Pipe Fittings

Flanges

Common Materials

• ASTM A105 carbon steel
• ASTM A350 LF2 low-temperature carbon steel
• ASTM A182 F304/F304L stainless steel
• ASTM A182 F316/F316L stainless steel
• ASTM A182 alloy steel grades

Applicable Standards

• ASME B16.5 (NPS 1/2"–24")
• ASME B16.47 Series A and B (NPS 26"–60")

Types of flange

● Weld Neck Flanges (WN)

Weld neck flanges feature a long tapered hub that provides a smooth stress transition between the flange and the pipe. They are designed for full-penetration butt welds and offer excellent resistance to pressure, temperature fluctuations, and cyclic loading.

Typical Applications: Oil & gas pipelines, refineries, power plants, and other critical services requiring maximum reliability.

● Slip-On Flanges (SO)

Slip-on flanges are installed by sliding the flange over the pipe and securing it with fillet welds on both the inside and outside. They offer easier alignment and lower installation costs than weld neck flanges.

Typical Applications: Water treatment, utility systems, fire protection, and medium-pressure industrial piping.

Common Ratings: ASME Class 150, 300, and 600; larger sizes are available in accordance with ASME B16.5 and ASME B16.47.

● Blind Flanges (BL)

Blind flanges have no bore opening and are used to seal the ends of piping systems, pressure vessels, and equipment nozzles. They also facilitate pressure testing, maintenance isolation, and future system expansion.

Typical Applications: Pipeline shutdowns, hydrostatic testing, and equipment isolation.

● Socket Weld Flanges (SW)

Socket weld flanges are designed with a recessed socket into which the pipe is inserted before being secured with an external fillet weld. They provide strong, leak-resistant connections for small-diameter piping systems.

Typical Applications: High-pressure small-bore piping, steam lines, and instrumentation systems.

Typical Size Range: NPS 1/2"–2".

● Threaded Flanges (THD)

Threaded flanges contain tapered internal threads that allow them to be screwed directly onto matching threaded pipes without welding. They are particularly useful where welding is impractical or undesirable.

Typical Applications: Low-pressure services, hazardous areas, and temporary installations.

Typical Size Range: NPS 1/2"–4".

● Lap Joint Flanges (LJ)

Lap joint flanges are used together with stub ends. The stub end is welded to the pipe, while the flange remains free to rotate, allowing easy bolt alignment and simplified disassembly.

Typical Applications: Systems requiring frequent maintenance, inspection, or dismantling, particularly when expensive alloy materials are used.

Pipe Flange Surface Processing

For CarbonSteel Flange,thesurfacecanbeelectrogalvanized,lightoiledandblackpainted.
For Stainless Steel Flange,the surface can apply color bleaching treatment, mirror-bright surface treatment and surface shading.

Flange Specification

Pressure Ratings

• Class 150
• Class 300
• Class 600
• Class 900
• Class 1500
• Class 2500

Elbows

Elbows are fittings used to change the direction of fluid flow within a piping system.

Classification

Long-radius elbows have a centerline radius of 1.5D and are the most commonly used type. Short-radius elbows have a radius of 1.0D and are generally selected when installation space is limited.

Elbow Specification

Manufacturing Methods

• Seamless Elbows: typically 1/2"–24"
• Welded Elbows: typically 24"–72"

Surface Treatments

• Anti-rust oil
• Black lacquer coating
• Hot-dip galvanizing

Tees

Tees are three-way fittings used to divide or combine fluid flow.

Connection Types

Butt Weld Tee

Socket Weld Tee

Threaded Tee

Size Range

1/2"–72"

Barred tees are commonly used in piggable pipelines to prevent pipeline pigs from entering branch connections.

Reducers

Reducers connect pipes of different diameters while maintaining smooth flow characteristics.

Types

Eccentric Reducers

Typically installed in horizontal pipelines to minimize the formation of air pockets in liquid systems or liquid accumulation in gas systems.

