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Threaded Fitting

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IMG 9410banner fastenerThreaded pipe fittings, abbreviated as THRDF, are a type of pipe connection used to join pipes and other components in a plumbing or piping system.  These fittings have threaded ends that allow them to be screwed onto the threaded ends of pipes or other fittings, creating a secure and leak resistant connection.  Threaded pipe fittings are commonly used in a variety of applications, including plumbing, industrial processes, and even in some residential plumbing systems.

Key Points about Threaded Pipe Fittings

Types of Threads  -  Threaded pipe fittings can have different types of threads, depending on the region and standards being used.  Some common types include NPT (National Pipe Thread), BSP (British Standard Pipe), and BSPT (British Standard Pipe Taper).  These threads are designed to create a tight seal when properly connected.
Materials  -  Threaded pipe fittings are typically made from materials such as brass, stainless steel, carbon steel, or PVC, depending on the application and the substances being transported through the pipes.  The choice of material depends on factors like corrosion resistance and pressure requirements.
Variety of Fittings  -  There is a wide range of threaded pipe fittings available to suit different needs.  Some common types of threaded fittings include elbows, tees, couplings, unions, caps, and plugs.  Each type serves a specific purpose in directing or controlling the flow of fluids through the piping system.
Installation  -  Installing threaded pipe fittings involves threading the fitting onto the pipe or another fitting.  It's important to use thread sealant or Teflon tape on the threads to ensure a tight seal and prevent leaks.  Over tightening can damage the threads, so it's crucial to apply the right amount of torque.
Advantages  -  Threaded pipe fittings are relatively easy to install and don't require soldering or welding, making them a popular choice for DIY projects and small plumbing repairs.  They are also reusable, allowing for easy disassembly and reassembly if needed.
Disadvantages  -  While threaded fittings are convenient, they may not be suitable for high pressure or high temperature applications.  The threads can become damaged over time, leading to leaks. In such cases, other types of connections like welded or flanged connections may be more appropriate.
Leak Prevention  -  Proper installation and the use of thread sealant are crucial for preventing leaks in threaded pipe fittings.  Regular maintenance and inspection are also important to ensure the integrity of the connections.

Threaded Pipe Fitting Classes

Threaded pipe fittings are generally four inches and smaller.  The reason for this size constraint is the pipe end needs to be threaded with a male type connection and die sizes are unobtainable in the larger diameters.

  • 45 Elbow, 90 Elbow, Cross, Lateral, Tee
    • Class 2000 - for use with Sch. 80 pipe.
    • Class 3000 - for use with Sch. 160 pipe.
    • Class 6000 - for use with Sch. XXH pipe.
  • Half Coupling, Full Coupling, Reducer, Round Cap, Union, Hammer Lug Union
    • Class 3000 - for use with Sch. 160 pipe.
    • Class 6000 - for use with Sch. XXH pipe.
  • Bushing (Flush and Hexagon)
    • Bushings are not identified by class and can be used for all classes.
  • Plug (Hexagon Head, Round Head and Square Head)
    • Plugs are not identified by class and can be used for all three classes.
  • Dimensions and tolerances in accordance with ANSI/ASME B16.11 - Forged Fittings, Socket-Welding and Threaded
  • Specifications for carbon steel forgings in accordance with ASTM A105
  • Threads in accordance with ANSI/ASME B1.20.1.  All internal and external threads shall be threaded with American National Standard Taper Pipe Threads.
  • FCS - forged carbon steel

Threaded Fitting Datasheets

 

Forged Fittings threaded Class Types

Class designations correspond to the maximum cold working pressure of fittings in pounds force per square inch.

Pressure Class2000300060009000
Socket Fitting - 80/XH 160 XXH
Threaded Fitting 80/XH 160 XXH -

 

The following links are for datasheets for the threaded fitting range sizes covered by ASME B16.11.  If you would like to browse the datasheets for pipe fittings, please visit our Fittings Datasheets page.

Forged Fittings threaded Sizes

  • Plugs and bushings are not identified by class.  They may be used for ratings up through Class 6000.
  • Dimension tolerances in accordance with ANSI/ASME B16.11 do no include laterals, reducers and unions.
  • Swages can be ordered in any combination of end.
  • Fittings with special dimensions, threads, or counterbores can be made by agreement between the manufacturer and purchaser.  If the fittings meet all of the requirements of this Standard, they can be considered in compliance, provided they are appropriately marked.
Fitting2000300060009000
45 Elbow 1/8 - 4 1/8 - 4 1/8 - 4 -
90 Elbow 1/8 - 4 1/8 - 4 1/8 - 4 -
Bushing, Flush 1/8 - 4 1/8 - 4 1/8 - 4 -
Bushing, Hex 1/8 - 4 1/8 - 4 1/8 - 4 -
Cap, Round - 1/8 - 4 1/8 - 2 -
Coupling, Full - 1/8 - 4 1/8 - 4 -
Coupling, Half - 1/8 - 4 1/8 - 4 -
Cross 1/8 - 4 1/8 - 4 1/8 - 4 -
Lateral - 1/4 - 2 1/4 - 1 1/4 -
Plug. Hex Head 1/8 - 4 1/8 - 4 1/8 - 4 -
Plug, Round Head 1/8 - 4 1/8 - 4 1/8 - 4 -
Plug, Square Head 1/8 - 4 1/8 - 4 1/8 - 4 -
Reducer - 1/8 - 4 1/8 - 4 -
Street Ell - 1/8 - 2 1/8 - 2 -
Tee 1/8 - 4 1/8 - 4 1/8 - 4 -
Union - 1/8 - 3 1/8 - 2 -

   

Threaded Fitting Advantages and Disadvantages

AdvantagesDisadvantages
  • Threaded fittings are relatively easy to install compared to some other types of fittings.  They can be assembled and disassembled quickly without the need for welding or special tools.
  • Threaded fittings are versatile and can be used in a wide range of applications.  They are available in various materials, sizes, and configurations to suit different piping systems.
  • Threaded fittings are often more cost effective than welded fittings because they don't require welding equipment or skilled welders.  This can lead to cost savings in both materials and labor.
  • Unlike some other types of connections, threaded fittings do not require special tools or equipment.  A wrench is typically sufficient for tightening or loosening the connections.
  • Threaded connections allow for adjustments in the field.  If there is a need to modify or extend a piping system, threaded fittings can be easily added or replaced without significant downtime.
  • Threaded fittings are generally not suitable for high pressure applications.  The threaded connection may be prone to leaks under high pressure, and welded connections are often preferred in high pressure systems.
  • Threaded connections may be more prone to leakage compared to welded connections, especially if they are not properly sealed using thread sealant or tape.  Proper installation is crucial to prevent leaks.
  • Threaded connections are generally weaker than welded connections.  This limits their use in applications where high strength is required.
  • In environments with significant vibration or movement, threaded connections may be more susceptible to loosening over time.  This can lead to potential leaks or failures.
  • Over time, repeated assembly and disassembly of threaded connections can lead to thread wear and galling, making it more difficult to achieve a tight seal.  Proper care must be taken during installation and maintenance.
  • While threaded fittings are available in various materials, certain materials may not be suitable for threading.  For example, brittle materials or those prone to corrosion may be challenging to thread.

 

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