Pipe Fittings are defined as the piping components that help in pipe routing for directional changes, size changes, and branch connections. Piping Elbows, Piping Reducers, Tee Connections, Olet Connections, Caps, Crosses, etc are pipe fittings and widely used in both the piping and plumbing industry. Different pipe fittings serve different functions as per layout or process requirements. Pipe fittings are manufactured as separate items and procured separately. Pipe fittings are connected to piping using various end connections. Pipe fittings play an important role in the proper functioning of pipes and tubes in various applications. In this article, we will study the overview of different types of pipe fittings used in the piping, pipeline, and plumbing industry.
Types of Pipe Fittings
Various types of pipe fitting are used in piping, plumbing, and pipeline industries. Common Pipe Fittings that are widely used in industries are listed below.
- Piping Elbow
- 900 Elbow
- 450 Elbow
- Long Radius Elbow
- Short Radius Elbow
- Equal Tee
- Reducing Tee
- Barred Tee
- Concentric Reducer
- Eccentric Reducer
- Half Coupling
- Full Coupling
- Reducing Coupling
- Piping Valves
- Gate Valve
- Ball Valve
- Check valve
- Plug Valve
- Needle Valve
- Butterfly Valve
- Globe Valve
- Equal Cross
- Reducing Cross
- Pipe Flanges
- Expansion Joint
- Steam Traps
- Long Radius Bend
- 3-D Bends
- 5-D Bends
- Miter Bend
However, note that if a pipe or pipeline is bent at a pipe fabrication shop to change the direction it is not a pipe fitting. Pipe fittings are always separate items from the pipe. Click on the Bold and italics words above to know about those items in detail as I had already published separate articles on those. We will discuss the remaining pipe fittings in the next paragraphs.
The following image (Fig. 1) shows various types of fittings for reference.
Pipe Union/Pipe fitting Union/Pipe Union Fitting
Pipe Union is a special type of pipe fitting that unites two pipes and can be easily detached without any deformation to the pipes. They provide a positive seal and easy assembly as well as disassembly. In pipe fitting applications, They are widely used mainly for small bore piping and plumbing industries. Pipe unions are made of Carbon steel, Stainless steel, Cast iron, Copper, Nichet, Aluminum, Plastic, Alloy materials depending on temperature, and service requirements.
A pipe union has three parts; A male end, A nut, and a female end. The female end has threads on the inside whereas threads are outside on the male end part. The nut provides the necessary pressure and seals the joint. Fig. 2 represents typical pipe unions used in the pipe fitting industry.
Adapters as pipe fittings are used to connect dissimilar pipes. Pipe adapters are available in various types for different applications. So care must be exercised while ordering to get the right type. They are classified as: Locking Pipe Adapter, Offset Pipe Adapter, Male Pipe Adapter, Female pipe Adapter, Straight Thread adapters, etc. They find their majority of applications in sanitary pipes for plumbing applications. Normally they are made of Steel, Cast iron, polymers, Brass, Aluminum, Bronze, and copper materials.
Pipe Olet Connections
Piping Olet is a self-reinforced branch connection used to connect small pipe branches from larger size main pipes. This is an alternative to a pipe to pipe branching. They are specially designed by a company called Bonney Forge. In places where the reducing tee is not available, piping olets are widely used. Piping olets are designed based on MSS SP-97 or ASME B 31.3. Different types of piping olets are available. Widely used piping olets are:
Weldolet: It’s a 900 branch connection and available for 2″ and more sizes. Weldolet pipe fittings are suitable for high temperature and pressure classes and widely used in the piping industry. Weldolets are available in two sizes; full size and reducing size. However, Reducing size is the most widely used weldolet.
Sockolet: Sockolets are also 900 branch connections but they are used to connect small-bore socket-welded piping to larger size Butt-welded Piping Header. Similar to weldolet, they too, come in full size and reducing size constructions.
Thredolet: Threadolets are 900 pipe fitting suitable to connect small-bore threaded fittings to Buttwelding Piping Connections.
Similarly there are other pipe olet fittings like Elbolet, Nipolet, Latrolet, Flexolet, Flangolet, Sweepolet, and Coupolet. Their pictorial representation is provided in Fig. 5.
