Wisconsin Administrative Code › Department of Safety and Professional Services › SPS 301-399 - Safety, Buildings, and Environment › SPS 326-360 - General, Part II › Chapter SPS 341 - Boilers And Pressure Vessels › Appendix D - EXCERPTS FROM: POWER PIPING CODE

Current through June 24, 2024
ANSI/ASME B31.1
2010 EDITION
FOREWORD
The general
philosophy
underlying this
					 Power Piping Code is to parallel those provisions of Section I, Power Boilers,
					 of the ASME Boiler and Pressure Vessel Code, as they can be applied to power
					 piping systems. The Allowable Stress Values for power piping are generally
					 consistent with those assigned for power boilers. This Code is more
					 conservative than some other piping codes, reflecting the need for long service
					 life and maximum reliability in power plant installations.
The Power Piping Code as currently written does not
					 differentiate between the design, fabrication, and erection requirements for
critical and noncritical piping systems,
except for certain
					 stress calculations and mandatory nondestructive tests of welds for heavy wall,
					 high temperature applications. The
problem involved
is to try
					 to reach agreement on how to evaluate criticality, and to avoid the inference
					 that noncritical systems do not require competence in design, fabrication, and
					 erection. Some day such levels of quality may be definable, so that the need
					 for the many different piping codes will be overcome.
There are many instances where the Code serves to
warn a designer,
fabricator, or erector against possible
					 pitfalls; but the Code is
not a handbook,
and cannot
					 substitute for education, experience, and sound engineering judgment.
Nonmandatory Appendices are included in the Code. Each
					 contains information on a specific subject, and is maintained current with the
					 Code. Although written in mandatory language, these Appendices are offered for
					 application at the user's discretion.
The Code
never intentionally puts a ceiling limit
					 on conservatism.
A designer is free to specify more rigid
					 requirements as he feels they may be justified.
Conversely, a designer
					 who is capable
of a more rigorous analysis than is specified in the
					 Code may justify a less conservative design, and still satisfy the basic intent
					 of the Code.
The Power Piping Committee strives to keep abreast of the
					 current technological improvements in new materials, fabrication practices, and
					 testing techniques; and endeavors to keep the Code updated to permit the use of
					 acceptable new developments.
INTRODUCTION
The ASME B31 Code for Pressure Piping consists of a number
					 of individually published Sections, each an American National Standard, under
					 the direction of ASME Committee B31, Code for Pressure Piping.
Rules for each Section have been developed considering the
					 need for application of specific requirements for various types of pressure
					 piping. Applications considered for each Code Section include:
B31.1 Power Piping: piping typically found in electric
					 power generating stations, in industrial and institutional plants, geothermal
					 heating systems, and central and district heating and cooling systems;
B31.3 Process Piping: piping typically found in petroleum
					 refineries, chemical, pharmaceutical, textile, paper, semiconductor, and
					 cryogenic plants, and related processing plants and terminals;
B31.4 Pipeline Transportation Systems for Liquid
					 Hydrocarbons and Other Liquids: piping transporting products which are
					 predominately liquid between plants and terminals and within terminals,
					 pumping, regulating, and metering stations;
B31.5 Refrigeration Piping: piping for refrigerants and
					 secondary coolants;
B31.8 Gas Transportation and Distribution Piping Systems:
					 piping transporting products which are predominately gas between sources and
					 terminals, including compressor, regulating, and metering stations; and gas
					 gathering pipelines;
B31.9 Building Services Piping: piping typically found in
					 industrial, institutional, commercial, and public buildings, and in multi-unit
					 residences, which does not require the range of sizes, pressures, and
					 temperatures covered in B31.1;
B31.11 Slurry Transportation Piping Systems: piping
					 transporting aqueous slurries between plants and terminals and within
					 terminals, pumping, and regulating stations.
B31.12 Hydrogen Piping and Pipelines: piping in gaseous and
					 liquid hydrogen service, and pipelines in gaseous hydrogen service.
This is the B31.1 Power Piping Code Section. Hereafter, in
					 this Introduction and in the text of this Code Section B31.1, where the word
Code
is used without specific identification, it means this
					 Code Section.
It is the owner's responsibility to select the Code Section
					 which most nearly applies to a proposed piping installation. Factors to be
					 considered by the owner include: limitations of the Code Section;
					 jurisdictional requirements; and the applicability of other codes and
					 standards. All applicable requirements of the selected Code Section shall be
					 met. For some installations, more than one Code Section may apply to different
					 parts of the installation. The owner is also responsible for imposing
					 requirements supplementary to those of the selected Code Section, if necessary,
					 to assure safe piping for the proposed installation.
Certain piping within a facility may be subject to other
					 codes and standards, including but not limited to:
ASME Boiler and Pressure Vessel Code, Section III: nuclear
					 power piping;
ANSI Z223.1 National Fuel Gas Code: piping for fuel gas
					 from the point of delivery to the connection of each fuel utilization
					 device;
NFPA Fire Protection Standards: fire protection systems
					 using water, carbon dioxide, halon, foam, dry chemical, and wet
					 chemicals;
NFPA 99 Health Care Facilities: medical and laboratory gas
					 systems;
NFPA 8503 Standard for Pulverized Fuel Systems: piping for
					 pulverized coal from the coal mills to the burners;
Building and plumbing codes, as applicable, for potable hot
					 and cold water, and for sewer and drain systems.
The Code sets forth engineering requirements deemed
					 necessary for safe design and construction of pressure piping. While safety is
					 the basic consideration, this factor alone will not necessarily govern the
					 final specifications for any piping system. The designer is cautioned that the
					 Code is not a design handbook; it does not do away with the need for the
					 designer or for competent engineering judgment.
To the greatest possible extent, Code requirements for
					 design are stated in terms of basic design principles and formulas. These are
					 supplemented as necessary with specific requirements to assure uniform
					 application of principles and to guide selection and application of piping
					 elements. The Code prohibits designs and practices known to be unsafe and
					 contains warnings where caution, but not prohibition, is warranted.
The specific design requirements of the Code usually
					 revolve around a simplified engineering approach to a subject. It is intended
					 that a designer capable of applying more complete and rigorous analysis to
					 special or unusual problems shall have latitude in the development of such
					 designs and the evaluation of complex or combined stresses. In such cases the
					 designer is responsible for demonstrating the validity of his approach.
This Code Section includes the following:
(a) references to acceptable material specifications and
					 component standards, including dimensional requirements and
					 pressure-temperature ratings
(b) requirements for design of components and assemblies,
					 including pipe supports
(c) requirements and data for evaluation and limitation of
					 stresses, reactions, and movements associated with pressure, temperature
					 changes, and other forces
(d) guidance and limitations on the selection and
					 application of materials, components, and joining methods
(e) requirements for the fabrication, assembly, and
					 erection of piping
(f) requirements for examination, inspection, and testing
					 of piping
(g) requirements for operation and maintenance of piping
					 systems
It is intended that this Edition of Code Section B31.1 and
					 any subsequent Addenda not be retroactive. Unless agreement is specifically
					 made between contracting parties to use another issue, or the regulatory body
					 having jurisdiction imposes the use of another issue, the latest Edition and
					 Addenda issued at least 6 months prior to the original contract date for the
					 first phase of activity covering a piping system or systems shall be the
					 governing document for all design, materials, fabrication, erection,
					 examination, and testing for the piping until the completion of the work and
					 initial operation.
Users of this Code are cautioned against making use of
					 revisions without assurance that they are acceptable to the proper authorities
					 in the jurisdiction where the piping is to be installed.
Code users will note that clauses in the Code are not
					 necessarily numbered consecutively. Such discontinuities result from following
					 a common outline, insofar as practicable, for all Code Sections. In this way,
					 corresponding material is correspondingly numbered in most Code Sections, thus
					 facilitating reference by those who have occasion to use more than one
					 Section.
The Code is under the direction of ASME Committee B31, Code
					 for Pressure Piping, which is organized and operates under procedures of The
					 American Society of Mechanical Engineers which have been accredited by the
					 American National Standards Institute. The Committee is a continuing one, and
					 keeps all Code Sections current with new developments in materials,
					 construction, and industrial practice. Addenda are issued periodically. New
					 editions are published at intervals of two to five years.
When no Section of the ASME Code for Pressure Piping,
					 specifically covers a piping system, at his discretion the user may select any
					 Section determined to be generally applicable. However, it is cautioned that
					 supplementary requirements to the Section chosen may be necessary to provide
					 for a safe piping system for the intended application. Technical limitations of
					 the various Sections, legal requirements, and possible applicability of other
					 codes or standards are some of the factors to be considered by the user in
					 determining the applicability of any Section of this Code.
The Committee has established an orderly procedure to
					 consider requests for interpretation and revision of Code requirements. To
					 receive consideration, inquiries must be in writing and must give full
					 particulars (see Mandatory Appendix H covering preparation of technical
					 inquiries). The Committee will not respond to inquiries requesting assignment
					 of a Code Section to a piping installation.
