MSS SP-97-2006
www.mss-hq.org
MSS
Integrally Reinforced Forged
Branch Outlet Fittings –
Socket Welding,
Threaded, and Buttwelding Ends
Standard Practice
Developed and Approved by the
Manufacturers Standardization Society of the
Valve and Fittings Industry, Inc.
127 Park Street, NE
Vienna, Virginia 22180
(703) 281-6613
Email: info@mss-hq.org
Copyright MSS
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MSS STANDARD PRACTICE SP-97
i
This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 105 and
the MSS Coordinating Committee. The content of this Standard Practice is the result of the efforts of
competent and concerned volunteers to provide an effective, clear, and non-exclusive specification that will
benefit the industry as a whole. This MSS Standard Practice is intended as a basis for common practice by
the manufacturer, the user, and the general public. The existence of an MSS Standard Practice does not in
itself preclude the manufacture, sale, or use of products not conforming to the Standard Practice.
Mandatory conformance is established only by reference in a code, specification, sales contract, or public
law, as applicable.
U.S. customary units in this SP are the standard; the metric units are for reference only.
Non-toleranced dimensions in this Standard Practice are nominal, and, unless
otherwise specified, shall be considered "for reference only".
In this Standard Practice all notes, annexes, tables, and figures are construed to be
essential to the understanding of the message of the Standard Practice and are
considered part of the text unless noted as “supplemental”.
Unless otherwise specifically noted in this MSS SP, any standard referred to herein
is identified by the date of issue that was applicable to the referenced standard(s) at
the date of issue of this MSS SP. (See Annex C).
Substantive changes in this 2006 edition are “flagged” by parallel bars as
shown on the margins of this paragraph. The specific detail of the change
may be determined by comparing the material flagged with that in the
previous edition.
Any part of this Standard Practice may be quoted. Credit lines should read 'Extracted from MSS SP-97, 2006,
with permission of the publisher, the Manufacturers Standardization Society.' Reproduction prohibited under
copyright convention unless written permission is granted by the Manufacturers Standardization Society of the
Valve and Fittings Industry, Inc.
Originally Approved June 1987
Copyright © 1987 by
Manufacturers Standardization Society
of the
Valve and Fittings Industry, Inc.
Printed in U.S.A.
Copyright MSS
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Not for ResaleNo reproduction or networking permitted without license from IHS
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MSS STANDARD PRACTICE SP-97
ii
TABLE OF CONTENTS
SECTION PAGE
1 SCOPE..................................................................................................................................................1
2 SERVICE DESIGNATION .................................................................................................................1
3 SIZE......................................................................................................................................................2
4 MARKING...........................................................................................................................................2
5 MATERIAL .........................................................................................................................................2
6 DESIGN AND DIMENSION ..............................................................................................................3
7 TESTS ..................................................................................................................................................3
TABLE
1 Correlation of Fittings Class with Schedule Number or Wall
Designation of Run Pipe for Calculation of Ratings ..........................................................................1
2 Branch Outlet Height - Buttwelding, Customary Units .....................................................................4
3 Branch Outlet Height - Threaded, Customary Units ..........................................................................5
4 Branch Outlet - Socket Welding, Customary Units ...........................................................................6
A 1 Branch Outlet Height - Buttwelding, Metric Units ............................................................................7
A 2 Branch Outlet Height - Threaded, Metric Units .................................................................................8
A 3 Branch Outlet - Socket Welding, Metric Units ..................................................................................9
FIGURE
1 Fitting Consolidation Gap Allowance ................................................................................................2
ANNEX
A Metric (SI) Tables ....................................................................................................................7, 8, 9
B Design Proof Test ...........................................................................................................................10
C Referenced Standards and Applicable Dates....................................................................................11
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MSS STANDARD PRACTICE SP-97
1
INTEGRALLY REINFORCED FORGED BRANCH OUTLET FITTINGS -
SOCKET WELDING, THREADED AND BUTTWELDING ENDS
1. SCOPE
1.1 This Standard Practice covers essential dimen-
sions, finish, tolerances, testing, marking, material,
and minimum strength requirements for 90 degree
integrally reinforced forged branch outlet fittings of
buttwelding, socket welding, and threaded types.
1.2 Fittings manufactured to this Standard Practice
are designed to make a fully reinforced branch
connection in accordance with applicable piping code
requirements, when attached, at an opening in a run
pipe by means of a full penetration weld.
