MSS SP-75: Specification for High-Test Wrought Butt Welding Fittings

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by  Manufacturers Standardization Society

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Legally Binding Document
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INCORPORATED BY REFERENCE and shall be considered legally
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HEED THIS NOTICE: Criminal penalties may apply for noncompliance.
e
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MSS SP-75-2004
Specification for High-Test,
Wrought, Butt-Welding
Fittings
Standard Practice
Developed and Approved by the
Manufacturers Standardization Society of the
Valve and Fittings Industry, Inc.
127 Park Street, NE
Vienna, Virginia 22180
Phone: [phone] www.mss-hq.com
Fax: [phone]
e-mail: [email protected]
MSS STANDARD PRACTICE SP-7S
This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 113 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. ThisMSS Standard Practice is intended as a basis for common practice by the manufac
turer, 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 can fanning to the Standard Practice. Mandatory confonnance is
established only by reference in a code, specification, sales contract, or public law, as applicable.
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 I\1SS SP. (See Annex A.)
In this Standard Practice all notes, annexes, tables, and figures are construed to be essential to the understanding
of the message of the standard, and are considered part of the text unless noted as "supplemental". All appendi
ces appearing in this document are construed as "supplemental". "Supplemental" infonnation does not include
mandatory requirements.
Substantive changes in this 2004 edition are "flagged" by parallel bars
as shown on the margins of this paragraph. The specific detail of the
change may be detennined by comparing the material flagged with that
in the previous edition.
Non-toleranced dimensions in this Standard Practice are nominal, and, unless otherwise specified,
shall be considered "for reference only".
Any part of this standard may be quoted. Credit lines should read 'extracted from MSS SP-75, 2004 with
permission oft he publisher, the Manufacturers Standardization Society. ' Reproduction prohibited under copy
right convention unless written permission is granted by the lVfanufacturers Standardization Society of the
Valve and Fittings IndustlY, inc.
Originally Approved September, 1970
Copyright ©, 1981 by
Manufacturers Standardization Society
of the
Valve and Fittings Industry, Inc.
Printed in U.S.A.
MSS STANDARD PRACTICE SP-7S
TABLE OF CONTENTS
SECTION PAGE
1 SCOPE ............................................................................................................................ 1
2 PRESSURE RATING ....................................................................................................... 1
3 SIZE ................................................................................................................................ 2
4 DESIGN PROOF-TEST .................................................................................................... 2
5 HYDROSTATIC TESTING .............................................................................................. 3
6 MATERIALS ................................................................................................................... 3
7 CH'EMICAL COMPOSITION ................................. '" ..................................................... 3
8 TENSILE PROPERTIES .................................................................................................. 3
9 HEAT TREATMENT ........................................................................................................ 4
10 TRANSVERSE GUIDED-WELD BEND-TESTS .......... ·. .................................................. .4
11 NOTCH-TOUGHNESS PROPERTIES ............................................................................. 5
12 FI,!'1'ING DIMENSIONS ................................................................................................. 5
l3 TOLERANCES FOR WELDING FITTINGS .................................................................... 5
14 MANUFACTURE ............................................................................................................ 6
15 NONDESTRUCTIVE EXAMINATION ........................................................................... 7
16 INSPECTION .................................................................................................................. 7
17 MARKING ....................................................................................................................... 8
TABLE 1 Maximum Limit of Chemical Elements .................................................................... 12
2 Tensile Requirements ........................................................................................... 12
3 Tolerances .......................................................................................................... 13
4 Dimensions of Long-Radius Elbows ...................... , ................................................. 14
5 Dimensions of 3R Elbows .................................................................................... 15
6 Dimensions of Straight Tees ................................................................................. 16
7 Dimensions of Reducing Outlet Tees ................... , ................................................ 17
8 Dimensions of Caps ............................................................................................ 20
9 Dimensions of Reducers ...................................................................................... 21
FIGURE 1 Recommended Bevel for Wall Thicknesses (t) at End of Fitting, 0.75 In. or Less .......... 9
2 Recommended Bevel for Wa1l Thicknesses (t) at End of Fitting, Greater Than 0.75 In ..... 9
3 Acceptable Design for Unequal Wall Thickness ...................................................... 10
4 Transverse-Face and Root-Bend Test Specimens .................................................... 10
5 Guided-Bend Test Jig ............................................................................................ 11
ANNEXA Referenced Standards and Applicable Dates .......................................................... 23
APPENDIX XI Supplementary Requirements ............................................................................... 24
APPENDIXX2 Longitudinal-Bead Underbead Cracking Test. ...................................................... 26
