oxyfuel system 1 uses an oxygen-fuel gas supply 2. In this case, the fuel supply 2b is an acetylene gas cylinder and has a conventional regulator 3.

[0095] The SAT valve 4 is directly connected to the regulator 3 outlet.

[0096] The SAT valve 4 is connected to the spray gun 7 via a hose 5 .

[0097] The fuel supply 2, regulator 3, SAT valve 4, hose 5 and spray gun 7 are all connected together and in fluid communication with each other.

[0098] When oxygen flows through the lance 7 from the oxygen inlet 9, the gas flow path in the lance 7 is designed to form a venturi tube. The venturi tube generates negative pressure to open the SAT valve 4, thereby allowing a sufficient amount of fuel gas to flow to the lance 7 through the hose 5.

[0099] The SAT valve 4 has a diaphragm which is large enough so that the venturi generated by the system is sufficient to open the demand valve.

[0100] The SAT valve 4 contains the pressure of the fuel supply 2 and allows fuel to flow only when the spray gun 7 requires it.

[0101] If the flow of fuel through the hose 5 is interrupted, or the pressure in the hose drops, the SAT valve 4 will shut off the flow of fuel in the hose 5. Such interruption may be caused by a number of events, such as a leak in the joint between the two components, the hose 5 being damaged, cut or broken by sparks and spatter that may have flown during operation, or the oxygen supply being shut off, causing a drop in demand on the venturi.

[0102] The need for the venturi is not only critical to the safety of the system 1, but it also helps to get enough fuel gas so that the operator can get the stoichiometric point or close to the stoichiometric point. This ratio is ideal for getting the best flame for acetylene at a temperature of 3150°C.

[0103] The fuel supply device is not limited to the use of acetylene, and any suitable fuel may be used, such as LPG, hydrogen, MPS and MAPP gas, propylene, butane, chemical alkane, etc.

[0104] It is envisioned that the concept described herein will be incorporated as part of all new oxy-fuel systems, as it greatly improves the safety of operators and equipment of such systems.

[0105] In the future, oxy-fuel systems will adopt this system as it not only ensures a more favorable flame, but also ensures the safety of the system as well as the users and the areas where the system is used.

[0106] The SAT system offers a significant safety improvement over the conventional systems currently in use as it does not allow any gas to escape from the system, thus preventing any gas from being accidentally ignited.

[0107] Figure 2 The spray gun 7 shown in is an injector spray gun for generating a heat source for heating, cutting, burning or welding. In a preferred example, it is designed as a cutting spray gun, comprising a spray gun head 2, a base body 24 and a handle 25 with an injector 23 designed as a longitudinal injector.

[0108] On the handle 25 there are hose connections 9 for oxygen and 8 for fuel gas (e.g. acetylene). The valves required for closing and regulating are usually located on the base body 24, i.e. the heating oxygen regulating valve 24.1, the fuel gas regulating valve 24.2 and the trigger arm 24.3 for setting the cutting oxygen volume flow. The cutting oxygen line 26 leads from the base body 24 to the spray gun head 22; the upstream fuel gas supply line 27 and the line 28 for heating oxygen lead to the injector 23. The nozzle assembly is inserted into the spray gun head 22, which comprises the heating nozzle 22.1 and the cutting nozzle 22.2. The base body 24 with the operating components 24.1, 24.2 and 24.3 can be made integrally with the handle 25 of the spray gun 7.

[0109] The ejector 23 is adapted to produce a Venturi effect, which is adapted to cause a pressure drop in the gas hose 5. To this end, the lance is operated under the condition that the supply pressure of the heated oxygen is higher than the supply pressure of the gas. The heated oxygen flowing into the ejector creates a negative pressure, so that the gas is sucked in and entrained. The heated oxygen and the gas are mixed in the mixing tube ( Figure 6 ; Fig. 9 ) and flows out through the cutting nozzle 22.2.