1.3 Fittings may be made to special dimensions,
size, shape, tolerances, or of other wrought material
by agreement between the manufacturer and the
purchaser.
2. SERVICE DESIGNATION
2.1 These fittings are designated by their size, type,
and class, as shown in Table 1.
2.2 Design temperature and other service conditions
shall be limited as provided by the applicable piping
code or regulation for the material of construction of
the fitting. Within these limits, the maximum allow-
able pressure of a fitting shall be that computed for
straight seamless run pipe of equivalent material (as
shown by comparison of composition and mechani-
cal properties in the respective material specifica-
tions). The wall thickness used in such computation
shall be that tabulated in ANSI B36.10M for the size
and applicable schedule of pipe reduced by
applicable manufacturing tolerances and other
allowances (e.g., threaded allowances).
2.3 Any corrosion allowance and any variation in
allowable stress due to temperature or other design
shall be applied to the pipe and fitting alike. The
pipe wall thickness corresponding to each Class of
fitting, for rating purposes only, is shown in Table 1.
TABLE 1
Correlation of Fittings Class With Schedule Number or
Wall Designation of Run Pipe for Calculation of Ratings
CLASS OF FITTING TYPE BRANCH SIZE PIPE WALL FOR RATING BASIS (a)
Standard
Extra Strong
Schedule 160
3000
6000
Buttwelding
Buttwelding
Buttwelding
Threaded & Socket Welding
Threaded & Socket Welding
NPS 1/8 – 24
NPS 1/8 – 24
NPS 1/2 – 6
NPS 1/8 – 4
NPS 1/2 - 2
Standard
Extra Strong
Schedule 160
Extra Strong
Schedule 160
(a) Note: The use of run or branch pipe wall thickness either thinner or thicker than shown in Table 1
constitutes a deviation from this Standard Practice and is provided for in Section 1.3.
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MSS STANDARD PRACTICE SP-97
2
3. SIZE
3.1 The branch outlet sizes considered in this
Standard Practice are shown in Table 1. Size on size
fittings shall be limited to outlet sizes 1/2 and larger.
3.2 The run (header) pipe size is limited only by
the pipe size range listed for each type fitting class.
3.3 The manufacturer has the option to consolidate
run sizes for a given branch size for economic
reasons, provided the designated consolidation gap
distance between the run pipe radius and the fitting
inlet radius does not exceed 1/16" (1.6 mm). See
Figure 1.
4. MARKING
4.1 Each fitting shall be permanently marked with
the required identification by raised lettering, and/or
by stamping, electro-etching or vibro tool.
4.2 The marking shall include (but it is not limited
to) the following:
a) Manufacturer's name or trademark.
b) Material Identification The material shall
be identified in accordance with the marking
requirements of ASTM Specifications,
including Heat Identification.
c) Class The Fitting Class - "STD" (Stan-
dard), "XS" (Extra Strong), "SCH 160"
(Schedule 160), "3000" or "6000". Alterna-
tively the designation 3M or 6M, as applicable,
may be used where "M" stands for 1,000.
d) Size The nominal size of the pipe that the
fitting's marking identifies - Run (or consoli-
dated range) NPS X Outlet NPS.
e) SP 97 This marking indicates compliance
with MSS SP-97.
4.3 Where size and shape of fittings do not permit
all of the above markings, they may be omitted in the
reverse order given above.
5. MATERIAL
5.1 The material for fittings shall consist of forgings,
bars, and seamless tubular products that conform to
the melting process requirements, chemical com-
position requirements, and mechanical property re-
quirements of the forging product form listed in Table
1, found in ASME B16.34, including notes.
FIGURE 1 Fitting Consolidation Gap Allowance
(Illustrative Only)
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MSS STANDARD PRACTICE SP-97
3
6. DESIGN AND DIMENSION
6.1 A run pipe having a branch connection is weak-
ened by the opening made in it. The branch connec-
tion must reinforce the opening and restore the
original strength of the run pipe. It is the intent of this
Standard Practice that these integrally reinforced
branch outlet fittings and the deposited weld metal
used to attach the fittings to run pipes contain all the
reinforcement required by the applicable piping
codes without the addition of saddles or pads.
6.1.1 The adequacy of the design of branch
connection fittings may be established by
mathematical analyses contained in pressure vessel or
piping codes, or, at the manufacturer's option, by
proof testing in accordance with Section 7 and Annex
B. Records of design or proof tests shall be available
at the manufacturer's facility for inspection by the
purchaser.