The approved reply to an inquiry will be sent directly to
					 the inquirer. In addition, the question and reply will be published as part of
					 an Interpretation Supplement issued to the applicable Code Section.
A Case is the prescribed form of reply to an inquiry when
					 study indicates that the Code wording needs clarification or when the reply
					 modifies existing requirements of the Code or grants permission to use new
					 materials or alternative constructions. The Case will be published as part of a
					 Case Supplement issued to the applicable Code Section.
The ASME B31 Standards Committee took action to eliminate
					 Code Case expiration dates effective September 21, 2007. This means that all
					 Code Cases in effect as of this date will remain available for use until
					 annulled by the ASME B31 Standards Committee.
Materials are listed in the Stress Tables only when
					 sufficient usage in piping within the scope of the Code has been shown.
					 Materials may be covered by a Case. Requests for listing shall include evidence
					 of satisfactory usage and specific data to permit establishment of allowable
					 stresses, maximum and minimum temperature limits, and other restrictions.
					 Additional criteria can be found in the guidelines for addition of new
					 materials in the ASME Boiler and Pressure Vessel Code, Section II and Section
					 VIII, Division 1, Appendix B. (To develop usage and gain experience, unlisted
					 materials may be used in accordance with para. 123.1.)
Requests for interpretation and suggestions for revision
					 should be addressed to the Secretary, ASME B31 Committee, Three Park Avenue,
					 New York, NY 10016-5990.
POWER PIPING
Chapter I
SCOPE AND DEFINITIONS
100 GENERAL
This Power Piping Code is one of several Sections of the
					 American Society of Mechanical Engineers Code for Pressure Piping, B31. This
					 Section is published as a separate document for convenience.
Standards and specifications specifically incorporated by
					 reference into this Code are shown in Table 126.1. It is not considered
					 practical to refer to a dated edition of each of the standards and
					 specifications in this Code. Instead, the dated edition references are included
					 in an Addenda and will be revised yearly.
100.1 Scope
Rules for this Code Section have been developed considering
					 the needs for applications which include piping typically found in electric
					 power generating stations, in industrial and institutional plants, geothermal
					 heating systems, and central and district heating and cooling systems.
100.1.1
This Code prescribes requirements for
					 the design, materials, fabrication, erection, test, inspection, operation, and
					 maintenance of piping systems.
Piping as used in this Code includes pipe, flanges,
					 bolting, gaskets, valves, relief devices, fittings, and the pressure containing
					 portions of other piping components, whether manufactured in accordance with
					 Standards listed in Table 126.1 or specially designed. It also includes hangers
					 and supports and other equipment items necessary to prevent overstressing the
					 pressure containing components.
Rules governing piping for miscellaneous appurtenances,
					 such as water columns, remote water level indicators, pressure gages, gage
					 glasses, etc., are included within the scope of this Code, but the requirements
					 for boiler appurtenances shall be in accordance with Section I of the ASME
					 Boiler and Pressure Vessel Code, PG-60.
The users of this Code are advised that in some areas
					 legislation may establish governmental jurisdiction over the subject matter
					 covered by this Code. However, any such legal requirement shall not relieve the
					 owner of his inspection responsibilities specified in para. 136.1.
100.1.2
Power piping systems as covered by
					 this Code apply to all piping and their component parts except as excluded in
					 para. 100.1.3. They include but are not limited to steam, water, oil, gas, and
					 air services.
(A) This Code covers boiler external piping as defined
					 below for power boilers and high temperature, high pressure water boilers in
					 which: steam or vapor is generated at a pressure of more than 15 psig [100 kPa
					 (gage)]; and high temperature water is generated at pressures exceeding 160
					 psig [1 103 kPa (gage)] and/or temperatures exceeding 250°F
					 (120°C).
Boiler external piping shall be considered as that piping
					 which begins where the boiler proper terminates at
(1) the first circumferential joint for welding end
					 connections; or
(2) the face of the first flange in bolted flanged
					 connections; or
(3) the first threaded joint in that type of connection;
					 and which extends up to and including the valve or valves required by para.
					 122.1.
The terminal points themselves are considered part of the
					 boiler external piping. The terminal points and piping external to power
					 boilers are illustrated by Figs. 100.1.2(A), l00.1.2(B), and l00.1.2(C).
Piping between the terminal points and the valve or valves
					 required by para. 122.1 shall be provided with Data Reports, inspection, and
					 stamping as required by Section I of the ASME Boiler and Pressure Vessel Code.
					 All welding and brazing of this piping shall be performed by manufacturers or
					 contractors authorized to use the appropriate symbol shown in Figs. PG-105.1
					 through PG-105.3 of Section I of the ASME Boiler and Pressure Vessel Code. The
					 installation of boiler external piping by mechanical means may be performed by
					 an organization not holding a Code symbol stamp. However, the holder of a valid
					 S, A, or PP Certificate of Authorization shall be responsible for the
					 documentation and hydrostatic test, regardless of the method of assembly. The
					 quality control system requirements of Section I of the ASME Boiler and
					 Pressure Vessel Code shall apply. These requirements are shown in Appendix J of
					 this Code.
The valve or valves required by para. 122.1 are part of the
					 boiler external piping, but do not require ASME Boiler and Pressure Vessel
					 Code, Section I inspection and stamping except for safety, safety relief, and
					 relief valves; see para. 107.8.2. Refer to PG-11.
Pipe connections meeting all other requirements of this
					 Code but not exceeding NPS ½ may be welded to pipe or boiler headers
					 without inspection and stamping required by Section I of the ASME Boiler and
					 Pressure Vessel Code.
See PDF for
					 diagram
See PDF for
					 diagram
See PDF for
					 diagram
See PDF for
					 diagram
(B) Nonboiler external piping includes all the piping
					 covered by this Code except for that portion defined above as boiler external
					 piping.
100.1.3
This Code does not apply to the
					 following:
(A) economizers, heaters, pressure vessels, and components
					 covered by Sections of the ASME Boiler and Pressure Vessel Code
(B) building heating and distribution steam and condensate
					 piping designed for 15 psig [100 kPa (gage)] or less, or hot water heating
					 systems designed for 30 psig [200 kPa (gage)] or less
(C) piping for hydraulic or pneumatic tools and their
					 components downstream of the first block or stop valve off the system
					 distribution header
(D) piping for marine or other installations under Federal
					 control
(E) towers, building frames, tanks, mechanical equipment,
					 instruments, and foundations
104.1.3 Straight Pipe Under External Pressure.
For determining wall thickness and stiffening requirements for straight
					 pipe under external pressure, the procedures outlined in UG-28, UG-29, and
					 UG-30 of Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code
					 shall be followed.
104.2 Curved Segments of Pipe
1
04.2.1 Pipe Bends.
Pipe bends shall be
					 subject to the following limitations:
(A) The minimum wall thickness shall meet the requirements
					 of para. 102.4.5 and the fabrication requirements of para. 129.
(B) Limits on flattening and buckling at bends may be
					 specified by design, depending upon the service, the material, and the stress
					 level involved. Where limits on flattening and buckling are not specified by
					 design, the requirements of para. 129.1 shall be met.
104.2.2 Elbows.
Elbows manufactured in
					 accordance with the standards listed in Table 126.1 are suitable for use at the
					 pressure-temperature ratings specified by such standards, subject to the
					 requirements of para. 106.
104.3
Intersections
104.3.1
Branch Connections
(A) This paragraph gives rules governing the design of
					 branch connections to sustain internal and external pressure in cases where the
					 axes of the branch and the run intersect, and the angle between the axes of the
					 branch and of the run is between 45 deg and 90 deg, inclusive.
Branch connections in which the smaller angle between the
					 axes of the branch and the run is less than 45 deg or branch connections where
					 the axes of the branch and the run do not intersect impose special design and
					 fabrication problems. The rules given herein may be used as a guide, but
					 sufficient additional strength must be provided to assure safe service. Such
					 branch connections shall be designed to meet the requirement of para.
					 104.7.
(B) Branch connections in piping may be made from materials
					 listed in Appendix A by the use of the following:
(B.1) fittings, such as tees, laterals, and crosses made in
					 accordance with the applicable standards listed in Table 126.1 where the
					 attachment of the branch pipe to the fitting is by butt welding, socket
					 welding, brazing, soldering, threading, or by a flanged connection.
(B.2) weld outlet fittings, such as cast or forged nozzles,
					 couplings and adaptors, or similar items where the attachment of the branch
					 pipe to the fitting is by butt welding, socket welding, threading, or by a
					 flanged connection. Such weld outlet fittings are attached to the run by
					 welding similar to that shown in Fig. 127.4.8 (E) or Fig. 127.4.8 (F), as
					 applicable. MSS SP-97 may be used for design and manufacturing standards for
					 integrally reinforced forged branch outlet fittings. Couplings are restricted
					 to a maximum of NPS 3.
(B.3) extruded outlets at right angles to the run pipe, in
					 accordance with (G) below, where the attachment of the branch pipe is by butt
					 welding.
