7D Pipe Bending

Bend Radius:

Definition: The bend radius is seven times the diameter of the pipe. This longer radius allows for smoother fluid flow compared to shorter-radius bends.

Calculation Example: For a pipe with a diameter of 6 inches, a 7D bend would have a radius of 42 inches (6 × 7).

Materials:

• Carbon Steel: Commonly used for its strength and durability in oil, gas, and water pipelines.
• Stainless Steel: Provides excellent corrosion resistance, ideal for chemical, food, and pharmaceutical industries.
• Alloy Steel: Suitable for high-temperature and high-pressure environments.
• Other Materials: Specialty materials such as Inconel, titanium, and duplex steel can be used depending on the application requirements.

Advantages:

• Reduced Pressure Loss: A larger radius bend (7D) reduces the resistance to flow, minimizing pressure drops and maintaining smoother fluid or gas flow.
• Lower Risk of Erosion: For abrasive fluids, a 7D bend reduces the wear and tear on the pipe walls, as the smooth transition decreases the impact of particles on the inside of the pipe.
• Enhanced Durability: Longer radius bends distribute mechanical stress more evenly, reducing the likelihood of pipe failure.
• Improved Flow Efficiency: The 7D bend provides a gentle change in direction, reducing turbulence and ensuring more efficient fluid transport.
• Suitable for High-Pressure Systems: 7D bends are often used in high-pressure systems because they can handle the stresses of a large-radius transition more effectively.

Standards and Specifications:

• ASME B31.3: Specifies the design requirements for process piping, including the use of large-radius bends like 7D bends.
• ASTM and API Standards: Governs material specifications and quality requirements for pipes used in various industries like oil and gas, power, and chemicals.
• DIN and ISO Standards: International standards that regulate pipe bending dimensions, material quality, and manufacturing tolerances.

Constants for Pipe Bends:

ASTM

• ASME/ANSI B16.49 Factory-Made Wrought Steel Buttwelding Induction Bends for Transportation and Distribution Systems
• ASTM A403 Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings
• ISO 2851 tainless steel bends and tees for the food

JIS

• JIS B2311 Universal steel butt-welding pipe fittings
• JIS B2312 Steel butt-welding pipe fittings
• JIS B2313 Steel plate butt-welding pipe fittings
• JIS B 2321:1995Aluminium and aluminium alloy butt-welding pipe fittings

EURO

• DIN 3867 Non-soldering compression couplings – Pressure bush for butt joints
• DIN 2609 Steel butt-welding pipe fittings; technical delivery conditions
• BS 1640 Specification for steel butt-welding pipe fittings for the petroleum industry
• BS 1965 Butt welding pipe fittings for pressure purpose
• STPG38

How to Calculate a Pipe Bend?

Pipe fittings are necessary to join together pipes, or to change the direction of an existing pipe. Pipes and pipe fittings are made of a variety of materials, depending on the fluid or gas being transported. Most pipe fittings tend to be either threaded or able to slip over the pipes they connect. Whether you are using steel pipes of PVC pipes, a chemical solvent is required to create a seal between the pipe and the fittings.

Measure the required length of the pipe to be installed, keeping in mind the extra length required where the pipe will be inserted into the fitting. Mark this length on the pipe.

Bevelled Ends

The ends of all buttweld fittings are bevelled, exceeding wall thickness 4 mm for austenitic stainless steel, or 5 mm for ferritic stainless steel. The shape of the bevel depending upon the actual wall thickness. This bevelled ends are needed to be able to make a “Butt weld”.

Welding Bevel acc.to ASME / ANSI B16.9 and ASME / ANSI B16.28

ASME B16.25 covers the preparation of buttwelding ends of piping components to be joined into a piping system by welding. It includes requirements for welding bevels, for external and internal shaping of heavy-wall components, and for preparation of internal ends (including dimensions and dimensional tolerances).

Our in-hourse R&D team developed bevel ends equipment are good using in thickness 2mm to 20mm pipe fittings, guarantee high efficiency and high quality.

These weld edge preparation requirements are also incorporated into the ASME standards (e.g., B16.9, B16.5, B16.34).

ASME B16.25 (BUTT WELD ENDS)

ASME B16.25 sets standards for the preparation of the ends of components that need to be welded together.

Cut square or slight chamfer, at manufacturer’s option for :

• t ≤ 0.19” carbon steel or ferritic alloy steels
  t ≤ 0.12” austenitic alloy steels

Buttweld Fittings general

A pipe fitting is defined as a part used in a piping system, for changing direction, branching or for change of pipe diameter, and which is mechanically joined to the system.

There are many different types of fittings and they are the same in all sizes and schedules as the pipe.