[0110] Figure 3 The demand valve 4 shown in FIG. 4 has a body defined by an upper cover 41 and a lower cover 42. The upper cover 41 has a central hole 45. The flow path is at an inlet opening 42.1 ( Figure 4 ) and outlet opening 42.2. The flow path is selectively opened and closed, as discussed further herein. The inlet nozzle 42b is screwed into the complementary threaded inlet opening 42.1. The outlet nozzle 42c is similarly screwed into the threaded outlet opening 42.2.

[0111] The two covers 41; 42 can be opened by snaps 43a ( Figure 5 ) and fixed cover 43b. The snap button 43a extends through the aligned holes 44a, 44b ( Figure 5 The holes 44a, 44b are spaced apart around the circumferential flanges 41.4, 42.4 of the upper and lower covers 41, 42 respectively.

[0112] Next, we will refer to Figure 4 and Figure 5 The internal components of the valve 4 will be described.

[0113] The inner surface of the flange receives a circumferential diaphragm 46 therebetween. An annular lip 46a extending downwardly on the flange of the diaphragm 46 is seated in an annular (groove) in the upper surface of the lower cover 42. The diaphragm 46 spans a circular opening 46b having a diameter of 54.7 mm. This corresponds to an effective diameter D of the diaphragm 46. M .

[0114] The ventilation nozzle 45b is located at the center of the upper surface of the upper cover 41. The nozzle 45b includes a ventilation hole.

[0115] A conical diffuser 47 is located in the center of the lower cover 42, with its apex operatively pointing upward. The diffuser 47 has an upper central hole at its apex. The diffuser hole is provided in the conical portion of the diffuser 47. The lower widest edge of the conical portion of the diffuser 47 terminates in a thickened cylindrical wall that is sealingly secured in a complementary annular receiving structure of the lower cover. The bottom surface of the diffuser 47 terminates in a downwardly extending tubular portion that has an external thread.

[0116] The support cap 46b located below the diaphragm 46 can move together with the diaphragm 46. The support cap 46 has a handle 46c extending downward in the center. The lower end of the handle 46c has a threaded blind hole. The handle 46c can slide and move tightly in the upper hole of the diffuser 47.

[0117] The valve closing member 48 has a short tubular portion with a radially extending upper flange including an upwardly extending circumferential edge. The upper ridge of the edge forms an O-ring seat 47a. A hole is provided on the tubular wall of the valve closing member 47.

[0118] The assembly pin 49 has an upper threaded end and a lower thickened end. The pin 49 extends through a central hole 48a in the valve closing member 48 and is screwed into a hole in the handle. The diameter of the thickened end is larger than the hole diameter 48a. This ensures that when the spring is biased upward and the diaphragm is assumed to be in a non-operating state, the pin 49 presses the valve closing member 48, in particular the edge of the closing member, against the O-ring to close the flow path through the valve 4. Figure 4 In the position shown, the flow path is closed. The diameter of the hole 48a is 5.9 mm. This corresponds to the diameter d of the valve seat. v .

[0119] A closing and fixing cap 50 with a coaxial, raised and threaded annular notch is screwed into the lower complementary threaded hole of the lower cover 42 .

[0120] The configuration of the valve 4 as described and shown is such that the valve is able to withstand a pressure of 26 bar without leaking. This is particularly due to the size of the tongue or ring which helps to secure the diaphragm 46 and the fixing screws 43b which hold together the body parts 41; 42 of the valve. The valve has a relatively large diaphragm 46, but when it is used in the above-mentioned oxy-fuel welding and cutting systems, it is set to open at -0.4 bar. Even if there is a slight leak in the gas supply line 5, let alone a rupture, the demand valve 4 will be closed, thereby ensuring the safety of the spray gun 7 and the connected system.

