ASME B31.3 design code

Design code for process piping as per ASME B31.3

Process Piping Code

As a means of fluid transportation, piping plays a very important role in the production process in the chemical industry, Petrochemical, upstream & downstream Oil & Gas Industry. Mechanical and facility engineers need to develop a deeper knowledge about design, coding & standardization, material selection, fabrication, and pipe maintenance, to be applied in the field effectively. at least Mechanical engineers working on a plant, must understand “Piping System Design for ASME Piping Process B31.3” and inspection repair & alteration for in service piping according to API 570.

ASME B31.3 contains requirements for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. It covers materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping.

This Code applies to piping for all fluids including:
(1) raw, intermediate, and finished chemicals;
(2) petroleum products;
(3) gas, steam, air and water;
(4) fluidized solids;
(5) refrigerants; and
(6) cryogenic fluids.

The rules in ASME B31.3 are for piping contained in:

• Petroleum Refineries
• Chemical
• Pharmaceutical
• Textile
• Paper
• Semiconductor
• Cryogenic plants
• Related processing Plant and terminals

Responsibilities in accordance with ASME rule B31.3 sorted according to the responsibility in the work of designing the piping system process, namely:


Have responsibility for plants built to meet the requirements of the CODE, including determining the requirements for Design, Construction, Examination, Inspection and Testing. Also important is that the Owner is also responsible for “designating piping” on certain types of fluids.


in this case it could also be EPC Company or anyone else involved in the Design process, who will be responsible for engineering design of Piping that is done is to meet the requirements of this CODE as well as additional requirements provided by the Owner.

Manufacturer, Fabricator, and Erector:

they are responsible for supplying materials, components and workers who meet the requirements in this CODE and Engineering Design.

Owner’s Inspector:

owner’s responsibility that the requirements of this CODE for Inspection, examinations and Testing have been met. In addition, this Code has the intention (Intent) to be an engineering requirement in an effort to design a piping system that is “safe” both in terms of design and installation. But, one thing to remember, that the Code does not apply to operation, examination, inspection, testing and maintenance or repair of piping that is already in operation or “in service”.

Although code is an “engineering requirement” for a safe design, in principle only use a simple approach. In other words, if designer has the ability to do a more detailed and in-depth analysis, then he could do so, by making documentation of the calculation results and of course must get approval from the Owner, and attach details of the design, construction, examination, inspection and testing for design in accordance with ASME B31.3, with calculation consistent with the design criteria of this Code.

Fluid Service Requirements in ASME B31.3:

Fluid services class determines in the selection and use of materials, components and joints. Fluid Service requirement itself includes a combination of “fluid properties, operating conditions and other factors such as in Appendix M, some examples are for example high pressure, toxic, and flammable a fluid.

There are several Category Fluids contained in ASME B31.3, namely:

1. Category D Fluid Services: Fluids incorporated in category D are Fluids that:

a. Non-Flammable, Non-Toxic and Non-Damaging to Human Skin
b. Design Gauge Pressure does not exceed 150 Psi or 1035 kPa.
c. Design Temperature from -29 C (-20F) to 186 C (366 F)
On the cover from Chapters I to VII, which could have used elements suitable for other types of Fluid services.

2. Category M Fluid Services: This category applies to fluids that if interacting with humans either through breathing or in direct contact, even in very small quantities, will be able to produce very serious and “irreversible” risks. Please see chapters VIII.

3. High Pressure Fluid Service: Fluid service which is categorized by owner, where the Design Pressure exceeds that allowed by ASME B16.5 PN420 (Class 2500) rating for specified design temperature and material group, as written in Chapter IX

4. Normal Fluid Service: this is a service fluid covered by B31.3, which is not included in The Fluid Category D, M and High Pressure Fluid Service.

  • For Metal Piping, the cover in B31.3 starts from Chapters I to Chapters IV (the base code), where fluid service requirement is found in:
    Chapters III for Materials
    Chapters II, Part 3, for components
    Chapters II, part 4, for joints.
  • As for Non-Metal Piping and Piping coated non-metal, on the cover in Chapters VII.
ASME B31.3 scope
ASME B31.3 scope

ASME B31.3 does not apply to the following:

  • Piping system designed has Internal Pressure of “Zero” or above “Zero but below 15 Psi (150 kPa)”, and the fluid is not Flammable, non-toxic and also non-damaging to human tissues, with a design temperature between -29C (-20F) to 186C (366 F).
  • Power Boiler in accordance with BPV Code Section I and External Piping Boiler that must conform with B31.1
  • Tubes, tube headers, crossovers, and Manifold of Fire Heaters, which are internal to the heater enclosure.
  • Pressure Vessel, Heat Exchanger, Pumps, Compressors and other equipment, including Internal Piping and connections to external piping.

disclaimer : Please refer to updated ASME B31.3 document ( Latest edition ) for more precise information.

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