Gas welding torch called a device that allows you to mix correctly flammable gas(or pairs flammable liquid) with oxygen and obtain a stable welding flame of the required power. Welding torches are included.
Classification of welding torches
Welding torches are classified according to several criteria:
a) according to the method of supplying oxygen and fuel, injection and non-injector gas burners are distinguished;
b) according to the type of flammable substance, burners are divided into gas (in which flammable gas is supplied) and liquid (in which gasoline or kerosene is sprayed);
c) depending on their purpose, burners can be universal or specialized;
d) depending on the number of gas flame flows, heating pads are divided into single-flame and multi-flame;
e) according to the method of use, burners are divided into manual and machine;
e) according to burner power there are low power(with acetylene consumption with acetylene consumption of 25-400 l/h, medium power (with acetylene consumption of 400-2800 l/h) and high power (with gas consumption of 2800-7000 l/h).
Classification and scope of application of torches for oxy-acetylene welding
According to GOST 1077, single-flame universal gas torches for oxy-acetylene welding are divided into four types: G1 (micro-power), G2 (low power), G3 (medium power), and G4 (high-power burners).
Low and medium power burners are most widely used. Low power burners are used with a thickness of 0.2-07mm. They come with four tips of different sizes.
Medium power torches are used for manual gas welding, or for surfacing, soldering and preheating of metals. The medium power burners come complete with a barrel and seven interchangeable nozzles of various sizes. The attachments are attached and fixed to the barrel using a union nut.
This configuration of the torches allows you to adjust the power of the welding flame over a wide range and produce a thickness of 0.5-30mm.
Design and principle of operation of injection and non-injector welding torches
The figure below shows the design of injection (top) and non-injector (bottom) welding torches.
Injection burners are most widely used in practice. The injector is a cylinder in which a small diameter channel for oxygen is made in the center, and radially located channels for combustible gas are made. Oxygen is supplied at a pressure exceeding the pressure of the combustible gas. Thus, with the help of an oxygen flow, combustible gas is sucked into the mixing chamber. This feeding principle is called injection.
Oxygen is supplied to the welding torch and passes through the connecting fitting (pos. 5) to the injector (pos. 7). The control valve (item 6) allows you to control the amount of oxygen supplied.
Passing through the central hole of the injector (pos. 7) under high pressure, oxygen creates a rarefied space in the mixing chamber (pos. 8) and sucks flammable gas into it, which is supplied through the radial channels of the injector. The combustible mixture formed in the mixing chamber is directed through the tip (item 2) to the mouthpiece (item 1). At the exit from the mouthpiece, the gas mixture burns, forming a welding flame. The tip is connected to the barrel of the welding torch using a union nut (item 3).
Injection welding torches come complete with replaceable tips. Replaceable tips differ in the diameter of the holes in the mouthpiece and injector, so you can change the power of the welding flame.
Injectorless burners do not have an injector. Oxygen and flammable gas are supplied to them at the same pressure (about 100 kPa). In such burners, instead of an injector, a conventional mixing nozzle is installed, which is screwed into the tip.
An injection burner is a burner in which the supply of combustible gas to the mixing chamber is carried out due to its suction by a stream of oxygen flowing at high speed from the nozzle opening. This gas suction process is more low pressure a stream of oxygen supplied with more high pressure, is called injection, and burners of this type are injection.
For normal operation injection burners it is necessary that the oxygen pressure be 0.15-0.5 MPa, and the acetylene pressure is much lower - 0.001-0.12 MPa. Injector burner diagram presented in Figure 1, a. Oxygen from the cylinder under operating pressure through the nipple, tube and valve 5 enters the injector nozzle 4. Coming out of the injector nozzle at high speed, oxygen creates a vacuum in the acetylene channel, as a result of which, passing through nipple 6, tube and valve 7, it is sucked into mixing chamber 3. In this chamber, oxygen, mixing with flammable gas, forms a flammable mixture. The combustible mixture, leaving through 1, is ignited and, burning, forms a welding flame. The supply of gases to the burner is regulated by oxygen valve 5 and acetylene valve 7, located on the burner body. Replaceable tips 2 are connected to the burner body with a union nut.