1 1
NISS STANDARD PRACTICE SP-75
SPECIFICATION FOR HIGH-TEST, WROUGHT, BUTT-WELDING FITTINGS
1. SCOPE 1.0) of equivalent grade, diameter and wall
thickness in accordance with the rules established
1.1 This specification covers factory-made, seam in the applicable sections of ASME B31.
less and electric fusion-welded carbon and low-al
loy steel, butt-welding fittings for use in high pres 2.2 All fittings produced in accordance with this
sure gas and oil transmission and distribution sys Standard Practice shall be designed to withstand a
tems, including pipelines, compressor statjons~ me field hydrostatic test pressure, after installation, at a
tering and regulating stations, and mains. pressure level equivalent to that required to develop
a hoop stress equal to the specified-minimum yield
1.2 This Standard Practice governs dimensions, strength for pipe ofequivalcnt grade and wall thick
tolerances, ratings, testing, materials, chemical and ness based on Barlow's Formula, without failure,
tensile properties, heat treatment, notch toughness leakage, or impairment of serviceability. Barlow's
properties, manufacture and marking for high-test, formula is defined as:
butt-welding fittings NPS 60 and smaller. Dimen
sional requirements for NPS 14 and smaller are pro p = 2St
vided by reference to ASME B 16.9. D
Where:
1.3 The term "welding fittings" applies to butt
welding fittings such as elbows, segments of elbows, P is the internal design pressure, psig;
return bends, caps, tees, single-or multiple-outlet ex
truded headers, reducers, and factory-welded exten S is the specified minimum yield strength of the pipe,
sions and transition sections.(l) psi;
1.4 Fittings may be made to special dimensions, t is the nominal wall thickness ofthe pipe, in inches;
sizes, shapes, and tolerances, or of wrought materi
als other than those covered by this Standard Prac D is the outside diameter of the pipe, in inches.
tice by agreement between the manufacturer and the
purchaser. When such fittings meet all other stipu 2.3 By agreement between the manufacturer and
lations of this Standard Practice they shall be con the purchaser, fittings may be tested at a higher pres
sidered as being in partial compliance therewith, sure providing the manufacturer is notified of the
providing they are appropriately marked. test pressure to be used.
1.4.1 Fittings manufactured in partial compliance, 2.4 The design shall take into consideration per
as provided in Section 1.4, shall be identified with formance requirements prescribed above as well as
"Part" following the respective grade designation. additional factors dictated by the shape of the part.
2. PRESSURE RATING 2.5 The design of fittings may be established by
mathematical analyses contained in nationally rec
2.1 The allowable internal-pressure ratings for pipe ognized pressure vessel or piping codes or, at the
fittings designed in accordance with this Standard manufacturer's option, by proof testing in accor
Practice shall be calculated as for straight seamless dance with Section 4. The design of fittings that
pipe (or welded pipe with a joint efficiency factor of cannot be qualified by mathematical analyses shall
be established by proof testing in accordance with
Section 4.
(I)Le ngt hs o fexte'nslO ns and tranSI.t.lo ns as agreed upon by
purchaser and manufacturer.
MSS STANDARD PRACTICE SP-75
3. SIZE 4.2.3 Hydrostatic pressure shall be applied until
the fitting ruptures. The actual test pressure prior to
3.1 The nominal size of the fittings refers to the rupture must at least equal the computed proof-test
nominal O.D. of the pipe to which it is attached. pressure. Alternately, the test is successful if the
assembly withstands, without rupture, 105 percent
4. DESIGN PROOF-TEST of the computed proof-test pressure defined in Sec
tion 4.2.4.
