What Is a Threaded Connection?

A threaded connection (commonly referred to as a threaded flange or threaded
fitting in piping systems) is a type of mechanical joint where the pipe is
screwed into the fitting or flange using matching male and female threads,
rather than being welded.

How It Works

The pipe has external threads and the flange or fitting has internal threads.
The pipe is screwed into the connection and tightened to create a seal. In
many oil and gas applications, thread sealant or pipe dope is applied to the
threads to improve sealing and prevent leaks.

Typical Applications

• Small-diameter piping systems (typically 2 inches and smaller)
• Low to medium pressure service
• Utility and instrument piping
• Temporary or easily disassembled piping systems
• Non-critical oil and gas service lines

Advantages

• No welding required (no hot work permit in many cases)
• Easy to assemble and disassemble
• Lower installation cost for small bore systems
• Useful in locations where welding is restricted

Disadvantages

• Limited to lower pressure and temperature applications
• Higher risk of leakage compared to welded joints
• Threads can wear or gall over time
• Not suitable for vibration-heavy or high-cycle systems

Threaded Connection vs. Welded Connection

Summary

A threaded connection is a mechanical piping joint where components are
screwed together using matching threads. In oil and gas applications, it is
mainly used for small-bore, low to medium pressure systems where ease of
installation and maintenance is important.