What is a Flammable Range in Welding?

The flammable range of a gas is the range over which it forms a flammable mixture with air at normal temperature and pressure (NTP). The minimum concentration of gas in air that will support combustion is called the lower explosive limit (LEL), while the maximum concentration is called the upper explosive limit (UEL). Mixtures with concentrations below the LEL are too lean to ignite, while those above the UEL are too rich.

The flammable range can be affected by a number of factors, including:

temperature,
pressure,
and the presence of other gases.

For example, raising the temperature will increase the flammable range of most gases because it increases the gas’s solubility in the air. Pressurizing a gas will have the opposite effect since the molecules are more likely to escape from the liquid phase into the gaseous phase.

Some gases have very wide flammable ranges, while others have very narrow ones. For example, methane has a flammable range of 5-15%, while hydrogen has a range of 4-74%.

Welding is a process that often uses flammable gases, so it’s important to be aware of the dangers they pose. When using welding equipment, always follow the manufacturer’s instructions and take precautions to avoid creating a fire or explosion hazard.

What is the flammable range of acetylene?

Acetylene has a flammable range of 2.5-82%. This means that it can form a flammable mixture with air over a wide range of concentrations. However, the minimum concentration required for combustion is 2.5%, so mixtures with less acetylene will not ignite. Likewise, mixtures with more than 82% acetylene are too rich to combust.

Are LEL and LFL the same?

No, LEL and LFL are not the same. The lower explosive limit (LEL) is the minimum concentration of a gas in air that will support combustion. The lower flammability limit (LFL) is the minimum concentration of a gas in air that will ignite in the presence of an ignition source. For most gases, the LFL is lower than the LEL, but for some gases, the two limits are close together.

What is the explosion range?

The explosion range is the difference between the upper and lower explosive limits. The range of concentrations over which gas can form a flammable mixture with air. The explosion range for gas is usually much narrower than its flammable range. For example, the explosion range of methane is 0.5-5%, while its flammable range is 5-15%. This means that methane mixtures are only explosive over a small range of concentrations. However, even mixtures that are outside the explosion range can be dangerous if they contain enough gas to support combustion.

Safety in welding

When welding, always follow the manufacturer’s instructions and take precautions to avoid creating a fire or explosion hazard. When using welding equipment, be aware of the dangers posed by flammable gases. If you are working with a gas that has a narrow flammable range, take extra care to avoid igniting it. If you are working with a gas with a wide flammable range, be aware that mixtures with high concentrations of the gas can be explosive. Always ventilate the area well to avoid accumulating too much gas. If you are using gas with a high explosion range, ensure no ignition sources are present.