Threaded pipe fittings

Threaded fittings are connecting elements used for pipeline installation. They provide a reliable and leak-proof connection of pipes using threads. Such fittings are used in water supply, heating, gas supply, and other utility systems.

Classification of Threaded Fittings by Design

• Couplings
  • Straight coupling: Has internal threads on both ends and is used to connect pipes of the same diameter.
  • Reducing coupling: Used to connect pipes of different diameters.
  • Hexagonal coupling: Convenient for installation using a wrench.
• Tees
  • Straight tee: Allows branching from the main pipe at a 90-degree angle.
  • Reducing tee: Used to connect a smaller pipe to the main pipeline.
• Elbows
  • Used to change the direction of the pipeline (most commonly at 45° or 90°).
  • Available with internal threads, external threads, or combined (internal-external).
• Crosses
  • Allow branching in two opposite directions from the main pipe.
• Nipples
  • Used for pipeline or equipment assembly/disassembly without welding.
• Barbed nipples
  • Feature external threads on both ends and are used to connect parts with internal threads.
• Bushings
  • Act as adapters with external threads of a larger diameter and internal threads of a smaller diameter.
• Caps and plugs
  • Caps have internal threads and seal the end of a pipe.
  • Plugs have external threads and serve the same purpose.
• Union fittings
  • Provide a quick-disconnect connection using a union nut. Available in straight or angled versions.
• Extensions
  • Used to increase connection length without changing the diameter.

Classification of Threaded Fittings by Material

The fitting material determines its strength, corrosion resistance, and temperature tolerance:

• Brass fittings:
  • Durable, long-lasting, and corrosion-resistant.
• Cast iron fittings:
  • Long-lasting but prone to corrosion; mainly used in industrial systems.
• Steel fittings (including stainless steel):
  • High strength; used in high-pressure systems.
• Polymer (plastic) fittings:
  • Lightweight, corrosion-resistant; suitable for cold water supply or irrigation systems.

Classification of Threaded Fittings by Purpose

Depending on their function, fittings can be categorized as:

• Connecting elements (couplings, nipples).
• Direction-changing elements (elbows).
• Branching elements (tees, crosses).
• Transitional elements (bushings, adapters).
• Sealing elements (caps, plugs).

Classification of Threaded Fittings by Thread Type

Threads can be:

• Internal.
• External.
• Combined (e.g., internal on one end and external on the other).