6.1.2 The codes permit a variety of attachment welds
for these fittings. Typical branch attachments are
shown in ASME B31.1 and B31.3.
6.1.3 Fittings shall be contoured to provide a good
fit at the opening in the run pipe. The run attachment
weld bevel angle design will vary with the size and
type of fitting and with the manufacturer. The size of
the run opening is dependent on the manufacturer's
specification.
6.2 Buttwelding Buttwelding end finish shall
comply with the standard welding bevel and root face
of ASME B16.25.
6.3 Threads Threads in threaded fittings shall
comply with ASME B1.20.1 requirements for NPT.
6.3.1 The minimum wall thickness at the root of the
thread at the hand tight plane shall be equal to or
greater than the nominal wall of the pipe schedule for
the appropriate fitting class, as shown in Table 1.
6.4 Socket Weld Socket Weld fittings shall meet
the minimum socket depth, minimum socket wall
thickness and socket diameter of ASME B16.11 for
the appropriate class.
6.5 The contour weld bevel angle on the longitudi-
nal section of the fittings shall be minimum of 35
degrees. The weld bevel angle on the transverse sec-
tion of the fitting is based on the manufacturer's
specification.
7. TESTS
7.1 Hydrostatic testing of wrought fittings is not
required by this Standard Practice. All fittings shall
be capable of withstanding, without leakage or
impairment of serviceability, a pressure equal to that
prescribed in the applicable code or regulation for
seamless pipe of equivalent material and schedule
listed in Table 1.
7.2 Proof testing is not required, but when
performed to meet the requirements of Section 6.1.1
shall be conducted in accordance with Annex B.
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MSS STANDARD PRACTICE SP-97
4
TABLE 2 Branch Outlet Height – Buttwelding, Customary Units
“A” (FACE OF FITTING TO CROTCH)
STANDARD EXTRA STRONG SCHEDULE 160 OUTLET NPS Reducing Full Reducing Full Reducing Full
1/8 .62 - .62 - - -
1/4 .62 - .62 - - -
3/8 .75 - .75 - - -
1/2 .75 .75 .75 .75 1.12 1.12
3/4 .88 .88 .88 .88 1.25 1.25
1 1.06 1.06 1.06 1.06 1.50 1.50
1-1/4 1.25 1.25 1.25 1.25 1.75 1.75
1-1/2 1.31 1.31 1.31 1.31 2.00 2.00
2 1.50 1.50 1.50 1.50 2.18 2.18
2-1/2 1.62 1.62 1.62 1.62 2.44 2.44
3 1.75 1.75 1.75 1.75 2.88 2.88
3-1/2 1.88 2.00 1.88 2.00 - -
4 2.00 2.00 2.00 2.00 3.31 3.31
5 2.25 2.25 2.25 2.25 3.69 3.69
6 2.38 2.38 3.06 3.06 4.12 4.12
8 2.75 2.75 3.88 3.88 - -
10 3.06 3.06 3.69 3.50 - -
12 3.38 3.38 4.06 3.94 - -
14 3.50 3.50 3.94 4.12 - -
16 3.69 3.69 4.18 4.44 - -
18 3.81 4.06 4.38 4.69 - -
20 4.00 4.62 4.69 5.00 - -
24 4.56 5.38 5.50 5.50 - -
Dimensions are in Inches
Tolerances: 1/8 – 3/4 ± .03 in.
1 – 4 ± .06 in.
5 – 12 ± .12 in.
14 – 24 ± .19 in.
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MSS STANDARD PRACTICE SP-97
5
TABLE 3 Branch Outlet Height – Threaded, Customary Units
“A” (FACE OF FITTING TO CROTCH)
THREADED OUTLET NPS 3000 6000
1/8 .75 -
1/4 .75 -
3/8 .81 -
1/2 1.00 1.25
3/4 1.06 1.44
1 1.31 1.56
1-1/4 1.31 1.62
1-1/2 1.38 1.69
2 1.50 2.06
2-1/2 1.81 -
3 2.00 -
4 2.25 -
Dimensions are in Inches
Tolerances: 1/8 – 1/4 ± .03 in.
1 – 4 ± .06 in.
