Safety technology of the hottest heating work

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Safety technology of heating work

the main purpose of heating forging materials is to improve the plasticity of metal and reduce the deformation resistance, so as to facilitate the deformation of metal and obtain good microstructure after forging

There are many kinds of forging heating furnaces. According to the different heat sources used, forging heating furnaces can be divided into flame heating furnaces and electric heating furnaces

I. fire fighting heating furnace

flame heating furnace has coal furnace, oil furnace and gas furnace according to different fuel types; According to the different structure of heating chamber, it can be divided into chamber furnace (single chamber furnace and double chamber furnace), semi continuous furnace and continuous furnace; According to the mechanized form of furnace bottom, it can be divided into trolley furnace and rotary bottom furnace. The forging workshop always selects certain furnace type heating equipment according to its specific working conditions and needs

several furnace structures and their safety technologies introduced in this section have universal significance in domestic forging production at present

(I) coal fired reverberatory furnace

the forging workshops with medium and small batch production generally use the reverberatory furnace with coal as fuel. Its structural diagram is shown in Figure 1. It is composed of combustion chamber, heating chamber, air supply device, heat exchanger, flue, chimney and other parts

Figure 1 structural diagram of reverberatory furnace

1 - primary air supply pipe 2 - horizontal furnace 3 - combustion chamber 4 - secondary air supply pipe 5 - fire wall 6 - heating chamber (furnace) 7 - charging and discharging furnace door 8 - blower 9 - chimney 10 - flue 11 - heat exchanger

the combustion chamber of reverberatory furnace can be divided into horizontal grate combustion chamber and stepped grate combustion chamber according to the location of its grate. The former is mostly thin coal seam combustion, while the latter adopts thick coal seam combustion

when using a reverberatory furnace, common industrial accidents include: gas poisoning, smoking, baking, scalding, smoking and burning. In order to prevent the occurrence of the above accidents, it is necessary to gradually improve the working conditions, change manual operation into mechanized operation, reduce the physical labor intensity of workers, and eliminate the inducing factors of accidents

(II) oil fired and gas fired furnaces

1. Chamber type oil fired (mostly burning heavy oil) and gas fired heating furnaces

are consistent in furnace structure. They do not need a special combustion chamber, but the fuel and air are evenly mixed by the heavy oil nozzle or gas burner and injected into the heating chamber for combustion. Heat exchangers can also be used to preheat air and gas as needed

Figure 2 shows a chamber type heavy oil furnace. The waste gas generated by combustion is discharged through the flue. The furnace mouth 4 on the front of the furnace is used for charging and discharging, and a furnace door is set outside it

Figure 2 Schematic diagram of chamber type heavy oil furnace

1 - nozzle 2 - heating chamber (furnace) 3 - flue 4 - furnace mouth

2. general nozzles and burners used in heavy oil furnace and gas furnace

heavy oil nozzle: the more evenly the heavy oil is mixed with air during combustion, the better and faster the combustion will be, and the less air will be required. Therefore, heavy oil must be sprayed into a fog during combustion, so that it can be evenly mixed with air, and then burned in the heating chamber. In order to ensure good spraying, the heavy oil must be pre filtered in the oil depot to make it free of dust and dirt, and the heavy oil must be preheated to 90 ℃ ~100 °. The heavy oil for combustion must be pressurized by the oil pump, generally (0.5~1.5) × 101325Pa。

gas burner: gas should be evenly mixed with air during combustion. It is sprayed by the gas burner and burned in the heating chamber. According to the required gas pressure, gas burners can be divided into low-pressure gas burners and high-pressure gas burners

because the high-pressure gas burner mixes the gas and air first, and then injects it into the heating chamber; Therefore, the combustion is relatively rapid and complete, and there is no obvious flame; High combustion temperature; Less fuel consumption. When using this burner, the preheating temperature of the gas cannot be higher than 400 ℃, otherwise it will cause explosion

3. A new type of burner for oil and gas - flat flame burner

in order to make the temperature in the furnace tend to be uniform and improve the quality of metal heating, the torch shaped Flame (which is the flame shape of the above general nozzle and burner when burning) must be changed. Therefore, according to the combustion characteristics of gas and oil, a new type of burner - flat flame burner has been promoted in recent years. The flame of this burner is disc-shaped, especially when the flame extends to the furnace wall, the flame will cling to the furnace wall and follow the trend to form a hood. (as shown in Figure 3), this makes the furnace temperature tend to be uniform, thus improving the heating and heating quality. The use of flat flame burners is much simpler than torch burners for ignition, and can improve working conditions and reduce environmental pollution

Figure 3 the form of flat disc flame in the furnace

1 - air intake 2 - oil intake 3 - combustion supporting air 4 - Blank

4. Precautions for safe operation of heavy oil furnace

(1) clean the oxide skin, broken bricks and dirt in the furnace. Check the oil pipe, air duct and heating pipe for cracks, air leakage and other faults

(2) open the flue gate and furnace door before ignition

(3) ignite the oil cotton yarn or rags with fire, open the throttle and damper in a small amount first (the nozzle must be heated before the oil melts), and then gradually open the throttle and damper after the oil burns

(4) when lighting the furnace, no one is allowed to stand on the front of the furnace door, and no one is allowed to look at the fire spout

(5) if it is found that the nozzle or nozzle installation port is blocked by oil residue and needs to be dredged, the throttle and air valve should be closed in advance before it can be allowed to be dredged

(6) it is forbidden to throw materials directly onto the bottom of the furnace. Materials should be placed on the charging platform in front of the furnace door before being pushed into the furnace