4.1 Proof tests shall be made as set forth herein as
evidence of the adequacy of the design references 4.2.4 Computed Proof-Test Pressure:
in Section 2. Records of design or successful proof
tests shall be available at the manufachlrer's facil P = 2 St which refers to the pipe which
D the fitting's marking identifies
ity for inspection by the purchaser.
(see Section 8.1.1) and, where:
4.2 Unless otherwise agreed upon between manu
P is the computed minimum proof-test pressure; psig
facturer and purchaser, the only required proof test
is a bursting strength test.
S is the actual tensile strength of the test fitting
material (determined on a specimen
4.2.1 Prototype fittings that are representative of
representative of the test fitting); psi
production and selected for test shall be identified
as to material, grade, and lot, including heat treat is the nominal pipe wall thickness; in inches
ment. They shall be inspected for dimensional com
pliance to this Standard Practice. D is the specified outside diameter of pipe; in inches
4.2.2 Straight seamless or welded pipe sections, 4.3 A successful proof test on a prototype fitting
with a calculated burst strength at least as great as selected as required in Section 4.2.1 may be used to
that calculated for the fittings, shall be welded to qualify other fittings to the extent described herein.
each end of the fitting to be tested. Any internal
misalignment greater than 0.06 inch shall be reduced 4.3.1 One test fitting may be used to qualify fit
by taper boring at a slope not over a 1 to 3 ratio. tings of similar designs that are no smaller than one
The length of pipe sections for closures shall be at half nor larger than two times the size of the test
least twice the pipe O.D. fitting.
4.2.2.1 Shorter lengths may be used as follows: 4.3.2 The test of a non-reducing fitting qualifies
reducing fittings that are of the same pattern.
1) The assembly must withstand at least 105 per
cent of the proof-test pressure computed in 4.3.3 The untested fitting must have a t / D ratio
Section 4.2.4. not less than one-half nor more than three times the
t / D of the test fitting.
2) Minimum length of pipe shall be one pipe O.D.
for NPS 14 and smaller. 4.3.4 The pressure retaining capacity of a fitting
made of various grades of steel will be essentially
3) Minimum length of pipe shall be one-halfpipe directly proportional to the tensile properties of the
O.D. for sizes larger than NPS 14. various grades .. Hence, it is necessary to test a pro
totype in only a single grade to prove the geometric
4.2.2.2 Test fluid shall be water or other liquid used design of the fitting.
for hydrostatic testing.
2
MSS STANDARD PRACTICE SP-75
4.3.5 A test on a prototype elbow qualifies elbows 7.2 The choice and use of alloying elements for
having longer radii than the test fitting providing fittings made from high-strength, low-alloy steels
they qualify under Sections 4.3.1 and 4.3.3. to give the tensile properties prescribed in Table 2
shall be made by the manufacturer and included and
5. HYDROSTATIC TESTING reported to identify the type of steel.
5.1 Welding fittings shall be capable of withstand 7.3 Carbon equivalent shall be computed by the
ing a hydrostatic test-pressure as specified in Sec following equation:
tion 2.2, but hydrostatic testing by the manufachlrer
C.E. = C + Mn + Cr + Mo + V + Ni + Cu
is not required.
6 5 15
6. MATERIALS and shall not exceed 0.45%.
6.1 The steel shall be fully killed and made using 8. TENSILE PROPERTIES
recognized melting practices to provide intended
heat-treat response and notch-toughness properties. 8.1 Tensile properties shall meet the requirements
Steel shall be made by open hearth, basic oxygen, as specified in Table 2.
or electric furnace process and shall be suitable for
field welding to other fittings, flanges, and pipe 8.1.1 A fitting may have thickness or yield strength
manufactured under the following specifications: or both unequal to the pipe with which it is intended
ASTMA53,A 106,A381,A234,A420,A 105,A to be used, provided the welding-end preparation at
694, or the corresponding ASME standard, or API the joint assures wall thickness of the fitting is at
5L, and :MSS SP-44. least equal to the specified pipe-wall thickness times
the ratio of the specified minimum yield strength of
6.2 The material for fittings shall consist of the pipe and the minimum-tested yield strength of
blooms, billets, slabs, forging quality bar, plate, the fitting (see Figures 3(a), (b), and (c) for joint
seamless or fusion-welded tubular products with preparation ).
filler metal added.
