BS 1387 Pipes

What is BS 1387?

BS 1387 is a crucial British standard that specifies requirements for steel pipes (including both galvanized and non-galvanized steel pipes). Its full title is "Specification for Screwed and socketed steel tubes and tubulars and for plain end steel tubes suitable for welding or for screwing to BS 21 pipe threads." These pipes are widely used in industries such as water supply, gas, structural support, and fencing. This standard covers both threaded and socketed steel tubes and plain end steel tubes. It has been superseded by the European standard EN 10255, but some countries still use it. It defines three wall thickness series: thin-wall, medium-wall, and heavy-wall.

Basic Content: BS 1387 specifies the technical requirements for threaded and socketed steel tubes and tubulars and plain end steel tubes suitable for welding or screwing to BS 21 pipe threads. It covers manufacturing processes, mechanical properties, appearance and integrity, connection methods, dimensions and tolerances, test methods, and protective requirements. Suitable for piping systems in industries such as oil and gas, chemicals, construction, and water supply.

Key Features:

Material: Specified steel pipe, available in either galvanized or black (non-galvanized) versions.

Manufacturing Process:
BS 1387 steel pipes are manufactured using processes including high-frequency welding (HFW) and seamless hot rolling. These pipes undergo pre-treatment, grinding, and spray coating to ensure a uniform and leveling coating.

Hot-Dip Galvanizing:
BS 1387 steel pipes can be hot-dip galvanized to enhance corrosion resistance and service life. Hot-dip galvanizing is a process in which molten metal reacts with an iron matrix to create an alloy layer, bonding the base and coating. This treatment produces a uniform coating with strong adhesion and a long service life.

Applications:
BS 1387 steel pipes are typically used for low- and medium-pressure piping and structural applications. They can be used in a variety of industrial and construction applications, including fluid transport, structural support, and other applications requiring steel pipe. The main types are as follows:

a. Fluid Transport: For water, gas, oil, and low-pressure fluids.
b. Structural Use: For scaffolding, framing, fencing, railings, and supporting structures.
c. Mechanical and Other Uses: For agriculture, HVAC systems, and general engineering applications.

End Types:
Screwed and Socketed: Pipes with screwed ends and sockets for connection.

Plain End: Pipes with plain ends suitable for welding or screwing to BS 21 pipe threads.

Common Names: In the market, steel pipes that meet BS 1387 standards are often referred to as "gas pipes" or "water-gas pipes."

Types and Classifications of BS 1387 Standards:

BS 1387 standard classifies steel pipes based on their manufacturing process, wall thickness, and coating:

1. Classification by Type and Wall Thickness

Light (Thin-Wall): Suitable for applications with relatively high working conditions, such as indoor water pipes. 

Medium (Medium Wall): The most commonly used type, suitable for general water, gas, and air systems.

Heavy (Thick Wall): Suitable for applications requiring more demanding conditions and higher mechanical strength, such as buried pipelines or areas subject to external impact.

2. Classification by Coating

Galvanized Steel Pipe (GI): Hot-dip galvanizing is applied to both the inner and outer surfaces of the pipe, providing excellent rust and corrosion resistance. This is the most common type and has a silver-gray color.
Black Steel Pipe: Ungalvanized steel pipe has a black oxide scale on the surface. It has poor corrosion resistance and usually requires anti-corrosion treatment such as painting before use.

BS 1387 Class B and Class C:

In BS 1387, Class B and Class C refer to different coating types and weights for steel pipes, not to material grades or pressure ratings.

The purpose of galvanizing is to form a protective layer on the steel surface to prevent rust and corrosion. Class C requires a thicker zinc layer than Class B, thus providing longer-lasting, more durable corrosion protection.

BS 1387 Class B - Light Galvanizing
Zinc coating requirements: The average zinc coating weight must be at least 375 g/m².
Equivalent zinc coating thickness: approximately 55 microns.

Features and Applications:
The zinc coating is relatively thin.
Suitable for indoor applications with low corrosiveness and relatively mild environments, such as indoor water supply pipes and indoor compressed air pipes.
The cost is slightly lower than heavy galvanized pipe.
The surface appearance is relatively smoother and more uniform.

BS 1387 Class C - Heavy Galvanizing
Zinc coating requirements: The average zinc coating weight must be at least 475 g/m². Equivalent zinc coating thickness: approximately 67 microns.

