Thursday, May 16, 2013

ASME B31.1: Power Piping Code


ASME B31.1, Power Piping Code, prescribes requirements for the design, material, fabrication, erection, test, and inspection of power and auxiliary service piping systems for electric generation stations, industrial and institutional plants, central and district heating plants, and district heating systems. It does not apply to piping systems covered by other sections of the Code for Pressure Piping, and other piping which is specifically excluded from the scope of this code. 

As explained earlier, the BEP is required to meet administrative jurisdictional requirements of ASME Section I; however, pipe connections meeting all other requirements of ASME B31.1 but not exceeding nominal pipe size (NPS) ¹⁄₂ may be welded to boiler external pipe or boiler headers without inspection and stamping required by ASME Section I.

Non-boiler external piping is defined as all the piping covered by ASME B31.1 with the exception of BEP. The nonboiler external piping must be constructed in accordance with the requirements of this code.

In addition to the piping systems covered by other sections of ASME B31, Pressure Piping Code, ASME B31.1 does not cover the following: 

● Economizers, heaters, pressure vessels, and components covered by the ASME Boiler and Pressure Vessel Code (except the connecting piping not covered by the ASME Boiler and Pressure Vessel Code shall meet the requirements of ASME B31.1)

● Building heating and distribution steam piping designed for 15 psig (100 kPa gauge) or less, or hot-water heating systems piping designed for 30 psig (200 kPa gauge) or less

● Piping for roof and floor drains, plumbing, sewers, and sprinkler and other fire protection systems

● Piping for hydraulic or pneumatic tools and their components downstream of the first stop valve off the system distribution header

Piping for marine or other installations under federal control

● Piping covered by other sections of ASME B31 and ASME Section III

● Fuel gas piping within the scope of ANSI Z 223.1, National Fuel Gas Code

● Pulverized fuel piping within the scope of NFPA

The requirements of this code apply to central and district heating systems for distribution of steam and hot water away from the plants whether underground or elsewhere, and geothermal steam and hot water piping both to and from wellheads.

The construction of fuel gas or fuel oil piping brought to plant site from a distribution system inside the plant property line is governed by the requirements of ASME B31.1 when the meter assembly is located outside the plant property line. In cases where the meter assembly is located within the plant property line, the requirements of this code shall apply to the fuel gas and fuel oil piping downstream from the outlet of the meter assembly (see Fig. below). 

Jurisdiction of ASME B31.1, B31.4, and B31.8 Over Fuel Gas
and Fuel Oil Piping.

This code also applies to gas and oil systems piping other than that shown in Fig. above. It covers air systems, hydraulic fluid systems piping, and the steam-jet cooling systems piping which are part of the power plant cycle. In addition, building services within the scope of ASME B31.9 but outside the limits of Paragraph 900.1.2 of B31.9 are required to be designed in accordance with ASME B31.1.

Effective Edition, Addenda, and Code Cases

Prior to the publication and implementation of ASME Section III for construction of nuclear power plant components, in some nuclear power plants the safety-related piping systems now classified as ASME Classes 1, 2, and 3 were constructed to earlier versions of AMSE B31.1. Therefore, the repairs and replacements of those safety-related piping systems may be made in accordance with the edition and addenda of ANSI B31.1 used for the original construction or the later edition and addenda of ANSI B31.1. Refer to Article IWA-4000 and Article IWA7000 of ASME Section XI for requirements related to repairs and replacements, respectively.

For power piping systems other than the nuclear safety-related piping systems constructed and new piping systems to be constructed to ASME B31.1, the following guidelines shall be used to determine the effective edition and addenda of ASME B31.1:
Editions are effective and may be used on or after the date of publication printed on the title page. Addenda are effective and may be used on or after the date of publication printed on the title page. 
The latest edition and addenda, issued six months prior to the original contract date for the first phase of the activity covering a piping system(s) shall be the governing document for design, materials, fabrication, erection, examination, and testing activities for the piping system(s) until the completion of the work and initial
operation.7 Unless agreement is specifically reached between the contracting parties, no code edition and/or addenda shall be retroactive.

Code cases may be used after they have been approved by the ASME Council. The provisions of a code case may be used even after its expiration or withdrawal, provided the code case was effective on the original contract date and it was used for original construction or was adopted prior to completion of work and the contracting parties agreed to its use.

Do not use revisions and code cases that are less restrictive than former requirements without having assurance that they have been accepted by the proper authorities in the jurisdictions where the piping is to be installed.

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