Figure 1 - Diagram of the injection burner (a) and injection device (b)
The injection device consists from injector 1 and mixing chamber 2. For normal injection great importance have right choice between the conical end of the injector 1 and the cone of the mixing chamber 2 and the sizes of the acetylene 3 and oxygen 4 channels. Malfunction of the device leads to backfire strikes, a decrease in the supply of acetylene in the combustible mixture, etc. oxygen is supplied at approximately the same pressure of 0.05-0.1 MPa. They are missing, which is replaced by a simple mixing nozzle screwed into the burner tip tube. The diagram of a non-injector burner is shown in the figure. along the rubber hose through nipple 4, adjustment 3 and special dosing channels it enters the burner mixer. Similarly, acetylene also enters the mixer through nipple 5 and valve 6. From the mixing chamber, the flammable mixture, passing through the tip tube 2, exits the mouthpiece 1 and, burning, forms a welding flame.
To form a normal welding flame, the combustible mixture must flow out of the torch mouthpiece channel at a certain speed. This speed must be equal to the burning speed. If the flow rate is greater than the burning rate, the flame breaks away from the mouthpiece and goes out. When the flow rate of the gas mixture is less than the combustion rate, the combustible mixture ignites inside the tip. Consequently, injectionless burners are less versatile, since they only operate on medium pressure fuel. For normal operation, injectionless burners are additionally equipped with an equal pressure regulator, which automatically ensures equality of the operating pressures of oxygen and acetylene.
Injection burners are called burners in which the formation of a gas-air mixture occurs due to the energy of a gas stream sucking air from the surrounding space into the burner. With low-pressure injection burners, only part of the air required for combustion (primary air) enters the combustion front. The rest of the air (secondary) enters the flame from the surrounding space.
Ris. 15. Low pressure injection burner
Since such burners do not inject all the air necessary for combustion, They are also called burners with partial air injection. Primary air in such burners makes up 40-60% of the air required for combustion.
Main parts injection burners are a primary air regulator, nozzle, mixer and manifold (Fig. 15).
Primary air regulator is a rotating disk that can move "from burner to burner." It regulates the amount of primary air entering the burner . The nozzle serves to impart speed to the gas jet, which provides suction required air. In the burner mixer occurs mixing of gas and air. From the mixer gas-air mixture enters collector, which distributes gas-air mixture through the outlet openings. The shape of the collector and the location of the holes depend on the type of burners and their purpose.
Low pressure injection burners have a number of positive qualities, due to which they are widely used in household gas appliances.
Advantages of low pressure injection burners:
Simplicity of design;
Stable operation of the burner when the load changes;
Possibility of complete combustion of gas;
No pressurized air supply.
Rice. 16. Stove burner
In Fig. 16 shows the burner of the stove table. The gas leaves the nozzle and enters the mixer, where a gas-air mixture is formed. The burner does not have a primary air supply regulator. When the gas pressure in the network increases beyond the limits of stable operation of the burner, partial separation is possible. In this case, it is necessary to reduce the gas supply to the burner using the burner tap. The burner nozzle is freely installed on the mixer. The lid has outlet holes through which the gas-air mixture exits. The burner is made of aluminum alloys.
The advantages of injection burners include their self-regulating property, i.e. maintaining a constant proportion between the amount of gas supplied to the burner and the amount of injected air. As the pressure increases, the amount of air entering the burner increases, and as the pressure decreases, it decreases. The limits of stable operation of injection burners are limited by the possibilities of flame separation and breakthrough: the gas pressure in front of the burner can be increased and decreased only within certain limits.