ASME / ANSI B16.9 dimension

ASME B16.9 Standard covers overall dimensions, tolerances,ratings, testing, and markings for factory-made wrought buttwelding fittings in sizes NPS 1⁄2 through NPS 48 (DN 15 through DN 1200).

Tolerances of Welded Fittings

All dimensions are given in inches. Tolerances are equal plus and minus except as noted.

1. Out-of-round is the sum of absolute values of plus and minus tolerance.
2. This tolerance may not apply in localized areas of formed fittings where increased wall thickness is required to meet design requirements of ASME B16.9.
3. The inside diameter and the nominal wall thicknesses at ends are to be specified by the purchaser.
4. Unless otherwise specified by the purchaser, these tolerances apply to the nominal inside diameter, which equals the difference between the nominal outside diameter and twice the nominal wall thickness.

The ASME B16.9 pipe fittings can be used under the jurisdiction of the ASME Boiler & Pressure Vessel Code (BPVC) as well as the ASME Code for pressure piping. Referencing pressure ratings of flanges per ASME B16.5, they can be designated as Classes 150, 300, 600, 900, 1500 and 2500. The allowable pressure ratings for ASME B16.9 pipe fittings may be calculated as for straight seamless pipe of equivalent material in accordance with the rules established in the applicable sections of ASME B31 Code for pressure piping.

Design of Fittings

The design of butt welding pipe fittings made to ASME B16.9 shall be established by one of the following methods: (a) mathematical analyses contained in pressure vessel or piping codes; (b) proof testing; (c) experimental stress analysis with hydrostatic testing to validate experimental results; (d) detailed stress analysis with results evaluation.

Standard Marking

Generally, ASME B16.9 pipe fittings shall be marked to show the following details: “trademark + material grade + wall thickness + size + heat number”. For example, “M ASTM A234 WP5 SCH80 6″ 385“. When steel stamps are used, care shall be taken so that
the marking is not deep enough or sharp enough to cause cracks or to reduce the wall thickness of the fitting below the minimum allowed.

Material & Manufacture

The ASME B16.9 fittings may be made from an extensive range of mateirals covering (1) carbon and low-alloy steels in accordance with ASTM A234 and ASTM A420; (2) austenitic and duplex stainless steels in accordance with ASTM A403 and ASTM A815; (3) nickel alloys in accordance with ASTM B366; (4) aluminum alloys in accordance with ASTM B361; and (5) titanium alloys in accordance with ASTM B363.

Pipe Fittings Dimensions Tolerance as per ASME B16.9:

Tube bending is essential for a wide range of industries. Our tube and pipe bending applications are used in everything from the automotive industry to shipbuilding, aerospace and much more. The automotive industry relies on mandrel bending machines to minimise the ovality that occurs on thin-walled tubes when they are bent. Our bending machines also help to eliminate wrinkles on the inside radius of the bend.

Two other industries that rely heavily on high quality tube bending are aerospace and aeronautics. In these industries, bends must be precise and there is no room for error. In aerospace, it is particularly important to produce bends with pinpoint accuracy. Our bending machines are perfect for industrial bending of tubes, pipes, square and rectangular profiles. Our mandrel bending machines can even bend profiles to a centreline radius as small as 1.5 x diameter.

Here are some common applications of pipe bend:

ASME American Society for Mechanical Engineers

This is one of the reputed organizations in the world developing codes and standards.
The schedule number for pipe fitting starts from ASME/ANSI B16. The various classifications of ASME/ANSI B16 standards for different pipe fittings are as follows:

• ASME/ANSI B16.1 – 1998 – Cast Iron Pipe Flanges and Flanged Fittings
• ASME/ANSI B16.3 – 1998 – Malleable Iron Threaded Fittings
• ASME/ANSI B16.4 – 1998 – Cast Iron Threaded Fittings
• ASME/ANSI B16.5 – 1996 – Pipe Flanges and Flanged Fittings
• ASME/ANSI B16.11 – 2001 – Forged Steel Fittings, Socket-Welding and Threaded
• ASME/ANSI B16.14 – 1991 – Ferrous Pipe Plugs, Bushings and Locknuts with Pipe Threads
• ASME/ANSI B16.15 – 1985 (R1994) – Cast Bronze Threaded Fittings
• ASME/ANSI B16.25 – 1997 – Buttwelding Ends
• ASME/ANSI B16.36 – 1996 – Orifice Flanges etc.

ASTM International American Society for Testing and Materials

This is one of the largest voluntary standards development organizations in the world. It was originally known as the American Society for Testing and Materials (ASTM).

