What type of inlet connection is required for a safety valve over 3 inches and over 15 psig?

For a safety valve that is over 3 inches in size and operates at pressures above 15 psig, a flanged or welded connection is required to ensure a secure and leak-proof seal. This is crucial because safety valves need to operate reliably under high pressure and any failure in the connection could lead to catastrophic results.

Flanged connections provide a strong mechanical joint that can withstand significant forces and vibrations, while welded connections offer even greater integrity, especially at high pressures. These types of connections create a larger surface area to distribute stress and help prevent leaks, which is essential when dealing with potentially hazardous materials.

Threaded connections, although used in various applications, do not offer the same level of robustness and may be more susceptible to leaks under high-stress conditions. Soldered connections are unsuitable as they lack the necessary strength and are typically used for lower-pressure systems. Compression fittings also do not provide the required reliability and strength for safety valves operating at elevated pressures. Thus, a flanged or welded connection is the only suitable choice for this scenario.