Essential Guide to Welding Gas Use and Safekeeping

The use of gases in welding mainly refers to the shielding gases used in gas shielded welding (including CO2 gas shielded welding and inert gas shielded welding), such as CO2, Ar, He, O2, Ar+CO2, Ar+O2, and the gases used in welding and cutting processes, such as O2-C2H2, H2, CH4, and liquefied petroleum gas.

Use and Storage of Gas Cylinders

Cylinders used for welding can be categorized based on their storage forms: compressed gas cylinders (such as oxygen, argon, and hydrogen cylinders), dissolved gas cylinders (acetylene cylinders), and liquefied gas cylinders (such as liquefied petroleum gas and CO2 cylinders). In general, gas shielded welding commonly employs gas supply from steel cylinders, therefore, it is essential to adhere to the relevant regulations of cylinder safety protocols.

The gas cylinders must undergo inspection.

The inspection stamp on the neck of the gas cylinder indicates that it is within the allowed time frame and bears the manufacturer’s stamp. The color of the cylinder must match the gas it contains.

Storage and transportation of gas cylinders

1.When storing and transporting, avoid direct exposure of the gas cylinders to heat (such as direct sunlight, proximity to heaters, or boilers). They should be stored in a cool, well-ventilated indoor area. During storage, use brackets for support to prevent impact and tipping.

2.During transportation, tighten the cylinder caps securely and handle them with care. It is strictly prohibited to drop, slide, or collide with cylinders from a height. When transporting cylinders by vehicle, ensure they are securely fastened.

Cylinders should be placed horizontally, with their heads facing in one direction. The height of the loaded cylinders should not exceed the height of the vehicle compartment, and it is preferable to use a container frame for vertical placement.

3.During the summer, measures should be taken to provide shade to prevent direct exposure to sunlight. Flammable materials, grease, and items with oil stains are not allowed to be transported in the same vehicle as oxygen cylinders. When transporting and storing acetylene and liquefied gas cylinders, they should be kept upright, and it is strictly prohibited to lay them horizontally.

Safety inspection before using gas cylinders

1.Are the valve and connecting pipe threads intact? Is the pressure test date of the gas cylinder expired?

2.Check for gas leaks and unresponsive gauge needles in the gas cylinder valve and pressure regulator. When inspecting, apply a small amount of soapy water, but avoid using open flames for illumination.

3.When using in winter, it is necessary to check for any freezing on the cylinder valve and pressure regulator. If frozen, use hot water and steam to thaw. Absolutely do not use open flames or red-hot iron for heating or use iron tools for knocking.

4.When gas welding, gas cutting, and arc welding equipment are used at the same workstation, check whether the cylinder body is in contact with the welding equipment conductor, and take appropriate measures to prevent the gas cylinder from becoming charged.

5.When gas cylinders are used at temporary work sites, check whether the cylinders are securely upright, and use appropriate supports to secure the gas cylinders.

6.The area around the gas cylinder storage should keep the cylinders at least 10 meters away from open flames, boilers, grinding wheels, and other heat sources, including molten metal splashes. If necessary, protective screens can be installed to isolate the gas cylinders from heat sources.

7.Fire hydrants and fire-fighting equipment such as dry powder and carbon dioxide fire extinguishers should be available near the work site. It is strictly prohibited to use carbon tetrachloride fire extinguishers to extinguish acetylene fires.

The use and management of gas cylinders

1.Gas cylinders should be equipped with dedicated pressure reducers and flashback arrestors. When opening, the operator should stand to the side and behind the valve outlet of the cylinder, and the action should be gentle. The opening sequence should be to first open the high-pressure valve, then the low-pressure valve. The closing sequence should be the same.

2.It is forbidden to strike or collide with the gas cylinder. The cylinder should not be placed near a heat source. The distance between hydrogen and oxygen and an open flame should generally be no less than 10 meters. If the valve of the cylinder is frozen, it should not be thawed with fire.

3.It is not allowed to use electromagnetic lifting equipment to move gas cylinders. In summer, exposure to direct sunlight should be prevented. The gas in the cylinder should not be completely used up, and the remaining gas pressure should be 0.5 to 1 MPa to prevent the backflow of air and other gases into the cylinder.

