scope:

ASME B31.3 is the generally accepted standard for process piping, worldwide. It is the de facto standard for piping for the oil, petro-chemical and chemical industries, worldwide. To facilitate its international use, ISO/ WD 15649, Petroleum and natural gas industries-piping, has been approved. This ISO standard makes a normative reference to ASME B31.3. It is an evergreen reference, as it is not tied to a specifi c edition. The ISO Standard also provides additional technical requirements, such as provisions for buried piping.

To facilitate use of ASME B31.3, as referenced by ISO 15649, in Europe, a guide was prepared by EEMUA. This guide, entitled "Guide to the Use of ISO 15649 and ANSI /ASME B31.3 for Piping in Europe in Compliance With the Pressure Equipment Directive," provides specifi c guidance on how to comply with the European Pressure Equipment Directive (PED) while using ISO 15649. Following this guide does not provide a presumption of conformity with the PED, therefore, the conformity assessment requirements of the PED must be followed in full.

Within the United States, ASME B31.3 is the recognized and generally accepted good engineering practice for process piping. It is specifi cally referenced by legislation in the following states (Alaska, California, Maryland and Oklahoma) and provinces of Canada (British Columbia, Northwest Territories, Ontario, Prince Edward Island, Quebec and Saskatchewan). However, it is also referenced by other Codes, Standards and regulations, such as NFPA and CFR. As such, it is often required by law, although not directly specifi ed in state regulations.

The ASME B31.3 Code was written with process piping in mind. It is very broad in scope, refl ecting the scope of process piping services. Although ASME B31 allows owners to select the piping code most appropriate to their piping installation, the following are typical examples of the types of facilities that ASME B31.3 is intended to cover:

• Chemical plants

• Oil refi neries

• Loading terminals

• Bulk processing plants

• Cryogenic piping

The Code was previously intended to cover all piping within the property limits of a process plant, with certain exclusions. The ASME B31 Codes now state that it is the owners' responsibility to decide which Code is most applicable to their piping system. However, these previously listed exclusions show the intent of the writers of the Code. The following items were excluded from coverage by earlier editions of ASME B31.3:

• Fire protection systems

• Sanitary and storm water systems

• Plumbing

• Piping in property set aside for transportation piping (ASME B31.4, B31.8, and B31.11)

• Piping within the jurisdiction of Section I of the ASME Boiler and Pressure Vessel Code (BPV) (i.e., boiler external piping)

Certain piping was considered optional:

• Steam piping from a boiler that is outside the jurisdiction of ASME BPV, Section I, which could be either ASME B31.1 or ASME B31.3

• Refrigeration piping that is part of a packaged system (factory-assembled), which could be either ASME B31.5 or ASME B31.3

Boiler external piping is the piping between a boiler casing and generally the fi rst block valve outside the boiler. This is within the jurisdiction of Section I of ASME BPVC, although Section I refers to the rules of ASME B31.1 for this piping.

Although the Code included building systems piping (e.g., heating systems) that are on the process plant property, other than items specifi cally excluded (e.g., sanitary), these are better covered by ASME B31.9. practice, it is doubtful that many people have used ASME B31.3 for their building systems piping in any case.

The Code excludes low pressure piping systems from its scope, if they meet all of the following conditions:

(1) the pressure is less than 105 kPa (15 psi);

(2) the pressure is not less than zero (i.e., no vacuum condition);

(3) the fl uid is nonfl ammable, nontoxic and not damaging to human tissue;

(4) the temperature is not less than −29°C (−20°); and

(5) the temperature is not greater than 186°C (366°F ).