Red Seal Gasfitter — Class A Practice Exam

What is the correct procedure for purging a gas system?

1. Introduce gas slowly while venting to atmosphere until the piping is clear of air

2. Fill the entire system with water

3. Use a vacuum pump to remove air

4. Flush the system with another gas

The correct answer is: Introduce gas slowly while venting to atmosphere until the piping is clear of air

The correct procedure for purging a gas system is to introduce gas slowly while venting to atmosphere until the piping is clear of air. This method is crucial because it ensures that any air within the gas lines is expelled safely and effectively. By venting to the atmosphere during the purging process, it prevents the potential buildup of explosive mixtures that could occur if air is trapped in the system when gas is introduced. Slowly introducing the gas helps control the pressure within the piping and allows for a gradual displacement of air, thereby minimizing the risk of gas leaks and ensuring safety. This practice is in line with industry standards and safety protocols for gas systems, emphasizing the importance of air removal to maintain the safe operation of appliances and pipelines. Filling the system with water is not appropriate for gas systems as water can cause corrosion, damages, and operational issues. Utilizing a vacuum pump to remove air may not be effective or practical in all systems and could overlook the necessary venting. Flushing the system with another gas could lead to contamination and unsafe conditions, which is why the recommended approach focuses on using the intended gas to purge the lines.