CODES & STANDARDS IN PIPING – SIMPLE EXPLANATION FOR BEGINNERS

In every plant – power plant, refinery, chemical, water treatment, food factory or even gas supply to your home – piping systems must be safe, reliable and easy to maintain. To achieve this, engineers do not design pipes as they wish. They follow well-defined codes and standards prepared by international organisations.

In this article we will understand:

• What is a Standard in engineering?
• What is a Code and how is it different from a standard?
• Main international standard-making bodies such as ASME, ISO, ANSI, DIN, API, JAS.
• Overview of the famous ASME B31 Pressure Piping codes used in industries.

What Is a Standard?

A standard is a document that gives clear technical rules, definitions and guidelines for designers, manufacturers and users. You can think of it as a “how to do” instruction book prepared by experts from industry, academia and government.

In simple words:

• A standard tells us the minimum requirements for material, dimensions, testing and quality.
• It helps to make sure that parts from different manufacturers can fit and work together.
• A designer uses the standard to design a product, and a manufacturer uses the same standard to produce it.
• Because everyone follows the same rules, the final equipment is safe, economical and interchangeable.

Example: ASME B16.5 is a standard for pipe flanges. If a flange is made as per ASME B16.5, a matching flange from any other vendor will fit correctly.

What Is a Code?

A code is a special type of standard that has become legally enforceable. When a government body accepts a standard and includes it in law, or when it is written into a contract, that standard is treated as a code.

In short:

• All codes are standards, but not all standards are codes.
• Codes focus mainly on safety requirements and protection of people, property and environment.
• If you do not follow the applicable code, the project may fail regulatory approval and the designer can be legally responsible.

For example, ASME Boiler and Pressure Vessel Code and ASME B31 Piping Codes are accepted by many authorities in the USA and other countries. In several US states these codes are part of law, so they are legally mandatory. Other countries may not adopt them directly, but they usually have similar national codes.

Important Standard-Making Organisations

Many international bodies publish standards which are widely used in mechanical and piping engineering. Below are some common names that every piping engineer should know.

• ANSI – American National Standards Institute
  ANSI is the coordinator of standards in the USA. It does not always write standards itself, but approves standards developed by other societies and gives them national status.
• ASME – American Society of Mechanical Engineers
  ASME is one of the most important organisations for mechanical and piping engineers. It publishes the Boiler & Pressure Vessel Code, ASME B31 piping codes and many standards for flanges, valves and fittings.
• ISO – International Organization for Standardization
  ISO is a global body with members from many countries. It publishes international standards on almost every topic – quality management (ISO 9001), environment (ISO 14001), piping components, materials and many more.
• DIN – Deutsches Institut für Normung (German Institute for Standardization)
  DIN publishes standards used widely in Germany and Europe. DIN pipe sizes and materials are very common in European projects.
• API – American Petroleum Institute
  API prepares standards and recommended practices for the oil & gas industry. Example: API 5L for line pipes, API 610 for centrifugal pumps.
• JAS – Japan Standards Association
  JAS and related Japanese bodies issue standards that are commonly used in Japanese plants and equipment.

All these organisations make sure that engineering products are safe, compatible and economical. Following their standards also helps companies to export products to other countries easily.

ASME B31 – Pressure Piping Code Family

One of the most famous piping related codes is ASME B31 – Code for Pressure Piping. Instead of one single book, B31 is divided into several parts. Each part covers a different type of piping system. As a piping engineer you will usually work with one or more of these codes depending on your project.

Below is a simple overview of the main B31 sections and their typical applications.

1. ASME B31.1 – Power Piping

ASME B31.1 is used for piping in power-generating plants and related facilities. Typical systems include:

• High-pressure and high-temperature steam lines from boiler to turbine.
• Feed water, condensate and auxiliary steam systems.
• Piping inside thermal power plants, cogeneration plants, and some industrial boilers.

Because of very high pressure and temperature, this code is quite conservative and gives strict requirements for design, stress analysis, materials and testing.

2. ASME B31.2 – Fuel Gas Piping (Withdrawn but Historically Important)

Earlier, ASME B31.2 was used for fuel gas piping systems, such as gas supply to houses, buildings and small industries. Later it was replaced by other fuel gas codes (like NFPA 54 / ANSI Z223.1 in the US), but you may still see the name in older drawings and documents.

The typical system is what we see in many diagrams – the gas main under the road, service line to the house, meter, regulator and house piping leading to appliances.

3. ASME B31.3 – Process Piping

ASME B31.3 is probably the most used piping code in the process industry. It covers piping systems in:

• Refineries and petrochemical plants
• Chemical plants
• Pharmaceutical and food plants (for process lines)
• Offshore platforms, LNG plants and many other facilities

The code handles a wide range of fluids – from low-pressure utilities to high-pressure, high-temperature, toxic and flammable services. It gives detailed rules for design, flexibility analysis, allowable stresses, fabrication, examination and testing.

