ASTM A790/A790M Austenitic Stainless Steel Pipe
ASTM A790/A790M
Standard Specification for Seamless and Welded Ferritic/Austenitic Stainless Steel Pipe
1. Scope
1.1 This specification 2 covers seamless and straight-seam welded ferritic/austenitic steel pipe intended for general corrosive service, with particular emphasis on resistance to stress corrosion cracking. These steels are susceptible to embrittlement if used for prolonged periods at elevated temperatures.
1.2 Optional supplementary requirements are provided for pipe when a greater degree of testing is desired. These supplementary requirements call for additional tests to be made and, when desired, one or more of these may be specified in the order.
1.3 Appendix X1 of this specification lists the dimensions of welded and seamless stainless steel pipe as shown in ANSI B36.19. Pipe having other dimensions may be furnished provided such pipe complies with all other requirements of this specification.
1.4 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. The inch-pound units shall apply unless the M designation of this specification is specified in the order.
N OTE 1—The dimensionless designator NPS (nominal pipe size) has been substituted in this standard for such traditional terms as nominal diameter, size, and nominal size.
2. Referenced Documents
2.1 ASTM Standards:
A 370 Test Methods and Definitions for Mechanical Testing of Steel Products
A 923 Test Methods for Detecting Detrimental Intermetallic Phase in Duplex Austenitic/Ferritic Stainless Steels
A 941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
A 999/A 999M Specification for General Requirements for Alloy and Stainless Steel Pipe
E 213 Practice for Ultrasonic Examination of Metal Pipe and Tubing
E 309 Practice for Eddy-Current Examination of Steel Tubular Products Using Magnetic Saturation
E 381 Method of Macroetch Testing Steel Bars, Billets,Blooms, and Forgings
E 426 Practice for Electromagnetic (Eddy-Current) Examination of Seamless and Welded Tubular Products, Austenitic Stainless Steel and Similar Alloys
E 527 Practice for Numbering Metals and Alloys in the Unified Numbering System (UNS)
2.2 ANSI Standards:
B1.20.1 Pipe Threads, General Purpose
B36.10 Welded and Seamless Wrought Steel Pipe
B36.19 Stainless Steel Pipe
2.3 SAE Standard:
2.3 SAE Standard:
SAE J 1086
2.4 Other Standard:
2.4 Other Standard:
SNT-TC-1A Personal Qualification and Certification in Nondestructive Testing
2.5 AWS Standard
2.5 AWS Standard
A5.9 Corrosion-Resisting Chromium and ChromiumNickel Steel Welding Rods and Electrodes
3. Terminology
3.1 Definitions—For definitions of terms used in this specification refer to Terminology A 941.
4. Ordering Information
4.1 Orders for material under this specification should include the following, as required, to describe the desired material adequately:
4.1.1 Quantity (feet, [metres], or number of lengths),
4.1.2 Name of material (ferritic/austenitic steel pipe),
4.1.3 Process (seamless or welded),
4.1.4 Grade (see Table 1),
4.1.5 Size (NPS designator or outside diameter and schedule number of average wall thickness),
4.1.6 Length (specific or random) (see Section 11),
4.1.7 End finish (section on ends of Specification A 999/A 999M),
4.1.8 Optional requirements (product analysis, Section 9;hydrostatic test or nondestructive electric test, Section 14),
4.1.9 Test report required (section on certification of Specification A 999/A 999M),
4.1.10 Specification designation, and
4.1.11 Special requirements and any supplementary requirements selected.
5. General Requirements
5.1 Material furnished under this specification shall conform to the applicable requirements of the current edition of SpecificationA 999/A 999M unless otherwise provided herein.
6. Materials and Manufacture
6.1 Manufacture:
6.1.1 The pipe shall be made by the seamless or an automatic welding process, with no addition of filler metal in the welding operation.
6.1.2 At the manufacturer’s option, pipe may be either hot-finished or cold-finished.
6.1.3 The pipe shall be pickled free of scale. When bright annealing is used, pickling is not necessary.
6.2 Discard—A sufficient discard shall be made from each ingot to secure freedom from injurious piping and undue segregation.