Review questions
1. What substances are formed during the complete combustion of natural gas?
2. What are the reasons for incomplete combustion of gas?
3. What is separation?
4. What are the reasons for the separation?
5. What is slippage?
6. What are the reasons for slippage?
7. What burners are called injection burners?
8. Describe the design of a low pressure injection burner.
9. What are the advantages of injection burners?
Equipment
Gas stoves
The majority of household gas-using equipment in Russia are gas stoves; there are more than 40 million of them in use.
Household stoves are designed for cooking. Their use for other purposes, in particular for space heating, is not permitted. Plates can work:
On natural gas with nominal pressure 130 mm h.s. or 200 mm H.S.;
On liquefied petroleum gas at nominal pressure 300 mm h.st.
To convert the stove from one type of gas or pressure to another type of gas (pressure), it is necessary to replace the burner nozzles. The nozzles should be marked with the hole size.
The stove is made in the form of a cabinet (Fig. 17), in which an oven and an auxiliary cabinet are mounted, where only non-combustible items can be stored.
At the top of the stove there is a table with cooking burners. The dishes are placed on the table grid, which must be removable and fixed on the table.
Table burners can have different design, but according to the principle of operation they are all low-pressure injection burners.
On modern four-burner stoves, the table burners come in three power ratings: low, normal (2 pcs.) and high.
To get to the gas pipeline of the stove - ramps, it is necessary to remove the table and switchboard. The ramp is made from steel pipe, most often with a nominal diameter of D y 15 (half an inch). Burner taps are installed on the ramp. The plate taps are conical; the plug is pressed against the body by a spring (Fig. 18).
Rice. 18. Plate tap
Tap must be recorded in closed position. The tap must be opened after the tap has been removed from its fixed position. Of all gas-using equipment, stove taps operate under the most difficult conditions, since they are located directly above the oven. When the oven is turned on, the hob taps can become hot. 145°C.
Crane lubricant must be refractory and ensure their operation for 3 years. The faucet rod is held in place by a locking screw. The faucet handle is placed on the rod.
Faucet handles modern stoves must have an indication so that by their position one can determine one of three tap positions: “Closed”, “Large flame” or “Small flame”. The valves turn from closed to open position counterclockwise.
Oven modern slabs have thermal insulation made of mineral wool, covered with aluminum foil on top. The oven has main burner(the most powerful burner on the stove), and there may also be a frying burner (grill). Simultaneous supply of gas to the main and frying burners is not allowed. When the main burner burns, the combustion products rise upward, which will not allow the frying burner located on top to burn normally. It will either go out or burn with incomplete combustion of the gas. To avoid simultaneous supply of gas to the main and frying burners, the tap for these burners is made common. When the tap is turned counterclockwise, the gas flows to the main burner, and when turned clockwise, it goes to the fryer.
Fry burner - low pressure injection. So that the heat from it goes down, it is made with an infrared burner. The burner flame heats up a metal panel or mesh until it glows; infrared radiation passes down through the air without loss and fries the food. Simultaneous operation of oven burners and table burners is allowed. In this case, the table burners must operate without interruption or flashover of the flame.
The oven door must be locked in the open and closed positions. The oven door glass is heat-resistant tempered. Trays and oven racks should move freely and not fall out of the guides when cold or hot.
There is a group of household stoves in which the table burners are gas, and electric heaters - heating elements - are installed in the oven. One heating element is installed at the bottom, the other at the top. Electric oven provides best quality baking compared to gas, since simultaneous operation of two heating elements is possible. This ensures a more uniform heat supply to the baked product. Main burner gas oven Most of the heat to the baked product is supplied from below, so baked goods burn quite often.
Modern stoves are increasingly equipped with devices that increase the convenience and safety of its use. These are electric ignition of burners, automatic “Gas control”, electric spit drive, oven thermostat.
Electric ignition of the burner occurs when a spark jumps between the burner nozzle and a spark gap installed nearby (Fig. 19).