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MSS STANDARD PRACTICE SP-97
6
TABLE 4 Branch Outlets – Socket Welding Customary Units
“C” MAX. OUTLET “B”
NPS MIN. (a) 3000 6000
1/8 0.38 0.41 -
1/4 0.38 0.41 -
3/8 0.38 0.50 -
1/2 0.38 0.63 0.94
3/4 0.50 0.63 1.00
1 0.50 0.88 1.13
1-1/4 0.50 0.88 1.19
1-1/2 0.50 0.94 1.25
2 0.62 0.94 1.44
2-1/2 0.62 1.00 -
3 0.62 1.19 -
4 0.75 1.19 -
(a) Note: "B" Minimum Socket Depth per ASME B16.11
Dimensions are in inches
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MSS STANDARD PRACTICE SP-97
ANNEX A
TABLE A1 Branch Outlet Height – Buttwelding, Metric Units
“A” (FACE OF FITTING TO CROTCH)
7
STANDARD EXTRA STRONG SCHEDULE 160 OUTLET OUTLET DN NPS Reducing Full Reducing Full Reducing Full
6 1/8 16 - 16 - - -
8 1/4 16 - 16 - - -
10 3/8 19 - 19 - - -
15 1/2 19 19 19 19 28 28
20 3/4 22 22 22 22 32 32
25 1 27 27 27 27 38 38
32 1-1/4 32 32 32 30 44 44
40 1-1/2 33 33 33 32 51 51
50 2 38 38 38 38 55 55
65 2-1/2 41 41 41 41 62 62
80 3 44 44 44 44 73 73
90 3-1/2 48 51 48 51 - -
100 4 51 51 51 51 84 84
125 5 57 57 57 57 94 94
150 6 60 60 78 78 105 105
200 8 70 70 99 99 - -
250 10 78 78 94 89 - -
300 12 86 86 103 100 - -
350 14 89 89 100 105 - -
400 16 94 94 106 113 - -
450 18 97 103 111 119 - -
500 20 102 117 119 127 - -
600 24 116 137 140 140 - -
Dimensions are in Millimeters
Tolerances: 1/8 – 3/4 ± 0.8mm
1 – 4 ± 1.6mm
5 – 12 ± 3.2mm
14 – 24 ± 4.8mm
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MSS STANDARD PRACTICE SP-97
8
ANNEX A (Continued)
Table A2 Branch Outlet Height – Threaded, Metric Units
“A” (FACE OF FITTING TO CROTCH)
THREADED OUTLET OUTLET DN NPS 3000 6000
6 1/8 19 -
8 1/4 19 -
10 3/8 21 -
15 1/2 25 32
20 3/4 27 37
25 1 33 40
32 1-1/4 33 41
40 1-1/2 35 43
50 2 38 52
65 2-1/2 46 -
80 3 51 -
100 4 57 -
Dimensions are in Millimeters
Tolerances: 1/8 – 1/4 ± 0.8mm
1 – 4 ± 1.6mm
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MSS STANDARD PRACTICE SP-97
ANNEX A (Continued)
TABLE A3 Branch Outlets – Socket Welding, Metric Units
9
“C” MAX. OUTLET OUTLET “B”
(a)DN NPS MIN. 3000 6000
6 1/8 10 10 -
8 1/4 10 10 -
10 3/8 10 13 -
15 1/2 10 16 24
20 3/4 13 16 25
25 1 13 22 29
32 1-1/4 13 22 30
40 1-1/2 13 24 32
50 2 16 24 37
65 2-1/2 16 25 -
80 3 16 30 -
100 4 19 30 -
(a) Note: "B" Minimum Socket Depths per ASME B16.11
Dimensions are in Millimeters
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MSS STANDARD PRACTICE SP-97
ANNEX B
DESIGN PROOF TEST
10
Alternately, the test is considered successful if the
assembly withstands, without rupture, a test pressure
of 105 percent of the computed test pressure defined
above.
B1. Proof Test Administration
B1.1 Proof tests shall be made as set forth herein
as evidence of the adequacy of branch connections
employing these outlet fittings.
B3. It is not necessary to conduct an individual
test of fittings in all combinations of sizes, wall
thickness, and pressure class. A successful proof test
on one prototype fitting may represent other similarly
proportioned fittings to the extent described herein.
B2. Proof Test Procedure
B2.1 Fittings selected for testing shall be
representative of production fittings, shall be
identified as to material, grade, and class, and shall
be inspected for compliance with this Standard
Practice.
B3.1 A successful test on a full size fitting may be
used to qualify other full sized fittings no smaller
than one-half nor larger than two-times the size of
the test fitting.
B2.2 Run and branch pipe sections, assembled with
a fittin