(B.4) piping directly attached to the run pipe by welding
					 in accordance with para. 127.4.8 or by socket welding or threading as
					 stipulated below:
(B.4.1) socket welded right angle branch connections may be
					 made by attaching the branch pipe directly to the run pipe provided.
(B.4.1.1) the nominal size of the branch does not exceed
					 NPS 2 or one-fourth of the nominal size of the run, whichever is
					 smaller.
(B.4.1.2) the depth of the socket measured at its minimum
					 depth in the run pipe is at least equal to that shown in ASME B16.11. If the
					 run pipe wall does not have sufficient thickness to provide the proper depth of
					 socket, an alternate type of construction shall be used.
(B.4.1.3) the clearance between the bottom of the socket
					 and the end of the inserted branch pipe is in accordance with Fig.
					 127.4.4(C).
(B.4.1.4) the size of the fillet weld is not less tha
					 n
					 1.09 times the nominal wall thickness of the branch
					 pipe.
(B.4.2) threaded right angle branch connections may be made
					 by attaching the branch pipe directly to the run provided
(B.4.2.1) the nominal size of the branch does not exceed
					 NPS 2 or one-fourth of the nominal size of the run, whichever is
					 smaller.
(B.4.2.2) the minimum thread engagement is: 6 full threads
					 for NPS ½ and NPS ¾ branches; 7 for NPS 1, NPS 1¼, and NPS
					 1½ branches; and 8 for NPS 2 branches. If the run pipe wall does not
					 have sufficient thickness to provide the proper depth for thread engagement, an
					 alternative type of construction shall be used.
(C)
Branch Connections Not Requiring
					 Reinforcement.
A pipe having a branch connection is weakened by the
					 opening that must be made in it. Unless the wall thickness of the branch
					 and/orrun pipe is sufficiently in excess of that required to sustain the
					 pressure, it is necessary to provide additional material in order to meet the
					 reinforcement requirements of (D) and (E) below. However, there are certain
					 branch connections for which supporting calculations are not required. These
					 are as follows:
(C.1) branch connections made by the use of a fitting (tee,
					 lateral, cross, or branch weld-on fitting), manufactured in accordance with a
					 standard listed in Table 126.1, and used within the limits of
					 pressure-temperature ratings specified in that standard.
(C.2) branch connections made by welding a coupling or half
					 coupling directly to the run pipe in accordance with Fig. 127.4.8(E), provided
					 the nominal diameter of the branch does not exceed NPS 2 or one-fourth the
					 nominal diameter of the run, whichever is less. The minimum wall thickness of
					 the coupling anywhere in the reinforcement zone (if threads are in the zone,
					 wall thickness is measured from the root of the thread to the minimum
					 O.D.)shall not be less than that of the unthreaded branch pipe. In no case
					 shall the thickness of the coupling be less than extra heavy or Class 3000
					 rating.
Small branch connections NPS 2 or smaller as shown in Fig.
					 127.4.8(F) may be used, provided
t
w
is not
					 less than the thickness of schedule 160 pipe of the branch size.
(C.3) integrally reinforced fittings welded directly to the
					 run pipe when the reinforcements provided by the fitting and the deposited weld
					 metal meets the requirements of (D) below.
(C.4) integrally reinforced extruded outlets in the run
					 pipe. The reinforcement requirements shall be in accordance with (G)
					 below.
(D)
Branch Connections Subject to Internal
					 Pressure Requiring Reinforcement
(D.1) Reinforcement is required when it is not provided
					 inherently in the components of the branch connection. This paragraph gives
					 rules covering the design of branch connections to sustain internal pressure in
					 cases where the angle between the axes of the branch and of the run is between
					 45 deg and 90 deg. Subparagraph (E) below gives rules governing the design of
					 connections to sustain external pressure.
(D.2) Figure 104.3.1(D) illustrates the notations used in
					 the pressure-temperature design conditions of branch connections. These
					 notations are as follows:
b
= subscript referring to branch
Do = outside diameter of pipe, in.
					 (mm)
d1 = inside centerline longitudinal
					 dimension of the finished branch opening in the run of the pipe, in.
					 (mm)
= [
D
ob
-2(
T
b
-A
)]/sin
[ALFA]
d2 = "half width" of reinforcing
					 zone, in. (mm)
= the greater of
d
1or
(T
b
-
A)
+
(T
h
-
A) +
					 d
1/2but in no case more than
D
oh
,
in. (mm)
h = subscript referring to run or header
L
4 = altitude of
					 reinforcement zone outside of run, in. (mm)
=
2.5
(T
b
-
A)
+
t
r
or
					 2.5
(T
h
-
A),
whichever is smaller
t
r
= thickness of attached reinforcing pad, in Example A, in. (mm); or
					 height of the largest 60 deg right triangle supported by the run and branch
					 outside diameter projected surfaces and lying completely within the area of
					 integral reinforcement, in Example B, in. (mm)
Tb, Th =
					 actual (by measurement), or minimum wall thickness of the branch or header
					 pipe, in. (mm), permissible under purchase specification
tmb, tmh = required minimum wall thickness, in. (mm), of
					 the branch or header pipe as determined by use of eq. (3) or (3A) in para.
					 104.1.2(A)
a = angle between axes of branch and run, deg
(D.2.1) If the run pipe contains a longitudinal seam which
					 is not intersected by the branch, the stress value of seamless pipe of
					 comparable grade may be used to determine the value of
t
mh
for the purpose
					 of reinforcement calculations only. If the branch intersects a longitudinal
					 weld in the run, or if the branch contains a weld, the weld joint efficiency
					 for either or both shall enter the calculations. If the branch and run both
					 contain longitudinal welds, care shall be taken to ensure that the two welds do
					 not intersect each other.
(D.2.2) The required reinforcement area in square inches
					 (square millimeters) for branch connections shall be the quantity
A7 = A6(2 -
					 sin a) = (tmh - A)d1 (2 - sin
					 a)
For right angle connections the required reinforcement
					 becomes
A7 = A6 =
					 (tmh - A)d1
The required reinforcement must be within the limits of the
					 reinforcement zone as defined in (D.2.4) below.
(D.2.3)The reinforcement required by (D.2) shall be that
					 provided by any combination of areas
A
1
,
					 A
2
,
					 A
3
,
					 A
4
,
and
A
5
,
as defined below
					 and illustrated in Fig. 104.3.1(D) where
A
1= area provided
					 by excess pipe wall in the run = (2
d
2 -
d
1)(
T
h
-
t
mh
)
A2 = area,
					 in.2 (mm2), provided by
					 excess pipe wall in the branch for a distance L4 above the run
=
2
L
4(
T
b
-
t
mb
)/sina
A3 = area provided by deposited weld
					 metal beyond the outside diameter of the run and branch, and for fillet weld
					 attachments of rings, pads, and saddles
A4 = area provided by a reinforcing
					 ring, pad, or integral reinforcement. The value of A4 may be taken in the same
					 manner in which excess header metal is considered, provided the weld completely
					 fuses the branch pipe, run pipe, and ring or pad, or integral reinforcement.
					 For welding branch connections refer to para. 127.4.8.
A5 = area provided by a saddle on
					 right angle connections
= (O.D. of saddle -
D
ob
)
t
r
A6 = pressure design area expected
					 at the end of service life
=
					 (
t
mh
-
A
)
d
1
Portions of the reinforcement area may be composed of
					 materials other than those of the run pipe, but if the allowable stress of
					 these materials is less than that for the run pipe, the corresponding
					 calculated reinforcement area provided by this material shall be reduced in the
					 ratio of the allowable stress being applied to the reinforcement area. No
					 additional credit shall be taken for materials having higher allowable stress
					 values than the run pipe.
(D.2.4)
Reinforcement Zone.
The
					 reinforcement zone is a parallelogram whose width shall extend a distance
d
2on each side of the centerline of the
					 branch pipe, and whose altitude shall start at the inside surface of the run
					 pipe and extend to a distance
L
4 from
					 the outside surface of the run pipe.
(D.2.5)
Reinforcement of Multiple Openings.
It is preferred that multiple branch openings be spaced so that their
					 reinforcement zones do not overlap. If closer spacing is necessary, the
					 following requirement shall be met. The two or more openings shall be
					 reinforced in accordance with (D.2), with a combined reinforcement that has a
					 strength equal to the combined strength of the reinforcement that would be
					 required for the separate openings. No portion of the cross section shall be
					 considered as applying to more than one opening, or be evaluated more than once
					 in a combined area.
When more than two adjacent openings are to be provided
					 with a combined reinforcement, the minimum distance between centers of any two
					 of these openings should preferably be at least 1½ times their average
					 diameter, and the area of reinforcement between them shall be at least equal to
					 50% of the total required for these two openings.
(D.2.6)
Rings, Pads, and Saddles.
Reinforcement provided in the form of rings, pads, or saddles shall
					 not be appreciably narrower at the side than at the crotch.