8.2 Tensile properties shall be determined in ac
6.3 The steel used shall be suitable welding-qual cordance with ASTM A 370.
ity carbon steels or of a suitable welding-quality
high-strength, low-alloy steel. 8.3 Test specimens shall be taken from the fitting
after final heat treatment or from a piece of pipe or
6.4 If preheating of the material is required to in plate of the same nominal thickness, same heat of
sure proper weldability under normal field condi steel from which the fitting is made, and which has
tions, the manufacturer shall state specific preheat been heat treated in a lot with any of the fitting(s) it
requirements and permanently indicate this on the represents (see Section 8.5).
fitting.
8.4 Test specimens shall be in accordance with
7. CHEMICAL COIV[POSITION
ASTM A 370 using full-size specimens or largest
sub-size specimens allowable. Yield strength shall
7.1 The determination of the chemical composi be detennined either by the 0.2% offset or the 0.5%
tion of the steel used in meeting the requirements of extension under load (EUL) method.
Table 1 shall be the responsibility of the manufac
hIrer.
3
MSS STANDARD PRACTICE SP-7S
8.S One tension test to detennine yield strength, 9.1.1 Stress Relieving Stress relieving shall be
tensile strength, and percent elongation in 2 in. shall limited only to guide-bar welds or fabrication welds
be made from each lot of fittings. A lot shall consist such as pup extensions, etc., unless otherwise agreed
of all fittings from the same heat of material of the upon betvveen the mamf[acturer and the purchaser.
same starting wall thickness, given the same heat Fittings shall be heated to a suitable temperature
treatment in a fUll1ace controlled within a range of below the transformation range, but not less than
SooF. The adequacy of the fUll1aCe to achieve and 1O OOoF, holding at temperature for not less than one
maintain temperature uniformity shall be established hour per inch of maximum thickness, but never less
by annual survey. Alternatively, thermocouples may than one-half hour and cooling in the furnace or in
be attached to a fitting in the lot or to a thennally air.
equivalent mass of material in contact with a fitting
in the lot. Thennocouples and other temperature 9.1.2 lVormalizing Fittings shall be uniformly
measuring recording devices shall be calibrated quar reheated above the transformation range (austenite
terly. range), held at this temperature a sufficient time to
achieve uniform temperature throughout the mass
8.6 When requested, fittings containing welds shall and cooled in air.
have one across the weld tension test made with the
axis transverse to the weld seam for each heat of 9.1.3 Normalizing & Tempering Fittings shall be
filler metal, or each heat of filler metal and batch of normalized in accordance with Section 9.1.2. They
flux for submerged arc welds, and for a given heat shall then be tempered by reheating to a tempera
treatment. Only the ultimate tensile strength need ture below the transformation range, but not less than
meet the minimum requirements of Table 2 (see 1000oP, held at temperature for a minimum of one
Appendix Xlc). hour per inch of maximum thickness, but not less
than one-half hour and cooled in the furnace or in
8.7 If the tension-test specimen from any lot fails aIr.
to conform to the requirements for the particular
grade ordered, the manufacturer may elect to make 9.1.4 Quenching & Tempering Fittings shall be
retests on two additional pieces from the same lot, unifonnly reheated above the transfonnation range,
each of which shall confonl1 to the requirements held at temperature sufficient to achieve unifonn
specified in Table 2. If one or both of the retests fail temperature throughout the mass and immediately
to confonn to the requirements, the manufacturer immersion quenched in a suitable liquid medium.
may elect to test each of the remaining pieces in the They shall then be reheated and tempered per Sec
lot. Retests are required only for the particular test tion 9.1.3. Quenching facilities shall be of suffi
with which the specimen did not comply originally. cient size and equipped to assure proper and uni
form cooling.
