Prior to purging, what must the piping system be cleared of?

The correct answer is that the piping system must be cleared of contaminants and air prior to purging. This is crucial for ensuring the safety and efficiency of operations involving gas systems.

Contaminants can include debris, liquid hydrocarbons, or other impurities that could interfere with the safe operation of the system. If contaminants are present, they may lead to blockages, corrosion, or other issues that could compromise the integrity of the piping system. By removing these contaminants, the system can function as intended without unwanted reactions or buildup.

Air is also a significant concern in gas piping systems because it contains oxygen, which can pose a risk of combustion or explosion if the system is later filled with combustible gas. Purging the system of air helps to create an inert environment that is safer for handling flammable gases.

Addressing moisture, while important, is secondary to ensuring that the system is free of contaminants and air. Moisture can lead to corrosion and other issues but is not the primary obstacle before proceeding with the purging process. Other choices, such as clearing gas only or all solid matter, do not fully encapsulate the critical need to eliminate both contaminants and air from the system.