[0121] Valve made of nylon This has many advantages, such as: there is a certain amount of memory in the event of deformation of the valve body and valve components, certainly more than the copper valves of the prior art, it performs better in gases such as acetylene, has a longer service life, and is easier to manufacture, especially considering that the pure copper content of copper valves must be less than 70%. Made so that galvanic corrosion will not occur.

[0122] The off-center vent hole on the side of the vent nozzle or spout is less likely to become contaminated, especially by manually operating the valve. The diaphragm cannot be manipulated by forcing a wire or other strip-shaped, substantially straight object through the vent hole to depress the diaphragm. The difficult path from the vent hole to the diaphragm makes it almost impossible to manipulate the diaphragm with a physical object through the vent hole.

[0123] Figure 6 Shown in longitudinal section is a lance head 32 of an injector lance 30 which can be used in an oxy-fuel system according to the invention.

[0124] The lance head 32 is intended to generate a sufficient Venturi effect to ensure that the vacuum-controlled demand valve in the upstream fuel supply line opens. The lance meets the requirements of DIN EN 5175 on the one hand, but in addition generates a specified high negative pressure of at least -0.3 bar, preferably at least -0.4 bar, which makes it possible to open the negative pressure valve (SAT valve 4) and to deliver the required amount of gas in order to adjust the flame in an optimal way, so that a gas surplus can also be generated.

[0125] The invention optimizes the ejector area, primarily the ratio and dimensions of the pressure and mixing nozzles, so that for the first time a well-defined underpressure of at least -0.3 bar, preferably at least -0.4 bar, can be generated in the gas supply line.

[0126] The suction effect at the gas connection achieved by the Venturi effect is primarily intended to provide safety protection against gas backflow into the gas line under all operating conditions of the respective gun or application.

[0127] The key point of the present invention is to generate a defined negative pressure in the gas pipeline to ensure the functionality of the entire system in combination with the negative pressure valve 4, thereby creating an absolutely leak-free and safe system.

[0128] Figure 6 The injector is designed as a longitudinal injector 33. A mixing nozzle 34 is formed in the lance head 32. The injector 33 is inserted between the mixing nozzle 34 and the oxygen and fuel gas path (8; 9) leading to the lance head 32. Oxygen flows from the oxygen line 9 into the pressure nozzle 33.5 at a pressure of, for example, 2.5 bar (preferred range: 2 to 8.5 bar). The fuel gas flows from the fuel gas path 8 at a lower pressure of, for example, 1 bar (preferred range: 0.4 to 1.7 bar) into an annular fuel gas chamber 33.7, which is fluidly connected to the pressure nozzle 33.5 on the one hand via a narrow nozzle outlet 33.6 and to the mixing nozzle 34 on the other hand.

[0129] The pressure nozzle 33.5 (oxygen) enters the annular gas chamber 33.7 through a hole 33.8 with a narrow nozzle outlet 33.6. Oxygen flows from the pressure nozzle 33.5 into the annular gas chamber 33.7 under high pressure and enters the mixing nozzle 34 located opposite. As a result, the oxygen flow generates a negative pressure in the annular gas chamber 33.7, so that the gas is fed at an effective negative pressure P negative Extracted from the gas chamber 33.7, oxygen and gas are mixed in the mixing nozzle 34 and the gas mixture enters the cutting nozzle 2.2 via the mixing channel 34.2 and the adjacent settling zone 34.3.

[0130] According to the present invention, the effective negative pressure P in the annular gas chamber 33.7 is negative At least -0.3 bar (at atmospheric pressure), preferably at least -0.4 bar, and preferably between -0.4 and -0.9 bar, particularly preferably between -0.42 and -8 bar. In addition to a negligible pressure drop of 10%, this effective negative pressure P can be established in the entire gas path 8. negative , until the demand valve 4 is inserted into the gas path 8. The vacuum-controlled safety valve 4 is designed to open the gas path 8 only at a gas negative pressure of at least 0.3 bar, otherwise it is closed.