6.3 Unless otherwise stated in the order, all pipe shall be furnished in the heat-treated condition as shown in Table 1.
TABLE 1 Heat Treatment
| UNS Designation | Type A | Temperature °F [°C] | Quench |
| S31200 |
1920–2010
[1050–1100]
|
Rapid cooling in water | |
| S31260 |
1870–2010
[1020–1100]
|
Rapid cooling in air or water | |
| S31500 |
1800–1900
[980–1040]
|
Rapid cooling in air or water | |
| S31803 |
1870–2010
[1020–1100]
|
Rapid cooling in air or water | |
| S32003 |
1850–2050
[1010–1120]
|
Rapid cooling in air or water | |
| S32101 | 1870 [1020] |
Quenched in water or rapidly
cooled by other means
|
|
| S32202 |
1800–1975
[980–1080]
|
Rapid cooling in air or water | |
| S32205 | 2205 |
1870–2010
[1020–1100]
|
Rapid cooling in air or water |
| S32304 | 2304 |
1700–1920
[925–1050]
|
Rapid cooling in air or water |
| S32506 |
1870–2050
[1020–1120]
|
Rapid cooling in air or water | |
| S32520 |
1975–2050
[1080–1120]
|
Rapid cooling in air or water | |
| S32550 | 255 | 1900 [1040] min | Rapid cooling in air or water |
| S32707 |
1975–2050
[1080–1120]
|
Rapid cooling in air or water | |
| S32750 | 2507 |
1880–2060
[1025–1125]
|
Rapid cooling in air or water |
| S32760 |
1960–2085
[1070–1140]
|
Rapid cooling in air or water | |
| S32808 |
1920–2100
[1050–1150]
|
Rapid cooling in air or water | |
| S32900 | 329 |
1700–1750
[925–955]
|
Rapid cooling in air or water |
| S32906 |
1870–2100
[1020–1150]
|
Rapid cooling in air or water | |
| S32950 |
1820–1880
[990–1025]
|
Air cool | |
| S33207 |
1905–2085
[1040–1140]
|
Rapid cooling in water or by other means | |
| S39274 |
1920–2060
[1025–1125]
|
Rapid cooling in air or water | |
| S39277 |
1975–2155
[1080–1180]
|
Rapid cooling in air or water |
A Common name, not a trademark, widely used, not associated with any one producer. 329 is na AISI number.
6.3.1 For seamless pipe, as an alternate to final heat treatment in a continuous furnace or batch-type furnace, immediately following hot forming while the temperature of the pipes is not less than the specified minimum solution treatment temperature, pipes shall be individually quenched in water or rapidly cooled by other means, except for UNS S32950, which shall be air cooled.
6.3.2 If the purchaser desires pipe without heat treatment subsequent to welding, the purchase order shall specify the following condition:
6.3.2.1 No final heat treatment of pipe fabricated from plate that has been heat treated as required by Table 1 for the particular grade is required, provided a sample of that heat of finished pipe or material representative of that heat of pipe as a prolongation of the weld passes the Test Methods A 923 Method B or C (See Note 2), including base metal, weld metal, and heat affected zone per heat. Each pipe supplied under this requirement shall be stenciled with the suffix “HT-O.”
6.3.2.2 For materials not listed in Table 3 of Test Methods A 923, the HT-O provision does not apply.
N OTE 2—The Test Methods A 923 test method (B or C) is at the manufacturer’s option, unless otherwise specified by the purchaser.
