MCC-NH Gas Fitters Practice Exam

What is the maximum pipe size for which threaded joints can be used without the approval of the AHJ?

1. 2 inches

2. 6 inches

3. 4 inches

4. 8 inches

The correct answer is: 4 inches

The maximum pipe size for which threaded joints can be used without the approval of the Authority Having Jurisdiction (AHJ) is 2 inches. Threaded joints are commonly utilized in gas fitting installations, but for larger diameters, the requirements become stricter to ensure safety and integrity. In the context of gas fittings, smaller diameter pipes, typically up to 2 inches, can use threaded joints without additional approval because they are generally considered sufficient for providing a reliable seal under normal operating conditions. This is consistent with safety codes that allow flexibility for common applications where conditions are manageable. As pipe sizes increase, the risks associated with potential leaks and mechanical failures grow, necessitating more robust joining methods or additional approvals. For pipe sizes larger than 2 inches, it is often recommended to use welded or flanged connections, which provide stronger seals due to increased structural integrity under pressure. Thus, the restriction on using threaded joints over 2 inches without AHJ approval reflects a commitment to safety standards in gas installations, wherein the integrity of the gas delivery system becomes increasingly critical. This ensures that installations meet applicable safety codes and minimizes risks associated with gas leaks.