Concentric Reducers

Used primarily in vertical piping systems or where maintaining the pipeline centerline is important.

Size Range

1/2"–80"

Other Common Pipe Fittings

Complete piping systems also utilize:

• Pipe Caps
• Crosses
• Stub Ends
• Couplings
• Unions
• Nipples
• Branch Outlets (Weldolet, Sockolet, Threadolet)
• Gaskets

These fittings address various installation, maintenance, and operational requirements.

Pipe Fittings Standards and Grade

Tee Manufacturing Process

Cap Manufacturing Process

Elbow Manufacturing Process

Reducer Manufacturing Process

Heat Treatment

Depending on material grade and project specifications, heat treatment processes may include:

• Normalizing
• Annealing
• Solution Annealing
• Quenching and Tempering
• Stress Relieving

These treatments improve mechanical properties and ensure compliance with project specifications.

For critical projects such as those involving ADNOC, Saudi Aramco, or MA'ADEN, heat treatment requirements must strictly follow approved procedures.

Inspection and Testing

Pipe fittings are typically subjected to the following inspections before shipment:

• Positive Material Identification (PMI)
• Visual Inspection
• Dimensional Inspection
• Chemical Composition Analysis
• Hardness Testing
• Impact Testing (when specified)
• Ultrasonic Testing (UT)
• Magnetic Particle Testing (MT)
• Liquid Penetrant Testing (PT)
• Radiographic Testing (RT)

Hydrostatic testing is generally performed when required by project specifications or purchaser requirements, rather than as a mandatory test for every fitting.

GNEE Pipe is China's professional one-stop supply chain enterprise for steel pipe fittings.

Q: What is a pipe fitting?

A: A pipe fitting is a component used to connect, change direction, branch, or terminate piping systems. It is used to assemble pipelines and control fluid or gas flow in industrial piping systems, including oil and gas, petrochemical, power generation, and water treatment applications.

Q: What are the most common pipe fittings?

A: The most common pipe fittings include elbows, tees, reducers, couplings, caps, and flanges. These fittings are used to change flow direction, connect different pipe sizes, branch pipelines, or close pipe ends in industrial piping systems.

Q: What materials are available for pipe fittings?

A: Common materials include:

• Carbon steel (ASTM A234 WPB, WPC)
• Stainless steel (304, 316, 316L)
• Low temperature steel (ASTM A420)
• Alloy steel (P11, P22, P91)

Q: What is a flange used for?

A: A flange is used to connect pipes, valves, pumps, and other equipment to form a secure and leak-tight piping system. It also allows easy assembly, disassembly, and maintenance of pipeline sections in industrial applications.

Q: What are common types of flanges?

A: The most common types of flanges include weld neck flanges, slip-on flanges, blind flanges, socket weld flanges, threaded flanges, and lap joint flanges. These flange types are widely used in piping systems to connect pipes, valves, and equipment while ensuring sealing integrity under different pressure and service conditions.

Q: What is the most used flange size?

A: The most commonly used flange sizes are 2 inches to 24 inches (DN50 to DN600), with 2", 4", 6", 8", and 12" being the most frequently used in industrial piping systems such as oil and gas, petrochemical, and power plants.

Q: What is tee in pipe fittings?

A: A tee in pipe fittings is a T-shaped fitting used to connect three sections of pipe, allowing flow to be split or combined at a 90-degree branch. It is commonly used in piping systems to distribute or collect fluid or gas flow.

Q: What are the two main types of tee fittings?

A: The two main types of tee fittings are equal tee (straight tee) and reducer tee (unequal tee). An equal tee has all three outlets of the same diameter, while a reducer tee has one branch outlet of a smaller diameter to connect different pipe sizes.

Q: What is a reducer?

A: A reducer is a pipe fitting used to connect two pipes of different diameters, allowing a smooth transition in flow size within a piping system. It is commonly used to reduce or increase pipeline size while maintaining stable fluid or gas flow.