[0131] Effective negative pressure P negativeThe distance A between the outlet of the narrow hole 33.8 (nozzle outlet 33.6) and the nozzle inlet 34.1 of the mixing nozzle 34 is largely determined. This distance corresponds to the width of the annular gas chamber 33.7. If the distance A is too narrow, the oxygen flow flowing out of the narrow nozzle outlet 33.6 can hinder the gas from entering the annular gas chamber 33.7. If the distance A is too large, the oxygen flow can be dispersed too much upstream of the nozzle inlet 34.1 of the mixing nozzle 34, so that it is already significantly mixed with the gas upstream of the mixing nozzle 34 and does not reach the effective negative pressure P in the gas path 8. negative In a preferred example, the distance A is 0.65 mm.

[0132] Influence of effective negative pressure P negative Another design parameter is the diameter ratio d / D between the diameter d of the narrow pressure nozzle outlet 33.6 and the diameter D at the nozzle inlet of the mixing nozzle 34. The diameter of the narrow nozzle outlet 33.6 is always smaller than the diameter D at the nozzle inlet 34.1 of the mixing nozzle 34, so that the diameter ratio d / D is less than 1. Particularly preferably, it is between 0.1 and 0.8, preferably between 0.14 and 0.5, most preferably between 0.2 and 0.4. If the diameter ratio d / D is very small, for example less than 0.1, the flow rate of oxygen is low, and therefore the gas volume and the power of the spray gun are also low. When the diameter ratio d / D is large, for example greater than 0.8, the Venturi effect and the suction force become smaller, so there is a possibility that an effective negative pressure P cannot be generated and maintained in the gas path. negative risk.

[0133] The above diameter ratio d / D applies to typical pressure nozzle diameters in the range of 0.3 to 5 mm. If d and D are made equally small, the diameter ratio remains the same, the suction increases, but pressure nozzle diameters less than 0.3 mm result in low gas flow and thus low spray gun performance.

[0134] In a preferred example, d is 0.57 mm, D is 1.9 mm, and the diameter ratio d / D is 0.3.

[0135] Fig. 9 The partial cross-section of a cutting lance 90 in FIG. 1 is used to explain the injector principle, using as an example a longitudinal injector insert inserted into the lance head. The following components can be identified:

[0136] 91: Heating oxygen inlet area

[0137] 92: Annular combustion chamber

[0138] 93: Pressure nozzle

[0139] 94: Pressure nozzle hole

[0140] 95: Mixing nozzle inlet. There is negative pressure P here negative, thereby sucking in gas.

[0141] 96: Mixing nozzle

[0142] 97: Mixing channel (upstream section): Here, oxygen flows into the center at high speed. This is how negative pressure is created in the mixing nozzle inlet area

[0143] 98: Mixing channel (downstream area): Relaxation section - oxygen is further mixed with gas here

[0144] 99: Spray gun head: the mixing section of two gases

[0145] Under typical operating conditions, the spray gun will generate a negative pressure P of at least -0.3 bar relative to atmospheric pressure. negative , such as negative pressure P negative It is -0.4bar.

[0146] Refer to the following Figure 3 An embodiment of the method according to the invention is explained in more detail.

[0147] Use according to Figure 3 The spray gun 30 of the embodiment configuration. Oxygen and fuel gas are supplied to the spray gun 30. The oxygen pressure at the oxygen cylinder pressure reducer is set to 5 bar, which is the pressure established in the oxygen pipeline 8, that is, the nominal oxygen pressure P O2 The pressure of the acetylene cylinder pressure reducer is set to 0.7 bar. This is the nominal gas pressure P H2 A safety valve (demand valve; SET valve) is inserted in the gas line downstream of the pressure reducer. The safety valve is vacuum controlled and will only open if the negative pressure in the upstream gas supply line reaches -0.3 bar or more (a higher negative pressure relative to atmospheric pressure).

