Millwright Level 1 Practice Exam

What is the draw limit for acetylene?

1. Cannot be emptied faster than 1/5 of its capacity per hour

2. Cannot be emptied faster than 1/6 of its capacity per hour

3. Cannot be emptied faster than 1/7 of its capacity per hour

4. Cannot be emptied faster than 1/8 of its capacity per hour

The correct answer is: Cannot be emptied faster than 1/7 of its capacity per hour

The correct answer highlights that acetylene must not be drawn from the cylinder faster than 1/7 of its capacity per hour. This limitation is crucial for maintaining safety and ensuring that the acetylene remains stable under pressure. Exceeding this draw limit can create a risk of instability and may lead to dangerous conditions, including potential combustion or explosion. Acetylene cylinders are filled with a solvent, such as acetone, which stabilizes the gas at higher pressures. If the gas is drawn off too quickly, the pressure inside the cylinder can drop too low, potentially causing a phase change that results in liquid acetylene being withdrawn. Liquid acetylene is highly unstable and much more hazardous than the gaseous form. Thus, the 1/7 draw limit is a safety measure designed to protect users and equipment by ensuring that the gas remains in a stable state throughout its use.