7. Chemical Composition
7.1 The steel shall conform to the chemical requirements as prescribed in Table 2.
TABLE 2 Chemical Requirements A
|
UNS
Designation B
|
Type C | C | Mn | P | S | Si | Ni | Cr | Mo | N | Cu | Others |
| S31200 | 0.030 | 2.00 | 0.045 | 0.030 | 1.00 | 5.5–6.5 | 24.0–26.0 | 1.20–2.00 | 0.14–0.20 | . . . | . . . | |
| S31260 | 0.030 | 1.00 | 0.030 | 0.030 | 0.75 | 5.5–7.5 | 24.0–26.0 | 2.5–3.5 | 0.10–0.30 | 0.20–0.80 |
W
0.10–0.50
|
|
| S31500 | 0.030 | 1.20–2.00 | 0.030 | 0.030 | 1.40-2.00 | 4.2–5.2 | 18.0–19.0 | 2.5–3.5 | 0.05–0.10 | . . . | . . . | |
| S31803 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 4.5–6.5 | 21.0–23.0 | 2.5–3.5 | 0.08–0.20 | . . . | . . . | |
| S32003 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 3.0–4.0 | 19.5-22.5 | 1.50–2.00 | 0.14–0.20 | . . . | . . . | |
| S32101 | 0.040 | 4.0-6.0 | 0.040 | 0.030 | 1.00 | 1.35–1.70 | 21.0–22.0 | 0.10–0.80 | 0.20–0.25 | 0.10–0.80 | . . . | |
| S32202 | 0.030 | 2.00 | 0.040 | 0.010 | 1.00 | 1.00–2.80 | 21.5–24.0 | 0.45 | 0.18–0.26 | . . . | . . . | |
| S32205 | 2205 | 0.030 | 2.00 | 0.030 | 0.020 | 1.00 | 4.5–6.5 | 22.0–23.0 | 3.0–3.5 | 0.14–0.20 | . . . | . . . |
| S32304 | 2304 | 0.030 | 2.50 | 0.040 | 0.040 | 1.00 | 3.0–5.5 | 21.5–24.5 | 0.05–0.60 | 0.05–0.20 | 0.05–0.60 | . . . |
| S32506 | 0.030 | 1.00 | 0.040 | 0.015 | 0.90 | 5.5–7.2 | 24.0–26.0 | 3.0–3.5 | 0.08–0.20 | . . . |
W
0.05–0.30
|
|
| S32520 | 0.030 | 1.50 | 0.035 | 0.020 | 0.80 | 5.5–8.0 | 24.0–26.0 | 3.0–5.0 | 0.20–0.35 | 0.5–3.00 | . . . | |
| S32550 | 255 | 0.040 | 1.50 | 0.040 | 0.030 | 1.00 | 4.5–6.5 | 24.0–27.0 | 2.9–3.9 | 0.10–0.25 | 1.50–2.50 | . . . |
| S32707 | 0.030 | 1.50 | 0.035 | 0.010 | 0.50 | 5.5–9.5 | 26.0–29.0 | 4.0–5.0 | 0.30–0.50 | 1.0 |
Co
0.5–2.0
|
|
| S32750 | 2507 | 0.030 | 1.20 | 0.035 | 0.020 | 0.80 | 6.0–8.0 | 24.0–26.0 | 3.0–5.0 | 0.24–0.32 | 0.5 | . . . |
| S32760 | 0.050 | 1.00 | 0.030 | 0.010 | 1.00 | 6.0–8.0 | 24.0–26.0 | 3.0–4.0 | 0.20–0.30 | 0.50–1.00 |
W
0.50–1.00
40 min D
|
|
| S32808 | 0.030 | 1.10 | 0.030 | 0.030 | 0.50 | 7.0–8.2 | 27.0–27.9 | 0.80–1.20 | 0.30–0.40 | . . . |
W
2.10–2.50
|
|
| S32900 | 329 | 0.080 | 1.00 | 0.040 | 0.030 | 0.75 | 2.5–5.0 | 23.0–28.0 | 1.00–2.00 | . . . | . . . | . . . |
| S32906 | 0.030 | 0.80-1.50 | 0.030 | 0.030 | 0.80 | 5.8–7.5 | 28.0–30.0 | 1.50–2.60 | 0.30–0.40 | 0.80 | . . . | |
| S32950 | 0.030 | 2.00 | 0.035 | 0.010 | 0.60 | 3.5–5.2 | 26.0–29.0 | 1.00–2.50 | 0.15–0.35 | . . . | . . . | |
| S33207 | 0.030 | 1.50 | 0.035 | 0.010 | 0.80 | 6.0–9.0 | 29.0–33.0 | 3.0–5.0 | 0.40–0.60 | 1.0 | . . . | |
| S39274 | 0.030 | 1.00 | 0.030 | 0.020 | 0.80 | 6.0–8.0 | 24.0–26.0 | 2.5–3.5 | 0.24–0.32 | 0.20–0.80 |
W
1.50–2.50
|
|
| S39277 | 0.025 | 0.80 | 0.025 | 0.002 | 0.80 | 6.5–8.0 | 24.0–26.0 | 3.0–4.0 | 0.23–0.33 | 1.20–2.00 | W 0.8–1.2 |
A Maximum, unless a range or minimum is indicated. Where ellipses (...) appear in this table, there is no minimum and analysis for the element need not be determined or reported.