• ASTM A105/A105M – Specification for Carbon Steel Forgings for Piping Applications
• ASTM A234/A234M – Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service
• ASTM A403/A403M – Specification for Wrought Austenitic Stainless Steel Piping Fittings
• ASTM A420/A420M – Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel for Low-Temperature Service

AWWA: American Water Works Association

AWWA About – Established in 1881, the American Water Works Association is the largest nonprofit, scientific and educational association dedicated to managing and treating water, the world’s most important resource.

• AWWA C110 – Ductile-Iron and Gray-Iron Fittings, 3 Inch Through 48 Inch (75 mm Through 1200 mm), for Water and Other Liquids
• AWWA C208 – Dimensions for Fabricated Steel Water Pipe Fittings

ANSI The American National Standards Institute

ANSI is a private, non-profit organization. Its main function is to administer and coordinate the U.S. voluntary standardization and conformity assessment system. It provides a forum for development of American national standards. ANSI assigns “schedule numbers”. These numbers classify wall thicknesses for different pressure uses.

MSS STANDARDS: Manufacturers Standardization Society

The Manufacturers Standardization Society (MSS) of the Valve and Fittings Industry is a non-profit technical association organized for development and improvement of industry, national and international codes and standards for: Valves, Valve Actuators, Valve Modification, Pipe Fittings, Pipe Hangers, Pipe Supports, Flanges and Associated Seals

• MSS SP-43 – Wrought Stainless Steel Butt-Welding Fittings Including Reference to Other Corrosion Resistant Materials
• MSS SP-75 – Specifications for High Test Wrought Buttwelding Fittings
• MSS SP-73 – Brazing Joints for Copper and Copper Alloy Pressure Fittings
• MSS SP-83 – Class 3000 Steel Pipe Unions, Socket-Welding and Threaded
• MSS SP-97 – Integrally Reinforced Forged Branch Outlet Fittings — Socket Welding, Threaded, and Buttwelding Ends
• MSS SP-106 – Cast Copper Alloy Flanges and Flanged Fittings Class 125,150, and 300
• MSS SP-119 – Factory-Made Wrought Belled End Socket Welding Fittings

Difference between “Standard” and “Codes”

Piping codes imply the requirements of design, fabrication, use of materials, tests and inspection of various pipe and piping system. It has a limited jurisdiction defined by the code. On the other hand, piping standards imply application design and construction rules and requirements for pipe fittings like adapters, flanges, sleeves, elbows, union, tees, valves etc. Like a code, it also has a limited scope defined by the standard.

Factors affecting standards

“Standards” on pipe fittings are based on certain factors like as follows:

• Pressure-temperature ratings
• Size
• Design
• Coatings
• Materials
• Marking
• End connections
• Dimensions and tolerances
• Threading
• Pattern taper etc.

BSP British Standard Pipe

BSP is the U.K. standard for pipe fittings. This refers to a family of standard screw thread types for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. This has been adopted internationally. It is also known as British Standard Pipe Taper threads (BSPT )or British Standard Pipe Parallel (Straight) threads (BSPP ). While the BSPT achieves pressure tight joints by the threads alone, the BSPP requires a sealing ring.

JIS Japanese Industrial Standards

This is the Japanese industrial standards or the standards used for industrial activities in Japan for pipe, tube and fittings and published through Japanese Standards Associations.

NPT National Pipe Thread

National Pipe Thread is a U.S. standard straight (NPS) threads or for tapered (NPT) threads. This is the most popular US standard for pipe fittings. NPT fittings are based on the internal diameter (ID) of the pipe fitting.

BOLTS & NUTS

We are manufacturer of Flange bolts & Nuts and supply high quality

• A193 = This specification covers alloy and stainless steel bolting material for pressure vessels, Valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications.
• A320 = Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for Low-Temperature Service.
• A194 = Standard specification for nuts in many different material types.

AN Here, “A” stands for Army and “N” stands for Navy

The AN standard was originally designed for the U.S. Military. Whenever, a pipe fitting is AN fittings, it means that the fittings are measured on the outside diameter of the fittings, that is, in 1/16 inch increments.

For example, an AN 4 fitting means a fitting with an external diameter of approximately 4/16″ or ¼”. It is to be noted that approximation is important because AN external diameter is not a direct fit with an equivalent NPT thread.

Dash (-) size

Dash size is the standard used to refer to the inside diameter of a hose. This indicates the size by a two digit number which represents the relative ID in sixteenths of an inch. This is also used interchangeably with AN fittings. For example, a Dash “8” fitting means an AN 8 fitting.

ISO International Organization for Standardization

ISO is the industrial pipe, tube and fittings standards and specifications from the International Organization for Standardization. ISO standards are numbered. They have format as follows:

“ISO[/IEC] [IS] nnnnn[:yyyy] Title” where

• nnnnn: standard number
• yyyy: year published, and
• Title: describes the subject

General standard

Wide variety for all areas of application