NFPA 54 does not permit threaded fittings above _____ inches diameter.

The National Fire Protection Association (NFPA) standard specifically addresses safety practices for the installation and maintenance of natural gas systems. According to NFPA 54, it is stipulated that threaded fittings cannot be used for pipes that exceed a certain diameter, which is 4 inches. This regulation is in place to ensure the integrity and safety of gas piping systems, as larger diameter pipes are subject to greater stresses and corrosive effects.

Using threaded fittings on larger pipes can lead to potential leakage or failure due to the increased risk associated with fittings that may not provide adequate support and sealing capacity. Therefore, limiting the use of threaded fittings to those with a diameter of 4 inches or smaller is a critical safety measure intended to mitigate risks in gas installations.

This particular detail is crucial for compliance with safety standards, and it ensures that systems operate securely without posing a risk of gas leaks or catastrophic failures. Recognizing this limitation is essential for professionals in the field to maintain safety and adhere to regulatory guidelines.