B New designation established in accordance with Practice E527 and SAE J 1086.
C Common name, not a trademark, widely used, not associated with any one producer. 329 is na AISI number.
D % Cr + 3.3 3 % Mo + 16 3 % N.
8. Heat Analysis
8.1 An analysis of each heat of steel shall be made by the steel manufacturer to determine the percentages of the elements specified.
9. Product Analysis
9.1 At the request of the purchaser’s inspector, an analysis of one billet or one length of flat-rolled stock from each heat,or two pipes from each lot, shall be made by the manufacturer.A lot of pipe shall consist of the following number of lengths of the same size and wall thickness from any one heat of steel:
| NPS Designator | Lengths of Pipe in Lot |
| Under 2 | 400 or fraction thereof |
| 2 to 5, incl | 200 or fraction thereof |
| 6 and over | 100 or fraction thereof |
9.2 The results of these analyses shall be reported to the purchaser or the purchaser’s representative and shall conform to the requirements specified in Section 7.
9.3 If the analysis of one of the tests specified in 8.1 or 9.1 does not conform to the requirements specified in Section 7, an analysis of each billet or pipe from the same heat or lot may be made, and all billets or pipe conforming to the requirements shall be accepted.
10. Tensile and Hardness Properties
10.1 The material shall conform to the tensile and hardness properties prescribed in Table 3.
TABLE 3 Tensile and Hardness Requirements
|
UNS
Designation
|
Type A |
Tensile Strength,
min, ksi
[MPa]
|
Yield Strength,
min,
ksi [MPa]
|
Elongation in 2 in. or 50 mm,
min, %
|
Hardness, max | |
| HBW | HRC | |||||
| S31200 | 100 [690] | 65 [450] | 25 | 280 | . . . | |
| S31260 | 100 [690] | 65 [450] | 25 | . . . | . . . | |
| S31500 | 92 [630] | 64 [440] | 30 | 290 | 30 | |
| S31803 | 90 [620] | 65 [450] | 25 | 290 | 30 | |
| S32003 | 90 [620] | 65 [450] | 25 | 290 | 30 | |
| S32101 | ||||||
|
t ≤0.187 in.
[5.00 mm]
|
101 [700] | 77 [530] | 30 | 290 | . . . | |
|
t >0.187 in.
[5.00 mm]
|
94 [650] | 65 [450] | 30 | 290 | . . . | |
| S32202 | 94 [650] | 65 [450] | 30 | 290 | 30 | |
| S32205 | 2205 | 95 [655] | 65 [450] | 25 | 290 | 30 |
| S32304 | 2304 | 87 [600] | 58 [400] | 25 | 290 | 30 |
| S32506 | 90 [620] | 65 [450] | 18 | 302 | 32 | |
| S32520 | 112 [770] | 80 [550] | 25 | 310 | . . . | |
| S32550 | 255 | 110 [760] | 80 [550] | 15 | 297 | 31 |
| S32707 | 133 [920] | 101 [700] | 25 | 318 | 34 | |
| S32750 | 2507 | 116 [800] | 80 [550] | 15 | 300 | 32 |
| S32760 B | 109 [750] | 80 [550] | 25 | 300 | . . . | |
| S32808 | 116 [800] | 80 [550] | 15 | 310 | 32 | |
| S32900 | 329 | 90 [620] | 70 [485] | 20 | 271 | 28 |
| S32906 | ||||||
|
Wall below
0.40 in.
[10 mm]
|
116 [800] | 94 [650] | 25 | 300 | 32 | |
|
Wall 0.40 in.
[10 mm]
and above
|
109 [750] | 80 [550] | 25 | 300 | 32 | |
| S32950 | 100 [690] | 70 [480] | 20 | 300 | 30 | |
| S33207 | ||||||
|
Wall below
0.157 in. (4 mm)
|
138 [950] | 112 [770] | 15 | 336 | 36 | |
|
Wall 0.157 in.
