Welding

How to Extinguish the Flame After Use in Gas Welding Safely and Efficiently

How to Extinguish the Flame After Use in Gas Welding

To extinguish the flame after use in gas welding, first, close the blowpipe control valves.

Then, check the nozzle tightness and pressures on the regulators.

If the flame continues to burn, close the oxygen and acetylene valves at the torch.

After that, close the cylinder valves or gas supply point isolation valves.

Open the torch valves to vent the pressure and ensure that no gas is being released.

Finally, recheck the nozzle tightness and pressures before relighting the torch.

It is important to follow these steps to safely extinguish the flame and prevent any potential accidents.


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Did You Know?

1. Did you know that gas welding flames can reach temperatures of up to 6,000 degrees Fahrenheit? That’s hotter than the surface of the sun!
2. The process of extinguishing the flame after gas welding is known as post-gas burnout. This ensures that all the residual gases are purged from the system, preventing any potential accidents.
3. While most gas welding flames are yellow or blue, some specialized processes, such as oxy-acetylene welding, produce a distinct green flame due to the presence of copper in the acetylene gas.
4. In gas welding, the flame color can indicate the type of gas being used. For instance, propane flames usually have a more orange hue, while acetylene flames tend to be brighter and have a bluish tint.
5. Properly extinguishing the flame after use is crucial, as it not only avoids potential leaks or accidents but also prevents the excessive consumption of gas, saving both money and resources.

Gas Cylinder Safety Guidelines

Gas welding using the oxyacetylene process generates a high-temperature flame that requires the combustion of pure oxygen and acetylene. The temperature of this flame can exceed 3000 degrees Celsius, making it the only gas mixture capable of melting steel.
For other metals with lower melting points, such as brazing, soldering, and cutting, gases like propane, LPG, or hydrogen can be used.

When working with gas cylinders, it is crucial to follow health and safety guidelines. Gases are supplied in high-pressure steel cylinders, which come in different colors to identify the type of gas stored inside. In the UK, the color coding for cylinders is being harmonized across Europe, with maroon cylinders indicating acetylene and white cylinders representing oxygen. Check for labels on cylinders that indicate the type of gas they contain.

To prevent the interchange of fittings, oxygen cylinders have a right-hand thread, while acetylene cylinders have a left-hand thread. When opening cylinders, you should always turn the key or knob anticlockwise. Similarly, to close the cylinders, turn the key or knob clockwise. Oxygen cylinders should be stored separately from fuel gas cylinders in an area free from combustible materials. It is recommended to store cylinders upright, securely fastened, and at least 3 meters away from fuel gas cylinders, or separated by a 30-minute fire resisting barrier. The storage area should be well ventilated and designated as a ‘No Smoking’ area.

Gas System Setup And Maintenance

When setting up the gas system for welding, it is crucial to ensure that the system is suitable for the pressure rating. Hoses should be free from leaks. The regulator is used to reduce the gas pressure to the working pressure required for the torch, and it should be fitted with high pressure and low-pressure gauges. To avoid gas leaks and ensure a proper connection, valve threads should be cleaned before attaching the regulator.

Cleaning of oxygen cylinders should be done using clean compressed air, while hydrogen cylinders should be blown out using compressed air. It is important to note that lubricating oils or sealants should never be used on oxygen cylinder threads.

During the setup and maintenance of the system, cylinders must be securely fastened at all times, and guards should never be loosened. When attaching the regulator to the cylinder, clean joints, and avoid using sealants. Additionally, before the attachment, ensure that the pressure adjustment screw is screwed out to prevent the unregulated flow of gas.

Proper Torch Handling And Ignition

In gas welding, compressed gases are mixed in the hand-held torch or blowpipe in the correct proportions. Hoses between the regulator and torch should be color-coded to avoid confusion. In the UK, red hoses are used for acetylene, while blue hoses are for oxygen. It is important to keep hoses short and periodically check them for damage from hot or sharp objects.

When using acetylene cylinders, it is crucial to ensure they are always used in an upright position. Before connecting the system or at the start of each shift, it is advised to purge the hoses and torch to remove any flammable gas mixtures. To prevent spontaneous ignition, the oxygen stream should not come into contact with oil.

To ignite the torch, a friction lighter or stationary pilot flame should be used to avoid burning the hands. Using matches is not recommended, especially in confined spaces. It is essential to keep the cylinders away from heat sources, and arc welding should not be performed close to the cylinder. Welders should wear tinted goggles to protect their eyes from the intense flame, and appropriate head shields and non-combustible clothing should be worn to ensure safety.

  • Ensure hoses are color-coded for easy identification.
  • Use acetylene cylinders in an upright position.
  • Purge the hoses and torch before each use.
  • Keep oxygen stream away from oil to prevent spontaneous ignition.
  • Use a friction lighter or pilot flame to ignite the torch.
  • Avoid using matches, especially in confined spaces.
  • Keep cylinders away from heat sources.
  • Do not perform arc welding close to the cylinder.
  • Use tinted goggles, head shields, and non-combustible clothing to protect yourself.

Safety Gear And Precautions For Welders

The safety of welders is of utmost importance when engaging in gas welding. The grade of filter for goggles used by welders should be determined by the intensity of the flame, which depends on the thickness of the metal being welded. This ensures optimal eye protection.