Q: Why are reducers used?

A: Reducers are used to connect pipes of different diameters and ensure a smooth transition of flow between larger and smaller pipe sizes. They help control flow rate, reduce pressure loss, and adapt pipeline systems to changing design or process requirements.

Q: What are the two types of reducers?

A: The two main types of reducers are concentric reducers and eccentric reducers.

Concentric reducers are used when the pipe centerlines are aligned, while eccentric reducers are used when maintaining a flat top or bottom surface is required to prevent air pockets or ensure proper drainage.

Q: How to choose a reducer?

A: To choose a reducer, consider the pipe size (NPS), pressure rating, material compatibility, and flow requirements. Use a concentric reducer for vertical or balanced flow systems, and an eccentric reducer for horizontal pipelines to prevent air or liquid accumulation. The selection should also comply with relevant standards such as ASME B16.9 and the system’s operating conditions.

Q: What are the types of elbows?

A: The most common types of pipe elbows are 45-degree elbows, 90-degree elbows, and 180-degree elbows (return bends). They are used to change the direction of flow in piping systems, with different angles selected based on space limitations and flow requirements.

Q: What are the four classifications of elbows?

A: The four most common classifications of elbows are 45-degree elbow, 90-degree elbow, 180-degree elbow (return bend), and long radius (LR) vs short radius (SR) elbows.

They are used to change flow direction in piping systems while controlling pressure loss and installation space requirements.

Q: What is a steel cap?

A: A steel cap is a pipe fitting used to seal the end of a pipeline. It is welded onto the pipe end to close it permanently or temporarily, preventing fluid or gas flow beyond the termination point in piping systems.

Q: What is a pipe cap for?

A: A pipe cap is used to close or seal the end of a pipe, preventing fluid or gas from flowing out. It is commonly installed in piping systems for pipeline termination, pressure testing, or future extension.

Q: What are the different types of pipe caps?

A: The most common pipe caps include butt-weld caps (BW caps), threaded caps, and socket-weld caps. They are used to seal the end of a pipeline, prevent leakage, and protect pipes from contamination or damage during operation or storage.

Q: What materials are available for pipe fittings?

A: Common materials include:

• Carbon steel (ASTM A234 WPB, WPC)
• Stainless steel (304, 316, 316L)
• Low temperature steel (ASTM A420)
• Alloy steel (P11, P22, P91)

Q: What is the difference between seamless and welded pipe fittings?

A: Seamless fittings are forged from a single piece of steel and provide higher strength and better pressure resistance. Welded fittings are cost-effective and suitable for lower-pressure applications.

Q: What is the difference between forged fittings and cast fittings?

A: Forged fittings are stronger and used for high-pressure systems. Cast fittings are more economical and used for low-pressure or non-critical applications.

Q: Can pipe fittings be used in high-temperature and high-pressure environments?

A: Yes, but material selection is critical. Alloy steel fittings (like ASTM A234 WP11 / WP22 / WP91) are recommended for high-temperature and high-pressure service conditions.

Q: How do you ensure quality control?

A: Quality assurance includes:

• Raw material chemical analysis
• Dimensional inspection
• Hydrostatic testing
• NDT testing (UT, RT, MT)
• Third-party inspection (SGS, BV, TUV)

Q: What is your delivery time for pipe fittings?

A: Standard sizes: 7–15 days
Bulk orders or custom products: 20–40 days depending on specifications and quantity.

Q: What packaging do you use for export?

A: We use seaworthy packaging including:

• Wooden cases
• Steel frames
• Plastic caps protection
• Waterproof wrapping for long-distance shipping

Q: Do you provide MTC and inspection certificates?

A: Yes. We provide:

• Mill Test Certificate (EN 10204 3.1 / 3.2)
• Material certificates
• Third-party inspection reports upon request