[0148] Before the cutting nozzle is inserted into the lance head, the pressure at the pressure nozzle is 4.1 bar. Due to the Venturi effect and the configuration of the ejector and mixing nozzle, a negative pressure of -0.44 bar relative to atmospheric pressure is established in the upstream gas supply line (measured at the connecting hose 5.2).

[0149] After the cutting nozzle for cutting sheet metal with a thickness of 10 to 100 mm is inserted into the lance head, a pressure of 4.1 bar is still present at the pressure nozzle. A negative pressure of -0.41 bar relative to atmospheric pressure is now established in the upstream gas supply line (measured at the connection hose 5.2). This effective negative pressure P negative It exists in the entire gas pipeline 7 up to the safety valve (except for a slight drop due to pipeline resistance). Since this negative pressure (relative to atmospheric pressure) is at least equal to or higher than (more negative than) the set value of -0.3 bar, the safety valve opens to start the cutting process.

[0150] Due to the relatively high negative pressure, it is even possible to increase the gas pressure and provide additional gas for the cutting process. This makes it possible to carry out the cutting process with an excess of gas, which is very useful, for example, when cutting particularly thick sheets.

[0151] If there is a leak in the upstream gas supply line between the demand valve and the mixing nozzle inlet, the set value of the effective negative pressure of -0.3 bar cannot be achieved because the gas escapes from there and the demand valve cannot open.

[0152] When the valve outlet opening d v The large size of the diaphragm is particularly noticeable in comparison to its small size. This is because D M / d v The higher the ratio, the greater the gas flow rate for the same suction. Or, to put it another way, with a higher ratio it is easier to set a gas surplus in the gas / oxygen mixture without reducing suction power too much.

[0153] It will be appreciated by those skilled in the art that the present invention is not limited to the precise details described herein.

Claims

1. An oxy-fuel system for supplying pressurized gas stored in a container to a spray gun, the system comprising the following components: (a) An upstream gas supply line located between the container and the spray gun; (b) A demand valve arranged in the upstream gas supply line; (c) A spray gun connected to an oxygen supply line, The lance comprises a venturi nozzle adapted to generate, under operating conditions, a negative pressure P of at least -0.3 bar relative to atmospheric pressure in the upstream gas supply line. negative , and the demand valve is vacuum controlled and configured to have a pressure set point for opening the demand valve, the pressure set point being negative relative to atmospheric pressure and equal to P negative or P negative More negative.

2. The oxygen-fuel system according to claim 1, characterized in that The pressure set point for opening the demand valve is at least -2.5 bar, preferably at least -3 bar, and most preferably at least -4 bar relative to atmospheric pressure.

3. The oxygen-fuel system according to claim 1 or 2, characterized in that: The demand valve is a diaphragm valve (or membrane valve), which includes: (a) A valve body, whose first port is connected to the container and whose second port is connected to the upstream gas supply line, (b) A diaphragm sandwiched in the valve body, (c) A closing member, which is coupled to the first side of the diaphragm and cooperates with a valve seat located between the valve inlet and the valve outlet. The closing member is adapted to open the passage between the valve inlet and the valve outlet when the pressure on the second side of the diaphragm is equal to or higher than (more negative relative to atmospheric pressure) the pressure set point.

4. The oxygen-fuel system according to claim 3, characterized in that The diaphragm has a diameter D M The circular cross section, where D M Larger than 50 mm, preferably larger than 52 mm, particularly preferably larger than 54 mm.

5. The oxygen-fuel system according to claim 4, characterized in that The valve seat is formed to have an inner diameter d V The valve opening is larger than D M / d v Greater than 8.5, preferably greater than 8.8, most preferably greater than 9.

1.