Safe practices and accident avoidance can be achieved by wearing appropriate head shields and non-combustible clothing. Leak detection is crucial before welding. Acetylene can be detected by its distinct smell, while oxygen is odorless. A weak solution of detergent or a leak-detecting solution can be used to detect leaks.

In the event of a gas leak in the welding equipment, it should be cured, and the area should be cleaned to remove any residue. Any leaks in hoses should be repaired using approved replacement hoses and couplings.

Detecting And Handling Gas Leaks

Gas leaks can pose a significant hazard during gas welding operations. It is crucial to conduct leak detection prior to welding. While acetylene leaks can be identified by their distinct odor, oxygen leaks are odorless. To assist in locating leaks, a weak detergent solution or a specialized leak-detecting solution can be used.

Once a gas leak is detected, immediate action must be taken to address the issue. Gas leaks should never be ignored, as they can be extremely dangerous. In the case of welding equipment, the leaks should be promptly fixed, and the surrounding area should be thoroughly cleaned to eliminate any remaining gas. If hoses are found to have leaks, they should be repaired using approved replacement hose and couplings to uphold the integrity of the entire system.

To summarize:

  • Gas leaks during gas welding operations pose hazards and require attention.
  • Acetylene leaks can be detected by their odor, while oxygen leaks are odorless.
  • A weak detergent solution or specialized leak-detecting solution can aid in leak identification.
  • Immediate action should be taken upon detecting a gas leak.
  • Leaks in welding equipment should be fixed, and the area should be cleaned.
  • Leaking hoses should be repaired using approved replacement hose and couplings.

Dealing With Backfires And Flashbacks

Backfires and flashbacks are potentially dangerous situations that can occur during gas welding. A backfire is when the flame ignites gases inside the nozzle and extinguishes itself. It is often caused by holding the torch too close to the workpiece. On the other hand, a flashback is a more severe situation where the flame burns inside the torch and may potentially pass back to the hose. Flashbacks are typically caused by incorrect gas pressures or a higher-pressure gas feeding into a lower-pressure gas stream.

To prevent these situations, non-return valves in hoses prevent reverse gas flow and the formation of flammable gas mixtures. Flashback arrestors are automatic flame trap devices that quench the flame and prevent it from reaching the regulator.

In the event of a backfire, it is essential to:

  • Close the blowpipe control valves
  • Check the nozzle tightness and pressures on regulators
  • Relight the torch

If the flame continues to burn, the oxygen and acetylene valves at the torch should be closed, followed by closing the cylinder valves or gas supply point isolation valves. Open the torch valves to vent the pressure, and then recheck the nozzle tightness and pressures before relighting the torch.

If a flashback occurs or there is a fire in the equipment, the oxygen and fuel gas supplies should be immediately isolated. First aid fire-fighting equipment should be used to control the fire, and emergency fire services should be called if necessary. After the equipment has cooled down, it is important to examine and replace any defective components.

After investigating a backfire and rectifying the fault, the torch may be relit. However, after a flashback, it is crucial to check the torch, hoses, and components for any damage and replace them if necessary. The flashback arrestor should also be checked and possibly replaced.

In conclusion, safely extinguishing the flame after gas welding is a vital aspect of the oxyacetylene process. By following proper safety guidelines and procedures, maintaining the gas system, using the correct torch handling techniques, wearing appropriate safety gear, detecting and handling gas leaks responsibly, and dealing with backfires and flashbacks effectively, welders can ensure a safe and efficient working environment during gas welding operations.

Frequently Asked Questions

Which valve is closed first while extinguishing flame in gas welding?

To ensure proper safety during gas welding, it is crucial to know the correct sequence for closing the valves. The acetylene torch valve should be the first to be closed while extinguishing the flame. By prioritizing the closure of this valve, any potential continuation of the acetylene flow, which supports the flame, is halted immediately. This precautionary measure reduces the risk of any accidental ignition or gas leakage that could lead to hazardous situations. Therefore, it is highly recommended to always close the acetylene torch valve first while extinguishing the flame in gas welding.

How is the flame adjusted after the acetylene is ignited?

When the acetylene is ignited, the flame can be adjusted by altering the oxygen levels. By adding more oxygen, the flame becomes oxidizing, while reducing the oxygen results in a carburizing or reducing flame. The neutral flame, commonly utilized in welding and cutting, is achieved by maintaining a balanced ratio of oxygen and acetylene. Adjusting the flame in this manner allows welders to control the heat and chemical reactions during the welding process, ensuring optimal welding conditions.

What is the temperature of reducing flame in gas welding?

The reducing flame in gas welding typically reaches a temperature ranging from 3100°C to 3500°C. The temperature most frequently employed is around 3200°C, which can be achieved with relative ease and without significant challenges.

Do you turn off oxygen or acetylene first?

When it comes to shutting off oxygen and acetylene in an oxy-fuel torch system, it is crucial to prioritize closing the oxygen valve first. This specific protocol is highly emphasized by Harris as an essential safety measure to adhere to. While there are other aspects to consider for the overall safe operation of torches, this step plays a significant role in ensuring a secure environment when working with acetylene as a fuel.

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