Rice. 19. Electric ignition circuit
In order for a spark to pierce the air between the spark gap and the burner nozzle, the stove has a voltage multiplier (VM), which increases the voltage to several thousand volts. Electric ignition happens single-spark, when after each press of the button a spark jumps, and multi-spark, when sparks jump at certain intervals all the time the ignition button is pressed. Multi-spark ignition is less likely to fail.
Quality is especially important operation of electric ignition of the main oven burner. Firstly, the oven burner is the most powerful, so a large amount of gas comes out through its nozzle. Secondly, a sheet is installed above the burner, resulting in a closed volume (one of the conditions for an explosion). If ignition does not occur within a few seconds, an explosion may occur. .
Do not electrically ignite the oven burners with the oven door closed.
Flame control device (automatic “Gas control”) should stop the gas supply to the burner when it goes out. As the experience of the emergency dispatch service shows, quite often the cause of gas pollution in the kitchen is gas escaping through the stove burners that are not burning. This can happen when the ignition is incorrect, when the gas is turned on to one burner and they try to ignite another, when boiling water splashes out of a pan, when a small flame is blown out by a draft, etc.
Automation "Gas control" consists of a thermocouple and a solenoid valve. When you press the tap handle, the valve opens and gas flows to the burner, where it is ignited. The thermocouple is heated by the burner flame. It begins to generate voltage, which is supplied to the electromagnet, which holds the valve in open position. Thermocouple heating time is 3-5 seconds, after which the handle the tap can be released. If the burner goes out for any reason, the thermocouple will cool down and stop producing voltage. The electromagnet will release the valve and the gas supply to the burner will stop.
Electric spit drive installed on back wall ovens. It consists of an electric motor and a mechanical gearbox that reduces the speed.
Oven thermostat maintains the set temperature in the oven when the main burner is operating. Opposite the main burner tap handle there are numbers on the distribution panel. Each number corresponds to the temperature in the oven that the main burner will maintain. As the temperature decreases, the gas supply to the burner increases and the temperature rises. If the temperature rises above the set value, the gas supply is reduced. The thermostat consists of a thermal cylinder, a capillary tube and a membrane. The thermal balloon is located in the oven and is connected by a capillary tube to a membrane that controls the valve in the tap. The entire system is filled with a special liquid. When the thermal cylinder is heated, the liquid expands, its pressure is transmitted through the tube to the membrane. The membrane moves the valve toward the seat, and the gas supply decreases.
If the oven does not have a thermostat, it is equipped with a temperature indicator that operates within a temperature range 160-270°C. The temperature indicator has a scale with numbers. The position of the arrow opposite this or that number corresponds to a certain temperature in the oven. The stove's passport contains a table that indicates what temperature corresponds to which temperature indicator number.
The electrical equipment of the stove operates from alternating current voltage 220 V, frequency 50 Hz. There are stoves whose electrical equipment operates from an autonomous source direct current(battery, batteries) with voltage from 1.5 to 12 V.
The average service life of a modern stove is at least 14 years old. The stove cannot be repaired if its oven burns out.
Plate faults
The faucet plug is difficult to turn- the tap must be lubricated with a special lubricant - NK-50, GAZ-41 and so on. The use of grease, technical petroleum jelly and similar lubricants is not allowed. The quality of the faucet depends on how well the plug is ground into the body. The plug of each tap is ground to the body individually. When lubricating the tap, it is important to ensure that the holes in the plug and body do not become clogged; they must be periodically cleaned.
Burner flame separation- if it is possible to regulate the supply of primary air, adjust it; in other cases, reduce the gas supply to the burner using a tap.
Leaks in connections. The design of the slab has many detachable connections. When the properties of sealing materials change (drying, aging), leaks appear in them, which are eliminated by using approved materials - flax, FUM tape, paronite, etc.