6. An oxygen-fuel system according to any one of the preceding claims, characterized in that The spray gun is a jet spray gun, which includes a spray gun body (24), a spray gun head (22) connected to the spray gun body (24), and a spray gun end (22.1) held in the spray gun head (22). Among them, a flow path is defined in the spray gun body (24), at least one of the flow paths is a gas supply line (8) extending from a gas inlet (5.2), and at least another flow path is an oxygen path (9) extending from an oxygen inlet (5.1). Among them, at least the conduit portions of the upstream gas supply line (8) and the oxygen supply line (9) are joined at a Venturi nozzle (33; 33.1) to form a common outlet path (34) extending through the spray gun end (22.1), · Among them, the Venturi nozzle includes a pressure nozzle (33.5), the pressure nozzle (33.5) is fluidly connected to the oxygen supply line (9) and has a nozzle outlet (33.6), · Among them, the outlet path includes a mixing nozzle (34) and a mixing nozzle inlet (34.1) for generating an oxygen-gas mixture, and wherein the venturi nozzle (33; 33.1) and the mixing nozzle (34) are adapted to generate, in an operating mode, a negative pressure P of at least -0.3 bar relative to atmospheric pressure. negative .

7. The oxygen-fuel system according to claim 6, characterized in that The diameter of the mixing nozzle inlet (34.1) is D, the diameter of the nozzle outlet (33.6) of the pressure nozzle (33.5) is d, and the diameter ratio d / D is applicable to: 0.1 < d / D < 0.8, preferably 0.15 < d / D < 0.5, and particularly preferably 0.2 < d / D < 0.

4.

8. The oxygen-fuel system according to claim 5 or 6, characterized in that: The venturi nozzle comprises at least one injection insert (33.1), in which or on which a gas chamber (33.7) is formed, the gas chamber (33.7) being fluidically connected to the upstream gas supply line (7) and adjacent to the mixing nozzle inlet (34.1), the nozzle outlet (33.6) of the pressure nozzle (33.5) being opposite to the mixing nozzle inlet, wherein a distance A between the nozzle outlet (33.6) of the pressure nozzle (33.5) and the mixing nozzle inlet (34.1) is arranged in a range between 0.2 mm and 2 mm, preferably between 0.25 mm and 1.5 mm, particularly preferably between 0.3 mm and 1.2 mm.

9. A method of operating an oxyfuel system according to any one of claims 1 to 8, comprising the following method steps: Through the upstream gas supply line at a nominal gas pressure P in the range of 0.5 to 2 bar H2 supplying gas to the spray gun, · Through an oxygen line with a nominal oxygen pressure P in the range of 2 to 10 bar O2 supplying oxygen to the lance, The lance is provided with a Venturi nozzle which is designed such that under operating conditions an effective negative pressure P of at least -0.3 bar relative to atmospheric pressure is set in the gas supply line. negative , ·in, The demand valve is vacuum controlled and configured to have a pressure set point for opening the demand valve, the pressure set point being negative relative to atmospheric pressure and equal to P negative or P negative More negative.

10. The method according to claim 9, characterized in that The negative pressure P set in the upstream gas supply pipeline (7) negative It is at least -0.4 bar relative to atmospheric pressure, preferably in the range of -0.4 to -0.8 bar, particularly preferably in the range of -0.42 to -0.6 bar, and the pressure set point for opening the demand valve is at least -2.5 bar relative to atmospheric pressure, preferably at least -3 bar, most preferably at least -4 bar.

11. The method according to claim 9 or 10, characterized in that: The fuel gas is acetylene, LPG, hydrogen, MPS, MAPP gas, propylene, butane or chemical alkane.

12. The method according to any one of claims 9 to 11, characterized in that A fuel gas-oxygen mixture at or close to the stoichiometric point, ie 35% acetylene and 65% oxygen or 82% oxygen and 18% LPG, or a fuel gas-oxygen mixture close to another stoichiometric point is used.

13. The method according to any one of claims 9 to 11, characterized in that A fuel gas-oxygen mixture is used having a superstoichiometric fuel gas content, preferably the excess fuel gas being at least 5% higher than in the stoichiometric mixture, most preferably at least 9% higher.

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