A vent hole shall be provided at the ring, pad, or saddle
					 to provide venting during welding and heat treatment. Refer to para.
					 127.4.8(E).
Rings, pads, or saddles may be made in more than one piece,
					 provided the joints between pieces have full thickness welds, and each piece is
					 provided with a vent hole.
(D.2.7)
Other Designs.
The adequacy of
					 designs to which the reinforcement requirements of para. 104.3 cannot be
					 applied shall be proven by burst or proof tests on scale models or on full size
					 structures, or by calculations previously substantiated by successful service
					 of similar design
See PDF for
					 diagram
See PDF for
					 diagram
(E)
Branch Connections Subject to External Pressure
					 Requiring Reinforcement.
The reinforcement area in square inches
					 (square millimeters) required for branch connections subject to external
					 pressure shall be
0.5
t
mh
d
1
					 (2 - sin a)
where
t
mh
is the required
					 header wall thickness determined for straight pipe under external pressure,
					 using procedures outlined in UG-28, UG-29, UG-30, and UG-31 of Section VIII,
					 Division 1, of the ASME Boiler and Pressure Vessel Code.
Procedures established heretofore for connections subject
					 to internal pressure shall apply for connections subject to external pressure
					 provided that
D
oh
,
					 D
ob
,
and
t
r
are reduced to compensate for external
					 corrosion, if required by design conditions.
(F)
Branch Connections Subject to External Forces
					 and Moments.
The requirements of the preceding paragraphs are
					 intended to assure safe performance of a branch connection subjected only to
					 pressure. However, when external forces and moments are applied to a branch
					 connection by thermal expansion and contraction, by dead weight of piping,
					 valves, and fittings, covering and contents, or by earth settlement, the branch
					 connection shall be analyzed considering the stress intensification factors as
					 specified in Appendix D. Use of ribs, gussets, and clamps designed in
					 accordance with para. 104.3.4 is permissible to stiffen the branch connection,
					 but their areas cannot be counted as contributing to the required reinforcement
					 area of the branch connection.
(G)
Extruded Outlets Integrally Reinforced
(G.1) The following definitions, modifications, notations,
					 and requirements are specifically applicable to extruded outlets. The designer
					 shall make proper wall thickness allowances in order that the required minimum
					 reinforcement is assured over the design life of the system.
(G.2)
Definition.
An extruded outlet
					 header is defined as a header in which the extruded lip at the outlet has an
					 altitude above the surface of the run which is equal to or greater than the
					 radius of curvature of the external contoured portion of the outlet; i.e.,
h
o
=
r
o
.
See nomenclature and
					 Fig. 104.3.1(G).
(G.3) These rules apply only to cases where the axis of the
					 outlet intersects and is perpendicular to the axis of the run. These rules do
					 not apply to any nozzle in which additional nonintegral material is applied in
					 the form of rings, pads, or saddles.
(G.4)The notation used herein is illustrated in Fig.
					 104.3.1(G). All dimensions are in inches (millimeters).
D
= outside diameter of run
d = outside diameter of branch pipe
d
b
=
					 corroded internal diameter of branch pipe
d
c
= corroded internal diameter of extruded outlet measured at the level of the
					 outside surface of the run
d
r
= corroded internal diameter of run
h
o
= height of the extruded lip. This must be equal to or greater than
r
o
, except as shown in (G.4.2) below.
L
8 = altitude of
					 reinforcement zone
- See PDF for diagram
T
o
= corroded finished thickness of extruded outlet measured at a height equal to
r
o
above the outside surface of the run
tb - A = actual thickness of branch
					 wall, not including corrosion allowance
th - A = actual thickness of run
					 wall, not including the corrosion allowance
t
mb
-
A
= required thickness of branch pipe according to wall
					 thickness eq. (3) or (3A) in para. 104.1.2(A), but not including any thickness
					 for corrosion
tmh
- A = required
					 thickness of the run according to eq. (3) or (3A) in para. 104.1.2(A), but not
					 including any allowance for corrosion
r1 = half width of reinforcement
					 zone (equal to d c)
ro = radius of curvature of
					 external contoured portion of outlet measured in the plane containing the axes
					 of the run and branch. This is subject to the following limitations:
(G.4.1)
Minimum Radius.
This dimension
					 shall not be less Than 0.05
d
except that on branch diameters
					 larger than NPS 30, it need not exceed 1.50 in. (38 mm).
(G.4.2)
Maximum Radius.
For outlet pipe
					 sizes 6 in. (150 mm) nominal and larger, this dimension shall not exceed
					 0.l0
d +
0.50 in. (0.l0
d
+ 12.7 mm). For
					 outlet pipe sizes less than NPS 6, this dimension shall be not greater Than
					 1.25 in. (32 mm).
(G.4.3) When the external contour contains more than one
					 radius, the radius of any arc sector of approximately 45 deg shall meet the
					 requirements of (G.4.1) and (G.4.2) above. When the external contour has a
					 continuously varying radius, the radius of curvature at every point on the
					 contour shall meet the requirements of (G.4.1) and (G.4.2) above.
(G.4.4) Machining other than grinding for weld cleanup
					 shall not be employed in order to meet the above requirements.
(G.5)
Required Area.
The required area is
					 defined as
A7 = K (tmh -
					 A) dc
where
K
shall be taken as follows.
For
d/D
greater Than 0.60,
K = 1.00
For
d/D
greater Than 0.15 and not
					 exceeding 0.60,
K = 0.6 + 2/3 d/D
For
d/D
equal to or less Than 0.15,
K = 0.70
The design must meet criteria that the reinforcement area
					 defined in (G.6) below is not less than the required area.
See PDF for
					 diagram
(G.6)
Reinforcement Area.
The
					 reinforcement area shall be the sum of areas
A1 + A2 +
					 A4
as defined below.
(G.6.l)Area
A
1 is the area lying within
					 the reinforcement zone resulting from any excess thickness available in the run
					 wall.
A1 =
					 dc(tn -
					 tmh)
(G.6.2) Area
A
2 is the area lying within
					 the reinforcement zone resulting from any excess thickness available in the
					 branch pipe wall.
A2 =
					 2L8(tb -
					 tmh)
(G.6.3) Area
A
4 is the area lying within
					 the reinforcement zone resulting from excess thickness available in the
					 extruded outlet lip.
A4 = 2ro
					 [To - (tb -
					 A)]
(G.7)
Reinforcement of Multiple Openings.
It is preferred that multiple branch openings be spaced so that their
					 reinforcement zones do not overlap. If closer spacing is necessary, the
					 following requirements shall be met. The two or more openings shall be
					 reinforced in accordance with (G) with a combined reinforcement that has a
					 strength equal to the combined strength of the reinforcement that would be
					 required for separate openings. No portion of the cross section shall be
					 considered as applying to more than one opening, or be evaluated more than once
					 in a combined area.
(G.8)In addition to the above, the manufacturer shall be
					 responsible for establishing and marking on the section containing extruded
					 outlets, the design pressure and temperature. The manufacturer's name or
					 trademarks shall be marked on the section.
104.3.3 Miters.
Miter joints, and the
					 terminology related thereto, are described in Appendix D. A widely spaced miter
					 with
See PDF for
					 diagram
shall be considered to be equivalent to a girth buttwelded
					 joint, and the rules of this paragraph do not apply. Miter joints, and
					 fabricated pipe bends consisting of segments of straight pipe welded together,
					 with q equal to or greater than this calculated value may be used within the
					 limitations described below.
(A) Pressure shall be limited to 10 psi (70 kPa) under the
					 following conditions:
(A.1) The assembly includes a miter weld with q > 22.5
					 deg, or contains a segment which has a dimension
B < 6tn
(A.2) The thickness of each segment of the miter is not
					 less than that determined in accordance with para. 104.1.
(A.3) The contained fluid is nonflammable, non-toxic, and
					 incompressible, except for gaseous vents to atmosphere.
(A.4) The number of full pressure cycles is less than 7,000
					 during the expected lifetime of the piping system.
(A.5) Full penetration welds are used in joining miter
					 segments.
(B) Pressure shall be limited to 100 psi (700 kPa) under
					 the conditions defined in (A.2), (A.3), (A.4), and (A.5) above, in addition to
					 the following:
(B.1) the angle q does not exceed 22.5 deg
(B.2) the assembly does not contain any segment which has a
					 dimension
B < 6tn
(C) Miters to be used in other services or at design
					 pressures above 100 psi (700 kPa) shall meet the requirements of para.
					 104.7.
(C.1) When justification under para. 104.7 is based on
					 comparable service conditions, such conditions must be established as
					 comparable with respect to cyclic as well as static loadings.
(C.2) When justification under para. 104.7 is based on an
					 analysis, that analysis and substantiating tests shall consider the
					 discontinuity stresses which exist at the juncture between segments; both for
					 static (including brittle fracture) and cyclic internal pressure.
(C.3) The wall thickness,
t
s
,
of a segment of a miter
					 shall not be less than specified in (C.3.1) or (C.3.2) below, depending on the
					 spacing.