4.Gas cylinders should be stored by category, and mixing different types of gas cylinders should be avoided. In the storage room for acetylene cylinders, mixing with other gas cylinders and flammable materials is strictly prohibited. Gas cylinders should undergo regular technical inspections as required, and the use of cylinders that have expired without inspection should be stopped.

5.When using new gas cylinders, carefully inspect the labels and stampings according to the gas cylinder safety inspection procedures and the dissolved gas cylinder safety inspection procedures. Those that do not meet the requirements should be taken out of service. Gas cylinders without protective caps or rings are strictly prohibited from being transported by vehicles.

The use and storage of oxygen

Safe use of oxygen

The purity of oxygen used for gas welding and cutting is very high, with primary purity not less than 99.2% and secondary purity not less than 99.5%. Oxygen is compressed into pipelines or steel cylinders using a compressor, with the pressure in the cylinder typically around 15 MPa and the pressure inside the cylinder pipeline ranging from 0.5 to 1.5 MPa.

Due to the high purity and pressure of industrial oxygen, special attention should be paid to its safe use. In addition to prohibiting contamination of storage containers and tools with grease, it is also important to prohibit the use of compressed oxygen instead of fresh air for ventilation or as a power source for pneumatic tools, or for blowing dust off work clothes. Oxygen should not be used to clear blockages in acetylene hoses.

The use and storage of oxygen cylinders

Oxygen cylinders are high-pressure containers used for storing and transporting oxygen. The pressure inside the cylinder is approximately 15 MPa, and it can store 6m³ of oxygen.

The cylinders are painted sky blue and labeled with “Oxygen” in black. Due to the high pressure inside the cylinders and the fact that oxygen is a highly reactive oxidizing gas, improper use could lead to an explosion. Therefore, several precautions should be observed when using oxygen cylinders:

1.The exterior of the oxygen cylinder, including the cap, should be painted sky blue and labeled with “Oxygen” in black paint to distinguish it from other cylinders. They should not be stored together with other types of cylinders.

2.When using oxygen, the cylinder should not be completely emptied. A minimum pressure of 0.1 to 0.2 MPa of oxygen should be maintained to conduct dust blowing tests during refilling and to prevent the mixing of other gases.

3.During the summer, oxygen cylinders should be protected from direct sunlight. They should be kept at a distance of at least 10 meters from welding torches, cutting torches, furnaces, and other sources of heat. Strict precautions should be taken to avoid impact during the handling and use of oxygen cylinders. Anti-vibration rubber rings must be present on the cylinders, and they should be moved using a handcart with care.

4.Oxygen cylinders must not come into contact with grease or oil, especially around the valve. When not in use, the valve of the oxygen cylinder should be tightly closed.

5.In accordance with cylinder inspection regulations, oxygen cylinders must undergo regular inspections. They should be inspected at least once every three years, and they can only be used if they pass the inspection. If severe corrosion is found on an oxygen cylinder, it should either be depressurized for use or discarded.

The use of an oxygen cylinder regulator

The oxygen cylinder regulator (also known as an oxygen gauge) is used to reduce the high-pressure oxygen stored in the cylinder to the working pressure and can flexibly adjust and maintain a stable working pressure.

When installing or removing the oxygen cylinder regulator, it is essential to strictly follow the following guidelines to ensure safety:

1.Before installing the regulator, slightly open the valve of the oxygen cylinder to release some oxygen, blow off any impurities from the bottle mouth, and ensure that the oxygen cylinder nozzle does not face the body during operation.

2.After checking that the regulator and bottle valve threads are in good condition, use a clean, oil-free tool to accurately and slowly screw the regulator onto the bottle valve.

3.Loosen the regulator adjustment screw and slowly open the gas cylinder valve. Check for leaks and ensure the high-pressure gauge needle is flexible and accurate. Once everything is normal, connect the gas delivery hose, gradually tighten the adjustment screw, and observe the low-pressure gauge to stop when it reaches the required pressure. Check for leaks again.

4.After finishing work, first close the gas cylinder valve, release the remaining gas inside the gauge and the pipeline, then loosen the adjusting nut, and remove the regulator. It is important to avoid transporting the cylinder with the regulator attached.