(4 mm) and above
|
138 [950] | 101 [700] | 15 | 336 | 36 | |
| S39274 | 116 [800] | 80 [550] | 15 | 310 | 32 | |
| S39277 | 120 [825] | 90 [620] | 25 | 290 | 30 | |
A Common name, not a trademark, widely used, not associated with any one producer. 329 is na AISI number.
B Prior to A 790/A 790M – 04, the tensile strength value for UNS 32760 was 109–130 ksi [750–895 MPa].
11. Lengths
11.1 Pipe lengths shall be in accordance with the following regular practice:
11.1.1 Unless otherwise agreed upon, all sizes from NPS 1 ⁄ 8 to and including NPS 8 are available in a length up to 24 ft (see Note 3) with the permissible range of 15 to 24 ft (see Note 3). Short lengths are acceptable and the number and minimum length shall be agreed upon between the manufacturer and the purchaser.
NOTE 3—This value applies when the inch-pound designation of this specification is the basis of purchase. When the M designation of this specification is the basis of purchase, the corresponding metric value(s) shall be agreed upon between the manufacturer and purchaser.
11.1.2 If definite cut lengths are desired, the lengths required shall be specified in the order. No pipe shall be less than the specified length and no more than 1 ⁄ 4 in. [6 mm] over it.
11.1.3 No jointers are permitted unless otherwise specified.
12. Workmanship, Finish, and Appearance
12.1 The finished pipes shall be reasonably straight and shall have a workmanlike finish. Imperfections may be removed by grinding, provided the wall thicknesses are not decreased to less than that permitted, in the Permissible Variations in Wall Thickness Section of Specification A 999/A 999M.
13. Mechanical Tests Required
13.1 Transverse or Longitudinal Tension Test—One tension test shall be made on a specimen for lots of not more than 100 pipes. Tension tests shall be made on specimens from 2 pipes for lots of more than 100 pipes.
13.2 Mechanical Testing Lot Definition —The term lot for mechanical tests applies to all pipe of the same nominal size and wall thickness (or schedule) that is produced from the same heat of steel and subjected to the same finishing treatment as defined as follows:
13.2.1 Where the heat treated condition is obtained, consistent with the requirements of 6.3, in a continuous heat treatment furnace or by directly obtaining the heat treated condition by quenching after hot forming, the lot shall include all pipe of the same size and heat, heat treated in the same furnace at the same temperature, time at heat, and furnace speed or all pipe of the same size and heat, hot formed and quenched in the same production run.
13.2.2 Where final heat treatment is obtained, consistent with the requirements of 6.3, in a batch-type heat-treatment furnace equipped with recording pyrometers and automatically controlled within a 50 °F [30 °C] or smaller range, the lot shall be the larger of (a) each 200 ft [60 m] or fraction thereof or (b) that pipe heat treated in the same batch furnace charge.
13.2.3 Where the final heat treatment is obtained, consistent with the requirements of 6.3, in a batch-type heat-treatment furnace not equipped with recording pyrometers and automatically controlled within a 50 °F [30 °C] or smaller range, the term lot for mechanical tests applies to the pipe heat treated in the same batch furnace charge, provided that such pipe is of the same nominal size and wall thickness (or schedule) and is produced from the same heat of steel.
13.3 Flattening Test—For pipe heat treated in a batch-type furnace, flattening tests shall be made on 5 % of the pipe from each heat-treated lot. For pipe heat treated by the continuous process, or by direct quenching after hot forming, this test shall be made on a sufficient number of pipes to constitute 5 % of the lot, but in no case less than two lengths of pipe.
13.3.1 For welded pipe with a diameter equal to or exceeding NPS 10, a transverse guided face bend test of the weld may be conducted instead of a flattening test in accordance with the method outlined in the steel tubular product supplement of Test Methods and Definitions A 370. The ductility of the weld shall be considered acceptable when there is no evidence of cracks in the weld or between the weld and the base metal after bending. Test specimens from 5 % of the lot shall be taken from the pipes or test plates of the same material as the pipe,the test plates being attached to the end of the cylinder and welded as a prolongation of the pipe longitudinal seam.