(C.3.1) For closely spaced miter bends (see Appendix D for
					 definition)
See PDF for
					 diagram
(C.3.2) For widely spaced miters (see Appendix D for
					 definition)
See PDF for
					 diagram
(The above equation requires an iterative or quadratic
					 solution for
t
s
.
)
104.3.4 Attachments.
External and internal
					 attachments to piping shall be designed so as not to cause flattening of the
					 pipe, excessive localized bending stresses, or harmful thermal gradients in the
					 pipe wall. It is important that such attachments be designed to minimize stress
					 concentrations in applications where the number of stress cycles, due either to
					 pressure or thermal effect, is relatively large for the expected life of the
					 equipment.
104.4 Closures
104.4.1 General.
Closures for power piping
					 systems shall meet the applicable requirements of this Code and shall comply
					 with the requirements described in (A) or (B) below. Closures may be
					 made
(A) by use of closure fittings, such as threaded or welded
					 plugs, caps, or blind flanges, manufactured in accordance with standards listed
					 in Table 126.1, and used within the specified pressure-temperature ratings,
					 or
(B) in accordance with the rules contained in the ASME
					 Boiler and Pressure Vessel Code, Section I, Power Boilers, PG-31, or Section
					 VIII, Pressure Vessels, Division 1, UG-34 and UW-13, calculated from
tm = t + A
where
t = pressure design thickness, calculated for the given
					 closure shape and direction of loading using appropriate equations and
					 procedures in Section I or Section VIII, Division 1 of the ASME Boiler and
					 Pressure Vessel Code.
The definition of
A
and the symbols used
					 in determining
t
shall have the definitions shown herein,
					 instead of those given in the ASME Boiler and Pressure Vessel Code.
Attachment of a welded flat permanent closure with only a
					 single fillet weld is not permitted.
104.4.2 Openings in Closures
. Openings in
					 closures may be made by welding, extruding, or threading. Attachment to the
					 closure shall be in accordance with the limitations provided for such
					 connections in para. 104.3.1 for branch connections. If the size of the opening
					 is greater than one-half of the inside diameter of the closure, the opening
					 shall be designed as a reducer in accordance with para. 104.6.
Other openings in closures shall be reinforced in
					 accordance with the requirements of reinforcement for a branch connection. The
					 total cross-sectional area required for reinforcement in any plane passing
					 through the center of the opening and normal to the surface of the closure
					 shall not be less than the quantity of
d
5
t,
where
d
5 = diameter of
					 the finished opening, in. (mm)
t
= as defined in (B) above
121.8 Structural Attachments
121.8.1 Nonintegral Type
(A) Nonintegral attachments include clamps, slings,
					 cradles, saddles, straps, and clevises.
(B) When clamps are used to support vertical lines, it is
					 recommended that shear lugs be welded to the pipe to prevent slippage. The
					 provisions of para. 12l.8.2(B) shall apply.
(C) In addition to the provision of (B) above, clamps to
					 support vertical lines should be designed to support the total load on either
					 arm in the event the load shifts due to pipe and/or hanger movement.
121.8.2 Integral Type
(A) Integral attachments include ears, shoes, lugs,
					 cylindrical attachments, rings, and skirts which are fabricated so that the
					 attachment is an integral part of the piping component. Integral attachments
					 shall be used in conjunction with restraints or braces where multiaxial
					 restraint in a single member is to be maintained. Consideration shall be given
					 to the localized stresses induced into the piping component by the integral
					 attachments. Where applicable, the conditions of para. 12l.8.1(C) are to
					 apply.
(B) Integral lugs, plates, angle clips, etc., used as part
					 of an assembly for the support or guiding of pipe may be welded directly to the
					 pipe provided the materials are compatible for welding and the design is
					 adequate for the temperature and load. The design of hanger lugs for attachment
					 to piping for high temperature service shall be such as to provide for
					 differential expansion between the pipe and the attached lug.
121.9 Loads and Supporting Structures
Considerations shall be given to the load carrying capacity
					 of equipment and the supporting structure. This may necessitate closer spacing
					 of hangers on lines with extremely high loads.
121.10 Requirements for Fabricating Pipe
					 Supports
Pipe supports shall be fabricated in accordance with the
					 requirements of para. 130.
PART 6
SYSTEMS
122 DESIGN REQUIREMENTS PERTAINING TO SPECIFIC PIPING
					 SYSTEMS
Except as specifically stated otherwise in this Part 6, all
					 provisions of the Code apply fully to the piping systems described
					 herein.
122.1
Boiler External Piping; in
					 Accordance With Para. 100.1.2(A) -Steam, Feedwater, Blowoff, and Drain Piping
122.1.1 General.
The minimum pressure and
					 temperature and other special requirements to be used in the design for steam,
					 feedwater, blowoff, and drain piping from the boiler to the valve or valves
					 required by para. 122.1 shall be as specified in the following paragraphs.
					 Design requirements for desuperheater spray piping connected to desuperheaters
					 located in the boiler proper and in main steam piping are provided in para.
					 122.4.
(A) It is intended that the design pressure and temperature
					 be selected sufficiently in excess of any expected operating conditions, not
					 necessarily continuous, to permit satisfactory operation without operation of
					 the overpressure protection devices. Also, since the operating temperatures of
					 fired equipment can vary, the expected temperature at the connection to the
					 fired equipment shall include the manufacturer's maximum temperature
					 tolerance.
(B) In a forced flow steam generator with no fixed steam
					 and water line, it is permissible to design the external piping, valves, and
					 fittings attached to the pressure parts for different pressure levels along the
					 path through the steam generator of water-steam flow. The values of design
					 pressure and the design temperature to be used for the external piping, valves,
					 and fittings shall be not less than that required for the expected maximum
					 sustained operating pressure and temperature to which the abutted pressure part
					 is subjected except when one or more of the overpressure protection devices
					 covered by PG-67.4 of Section I of the ASME Boiler and Pressure Vessel Code is
					 in operation. The steam piping shall comply with the requirements for the
					 maximum sustained operating conditions as used in (A) above, or for the design
					 throttle pressure plus 5%, whichever is greater.
(C) Provision shall be made for the expansion and
					 contraction of piping connected to boilers to limit forces and moments
					 transmitted to the boiler, by providing substantial anchorage at suitable
					 points, so that there shall be no undue strain transmitted to the boiler. Steam
					 reservoirs shall be used on steam mains when heavy pulsations of the steam
					 currents cause vibration.
(D) Piping connected to the outlet of a boiler for any
					 purpose shall be attached by
(D.1) welding to a nozzle or socket welding fitting
(D.2) threading into a tapped opening with a threaded
					 fitting or valve at the other end
(D.3) screwing each end into tapered flanges, fittings, or
					 valves with or without rolling or peening
(D.4) bolted joints including those of the Van Stone
					 type
(D.5) blowoff piping of firetube boilers shall be attached
					 in accordance with (D.2) above if exposed to products of combustion or in
					 accordance with (D.2), (D.3), or (D.4) above if not so exposed
(E) Nonferrous pipe or tubes shall not exceed NPS 3 in
					 diameter.
(F) American National Standard slip-on flanges shall not
					 exceed NPS 4. Attachment of slip-on flanges shall be by double fillet welds.
					 The throats of the fillet welds shall not be less Than 0.7 times the thickness
					 of the part to which the flange is attached.
(G) Hub-type flanges shall not be cut from plate
					 material.
(H) American National Standard socket welded flanges may be
					 used in piping or boiler nozzles provided the dimensions do not exceed NPS 3
					 for Class 600 and lower and NPS 2½ in Class 1500.
122.1.2 Steam Piping
(A) The value of
P
to be used in the
					 formulas in para. 104 shall be as follows:
(A.1) For steam piping connected to the steam drum or to
					 the superheater inlet header up to the first stop valve in each connection, the
					 value of
P
shall be not less than the lowest pressure at which
					 any drum safety valve is set to blow, and the
S
value shall
					 not exceed that permitted for the corresponding saturated steam
					 temperature.
(A.2) For steam piping connected to the superheater outlet
					 header up to the first stop valve in each connection, the design pressure,
					 except as otherwise provided in (A.4) below shall be not less than the lowest
					 pressure at which any safety valve on the superheater is set to blow, or not
					 less than 85% of the lowest pressure at which any drum safety valve is set to
					 blow, whichever is greater, and the
S
value for the material
					 used shall not exceed that permitted for the expected steam temperature.
(A.3) For steam piping between the first stop valve and the
					 second valve, when one is required by para. 122.1.7, the design pressure shall
					 be not less than the expected maximum sustained operating pressure or 85% of
					 the lowest pressure at which any drum safety valve is set to blow, whichever is
					 greater, and the
S
value for the material used shall not
					 exceed that permitted for the expected steam temperature.