Ignition of stove burners
Ignition of the burners is described in this section within the scope of instruction, that is, as it should be explained to the subscriber during the initial start-up of gas:
Make sure there is no smell of gas;
Open the window;
Check the draft in the ventilation duct;
Make sure that the taps on the stove are closed;
Open the tap on the lower side;
Bring a lit match to the burner being lit, open the burner tap;
Adjust combustion, ensure stable operation of burners;
Do not leave the operating stove unattended;
At the end of use, close the taps on the stove and the tap on the lowering.
Instantaneous water heaters
The columns are designed for hot water supply - heating water used for sanitary purposes: washing, bathing, washing dishes, etc.
The main components of the column are (Fig. 20):
Gas outlet;
Heat exchanger (radiator);
Main burner;
Security automation.
Rice. 20. Column
The gas outlet serves to remove combustion products into the smoke outlet of the device. Columns are installed with combustion products discharged into the chimney. The cross-sectional area of the chimney should not be less area cross-section of the smoke exhaust pipe of the column.
The heat exchanger serves for heating the combustion products of water flowing through it. It consists of a heater and a fire chamber (“jacket”) surrounded by a coil. A heater is a system of copper tubes on which copper plates are mounted and soldered. The use of copper is due to its chemical resistance and high thermal conductivity. Recently, columns with a bimetallic heat exchanger have appeared. This copper tube, the fins of which are made of a steel plate.
Column main burner- low pressure injection. It has great power to warm up running water, especially in winter, in the short time until the water is flowing through the radiator.
Column safety automation controls:
Water flow;
Pilot flame (or main burner);
Draft in the chimney;
Increasing the water temperature above the set one (not on all water pumps).
Automation based on water flow- block crane- consists of two parts - gas and water. This is the most complex column assembly. The block valve ensures gas supply to the main burner when the water intake is opened (there is a water flow) and the main burner is turned off when the water intake is stopped (no flow). In addition, the block tap blocks the main burner when the igniter is ignited: first the igniter lights up and only then the main burner. The block tap has a cone valve that provides manual control of the gas supply to the main burner.
The igniter is an injection burner low pressure, low power (on modern speakers - no more than 350 W). The pilot burner has two functions:
Lights the main burner;
Ensures the operation of automation.
Automatic flame safety on modern speakers there can be two types. In the first case, it consists of a thermocouple and a solenoid valve. When the igniter goes out, it stops the gas supply to the main burner and igniter. In the second case, flame control produced by an ionization sensor, which can monitor the flame of the igniter or the main burner. Closes when there is no flame solenoid valve at the gas inlet to the column.
Automatic traction should stop the gas supply to the main burner and igniter if there is no draft in the chimney. The response time is not less than 10 seconds, but not more than 60 seconds.
Automation for maximum water temperature turns off the main burner and igniter when the water heats above a certain temperature. She protects radiator against overheating, at which it fails (operation temperature - 90-95°C), or from scale formation in the heat exchanger. In this case, the response temperature is about 80°C. Automation for maximum water temperature is available only on modern water dispensers. Most modern models The dispensers have automatic controls that change the gas supply to the burner depending on the water flow through the dispenser.
The average service life of modern speakers is at least 12 years.
Column KGI-56
The KGI-56 column has long been out of production, but a fairly large number of these devices are in operation. The simplicity of the design, reliability, and the availability of spare parts mean that the KGI-56 will be in operation for a long time. Column KGI-56 has the following technical characteristics:
water pressure - 0.5-6 kgf/cm2;
water consumption - 7-10 l/min.
Heat exchanger (radiator) KGI-56 has a high firing chamber surrounded by a coil, which is soldered to the “shirt”.
Burner KGI-56 - single-nozzle, which caused the high fire chamber of the radiator, since the gas does not mix well with the primary air.