8.8 It shall be permissible to cold flatten test speci
mens. ]0. TRANSVERSE GUIDED-WELD
BEND-TESTS
9. HEAT TREATMENT
10.1 Transverse guided-weld bend-tests shall be
9.1 All fittings shall be furnished in the heat treated performed only when specified on the order (see
condition. Hot formed fittings shall be cooled be Appendix Xl b).
low the lower critical temperature prior to heat treat
ment. Fittings shall be heat treated by one or more 10.2 Transverse-weld test specimens shall be sub
of the following procedures: jected to face and root-guided bend-tests. The speci
mens shall be approximately 1.5 in. wide, at least 6
4
MSS STANDARD PRACTICE SP-75
in. long with the weld at the center and shall be ma pendicular to the surface. For plate, specimens may
chined in accordance with Figure 4. The face-bend be taken transverse to the direction of rolling.
specimen shall be bent with the inside surface ofthe
pipe against the plunger and the root-bend speci 11.2 Specimens shall be taken from representative
men with the outside surface against the plunger. heats of steel used in manufacture of fittings or from
The dimensions of the plunger for the bending jig representative fittings, plates or pipe receiving the
shall be in accordance with Figure 5 and the other same heat treatment to determine the typical notch
dimensions shall be substantially as shown in Fig toughness properties of a given material.
ure 5.
11.3 From each heat of steel, one set (three speci
10.3 The bend-test shall be acceptable if no cracks mens) shall be tested at 20°F or lower and show 20
or other defects exceeding 0.12 in. in any direction ft. Ibs. minimum average. Percent shear shall be
are present in the weld metal or between the weld reported for infonnational purposes only.
metal and the fitting metal after the bending. Cracks
that originate along the edges of the specimen during 11.4 Notch-toughness testing ofNPS 14 and smaller
testing and that are less than 0.25 in. measured in is not required unless grades WPHY 65 or higher
any direction, shall not be considered unless obvi are supplied or the purchaser specifies testing.
ous defects are observed.
12. FITTING DIlVlENSIONS
10.4 Two weld-bend test specimens, as described
in Section 10.2, shall be cut from a specimen from 12.l One of the principles of this Standard Practice
each lot. The specimens may be taken from a fit is the maintenance of a fixed position for the weld
ting or from sample plates as described in Section ing ends with reference to the center line of the fit
8.3. tings or the overall dimensions, as the case may be.
Dimensional standards for fittings NPS 16 and larger
10.5 If either test fails to confonn to specified re are shown in Tables 3 through 9. Dimensional stan
quirements, the manufacturer may elect to make re dards and tolerances for NPS 14 and smaller sizes
tests on two additional specimens from the same lot, are contained in ASME B16.9.
each of which shall conform to the requirements
specified in Section 10.3. If any of these specimens 13. TOLERANCES FOR WELDING FITTINGS
fail to confonl1 to the requirements, the manufac
turer may elect to test prolongations from each of 13.1 Tolerances The tolerances for fittings NPS
the remaining fittings in the lot. 16 and larger are shown in Table 3 and are appli
cable to the nominal dimensions given in Tables 4
10.6 If the test results of any tests of a lot do not through 9 inclusive.
conform to the requirements specified above, retests
shall be made on additional fittings of double the 13.2 Wall Thickness The minimum wall thick
original number from the same lot, each of which ness may be 0.01 in. under the nominal thickness,
shall conform to the requirements specified. except that isolated non-continuous reductions are
pennitted, provided the remaining wall thickness is
11. NOTCH-TOUGHNESS PROPERTIES not diminished to less than 93.5% of the specified
nominal. This tolerance does not apply to areas
11.1 Notch-toughness properties shall be detennined where the proof test has indicated the need for rein
with full size Charpy Type A-V notch specimens in forcement.
accordance with ASTM A 370. Subsize specimens
shall be used only when material to be tested is of 13.3 Welding Ends Unless otherwise specified,
insufficien t thickness. All specimens shall be taken the details of the welding end preparation shall be
with the axis of the specimen transverse to the di in accordance with Figures 1 and 2. The root face
rection of flow (of medium) and with the notch per-
5