Safe use of the hottest gas welding and cutting eq

Safe use of gas welding and gas cutting equipment and tools

I. safe use of gas welding and gas cutting equipment

1. Structure of common gas cylinders

oxygen and hydrogen cylinders used for gas welding and gas cutting belong to compressed cylinders, acetylene cylinders belong to dissolved cylinders, and petroleum cylinders belong to liquefied cylinders

(1) structure of oxygen bottle

oxygen bottle is a special high-pressure container for storing and transporting oxygen. Oxygen cylinders are usually rolled into seamless cylindrical containers with high-quality carbon steel or low-alloy structural steel. The volume of the commonly used gas cylinder is 40L, and the oxygen pressure in the cylinder is 15MPa, which can store 6m3 of oxygen. Before the oxygen cylinder leaves the factory, in addition to the strict inspection of all parts of the oxygen cylinder, it is also necessary to conduct a hydrostatic test on the cylinder body. Generally, the test pressure is 1.5 times the working pressure. And make obvious marks on the spherical part of the upper part of the bottle. The marks indicate: cylinder number, working pressure and test pressure, next pressure test date, steel seal of the inspector, steel seal of the inspection department of the manufacturer, capacity and weight of the cylinder, manufacturer, ex factory date, etc. In addition, internal and external surface inspection and hydrostatic test must be carried out regularly during the use of oxygen cylinders; The surface of the oxygen cylinder is sky blue and marked with "black paint"; Oxygen rdquo; Words

(2) structure of acetylene cylinder

acetylene cylinder is a special container for storing and transporting acetylene gas, and its shape is similar to that of oxygen cylinder. Its structure is more complex than that of an oxygen cylinder, mainly because acetylene cannot be pressed into an ordinary cylinder at high pressure. Instead, necessary measures must be taken to press acetylene into the cylinder by taking advantage of the fact that acetylene can be dissolved in acetone. The cylinder body of acetylene is made of high-quality carbon structural steel or low-alloy structural steel by rolling and welding. The volume of acetylene cylinder is 40L. Generally, 6 ~ 7kg acetylene can be dissolved in acetylene cylinder. The working pressure of acetylene cylinder is 1.5MPa, and the pressure of hydrostatic test is 6Mpa. The surface of acetylene cylinder is white and marked with red words acetylene and fire are not accessible

(3) structure of liquefied petroleum gas cylinder

liquefied petroleum gas cylinder is a special container for storing liquefied petroleum gas. According to different dosage and use methods, the storage capacity of gas cylinders is Lokg, 15kg, 36kg and other specifications, and gas storage tanks with a capacity of 1t, 2T or larger can also be manufactured. The cylinder is made of 16Mn, A3 steel or 20 high-quality carbon steel. The maximum working pressure of the gas cylinder is 1.6Mpa, and the hydrostatic test is 3Mpa. After the cylinder passes the test and identification, the metal nameplate of the cylinder is marked with contents similar to those indicated by the oxygen cylinder. The surface of the gas cylinder is silver gray and has ldquo; Liquefied petroleum gas rdquo; Red words

2. Causes of gas cylinder explosion accident

(1) the material, structure and manufacturing process of the gas cylinder do not meet the safety requirements

(2) due to poor storage and use, it is exposed to sunlight, open fire, thermal radiation, etc

(3) during handling and loading, the cylinder falls from a height, tilts or rolls, causing severe impact

(4) the cylinder valve is not protected by the cylinder cap, and is subject to vibration or improper use, resulting in loose sealing, leakage, even damage to the cylinder valve, and high-pressure air flow rushing out

(5) the gas opening speed is too fast, and static sparks are generated when the gas flows rapidly through the bottle valve

(6) there is grease on the valve, valve rod or pressure reducing valve of the oxygen cylinder, or other combustible gases are mixed in the oxygen cylinder

(7) gas leakage occurs in combustible gas cylinders (acetylene, hydrogen, petroleum cylinders)

(8) the porous material filled in the acetylene cylinder sinks, creating a clear space, making the acetylene gas in a high-pressure state

(9) when the acetylene cylinder is in a horizontal state or a large amount of acetylene is used, acetone flows out with it

