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BS 1139 PIPE standard and related products：

First of all, it is necessary to clarify a key point: BS 1139 is a series of standards mainly targeting steel pipes used for scaffolding and structural purposes. It is not a single standard, and the "BS 1139 PIPE" you mentioned usually specifically refers to the part about steel pipes in this standard.

At present, BS 1139 has been replaced by the updated European standards (EN standards), but these EN standards are still usually numbered "BS EN" in the UK and largely inherit BS 1139 in terms of content and requirements. Understanding BS 1139 is the foundation for understanding current standards.

The BS 1139 series of standards are mainly divided into several parts, among which the most important ones are:

• BS 1139-1: Specifies the requirements for steel pipes used in scaffolding and general structural purposes. This is the key content we want to introduce.
• BS 1139-2: It standardizes the requirements for scaffold couplings.
• BS 1139-3: It standardizes the requirements for scaffolding boards.
• BS 1139-4: Specifies the requirements for node boards.

Current status: BS 1139 has been replaced by the following European standards (EN), which are adopted as national standards in the UK and are numbered BS EN:

• Steel pipes: BS EN 10219-1 and BS EN 10219-2 (cold-formed welded structural hollow steel sections)
• Scaffolding couplings: BS EN 12811-1

Although it has been replaced, in oral communication within the industry, pipes that meet the structural steel Pipe standards are still habitually referred to as "BS 1139 Pipe" or "BS 1139 Tube".

These standards impose very strict and specific requirements on cold-formed welded hollow steel pipes used for scaffolding and structures to ensure their safety, reliability and interchangeability.

The main technical requirements include:

1. Dimensions and tolerances

• It specifies the precise dimensions of the outer diameter (OD), wall thickness (WT), and length, as well as the allowable deviations (tolerances).
• Common sizes include: outer diameter 48.3mm (this is the most common size for scaffolding pipes), 42.4mm, 33.7mm, etc. The wall thickness is usually 3.2mm, 4.0mm, etc.
• Strict tolerances ensure that the connections between pipes (such as when inserting sleeves or connecting with fasteners) can fit tightly, guaranteeing the rigidity and stability of the structure.

2. Material

• Steel pipes are usually made of non-alloy steel and must meet specific steel grade requirements, such as S235JRH, S275J0H or S355J2H (in accordance with EN 10219). These codes represent the yield strength of the steel (such as 235, 275, 355 N/mm²) and impact toughness.
• The material must have good weldability, formability and a certain degree of toughness (especially in low-temperature environments).

3. Manufacturing process

It must be made by cold bending and arc welding.

The weld seam must be complete, continuous and fully fused with the base metal. The weld area needs to be trimmed so that it does not significantly protrude above the surface of the pipe body to ensure the smooth installation of the fasteners.

4. Mechanical properties:

• Yield Strength: The minimum requirement, for example, the yield strength of S235 shall not be less than 235 N/mm². This is a key indicator for calculating the bearing capacity of a structure.
• Tensile Strength (Tensile strength) : the minimum requirement, for example, the tensile strength of S235 is between 360 and 510 N/mm².
• Elongation: It specifies the minimum elongation at fracture, reflecting the ductility of the material, which is crucial for safety (to avoid brittle fracture).

5. Testing and Inspection:

• Pressure test: The steel pipe must be capable of withstanding a certain internal fluid pressure without leakage or rupture.
• Flattening test: A section of the pipe is flattened to a specified distance to test its ductility and weld quality. The weld area must not crack first.
• Bend test: To examine the formability of the material.
• Impact test: To examine the toughness of materials at low temperatures.
• Appearance and surface quality: The pipe should have no defects that are harmful to the application. Usually with a layer of protective mill scale or coated with protective paint.

6. Marking and Certification:

• Each pipe or each bundle of pipes must have clear and non-erasable markings, including: manufacturer's name or trademark, standard number (e.g. BS EN 10219), steel grade, dimensions, etc.
• The manufacturer shall provide a certificate of conformity to prove that the batch size of the product complies with the standard requirements.

Compared with ordinary welded steel pipes or black steel pipes, the uniqueness of BS 1139 (and its subsequent standards) pipes lies in:

1. High strength-to-weight ratio:While ensuring high strength (such as a yield strength of 355MPa), the pipe wall is relatively thin, making the structure lightweight and having strong load-bearing capacity.

2. Extremely high dimensional accuracy and consistency: This is its most core feature. Strict outer diameter and roundness tolerances ensure a perfect and reliable fit with various scaffolding fasteners (such as clamps and sleeves), preventing loosening of connection points, which is the core of construction safety.

3. Outstanding metallurgical and mechanical properties: It not only specifies strength but also ductility and toughness, ensuring that the pipe can deform (warning) under external force rather than suddenly undergo brittle fracture.

4. Strict quality assurance system: From raw materials to finished products, all undergo a series of rigorous tests and inspections, and require traceable certifications to ensure the reliability of quality.

5.Standardization and universality: As an internationally widely recognized standard, it enables components from different manufacturers to be interchangeable, facilitating leasing, procurement, and engineering construction on a global scale.

Due to its outstanding performance, the application of BS 1139 steel pipes has far exceeded the traditional scaffolding field:

1. Scaffolding system: It is the most important and traditional application. The vertical rods, horizontal rods and diagonal braces that constitute various systems such as coupler-type scaffolding and portal scaffolding.

2. Support structures: Large temporary support structures and formwork support systems used on construction sites.

3. Structural Application

• Building structures: Roof trusses, spatial grid structures, canopies, handrails and railings, etc. used in modern buildings. Its beautiful circular cross-section and structural efficiency are highly favored by architects and engineers.

• Stage and exhibition: Used for building stage trusses, lighting frames and temporary structures for concerts, theaters and exhibitions. Its lightweight and quick assembly features are highly suitable for these fields.

4. Agricultural and industrial equipment: Used for manufacturing agricultural machinery frames, storage shelves, simple factory structures, guardrails, etc.

5. Creativity and Design: Due to its easy cutting and welding properties, it is often used by designers and artists to make furniture, sculptures and various creative installations.

BS 1139 PIPE is essentially a set of strict quality specifications for cold-formed welded hollow steel pipes. Its core value lies in ensuring that the temporary or permanent structures constructed with it have the highest safety and reliability through ultimate dimensional accuracy, reliable material properties and strict quality control. Although the original standard has been replaced by the European standard, its spirit and core requirements have been carried forward, making the name "BS 1139" still a synonym for high-quality structural steel pipes in the industry to this day.

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