Features and Applications:
The thicker the zinc coating, the stronger its corrosion resistance.

Suitable for more demanding environments, such as:
Exposed outdoor pipes (railings, scaffolding pipes);
Buried pipes (corrosive soil);
Industrial environments, coastal areas (high-salt air), and other highly corrosive environments.

Longer service life, but higher cost.
The surface may appear rougher, with more noticeable zinc spangles.

Relationship with "Light/Medium/Heavy" pipes:

"Light/Medium/Heavy Duty" refers to the wall thickness of the steel pipe itself, which determines the pipe's mechanical strength and pressure-bearing capacity.
"Class B/Class C" refers to the weight of the zinc coating applied to the pipe, which determines its corrosion resistance.

These are two separate specifications. You can order a "Medium Duty, Class C" pipe, which has both a medium wall thickness and a heavy zinc coating.

BS 1387 Standard Dimensions and Mechanical Properties:

1. Threaded Ends: One of its most notable features. The pipe ends are machined with standard tapered pipe threads (such as BS 21, now ISO 7-1), facilitating connection with corresponding threaded fittings (such as pipe elbows, tees, and unions), eliminating the need for welding.

2. Unique Sizes: BS 1387 uses a unique nominal diameter system rather than direct outside or inside diameters. For example, common sizes include 1/2" (21.4mm), 3/4" (26.9mm), 1" (33.7mm), and 1-1/4" (42.4mm). It's important to note that these outside diameters differ from the later commonly used ISO standards.

3. Clear Mechanical Requirements: The standard specifies tensile strength, flattening tests, and bend tests for steel pipes to ensure they can withstand certain fluid pressures and mechanical stresses.

4. Hydrostatic Testing: Every pipe undergoes a hydrostatic test at a specified pressure before leaving the factory to ensure its leak-tightness and strength.

BS 1387 Round Tube Specifications:

Typical Applications of BS 1387:

1. Building water supply and drainage systems: particularly cold water pipes.
2. Gas distribution pipelines: low-pressure indoor and outdoor gas networks.

3. Structural Applications: scaffolding, framing, fencing, railings, and supporting structures. 

4. Pipes for fire sprinkler systems.

5. Industrial piping.

Current Status and Replacement Standards:

Standard Status:
BS 1387 has been superseded by the newer European Standard (EN standard). However, it is still widely referenced and used in many older projects and specific regions. Key replacement standards include:

EN 10255: "Non-alloy steel welded pipes suitable for threaded and compression fittings"
This is the most direct successor to BS 1387. EN 10255 also specifies thin-wall, medium-wall, and heavy-wall series. The dimensions and applications are very similar to BS 1387, and technically harmonized and unified.

EN 10305 series: "Steel pipes for precision purposes"
ISO 65: "Carbon steel pipes suitable for ISO 7-1 threads"

Important Note:
Although BS 1387 has been superseded, it is still encountered in the following situations:

1) Maintenance and renovation of existing, older facilities. 

2) Some countries and regions still use the British Standards system.

3) Out of habit, users still refer to steel pipes that comply with newer standards such as EN 10255 as BS 1387 pipes.

Purchasing Tips:

When ordering or replacing BS 1387 galvanized pipe, you will need to specify:
Nominal diameter (e.g., 1/2", 1")
Wall thickness (light, medium, heavy)
Coating grade (Class B or Class C)

If your environment presents a high corrosion risk or pipe replacement is difficult, we strongly recommend Class C (heavy galvanized) for a longer service life. For general indoor applications, Class B is generally sufficient.

Conclusion:

BS 1387 is a classic standard for threaded steel pipes used for low-pressure fluid transportation. Its reliable performance, convenient threaded connections, and wide applicability have left a deep impression worldwide, particularly in Commonwealth countries and regions heavily influenced by the UK. Although it has been superseded by more modern EN standards, its technical requirements and product form factors continue to be preserved in the newer standards. When purchasing or discussing products, be sure to confirm whether strict compliance with the older BS 1387 standard is required or whether products complying with modern equivalents (such as EN 10255) are acceptable.

Read more: Galvanized ERW Carbon Steel Pipe or Guide for Selecting the Thickness of Galvanized Steel Pipe