(7) when charging, discharging or turning over the blank in the furnace, the error caused by the weight of the piston, test piece and fixture such as the throttle and damper must be eliminated and turned down, so as to burn the operator with the spray of the fire tongue

(8) when using fire hooks, tongs, and crowbars, pay attention to whether there is someone behind you. After use, don't throw them around in a bowl shape, so as to prevent people from being injured

(9) when handling materials, attention should be paid to prevent burrs and handles. When handling materials by multiple people, unified call signs, coordinated steps and mutual care should be taken

(10) inflammables are strictly prohibited around the heating furnace

(11) at the end of the work, close the throttle first, then close the damper, put down the ram and lower the furnace door

(12) clean the sanitation in front of and behind the furnace to eliminate the hidden danger factors that are easy to cause fire

5. safety operation matters when using industrial gas burners

preparations before using gas burners:

(1) check whether the gas valves on each burner are all closed. If there is a gas leak, it must be repaired before use

(2) open the boiler door

(3) open the flue gate

(4) turn on the air valve on each burner, and then turn on the blower to discharge the gas accumulated in the furnace

(5) check whether the gas pressure is normal. If there is a jump, check the reason and make it normal before ignition

safety operation regulations for gas stove:

(1) no one is allowed to stand at the door of the stove during ignition

(2) open the air valve on the burner a little; Ignite the ignition rod, insert it into the ignition hole, make the flame close to the combustion burner, and then open the gas valve on the burner, and the gas will burn when it meets the fire

(3) it is strictly forbidden to open the gas valve on the burner before the ignition rod is inserted into the ignition hole to avoid explosion

(4) the burners must be ignited and adjusted one by one from top to bottom, from inside to outside, and all burners must not be opened and ignited at the same time

(5) if the gas valve on the burner fails to ignite after being opened, the gas valve must be closed immediately, the air valve must be opened to drain the gas in the furnace, and then the secondary ignition must be carried out

(6) long and yellow flame is the phenomenon of incomplete combustion of gas, so it is necessary to open the air valve or turn down the gas valve. Short flame with harsh noise is the phenomenon of excessive air, so it is necessary to turn down the air valve or turn on the gas valve

(7) close the furnace door

(8) adjust the flue gate to make the furnace burn under slight positive pressure

operating procedures for deactivating the gas stove:

(1) first close the gas valve and air valve on each burner one by one

(2) close the main gas valve and the main air valve

(3) stop the blower air supply

(4) close the furnace door and flue gate

precautions for the use of gas stove:

(1) in case of power failure or blower failure during use, close the gas valve immediately

(2) if the gas pressure jumps too much, the furnace needs to be stopped

(3) in case of gas pipeline leakage, immediately notify the repair organization to send personnel to deal with it, and take the following measures:

1) avoid kindling (such as smoking, turning on and off electrical equipment, etc.)

2) close the relevant gas valve

3) open the doors and windows

4) keep a certain distance from the air leakage point to protect the site

II. Semi continuous heating furnace and continuous heating furnace

as mentioned above, according to the different structure of heating chamber, in addition to chamber furnace, there are semi continuous heating furnace and continuous heating furnace. Semi continuous type is used more in die forging production. The ratio of length to width of semi continuous furnace is less than 4 as reported; The length width ratio of continuous furnace is greater than 6. The latter, of course, has higher thermal efficiency. The structures of semi continuous heating furnace and continuous heating furnace are shown in Figure 4 and figure 5 respectively

Figure 4 pusher semi continuous heating furnace

Figure 5 pusher continuous heating furnace

1 - pusher 2 - charging port 3 - low temperature zone 4 - high temperature zone 5 - burner or nozzle 6 - discharge port 7 - water cooling pipe 8 - flue

the billets heated by this kind of heating furnace are pushed from the low temperature zone to the high temperature zone along the furnace bottom by mechanical, pneumatic or hydraulic pushers. The billets are preheated, heated and burned in turn during the moving process. It should be noted that the bottom of the heating furnace is easy to be scratched into pits by the blank, or bulges due to the accumulation of oxide skin, which needs to be cleaned in time

semi continuous or continuous heating furnace can burn gas or heavy oil, and its operation safety precautions are the same as that of chamber furnace

III. electric heating furnace

(I) working principle

use electricity to heat metal materials, because the heating temperature is accurately controlled; Oxide skin fire; Good working conditions are welcomed by people. Common electric heating methods include induction heating, contact electric heating and resistance heating

both induction heating and contact heating actually use a kind of heater. The sensor style is determined by the shape and size of the heated blank. Contact heating has more strict requirements on the surface roughness and shape and size of the heated blank. In contrast, resistance heating furnace has been widely used because of its strong versatility

the resistance heating furnace also has familiar access control cards and second-generation ID cards, which are the use of various types of this technology. The box type resistance furnace is commonly used in the forging workshop, and its furnace structure is shown in Figure 6. The billets are loaded into the furnace from the furnace mouth, and the electricity can be sent for heating after the furnace door is closed. The electric heater (resistance wire) transfers heat to the blank by radiation to heat it to the required temperature. The lifting and lowering of the furnace door is controlled by a pedal transmission device

(II) safe operation of electric furnace

precautions for safe operation should be observed when using electric furnace:

1. Always check the safety of furnace and whether the grounding wire is good

2. In addition to wearing labor protection articles, when hooking up and shoveling fire, the handle of the tool should be covered with insulating rubber hose, and the foot should be padded with rubber pad to prevent scalding or electric shock

3. before work

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