(A.4) For boilers installed on the unit system (i.e., one
					 boiler and one turbine or other prime mover) and provided with automatic
					 combustion control equipment responsive to steam header pressure, the design
					 pressure for the steam piping shall be not less than the design pressure at the
					 throttle inlet plus 5%, or not less than 85% of the lowest pressure at which
					 any drum safety valve is set to blow, or not less than the expected maximum
					 sustained operating pressure at any point in the piping system, whichever is
					 greater, and the
S
value for the material used shall not
					 exceed that permitted for the expected steam temperature at the superheater
					 outlet. For forced-flow steam generators with no fixed steam and water line,
					 the design pressure shall also be no less than the expected maximum sustained
					 operating pressure.
(A.5) The design pressure shall not be taken at less than
					 100 psig [700 kPa (gage)] for any condition of service or material.
122.1.3 Feedwater Piping
(A) The value of
P
to be used in the
					 formulas in para. 104 shall be as follows:
(A.1) For piping from the boiler to and including the
					 required stop valve and the check valve, the minimum value of
P
except as permitted in para. 122.1.3(A.4) shall exceed the
					 maximum allowable working pressure of the boiler by either 25% or 225 psi (1
					 550 kPa), whichever is the lesser. For an installation with an integral
					 economizer without valves between the boiler and economizer, this paragraph
					 shall apply only to the piping from the economizer inlet header to and
					 including the required stop valve and the check valve.
(A.2) For piping between the required check valve and the
					 globe or regulating valve, when required by para. 122.1.7(B), and including any
					 bypass piping up to the shutoff valves in the bypass, the value of
P
shall be not less than the pressure required to feed the
					 boiler.
(A.3) The value of
P
in the formula shall
					 not be taken at less than 100 psig [700 kPa (gage)] for any condition of
					 service or material, and shall never be less than the pressure required to feed
					 the boiler.
(A.4) In a forced flow steam generator with no fixed steam
					 and water line, the value of
P
for feedwater piping from the
					 boiler to and including the required stop valve may be in accordance with the
					 requirements of para. 122.1.1(B).
(B) The
S
value used, except as permitted
					 in (A.4) above, shall not exceed that permitted for the temperature of
					 saturated steam at the maximum allowable working pressure of the boiler.
(C) The size of the feed piping between the boiler and the
					 first required valve [para. 122.1.7(B)] or the branch feed connection [para.
					 122.1.7(B.4)] shall, as a minimum, be the same as the boiler connection.
122.1.4 Blowoff and Slowdown Piping.
Blowoff
					 and blowdown piping are defined as piping connected to a boiler and provided
					 with valves or cocks through which the water in the boiler may be blown out
					 under pressure. This definition is not intended to apply to (i) drain piping,
					 and (ii) piping such as used on water columns, gage glasses, or feedwater
					 regulators, etc., for the purpose of determining the operating condition of the
					 equipment. Requirements for (i) and (ii) are described in paras. 122.1.5 and
					 122.1.6. Blowoff systems are operated intermittently to remove accumulated
					 sediment from equipment and/or piping, or to lower boiler water level in a
					 rapid manner. Blowdown systems are primarily operated continuously to control
					 the concentrations of dissolved solids in the boiler water.
(A) Blowoff piping systems from water spaces of a boiler,
					 up to and including the blowoff valves, shall be designed in accordance with
					 (A.1) to (A.4) below. Two shutoff valves are required in the blowoff system;
					 specific valve requirements and exceptions are given in para.
					 122.1.7(C).
(A.1) The value of
P
to be used in the
					 formulas in para. 104 shall exceed the maximum allowable working pressure of
					 the boiler by either 25% or 225 psi (1 550 kPa) whichever is less, but shall be
					 not less than 100 psig [690 kPa (gage)].
(A.2) The allowable stress value for the piping materials
					 shall not exceed that permitted for the temperature of saturated steam at the
					 maximum allowable working pressure of the boiler.
(A.3) All pipe shall be steel except as permitted below.
					 Galvanized steel pipe and fittings shall not be used for blowoff piping. When
					 the value of
P
does not exceed 100 psig [690 kPa (gage)],
					 nonferrous pipe may be used and the fittings may be bronze, cast iron,
					 malleable iron, ductile iron, or steel.
CAUTION: Nonferrous alloys and austenitic stainless
					 steels may be sensitive to stress corrosion cracking in certain aqueous
					 environments.
When the value of
P
exceeds 100 psig [690
					 kPa (gage)], the fittings shall be steel and the thickness of pipe and fittings
					 shall not be less than that of Schedule 80 pipe.
(A.4) The size of blowoff piping shall be not less than the
					 size of the connection on the boiler, and shall be in accordance with the rules
					 contained in the ASME Boiler and Pressure Vessel Code, Section I, PG-59.3,
					 PMB-12, and PEB-12.
(B) The blowdown piping system from the boiler, to and
					 including the shutoff valve, shall be designed in accordance with (B.1) through
					 (B.4) below. Only one shutoff valve is required in the blowdown system.
(B.1) The value of
P
to be used in the
					 formulas in para. 104 shall be not less than the lowest set pressure of any
					 safety valve on the boiler drum.
(B.2) The allowable stress value for the piping materials
					 shall not exceed that permitted for the temperature of saturated steam at the
					 maximum allowable working pressure of the boiler.
(B.3) All pipe shall be steel except as permitted below.
					 Galvanized steel pipe and fittings shall not be used for blowdown piping. When
					 the value of
P
does not exceed 100 psig [690 kPa (gage)],
					 nonferrous pipe may be used and the fittings may be bronze, cast iron,
					 malleable iron, ductile iron, or steel.
CAUTION: Nonferrous alloys and austenitic stainless
					 steels may be sensitive to stress corrosion cracking in certain aqueous
					 environments.
When the value of
P
exceeds 100 psig [690
					 kPa (gage)], the fittings shall be steel and the thickness of pipe and fittings
					 shall not be less than that of Schedule 80 pipe.
(B.4) The size of blowdown piping shall be not less than
					 the size of the connection on the boiler, and shall be in accordance with the
					 rules contained in the ASME Boiler and Pressure Vessel Code, Section I,
					 PG-59.3, PMB-12, and PEB-12.
(C) The blowoff and blowdown piping beyond the required
					 valves described in (A) and (B) above are classified as nonboiler external
					 piping. The requirements are given in para. 122.2.
122.1.5 Boiler Drains
(A) Complete drainage of the boiler and attached piping
					 shall be provided to the extent necessary to ensure proper operation of the
					 steam supply system. The pipe, fittings, and valves of any drain line shall not
					 be smaller than the drain connection.
(B) If the drain lines are intended to be used both as
					 drains and as blowoffs, then two valves are required and all conditions of
					 paras. 122.1.4, 122.1.7(C), and 122.2 shall be met.
(C) Miniature boilers constructed in accordance with the
					 rules contained in the ASME Boiler and Pressure Vessel Code, Section I, Parts
					 PMB and PEB may use a single valve where drain lines are intended to be used
					 for both blowoff and periodic automatic or manual flushing prior to startup.
					 The single valve shall be designed for blowoff service but need not have
					 locking capability.
(D) When a drain is intended for use only when the boiler
					 is not under pressure (pressurizing the boiler for rapid drainage is an
					 exception), a single shutoff valve is acceptable under the following
					 conditions: either the valve shall be a type that can be locked in the closed
					 position or a suitable flanged and bolted connection that accepts a blank
					 insert shall be located on the downstream side of the valve. When a single
					 valve is used, it need not be designed for blowoff service. Single valves on
					 miniature boilers constructed in accordance with the rules contained in the
					 ASME Boiler and Pressure Vessel Code, Section I, Parts PMB and PEB do not
					 require locking capability.
(E) Drain piping from the drain connection, including the
					 required valve(s) or the blanked flange connection, shall be designed for the
					 temperature and pressure of the drain connection. The remaining piping shall be
					 designed for the expected maximum temperature and pressure. Static head and
					 possible choked flow conditions shall be considered. In no case shall the
					 design pressure and temperature be less than 100 psig [690 kPa (gage)] and
					 220°F (105°C), respectively.
122.1.6 Boiler External Piping -Miscellaneous
					 Systems
(A) Materials, design, fabrication, examination, and
					 erection of piping for miscellaneous accessories, such as water level
					 indicators, water columns, gage cocks, and pressure gages, shall be in
					 accordance with the applicable sections of this Code.
(B) The value of
P
to be used in the
					 formulas in para. 104 shall be not less than the maximum allowable working
					 pressure of the boiler except as provided by para. 122.1.1(B).
(C) Valve requirements for water level indicators or water
					 columns, special gage glass and gage cock requirements, minimum line sizes, and
					 special piping configurations required specifically for cleaning, access, or
					 reliability shall be in accordance with PG-60 of Section I of the ASME Boiler
					 and Pressure Vessel Code.
