A Basic Introduction to Fittings
Fittings are one of the most significant components in piping, pipelines, and industrial facilities. They serve as connections between two or more sections of pipe and other equipment within these systems. Essentially, fittings are used to join pipes and equipment to achieve a proper and standardized design. Without fittings, it would be impossible to create a complete and functional piping system. In fact, fittings help optimize the overall design.
The type and quantity of fittings used in a system depend on various parameters such as design & calculations, applicable standards, process conditions, and more. Fittings are available in a wide range of connection types, including:
- Threaded
- Socket weld
- Butt weld
- Grooved
- Compression
- Solvent weld (glue)
- Push-fit
- Press-fit
They are commonly used in applications such as oil and gas, chemical processing, power plants, steam and high-temperature fluids, cryogenic fluids, neutral fluids, air, water, sewage, plumbing, HVAC, pharmaceuticals, food industries, and more.
Types of Fittings
Flanges
Flanges are Mechanical components that can be used individually or in pairs to connect securely to the surface of another component. They include holes for stud bolts that connect two flanges together, creating a strong, leak-proof joint between pipes or equipment. Their importance is highlighted in standards such as ASME B16.5 and ASME B16.47, which provide detailed classifications and tables.
- Connection types: Weld neck, slip-on, lap joint, socket weld, threaded
- Face types: Raised Face (RF), Flat Face (FF), Ring Joint (RJ)
Blind Flange: A flange without a hole for fluid passage, used to block pipes and prevent leakage—especially during maintenance or overhaul.
Elbow
Available in 90°, 45°, and street types, elbows are used to change the direction of piping and connect to the next pipe or equipment.
Tee
Equal and reducing tees create branches in piping systems. The choice depends on the size of the connections.
Coupling & Reducing Coupling
Used as an interface between two pipe sections or equipment.
Cap & Plug
Both block pipes to prevent fluid passage. Caps cover the pipe end externally, while plugs fit inside the pipe.
Reducer (Concentric & Eccentric)
Reducers decrease pipe size to meet process specifications.
Union
A three-part fitting used to join and align pipes when the piping system is rigid and lacks flexibility.
Nipple & Swage Nipple
Short pipe sections used to extend piping length or enable quick connections. Swage nipples act as reducers.
Adaptor
Similar to nipples, typically available in sizes from 1/8” to 2”.
Bushing
Used for threaded connections between different sizes, with one side usually male-threaded and the other female-threaded.
Cross
Cross fitting is used when a four-way connection is required in a piping system. It allows for the integration of four pipes at a single junction, typically to meet specific design requirements.
Wye Fitting
Similar to a tee but with a branch angled at 45°.
Olets
Olets are branch connection fittings used to create a strong, reliable connection to a piping system. Common types include Weldolet, Sockolet, and Threadolet, among others. The choice of olet depends on the specific application and design requirements.
Materials Used for Fittings
Material selection depends on application parameters such as pressure, temperature, corrosion, erosion, and fluid properties. Common materials include:
- Carbon Steel: ASTM 234, A105, A106, A350, A420, A694, and more.
- Stainless Steel (SS): 304, 316, 321, Duplex 2205, Duplex 2304, Duplex 2101, Duplex 2507, Hyper Duplex S33207/S33707, and more.
- Alloy Steel: ASTM 691, A694, A335, A182, A350, and more.
- Super Alloys: INCONEL (600, 601, 625, 718, 800/800H/800HT), HASTELLOY (C276, C22, B2), MONEL (400, K-500), and more.
- Galvanized Steel: Is Steel or Iron that is Zinc-coated for corrosion resistance. Typically used in construction and/or building applications.
- Cast Iron: Class (150, 200, 250) and more.
- Ductile Iron: Class (50, 52, 53), and more.
- Titanium & Titanium Alloys: Grades (1, 2, 3, 4, 5, 7, 9, 12, 23), and more.
- Copper: Types K, L, M
- Brass: SCH40(STD), SCH80
- Aluminum: Types L, M, XS
- HDPE / MDPE: PN (4, 6, 10, 12.5, 16, 20, 25, 32, 40, 50), and more.
- PVC / CPVC: SCH40, SCH80, SCH120/160
- Composite Materials: GRP, GRV, ERV, GRUP, and more.
Standards for Fittings
Fittings must comply with standards based on application, material, size, and specifications. Common standards include:
- ASME B16.5
- ASME B16.47
- ASME B31
- API
- ASTM
- ISO
- MSS
- NFPA
- AWWA
About American Industrial Supply, Inc. American Industrial Supply, Inc. maintains a comprehensive inventory of fittings from 1/8″ through 48″ in a wide range of grades and specifications. We support applications involving high pressure, high temperature, cryogenic service, low temperature, corrosive environments, and more. Our fittings are available with various end configurations, including plain end, grooved, threaded, and coupled (T&C), in both domestic and imported options—all ready for prompt delivery.