Rice. 21. Thermal valve diagram
The burner is equipped with a flame automatic (thermal valve), which consists of a bimetallic plate on which the valve is suspended, and an igniter (Fig. 21). When the bimetallic plate is heated with an igniter, it bends and the valve opens the gas passage to the burner. When the pilot light goes out, the plate cools down, straightens, and the valve blocks the gas passage to the main burner.
Block crane consists of gas and water parts, which are attached to each other with three screws (Fig. 22). Block crane ensures gas supply to the main burner in the presence of water intake and its shutdown when water intake is stopped (automation based on water flow).
Rice. 22. Block crane KGI-56
In the gas part There are two cone valves: one regulates the gas supply to the main burner, the other to the igniter. There is a valve in the tap on the main burner that opens the gas supply under the action of the water part rod. A small spring presses on the valve, and a large spring serves to fix the plug in the body.
In the water part A membrane is sandwiched between the lid and the body, on which the plate with the rod rests. Cold water is supplied to the water part from below. Through a hole with a diameter of 3.3 mm, pressure cold water is transferred to the submembrane space of the water part of the block tap. Therefore, the pressure under the membrane is equal to the water pressure in the water supply.
The water then passes through the radiator and returns to the water part. In this case, the heated water transfers pressure through a hole with a diameter of 2 mm to the water filling the supra-membrane space. This pressure when water flows through the column will always be less than that which presses on the membrane from below, due to the difference in the diameters of the holes in the sub- and supra-membrane space and losses due to friction. The membrane bends upward, pushing out the plate with the rod. The rod lifts the valve above the plug seat of the gas part of the block tap, overcoming the action of the small spring on top of the valve and opening the passage of gas from the internal cavity of the plug to the burner. When the water flow stops, the pressure under the membrane and above the membrane is equalized, the membrane stops lifting the rod. The valve, under the action of a small spring, will close the gas passage.
Burners are divided into injection and non-injector, single-flame and multi-flame, for gaseous fuels (acetylene, etc.) and liquid (kerosene vapor). The most widely used are injection burners operating on a mixture of acetylene and oxygen.
Diagram and principle of operation of an injection burner. The burner consists of two main parts - the barrel and the tip (Fig. 64). The barrel has oxygen 1 and acetylene 16 nipples with tubes 3 And 15 , handle 2 , frame 4 with oxygen 5 and acetylene 14 valves. WITH right side burner (if you look in the direction of gas flow) there is an oxygen valve 5 , and on the left side there is an acetylene valve 14 . The valves are used to start, regulate the flow and stop the gas supply when the flame is extinguished. Tip consisting of an injector 13 , mixing chamber 12 and mouthpiece 7 , is attached to the burner barrel body with a union nut.
Injector 13 is a cylindrical part with central channel small diameter - for oxygen and peripheral, radially located channels - for acetylene. The injector is screwed into the mixing chamber of the tip and is located in the assembled burner between the mixing chamber and the gas supply channels of the burner body. Its purpose is to create a rarefied state with an oxygen stream and suck in acetylene supplied under a pressure of at least 0.01 kgf/cm 2 . The vacuum behind the injector is achieved due to the high speed (about 300 m/s) of the oxygen jet. The pressure of oxygen entering through valve 5 ranges from 0.5 to 4 kgf/cm 2 .
The injection device is shown in Fig. 65.
In the mixing chamber, oxygen is mixed with acetylene and the mixture enters the mouthpiece channel. The flammable mixture leaving the mouthpiece at a speed of 100 - 140 m/s burns when ignited, forming an acetylene-oxygen flame with a temperature of up to 3150°C.
The torch kit includes several tip numbers. For each tip number, the dimensions of the injector channels and the dimensions of the mouthpiece are established. In accordance with this, the consumption of oxygen and acetylene during welding changes.
The design of propane-butane-oxygen burners differs from acetylene-oxygen burners in that there is a device in front of the mouthpiece 10 (Fig. 64) for heating the propane-butane-oxygen mixture. Additional heating is necessary to increase the flame temperature. The regular mouthpiece is replaced by a modified mouthpiece design.