(10) the cylinder is overfilled and the pressure in the cylinder is too high when heated

(11) the cylinder has not been subject to regular technical inspection

3. Safe use of gas cylinders

(1) oxygen cylinders

a. before leaving the factory, oxygen cylinders must be subject to strict technical inspection in accordance with the provisions of the gas cylinder safety supervision regulations. After passing the inspection. Obvious marks shall be made on the spherical part of the cylinder

b. when filling the oxygen cylinder, the external inspection must be carried out first, and the gas in the cylinder must be carefully identified. It is not allowed to fill at will

c. oxygen cylinders must wear caps during transportation and avoid collision with each other. They cannot be transported with cylinders of combustible gases, Oils and other combustibles. When handling gas cylinders, special trolleys must be used and fixed firmly. Do not roll the oxygen cylinder on the ground

d. generally, oxygen cylinders should be placed upright and must be placed firmly to prevent dumping

e. when taking out the bottle cap, it can only be rotated by hand or wrench, and it is forbidden to knock with iron

f. before installing the pressure reducer on the bottle valve, unscrew the bottle valve, blow out the impurities in the air outlet, and gently close the valve. After installing the pressure reducer, open the valve slowly. Opening it too fast may cause the pressure reducer to burn and explode

g. when installing the pressure reducer on the bottle valve/the nut connected with the valve port should be firmly screwed to prevent falling off when opening the gas, and the human body should avoid the direction of valve ejection

h. it is strictly forbidden to stick flammable substances and grease on oxygen cylinder valves, oxygen pressure reducers, welding torches, cutting torches, oxygen hoses, etc., so as to avoid fire or explosion

i. when using oxygen cylinders in summer, they must be placed in the shed and no sunlight is allowed; In winter, don't put it on the stove or too close to the heating to prevent explosion

j. prevent the oxygen cylinder valve from freezing in winter. In case of freezing, only hot water and steam can be used to thaw. It is strictly forbidden to bake with open fire or knock with iron, so as not to cause the bottle valve to break

k. don't use up all the oxygen in the oxygen cylinder. Finally, leave 0.1 ~ 0.2MPa of oxygen to identify the nature of the gas during oxygen charging and prevent air or combustible gas from flowing back into the oxygen cylinder

l. keep away from high temperature, open fire, molten metal splash, combustible and explosive substances in the gas cylinder warehouse and when using gas cylinders. Generally, the distance is more than 10m

m. oxygen cylinders must be checked regularly and can only be used after they are qualified

n. when the oxygen cylinder valve is on fire, the valve should be closed quickly and the gas supply should be stopped to make the flame extinguish by itself. In case of fire in adjacent buildings or combustibles, the oxygen cylinder should be moved to a safe place as soon as possible to prevent explosion caused by high heat in the fire site

(2) acetylene cylinder

in addition to the safe use of oxygen cylinders, the following points should be strictly observed when using acetylene cylinders:

① acetylene cylinders should not be subjected to severe vibration and impact, so as to avoid acetylene cylinder explosion

② acetylene cylinders should be placed upright when in use, and cannot lie down, so as to avoid the outflow of propylene and cause combustion and explosion

③ the connection between acetylene pressure reducer and acetylene cylinder valve must be reliable, and it is strictly prohibited to use it in case of gas leakage

④ open the acetylene cylinder valve slowly, not more than one and a half revolutions, generally only 3/4 revolutions

⑤ the temperature of the acetylene cylinder surface should not exceed 30 ~ 40 ℃, because high temperature will reduce the solubility of acetone to acetylene and sharply increase the acetylene pressure in the cylinder

⑥ acetylene in acetylene cylinder cannot be used up completely, and acetylene gas above 0.03mpa must be left at last. Close the bottle valve tightly to prevent air leakage

⑦ when the acetylene cylinder valve is frozen, it cannot be baked with open fire. If necessary, thaw with warm water below 40 ℃

⑧ when using acetylene cylinders, they should be installed in type flashback preventer to prevent flashback from passing into the cylinder

(3) liquefied petroleum gas cylinders

① the same as oxygen cylinders A. ~ n

② corrosion of petroleum gas on ordinary rubber pipes and gaskets denipe's new advanced manufacturing plant in Suzhou, China, has been officially put into operation, which is easy to cause air leakage, so rubber pipes and gaskets with strong oil resistance must be used

