MCC-NH Gas Fitters Practice Exam

When should a leak test be performed as opposed to a pressure test?

1. When detecting moisture

2. Leak tests use fuel gas, pressure tests use inert gas

3. During installation only

4. At any service interval

The correct answer is: Leak tests use fuel gas, pressure tests use inert gas

The correct answer is that leak tests use fuel gas, while pressure tests use inert gas. Leak tests are essential when you want to ensure that a gas piping system is tight and that there are no leaks present. These tests are typically conducted using the gas that the system is designed to carry, allowing for a more realistic assessment of how the system will function under normal operating conditions. Since fuel gas is used, it directly verifies that the connections and joints can withstand the operational pressures without any leakage. On the other hand, pressure tests are generally performed with an inert gas, such as nitrogen or air, and are used to check a system for integrity under a controlled pressure. This is usually done before the system is put into service to ensure that it can handle the pressures it will encounter without leaking. While there may be considerations for testing during installation or at service intervals for maintenance, the nature of the gases used in these tests distinguishes when each type is appropriate and necessary. Understanding these differences is crucial for ensuring the safety and reliability of gas systems.