In terms of safety management, the use of an oxygen cylinder regulator should strictly adhere to the following regulations to ensure safety:

1.It is strictly prohibited to use the oxygen cylinder regulator for other gases, such as acetylene, liquefied petroleum gas, hydrogen, etc. The internal parts of the regulator should not be disassembled or interchanged at will.

2.When the regulator freezes, it should be thawed using clean warm water and steam, and it should never be heated using fire or red-hot iron. It should not be stored together with parts containing grease. When not in use for an extended period, it should not be sealed with grease-based coatings.

3.When using a new oxygen cylinder regulator, it should be operated correctly according to the instructions. The pressure gauge on the regulator must undergo regular inspections.

The Use and Storage of Acetylene

Explosive Characteristics of Acetylene

Acetylene is a flammable gas commonly used in gas welding and cutting. It possesses dangerous explosive characteristics, requiring strict attention to safety during use. Pure acetylene gas, untouched by an open flame, can self-heat when the pressure reaches 0.15 to 2.0 MPa, and may explode at temperatures of 550°C. Mixing acetylene with other gases also greatly increases the risk of explosion.

1.The mixture of acetylene and air is highly explosive. When the acetylene content in the mixture ranges from 2.3% to 8%, it can explode upon contact with sparks. When the acetylene content is between 7% and 13%, its explosiveness is even more pronounced. To prevent the explosion of mixed gases, acetylene cylinders are equipped with a specific “venting valve” for releasing mixed gases into the air before ignition.

2.When oxygen and acetylene mixtures encounter a source of ignition, they can also explode, with a greater explosive force than acetylene-air mixtures.

As oxygen is generally pressurized at around 0.5 MPa and acetylene at pressures below 0.15 MPa, it is crucial not to open the oxygen valve too wide during use, to prevent excessive oxygen pressure in the mixed gas. This precaution avoids the risk of unvented oxygen flowing back into the acetylene pipeline and causing an explosion.

The Use and Storage of Acetylene Cylinders

An acetylene cylinder is a steel container used for storing and transporting welding acetylene. Its outer surface is painted white and labeled with red markings stating “Acetylene” and “No Fire or Flame.” The cylinder is equipped with a dedicated acetylene gas valve.

The working pressure of the acetylene cylinder is 1.55 MPa. Due to the flammability and explosiveness of acetylene, cautious handling is essential. In addition to adhering to the requirements for using oxygen cylinders, strict compliance with the following points is also necessary:

1.Acetylene cylinders should not be subjected to severe vibrations and impacts to prevent the settling of porous filler inside the cylinder, which could create voids and affect acetylene storage.

2.When in use, acetylene cylinders should be kept upright. Horizontal placement can cause acetone to flow out and even seep into the acetylene rubber hose and welding or cutting torches through the pressure reducer, leading to combustion and explosions.

3.The surface temperature inside the acetylene cylinder should not exceed 30-40°C. Elevated temperatures can reduce the solubility of acetone in acetylene, causing a rapid increase in acetylene pressure inside the cylinder, leading to explosions.

4.The connection between the acetylene regulator and the cylinder valve must be secure. Under no circumstances should the system be used if there is a gas leak, as this could result in the formation of a mixture of acetylene and air, leading to explosion incidents upon contact with an open flame.

5.When using acetylene, it is strictly prohibited to deplete the entire volume of acetylene in the cylinder. A certain residual pressure must be maintained based on the temperature, and the cylinder valve must be tightly closed to prevent gas leaks.

  • Between -5°C and 0°C, the residual pressure should not be less than 0.05MPa.
  • Between 0°C and 15°C, the residual pressure should not be less than 0.098MPa.
  • Between 15°C and 25°C, the residual pressure should not be less than 0.196MPa.
  • Between 25°C and 35°C, the residual pressure should not be less than 0.294MPa.

In addition to the handling and usage of acetylene, other commonly used gases such as argon and carbon dioxide also require specific handling and usage protocols. When using argon gas cylinders, it is strictly prohibited to knock or collide with them.

If the valve of the cylinder is frozen, it should not be thawed with fire. Electromagnetic lifting equipment should not be used to move argon gas cylinders. In summer, they should be protected from direct sunlight. The gas inside the cylinder should not be completely used up, and argon gas cylinders should generally be stored upright.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top