What is the maximum liquid-fill percentage for propane in a cylinder?

What is the maximum liquid-fill percentage for propane in a cylinder?

• A. 80%
• B. 40%
• C. 60%
• D. 100%

Answer: (A)

Propane in a cylinder is stored as a liquid, but it expands a lot when it warms and as it turns into gas. To keep the cylinder safe, there must be space for that expansion and for the gas to form. Filling a cylinder to the very top would leave no room for this vapor space, which could cause overpressure and venting or even a rupture. That’s why the standard practice is to fill the cylinder with liquid propane to 80% of its internal water capacity, leaving 20% as vapor space. This 80% limit provides a safe margin to accommodate temperature changes and gas expansion during use. Filling less than 80% wastes capacity and is not necessary for safety, while filling to 100% would remove the needed headspace and is unsafe.

Propane in a cylinder is stored as a liquid, but it expands a lot when it warms and as it turns into gas. To keep the cylinder safe, there must be space for that expansion and for the gas to form. Filling a cylinder to the very top would leave no room for this vapor space, which could cause overpressure and venting or even a rupture. That’s why the standard practice is to fill the cylinder with liquid propane to 80% of its internal water capacity, leaving 20% as vapor space. This 80% limit provides a safe margin to accommodate temperature changes and gas expansion during use. Filling less than 80% wastes capacity and is not necessary for safety, while filling to 100% would remove the needed headspace and is unsafe.