4. ASME B31.4 – Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

ASME B31.4 is used for long-distance liquid pipelines. Typical examples are:

• Cross-country pipelines carrying crude oil or refined products.
• Slurry pipelines transporting mixture of solids and liquids.
• Pipelines connecting terminals, tank farms and pumping stations.

The code focuses on issues important for pipelines: route selection, temperature changes along the length, buried conditions, road/rail crossings and station piping.

5. ASME B31.5 – Refrigeration Piping and Heat Transfer Components

As the name suggests, ASME B31.5 deals with refrigeration systems. These include:

• Industrial refrigeration plants
• Large cold storage facilities
• Chillers and cooling packages where refrigerants like ammonia, Freon, etc. are used

Refrigerants can be toxic or flammable, and they operate at specific pressure–temperature combinations. B31.5 provides special design rules and safety requirements for such systems.

6. ASME B31.8 – Gas Transmission and Distribution Piping Systems

ASME B31.8 is the main code for gas pipelines. It covers:

• High-pressure gas transmission lines running across long distances.
• Gas distribution networks in cities.
• Compressor station piping and related facilities.

The code deals with issues like location class, population density, design factor, wall thickness selection, pressure testing and protection against external loads.

7. ASME B31.9 – Building Services Piping

ASME B31.9 is used for piping inside buildings for services such as:

• Hot and cold water supply
• Heating and air-conditioning piping
• Non-flammable, non-toxic fluids within commercial and residential buildings

It is generally less stringent than B31.1 or B31.3 because the pressures and temperatures are lower, but it still ensures safe installations in offices, malls, hospitals and other buildings.

8. ASME B31.11 – Slurry Transportation Piping Systems

ASME B31.11 covers piping systems used to transport slurries – mixtures of solids and liquids. Typical examples are:

• Mining pipelines carrying ore slurry.
• Coal or ash slurry lines in power plants.

The presence of solid particles creates strong erosion and abrasion, so the code considers material selection, internal wear and special operating conditions.

9. ASME B31.12 – Hydrogen Piping and Pipelines

Hydrogen is becoming very important in the clean energy transition. ASME B31.12 provides rules for hydrogen piping and pipelines used in production plants, storage, fueling stations and transmission networks.

Hydrogen can cause problems like hydrogen embrittlement in some metals and has different leak and flammability characteristics compared to natural gas. Therefore B31.12 gives special stress limits, material restrictions and design guidance to keep systems safe.

Why Understanding Codes & Standards Is Important

For a piping engineer, knowledge of the relevant codes and standards is as important as knowledge of software or drawing tools. Some key benefits are:

• Safety: Correct application of codes prevents failures, leaks and accidents.
• Legal compliance: Projects must meet the requirements of local authorities and international regulations.
• Quality and reliability: Standardized design and testing lead to reliable plants with longer life.
• Ease of communication: When everyone uses the same codes, engineers from different countries can work smoothly on the same project.
• Better career growth: Engineers who understand ASME, ISO, API and similar standards are always in high demand worldwide.

Conclusion

Codes and standards are the backbone of piping design. A standard is a agreed-upon set of rules and guidelines, while a code is a standard that has legal power. Organisations like ASME, ISO, ANSI, DIN, API and JAS create these documents so that engineers can design safe and economical systems.

Among them, the ASME B31 series is especially important for pressure piping. From power plants (B31.1) and process plants (B31.3) to city gas networks (B31.8), building services (B31.9), slurry lines (B31.11) and hydrogen systems (B31.12), each part of B31 focuses on a specific application.

If you are a student or a young engineer, start by learning: What code applies to your project? Once you know that, you can go deeper into the details of design, stress analysis and fabrication. This habit will make your designs more professional and will strongly support your long-term piping engineering career.

Quick FAQ on Piping Codes & Standards

Q1: Which ASME B31 code is most common for process plants?

ASME B31.3 – Process Piping is the main code used in refineries, chemical plants, LNG facilities and similar projects.

Q2: Is ASME B31 mandatory in every country?

Not always. Some countries make ASME codes part of their law, while others have their own national codes. However, many international projects still follow ASME B31 because it is trusted and widely accepted.

Q3: As a beginner, which standards should I know first?

Start with the basics: ASME B31.3 or B31.1 (depending on your industry), plus common component standards like ASME B16.5 (flanges), ASME B16.9 (fittings) and material standards from ASTM / DIN / ISO.

Keep learning – every code you understand makes you a stronger and more confident piping engineer.