Red Seal Gasfitter — Class B Practice Exam

What is one method for purging gas lines?

1. Injecting water into the lines

2. Displacing air or other gases from the lines with natural gas

3. Flushing with chemicals

4. Using a vacuum pump to remove impurities

The correct answer is: Displacing air or other gases from the lines with natural gas

The method of displacing air or other gases from the lines with natural gas is a standard and effective procedure for purging gas lines. This process involves introducing natural gas into the piping system, which pushes out any residual air or other gases that may be present. This is essential because the presence of air in a gas line can create a risk of explosion or combustion issues, as gas can mix with air to form an explosive mixture. Purge operations are crucial when installing new lines or after any maintenance that could introduce air into the system. By ensuring that the lines are filled with gas rather than air, gasfitters can maintain safe operating conditions and prevent potential hazards associated with improper gas mixtures. Other methods such as injecting water into the lines or flushing with chemicals are not acceptable for purging gas lines, as they can introduce unwanted substances that compromise the integrity of the gas system. Using a vacuum pump may also remove some impurities, but does not provide the necessary displacement of air and is not a standard practice for purging gas lines.