③ petroleum gas is heavier than air, easy to flow to low places, and volatile, and will cause combustion accidents in case of open fire. Therefore, the use site should be well ventilated for air convection

④ the pressure inside the gas cylinder is directly proportional to the utilization temperature of the flocking like material on the column in Figure 10. As the temperature rises, the pressure in the cylinder also increases, so the cylinder should be away from heat sources and radiators

⑤ when using petroleum cylinders in winter, they can be heated with warm water below 40 ℃. It is strictly forbidden to bake by fire or heat with boiling water

⑥ excessive petroleum gas can cause suffocation, so pay attention to ventilation when using

⑦ when LPG is ignited, ignite the igniter first and then turn on the gas

⑧ do not pour out the residual liquid of LPG by yourself to prevent fire in case of fire

in a word, all kinds of gas cylinders must be subject to regular technical inspection in accordance with the requirements of the national gas cylinder safety supervision regulations

in the case of centralized supply of gas for welding and cutting, acetylene, oxygen, etc. are transported by conduit. All gas transmission pipelines belong to pressure pipelines. Therefore, its design, formulation, installation, use and maintenance should not only consider the characteristics of the transmission medium, but also meet the requirements of national departments for pressure pipelines

II. Safe use of gas welding and gas cutting tools

welding torches and cutting torches are the main tools for gas welding and gas cutting. In use, the proportion and heat of oxygen and combustible gas should be easily adjusted, and the weight should be light, safe and reliable

(1) classification of welding torches

according to the mixing mode of combustible gas and oxygen, they are divided into two types: injection type and isobaric type; According to the type of combustible gas, it can be divided into acetylene, hydrogen, petroleum gas and other types; According to the number of flames, it can be divided into single flame and multi flame; According to the method of use, it can be divided into manual and mechanical

at present, most welding torches used in China are injection type. In this kind of welding torch, the flow of acetylene mainly depends on the injection and absorption of oxygen, so whether medium pressure or low pressure acetylene is used, the welding torch can work normally

(2) safe use of welding torch

① before ignition, the injection and suction performance of the injection and suction welding torch must be checked to see whether it is normal, and whether there is air leakage at the connecting parts of the welding torch and the needle valve adjusting the handwheel

② ignition can only be carried out after passing the above inspection. When igniting, first turn on the acetylene wheel, ignite acetylene, and immediately turn on the oxygen regulating handwheel to regulate the flame. Compared with the method of switching on oxygen first and then acetylene, this ignition method has the advantages that it can avoid the detonation phenomenon during ignition, it is easy to find out whether the welding torch is blocked, the flame gradually becomes stronger from weak, and the flame combustion is stable. Its disadvantage is that it emits black smoke when it is just ignited, which affects environmental sanitation. You can also turn on the oxygen regulating hand wheel slightly before turning on the acetylene regulating hand wheel and start the ignition immediately. This method can eliminate the disadvantage of emitting black smoke, but once the welding torch is blocked, oxygen may enter the acetylene channel and form tempering conditions. From the perspective of safe operation requirements, it is recommended to adopt the previous operation method

③ when the flame is stopped, the acetylene regulating hand wheel should be turned off first to prevent backfire and black smoke

④ all gas paths of the welding torch are not allowed to be contaminated with grease, so as to prevent oxygen from burning and exploding when encountering grease

⑤ select the appropriate welding torch and nozzle according to the thickness of the weldment. Tighten the welding nozzle with a wrench until there is no air leakage

⑥ in the process of use, if air leakage is found in the gas path or valve, stop working immediately and continue to use after the air leakage is eliminated

⑦ do not lay the burning welding torch on the weldment or the ground

⑧ when the welding nozzle head is blocked, it is strictly forbidden to rub the nozzle head with the flat plate, and the through needle should be used to clean it to eliminate the blockage

⑨ after the work is suspended or finished, the oxygen and acetylene cylinders should be closed, and the pointer of the pressure gauge should be adjusted to zero. At the same time, coil the welding torch and hose, hang them on the shelf near the wall or remove the rubber