Technical characteristics of injection burners. Currently, the industry produces welding torches of medium power - "Zvezda", GS-3 and low power - "Zvezdochka" and GS-2. The “Moscow” and “Malyutka” burners, produced before 1971, are also in operation.
Torches "Moscow", "Zvezda" and GS-3 are designed for manual oxy-acetylene welding of steel with a thickness of 0.5 - 30 mm.
The medium power burner kit includes a barrel and seven tips attached to the burner barrel with a union nut (Table 15). The required set includes tips No. 3, 4 and 6, which are most often needed when performing welding work, other tips are supplied upon customer request. Burners "Zvezdochka", GS-2 and "Malyutka" are supplied with tips No. 0, 1, 2, 3. In burners "Zvezda", GS-3, "Zvezdochka" the mouthpieces are made of bronze Br.Kh 0.5, metal more more resistant than MZ copper, which was used for the manufacture of mouthpieces for “Moscow” and “Malyutka” burners. For this reason, the service life of the burners produced is increased compared to those produced previously.
Burners of the GS-3 type work with hoses with a diameter of 9 mm. Low-power torches "Malyutka", "Zvezdochka" and GS-2 are designed for welding steels with a thickness of 0.2 - 4 mm. GS-2 burners work with rubber hoses with a diameter of 6 mm.
For the propane-butane-oxygen mixture, the industry produces burners of the GZU-2-62-I and GZU-2-62-II types; the first is intended for welding steel with a thickness of 0.5 to 7 mm, the second is for heating the metal. For flame cleaning of metal surfaces from rust, old paint etc. Oxy-acetylene burner G AO is produced (acetylene burner, cleaning). The width of the surface processed by the burner in one pass is 100 mm.
For metal hardening, NAZ-58 tips are produced for the GS-3 burner barrel.
Welding and other types of metal processing with a propane-butane-oxygen flame can be performed with a GZM-2-62M torch with four tips.
Malfunction of the injection device leads to backfire and a decrease in the supply of acetylene in the combustible mixture. The acetylene reserve is an increase in its flow rate when the acetylene valve of the burner is fully open compared to the nominal flow rate for a given mouthpiece number. The causes of these problems may be clogging of the oxygen channel, excessive increase in its diameter due to wear of the acetylene channels, displacement of the injector relative to the mixing chamber, and external damage to the injector. For normal operation of the burner, the diameter of the outlet channel of the mouthpiece must be equal to the diameter of the channel of the mixing chamber, and the diameter of the injector channel must be 3 times smaller.
The injector seat is adjusted for the injectors included in the burner kit.
Injectors from the Moscow burner can be used in the Zvezda burner, and injectors from the Malyutka burner can be used in the Zvezdochka burner.
The burner is checked for injection (vacuum) every time before starting work and when changing the tip. To do this, remove the acetylene sleeve from the nipple and open the oxygen valve. In the acetylene nipple of a working burner, a suction should be created, which can be detected by touching the nipple hole with a finger.
Maintaining the mouthpiece in proper condition ensures a normal flame in shape and size (see Chapter X). Mouthpieces work in conditions high temperature, are subject to mechanical destruction from welding spatter and require maintenance (cleaning, cooling, etc.). Scores, scuffs, and carbon deposits on the walls of the outlet channel of the mouthpiece reduce the rate of exit of the combustible mixture and contribute to the formation of pops and backfires, distorting the shape of the flame. These shortcomings are eliminated by trimming the end of the mouthpiece by 0.5 - 1 mm, calibrating and polishing the outlet hole.
After each repair, burner parts must be degreased with B-70 gasoline.
Injectorless burners operate under the same pressure of oxygen and acetylene, equal to 0.1 to 0.8 kgf/cm2. These burners provide a more constant composition of the combustible mixture during operation. Non-injector burners can be powered with acetylene, either from cylinders or from medium pressure generators.