122.1.7 Valves and Fittings.
The minimum
					 pressure and temperature rating for all valves and fittings in steam,
					 feedwater, blowoff, and miscellaneous piping shall be equal to the pressure and
					 temperature specified for the connected piping on the side that has the higher
					 pressure, except that in no case shall the pressure be less than 100 psig [690
					 kPa (gage)], and for pressures not exceeding 100 psig [690 kPa (gage)] in
					 feedwater and blowoff service, the valves and fittings shall be equal at least
					 to the requirements of the ASME standards for Class 125 cast iron or bronze, or
					 Class 150 steel or bronze.
(A)
Steam Stop Valves.
Each boiler
					 discharge outlet, except safety valve or safety relief valve connections, or
					 reheater inlet and outlet connections, shall be fitted with a stop valve
					 located at an accessible point in the steam-delivery line and as near to the
					 boiler nozzle as is convenient and practicable.
(A.1) Boiler stop valves shall provide bidirectional
					 shutoff at design conditions. The valve or valves shall meet the requirements
					 of para. 107. Valves with resilient (nonmetallic) seats shall not be used where
					 the boiler maximum allowable working pressure exceeds 150 psig (1 035 kPa) or
					 where the system design temperature exceeds 366°F (186°C). Valves of
					 the outside screw and yoke, rising stem style are preferred. Valves other than
					 those of the outside screw and yoke, rising stem style shall meet the following
					 additional requirements.
(A.1.A) Each valve shall be equipped with a position
					 indicator to visually indicate from a distance whether the valve is open or
					 closed.
(A.1.B) Quarter turn valves shall be equipped with a slow
					 operating mechanism to minimize dynamic loadings on the boiler and attached
					 piping. Either a quick-opening manual quarter-turn valve or an automatic
					 solenoid valve may be used on miniature boilers constructed in accordance with
					 the rules contained in the ASME Boiler and Pressure Vessel Code, Section I,
					 Parts PMB and PEB. Manual quarter-turn valves shall be provided with a handle
					 or other position indicator to indicate from a distance whether the valve is
					 open or closed.
(A.2) In the case of a single boiler and prime mover
					 installation, the stop valve required herein may be omitted provided the prime
					 mover throttle valve is equipped with an indicator to show whether it is opened
					 or closed, and it is designed to withstand the required boiler hydrostatic
					 test.
(A.3) When two or more boilers are connected to a common
					 header, or when a single boiler is connected to a header having another steam
					 source, the connection from each boiler having a manhole opening shall be
					 fitted with two stop valves having an ample free-blow drain between them. The
					 preferred arrangement consists of one stop-check valve (located closest to the
					 boiler) and one valve of the style and design described in (A.1) above.
					 Alternatively, both valves may be of the style and design described in (A.1)
					 above.
When a second stop valve is required, it shall have a
					 pressure rating at least equal to that required for the expected steam pressure
					 and temperature at the valve, or a pressure rating at least equal to 85% of the
					 lowest set pressure of any safety valve on the boiler drum at the expected
					 temperature of the steam at the valve, whichever is greater.
(A.4) All valves and fittings on steam lines shall have a
					 pressure rating of at least 100 psig [690 kPa (gage)] in accordance with the
					 applicable ASME standard.
(B)
Feedwater Valves
(B.1) The feedwater piping for all boilers, except for high
					 temperature water boilers complying with the requirements of (B.8) below, and
					 for forced flow steam generators with no fixed steam and water line complying
					 with the requirements of (B.9) below, shall be provided with a check valve and
					 a stop valve or cock between the check valve and the boiler. The stop valve or
					 cock shall comply with the requirements of (C.5) below.
(B.2) The relative locations of the check and stop (or
					 cock) valves, as required in (B.1) above, may be reversed on a single
					 boiler-turbine unit installation.
(B.3) If a boiler is equipped with a duplicate feed
					 arrangement, each such arrangement shall be equipped as required by these
					 rules.
See PDF for
					 diagram
(B.4) When the supply line to a boiler is divided into
					 branch feed connections and all such connections are equipped with stop and
					 check valves, the stop and check valves in the common source may be
					 omitted.
(B.5) When two or more boilers are fed from a common
					 source, there shall also be a globe or regulating valve in the branch to each
					 boiler located between the check valve and the source of supply. A typical
					 arrangement is shown in Fig. 100.1.2(B).
(B.6) A combination stop and check valve in which there is
					 only one seat and disk, and in which a valve stem is provided to close the
					 valve, shall be considered only as a stop valve, and a check valve shall be
					 installed as otherwise provided.
(B.7) Where an economizer or other feedwater heating device
					 is connected directly to the boiler without intervening valves, the feed valves
					 and check valves required shall be placed on the inlet of the economizer or
					 feedwater heating device.
(B.8) The recirculating return line for a high temperature
					 water boiler shall be provided with the same stop valve, or valves, required by
					 (B.1) and (B.3) above. The use of a check valve in the recirculating return
					 line is optional. A check valve shall not be a substitute for a stop
					 valve.
(B.9) The feedwater boiler external piping for a forced
					 flow steam generator with no fixed steam and water line may terminate up to and
					 including the stop valve(s) and omitting the check valve(s) provided that a
					 check valve having a pressure rating no less than the boiler inlet design
					 pressure is installed at the discharge of each boiler feed pump or elsewhere in
					 the feedline between the feed pump and the stop valve(s).
(B.10) Wherever globe valves are used within BEP feedwater
					 piping for either isolation or regulation, the inlet shall be under the disk of
					 the valve.
(C)
Blowoff Valves
(C.1) Ordinary globe valves as shown in Fig. 122.1.7(C)
					 sketch (a), and other types of valves that have dams or pockets where sediment
					 can collect, shall not be used on blowoff connections.
(C.2) Y-type globe valves as shown in Fig. 122.1.7(C)
					 sketch (b) or angle valves may be used in vertical pipes, or they may be used
					 in horizontal runs of piping provided they are so constructed or installed that
					 the lowest edge of the opening through the seat is at least 25% of the inside
					 diameter below the centerline of the valve.
(C.3) The blowoff valve or valves, the pipe between them,
					 and the boiler connection shall be of the same size except that a larger pipe
					 for the return of condensate may be used.
(C.4) For all boilers [except electric steam boilers having
					 a normal water content not exceeding 100 gal (380 L), traction-purpose, and
					 portable steam boilers; see (C.11) and (C.12) below] with allowable working
					 pressure in excess of 100 psig [690 kPa (gage)], each bottom blowoff pipe shall
					 have two slow-opening valves, or one quick-opening valve or cock, at the boiler
					 nozzle followed by a slow-opening valve. All valves shall comply with the
					 requirements of (C.5) and (C.6) below.
(C.5) When the value of
P
required by
					 para. 122.1.4(A.1) does not exceed 250 psig [1 725 kPa (gage)], the valves or
					 cocks shall be bronze, cast iron, ductile iron, or steel. The valves or cocks,
					 if of cast iron, shall not exceed NPS 2½ and shall meet the requirements
					 of the applicable ASME standard for Class 250, as given in Table 126.1, and if
					 of bronze, steel, or ductile iron construction, shall meet the requirements of
					 the applicable standards as given in Table 126.1 or para. 124.6.
(C.6) When the value of
P
required by
					 para. 122.1.4(A.1) is higher than 250 psig [1 725 kPa (gage)], the valves or
					 cocks shall be of steel construction equal at least to the requirements of
					 Class 300 of the applicable ASME standard listed in Table 126.1. The minimum
					 pressure rating shall be equal to the value of
P
required by
					 para. 122.1.4(A.1).
(C.7) If a blowoff cock is used, the plug shall be held in
					 place by a guard or gland. The plug shall be distinctly marked in line with the
					 passage.
(C.8) A slow-opening valve is a valve which requires at
					 least five 360 deg turns of the operating mechanism to change from fully clo
					 sed to fully opened.
(C.9) On a boiler having multiple blowoff pipes, a single
					 master valve may be placed on the common blowoff pipe from the boiler, in which
					 case only one valve on each individual blowoff is required. In such a case,
					 either the master valve or the individual valves or cocks shall be of the
					 slow-opening type.
(C.10) Two independent slow-opening valves, or a
					 slow-opening valve and a quick-opening valve or cock, may be combined in one
					 body and may be used provided the combined fitting is the equivalent of two
					 independent slow-opening valves, or a slow-opening valve and a quick-opening
					 valve or cock, and provided further that the failure of one to operate cannot
					 affect the operation of the other.
(C.11) Only one blowoff valve, which shall be either a
					 slow-opening or quick-opening blowoff valve or a cock, is required on traction
					 and/or portable boilers.
(C.12) Only one blowoff valve, which shall be of a
					 slow-opening type, is required for the blowoff piping for forced circulation
					 and electric steam boilers having a normal water content not exceeding 100 gal
					 (380 L). Electric boilers not exceeding a normal water content of 100 gal (380
					 L) and a maximum MAWP of 100 psig [690 kPa (gage)] may use a quick-opening
					 manual or slow-opening automatic quarter-turn valve up to NPS 1. Electric
					 boilers not exceeding a normal water content of 100 gal (380 L) but with a MAWP
					 greater than 100 psig [690 kPa (gage)] shall only use either a slow-opening
					 type manual or automatic valve, regardless of size.