A piping cross is also popular as a four-way pipe fitting as it consists of one inlet and three outlet connections or vice versa. They are not that popular in the oil and gas industries and seldom used. They are used in fire sprinkler systems. In piping crosses, four piping connections meet at one common point.
Wye pipe fittings are also called lateral connections. the name wye came because it resembles the letter “Y”. Such type of pipe fittings are used in drainage systems and have a branch line at 45 degrees to keep the flow of water smooth. This kind of pipe fitting has a low frictional loss and very low turbulence.
Caps and Plugs
Caps and Plugs are pipe fittings that are used to close the piping ends. They cover the piping ends and provides a tight seal. They are widely used in pipe dead ends or at future connections.
Bushings as pipe fittings combine different pipe sizes together. They decrease the larger size to the size of the smaller pipe. In comparison to a union or coupling, Bushings occupy very little space.
Long Radius Bend
Long radius pipe bends are used in fluid transportation pipelines requiring pigging. Such pipe fittings has very less pressure drop and smooth flow due to their long radius and smooth direction change. Common long radius pipe bends are 3D and 5D Pipe bends where D is the pipe size.
A barb is a useful pipe fitting used in the plumbing system. Barbs connect the flexible tubing to pipes. They have a male-threaded end on one side and the other end has a single or a multi-barbed tube that is inserted in the flexible tubing.
Pipe Fittings Types based on Uses/Purposes
Depending on the use of pipe fitting, they can be classified as follows:
- Pipe fitting types to extend or terminate pipe runs
- Pipe Fittings for Direction Change
- Pipe fitting types to connect two or more pipes
- Side-inlet Elbows
- Pipe fittings for size change
- Reducing Tee
- Pipe fittings for flow control
Pipe Fittings Selection Criteria
Various factors need to be considered for selecting proper pipe fittings. Few of them are listed below for reference:
- Materials of construction: Pipe fitting material must be compatible with the service and temperature. Normally the material selected is the same as pipe material.
- End Connection types: The buyer must be aware of the end connection types before purchasing any pipe fitting.
- Type of pipe fitting: Pipe fittings are also identified by the type of fitting like threaded or slip, male or female. So, it’s the buyer’s responsibility to choose the correct pipe fitting type.
- Pipe Fitting Size: The size of the fitting must be known prior to the selection of the fitting. Normally, the OD or ID of the connecting pipe decides the pipe fitting size.
- Schedule or Thickness: Pipe fittings are also available at various thickness ranges similar to a pipe. So, before pipe fitting selection, the thickness must be ensured.
- Pressure Rating: The internal pressure is also an important factor for proper pipe fitting selection.
- Pipe Fitting Standards and codes: Various codes and standards are available for pipe fittings. The buyer should select the correct one before placing the order. For example, ASTM, ASME, DIN, BSP, MSS, ISO, etc. are certain standards assigned to pipe fittings and those standards govern their design and use.
Pipe Fitting Standards
Pipe Fittings are dictated by the following codes and standards:
- ASME B16.9
- ASME B16.28
- ASME B16.11
- ASME B16.1
- ASME B16.3
- ASME B16.4
- ASME B16.5
- ASME B16.14
- ASME B16.15
- ASME B16.25
- ASME B16.36
Pipe Fitting Materials
Various materials from which pipe fittings are manufactured are:
- Carbon Steel: A-105; A-234; A-216
- Stainless Steel: A-182; A-403; A-351
- Low Alloy Steel: A-182; A-234; A-217
- LTCS: A-350; A-420; A-352
- Nickel and Nickel Alloys
- Fiberglass / Composite
- Iron (Gray / Cast/ Ductile)
- Polyethylene (PE)
- Polypropylene (PP)
- PVC (Polyvinyl Chloride)
Applications of Pipe Fittings
Pipe fittings are highly popular and widely used in the following industries:
- Oil and Gas
- Food, Beverage, and Dairy
- Process Instrumentation
- Pulp and Paper
- Marine & dredging
- Road & highway construction
- Ventilation etc.