Pipe Fitting Style

  • Blinds (also known as paddle blinds because of their flat, round, or paddle-like shape) are flanges used for temporarily blocking flow in a pipe to allow work further down the pipe. Blinds can be slipped between flanges to block the flow in a pipe.
  • Butt welds connections are unthreaded, with a chamfer end, and are welded onto pipes or other fittings. They come in various shapes for reducing, terminating or changing the direction of pipe, and can offer a superior seal to threaded fittings.
  • Lap joints are connections used for slipping over lapped pipe and holding pieces of pipe together. Multiple lap joints can be bolted together to provide extra connection strength and are often used because they can be disassembled more easily than welded connections.
  • Slip-on connections, also called clamps, slide over pipe and are welded in place to connect pieces of pipe. Multiple slip-on fittings can be bolted together for added strength, but overall these flanges are best suited for low-pressure applications.
  • Socket welds are unthreaded connections used for high pressure applications. They have an internal pocket for better flow and can be internally welded for increased strength.
  • Straight thread connections have  rounded parallel ridges (threads), and are often used for mechanical fittings where a water-tight seal is not necessary; one can be created by welding or adding an O-ring. Types include National Pipe Straight Mechanical (NPSM), National Pipe Straight Locknut (NPSL), National Pipe Straight Hose (NPSH), garden hose (GHT) and fire hose coupling (NST).
  • Threaded connections have parallel ridges (threads) that, when screwed together with another threaded fitting, form a seal. Threaded pipes are often used for transporting gases and liquids because of their ability to create an effective seal. National Pipe Taper Thread (NPT) fittings have a 60-degree thread angle, flattened peaks and valleys, and slightly tapered ends. When mated, the tapered threads create a seal. FPT (female pipe thread) fittings have internal threads, MPT (male pipe thread) fittings have external threads, and both are types of NPT.
  • Unthreaded, or plain, connections have smooth surfaces for sliding into or around pipes to form a seal. They can also be butted up against unthreaded pipe and welded, cemented or clamped together.