(D)
Safety Valves
(D.1) Safety valves, relief valves, and safety relief
					 valves shall conform to the requirements of PG-67, PG-68, PG-69, PG-70, PG-71,
					 PG-72, and PG-73 of Section I of the ASME Boiler and Pressure Vessel
					 Code.
Boiler or Ves
sel Pressure
Design Pressure [Note (1)]
MAWP
kPa (gage)
psig
kPa (gage)
Below 250
1 725
Note (2)
Note (2)
250-600
1 725-4135
250
1 725
601-900
4 136-6205
400
2 760
901-1,500
6 206-10340
600
4 135
1,501 and higher
10 341
and
higher
900
6 205
122.2 Blowoff and Blowdown Piping in Nonboiler
					 External Piping
Blowoff and blowdown piping systems shall be, where
					 possible, self-draining and without pockets. If unavoidable, valved drains at
					 low points shall allow system draining prior to operation. In order to minimize
					 pipeline shock during the operation of blowoff systems, 3D pipe bends (minimum)
					 should be used in preference to elbows, and wye or lateral fittings should be
					 used in preference to tee connections.
(A)
From Boilers
(A.1) Blowoff piping, located between the valves described
					 in para. 122.1.4(A) and the blowoff tank or other point where the pressure is
					 reduced approximately to atmospheric pressure and cannot be increased by
					 closing a downstream valve, shall be designed for the appropriate pressure in
					 accordance with Table 122.2. The provisions of paras. 122.1.4 (A.3) and 122.1.7
					 shall apply. The size of non-BEP blowoff header to the safe point of discharge
					 shall not be smaller than the largest connected BEP blowoff terminal [see para.
					 122.1.4(A.4)].
(A.2) Blowdown piping, in which the pressure cannot be
					 increased by closing a downstream valve, shall be designed for the appropriate
					 pressure and temperature in accordance with Table 122.2. The provisions of
					 para. 122.1.4(B.3) shall apply. The size of non-BEP blowdown piping between the
					 shutoff valve described in para. 122.1.4(B) and the flow control valve shall
					 not be smaller than the BEP boiler shutoff valve [see para. 122.1.4(B.4)]
					 unless engineering calculations confirm that the design flow rate can be
					 achieved with a smaller piping size without flashing the blowdown prior to the
					 flow control valve.
(A.3) When the design pressure of Table 122.2 can be
					 exceeded due to closing of a downstream valve, calculated pressure drop, or
					 other means, the entire blowoff or blowdown piping system shall be designed in
					 accordance with paras. 122.1.4(A) and 122.1.7 for blowoff and para. 122.1.4(B)
					 for blowdown piping.
(A.4) Non-BEP blowdown piping downstream of the flow
					 control valve shall not be smaller - and preferably will be larger - than the
					 connection on the boiler [see para. 122.1.4(B.4)].
(B) From
Pressure Vessels Other Than Boilers
(B.1) The design pressure and temperature of the blowoff
					 piping from the pressure vessel to and including the blowoff valve(s) shall not
					 be less than the vessel MAWP and corresponding design temperature.
122.3 Instrument, Control, and Sampling
					 Piping
(A) The requirements of this Code, as supplemented by para.
					 122.3, shall apply to the design of instrument, control, and sampling piping
					 for safe and proper operation of the piping itself.
(B) The term "Instrument Piping" shall apply to all valves,
					 fittings, tubing, and piping used to connect instruments to main piping or to
					 other instruments or apparatus or to measuring equipment as used within the
					 classification of para. 100.1.
(C) The term "Control Piping" shall apply to all valves,
					 fittings, tubing, and piping used to interconnect pneumatically or
					 hydraulically operated control apparatus, also classified in accordance with
					 para. 100.1, as well as to signal transmission systems used to interconnect
					 instrument transmitters and receivers.
(D) The term "Sampling Piping" shall apply to all valves,
					 fittings, tubing, and piping used for the collection of samples, such as steam,
					 water, oil, gas, and chemicals.
(E) Paragraph 122.3 does not apply to tubing used in
					 permanently closed systems, such as fluid-filled temperature responsive
					 devices, or the temperature responsive devices themselves.
(F) Paragraph 122.3 does not apply to the devices,
					 apparatus, measuring, sampling, signaling, transmitting, controlling,
					 receiving, or collecting instruments to which the piping is connected.
122.3.1 Materials and Design.
The materials
					 utilized for valves, fittings, tubing, and piping shall meet the particular
					 conditions of service and the requirements of the applicable specifications
					 listed under general paras. 105, 106, 107, and 108 with allowable stresses in
					 accordance with the Allowable Stress Tables in Appendix A.
The materials for pressure retention components used for
					 piping specialties such as meters, traps, and strainers in flammable,
					 combustible, or toxic fluid systems shall in addition conform to the
					 requirements of paras. 122.7 and 122.8.
122.5 Pressure-Reducing Valves
122.5.1 General.
Where pressure-reducing
					 valves are used, one or more relief devices or safety valves shall be provided
					 on the low pressure side of the system. Otherwise, the piping and equipment on
					 the low pressure side of the system shall be designed to withstand the upstream
					 design pressure. The relief or safety devices shall be located adjoining or as
					 close as practicable to the reducing valve. The combined relieving capacity
					 provided shall be such that the design pressure of the low pressure system will
					 not be exceeded if the reducing valve fails open.
122.5.2 Bypass Valves.
Hand controlled bypass
					 valves having a capacity no greater than the reducing valve may be installed
					 around pressure reducing valves if the downstream piping is protected by relief
					 valves as required in para. 122.5.1 or if the design pressure of the downstream
					 piping system and equipment is at least as high as the upstream
					 pressure.
122.5.3 Design of Valves and Relief Devices.
Pressure reducing and bypass valves, and relief devices, shall be designed for
					 inlet pressure and temperature conditions. Safety and relief valves shall be in
					 accordance with the requirements of para. 107.8 of this Code.
122.6 Pressure Relief Piping
Pressure relief piping within the scope of this Code shall
					 be supported to sustain reaction forces, and shall conform to the requirements
					 of paras. 122.6.1 and 122.6.2.
122.6.1 Piping to Pressure-Relieving Safety
					 Devices
(A) There shall be no intervening stop valve(s) between
					 piping being protected and the protective device(s).
(B) Diverter or changeover valves designed to allow
					 servicing of redundant protective devices without system depressurization may
					 be installed between the piping to be protected and the required protective
					 devices under the following conditions:
(B.1) Diverter or changeover valves are prohibited on
					 boiler external piping or reheat piping.
(B.2) One hundred percent (100%) of the required relieving
					 capacity shall be continuously available any time the system is in
					 service.
(B.3) Positive position indicators shall be provided on
					 diverter or changeover valves.
(B.4) Positive locking mechanisms and seals shall be
					 provided on diverter or changeover valves to preclude unauthorized or
					 accidental operation.
(B.5) Diverter or changeover valves shall be designed for
					 the most severe conditions of pressure, temperature, and loading to which they
					 are exposed, and shall be in accordance with para. 107.
(B.6) Provision shall be made to safely bleed off the
					 pressure between the isolated protective device and the diverter or changeover
					 valve.
122.6.2 Discharge Piping From Pressure-Relieving
					 Safety Devices
(A) There shall be no intervening stop valve between the
					 protective device or devices and the point of discharge.
(B) When discharging directly to the atmosphere, discharge
					 shall not impinge on other piping or equipment and shall be directed away from
					 platforms and other areas used by personnel.
(C) It is recommended that individual discharge lines be
					 used, but if two or more reliefs are combined, the discharge piping shall be
					 designed with sufficient flow area to prevent blowout of steam or other fluids.
					 Sectional areas of a discharge pipe shall not be less than the full area of the
					 valve outlets discharging thereinto and the discharge pipe shall be as short
					 and straight as possible and so arranged as to avoid undue stresses on the
					 valve or valves.
(D) Discharge lines from pressure-relieving safety devices
					 within the scope of this Code shall be designed to facilitate drainage.
(E) When the umbrella or drip pan type of connection is
					 used, the discharge piping shall be so designed as to prevent binding due to
					 expansion movements.
(F) Drainage shall be provided to remove water collected
					 above the safety valve seat.
(G) Carbon steel materials listed in Appendix A may be used
					 for discharge piping which is subjected to temperatures above 800°F
					 (427°C) only during operation of pressure relieving safety devices provided
					 that
(G.1) the duration of pressure relieving safety device
					 operation is self-limiting
(G.2) the piping discharges directly to atmosphere
(G.3) the allowable stresses for carbon steel materials at
					 temperatures above 800°F (427°C) shall be taken from Section II, Part
					 D, Table 1A for materials applicable to Section I and Section VIII, Division 1
					 of the ASME Boiler and Pressure Vessel Code.
See PDF for
					 diagram
See PDF
					 for diagram