Special burners. For gas-flame processing of materials, it is sometimes advisable to use special burners. The industry produces burners for heating metal for the purpose of heat treatment, removing paint, rust, burners for soldering, welding thermoplastics; flame surfacing, etc. The fundamental design of special torches is in many ways similar to the torch used for welding metals. The difference lies in the shape and size of the mouthpieces, as well as in the heat output, shape and size of the flame. Special burners are produced for any flammable gas.
Control questions
1. Why for gas welding Is acetylene the main flammable gas used?
2. Tell us about the classification of acetylene generators.
3. What role does the injector play in the burner?
4. What effect does the injection device and mouthpiece design have on the operation of the burner?
5. What types of special burners are there?
Gas welding is welding using molten metal. During this process, the edges of the metal parts of the parts are heated to the melting point by the flame of a gas burner.
The high temperature at which the metal melts occurs from the ignition of the gas-oxygen mixture. Melted filler wire is used to fill the voids that occur when the edges of the metal meet.
Torches for gas welding.
To obtain the welding flame necessary for working with metals, a torch is used. With its help, you can control the power and volume of the flame within established limits. Despite all the external simplicity of the product, the torch is a complex and significant element in welding.
Figure No. 1 shows a gas burner flame with temperature indicators.
According to their design, gas welding torches are divided into:
- injection;
- non-injector.
According to the fuel used:
- acetylene;
- for other gases and liquid fuels.
The order of use may be:
- manual,
- by machine.
Injector and non-injector torches for gas welding.
The structural presence of a jet pump in the burner is determined by the pressure level at which fuel is supplied to it. If it is high, then no additional injection is required; the fuel is supplied under its own. At low pressure you need large quantity gas, so forced supply is used using an injector. To create a welding flame, you need to obtain a high-quality mixture of oxygen and fuel in the mixing chamber of the torch.
A burner without an injector has a simpler design. Fuel and oxygen are supplied to the mixer simultaneously using a supply system consisting of hoses, required quantity taps (valves), nipples. A homogeneous mixture is formed in the mixer.
The homogeneous mixture flows through the tip tube to the mouthpiece, ignites and creates a flame for welding. To ensure that the combustion process matches necessary requirements, the pressure with which the mixture is supplied from the mouthpiece must be within strictly defined limits. If the speed is higher than the set one, the flame, breaking away from the burner cut, will go out. If it is lower, then the mixture, getting inside the burner, will explode in it. The supply speed of the flammable mixture (acetylene-oxygen) varies from 70 to 160 m/sec, it depends on the type of mouthpiece, the size of the channel, and the percentage composition of the mixture.
High pressure burners can use hydrogen or methane. It is easy to use and easy to set up. But, in comparison with low pressure injection burners, they are used much less frequently.
Low pressure burner operation.
Oxygen under high pressure (about 4 atmospheres) enters the burner through a supply system consisting of a nipple and an adjustment valve. Passes through the injector with high speed. Under the influence of a stream of oxygen, a pressure below atmospheric pressure is created in the chamber of the jet pump and flammable gas is sucked in. It enters through the nipple and valve into the injector chamber, and then into the mixing chamber, connects with oxygen, and flows through the channel to the mouthpiece at a speed within strict limits.
The oxygen consumption does not change and is not affected by external factors, unlike the consumption of the gas used. An increase in the temperature of the mouthpiece and burner tip, a change in pressure, and an increase in resistance increase the consumption of acetylene.
Other types of burners.
In some industries, gas welding torches operating on liquid fuels such as gasoline or kerosene have been used. The principle is based on the spraying of a kerosene-oxygen mixture and the evaporation of fine-droplet fuel from heating from the mouthpiece.
For trouble-free operation, currently used burners must meet the following safety requirements:
- the welding flame must be of a certain shape;
- adjusting the flame within the required limits;
- resistance to external influences and operational safety;
- ease of use.