14. Hydrostatic or Nondestructive Electric Test
14.1 Each pipe shall be subjected to the nondestructive electric test or the hydrostatic test. The type of test to be used shall be at the option of the manufacturer, unless otherwise specified in the purchase order.
14.2 The hydrostatic test shall be in accordance with Specification A 999/A 999M, except that the value for S to be used in the calculation of the hydrostatic test pressure shall be equal to 50 % of the specified minimum yield strength of the pipe.
14.3 Nondestructive Electric Test:
Nondestructive electric tests shall be in accordance with Practices E 213 or E 309.
14.3.1 As an alternative to the hydrostatic test, and when specified by the purchaser, each pipe shall be examined with a nondestructive test in accordance with Practices E 213 or E 309. Unless specifically called out by the purchaser, the selection of the nondestructive electric test will be at the option of the manufacturer. The range of pipe sizes that may be examined by each method shall be subject to the limitations in the scope of the respective practices.
14.3.1.1 The following information is for the benefit of the user of this specification:
14.3.1.2 The reference standards defined in 14.3.1.3-14.3.1.5 are convenient standards for calibration of nondestructive testing equipment. The dimensions of these standards should not be construed as the minimum size imperfection detectable by such equipment.
14.3.1.3 The ultrasonic testing (UT) can be performed to detect both longitudinally and circumferentially oriented defects. It should be recognized that different techniques should be employed to detect differently oriented imperfections. The examination may not detect short, deep, defects.
14.3.1.4 The eddy-current testing (ET) referenced in this specification (see Practice E 426) has the capability of detecting significant discontinuities, especially the short abrupt type.
14.3.1.5 A purchaser interested in ascertaining the nature(type, size, location, and orientation) of discontinuities that can be detected in the specific application of these examinations should discuss this with the manufacturer of the tubular product.
14.4 Time of Examination—Nondestructive testing for specification acceptance shall be performed after all mechanical processing, heat treatments, and straightening operations.This requirement does not preclude additional testing at earlier stages in the processing.
14.5 Surface Condition:
14.5.1 All surfaces shall be free of scale, dirt, grease, paint,or other foreign material that could interfere with interpretation of test results. The methods used for cleaning and preparing the surfaces for examination shall not be detrimental to the base metal or the surface finish.
14.5.2 Excessive surface roughness or deep scratches can produce signals that interfere with the test.
14.6 Extent of Examination:
14.6.1 The relative motion of the pipe and the transducer(s),coil(s), or sensor(s) shall be such that the entire pipe surface is scanned, except as in 14.6.2.
14.6.2 The existence of end effects is recognized and the extent of such effects shall be determined by the manufacturer and, if requested, shall be reported to the purchaser. Other nondestructive tests may be applied to the end areas, subject to agreement between the purchaser and the manufacturer.
14.7 Operator Qualifications—The test unit operator shall be certified in accordance with SNT-TC-1A, or an equivalent recognized and documented standard.
14.8 Test Conditions:
14.8.1 For eddy-current testing, the excitation coil frequency shall be chosen to ensure adequate penetration yet provide good signal-to-noise ratio.
14.8.2 The maximum eddy-current coil frequency used shall be as follows:
On specified walls up to 0.050 in.—100 KHz max
On specified walls up to 0.150 in.—50 KHz max
On specified walls over 0.150 in.—10 KHz max
14.8.3 Ultrasonic—For examination by the ultrasonic method, the minimum nominal transducer frequency shall be 2.00 MHz and the maximum nominal transducer size shall be 1.5 in. If the equipment contains a reject notice filter setting, this shall remain off during calibration and testing unless linearity can be demonstrated at that setting.
14.9 Reference Standards—Reference standards of convenient length shall be prepared from a length of pipe of the same grade, size (NPS, or outside diameter and schedule or wall thickness), surface finish and heat treatment condition as the pipe to be examined.
14.9.1 For Ultrasonic Testing, the reference ID and OD notches shall be any one of the three common notch shapes shown in Practice E 213, at the option of the manufacturer. The depth of each notch shall not exceed 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in., whichever is greater. The width of the notch shall not exceed twice the depth. Notches shall be placed on both the OD and ID surfaces.
14.9.2 For Eddy-Current Testing, the reference standard shall contain, at the option of the manufacturer, any one of the following discontinuities:
14.9.2.1 Drilled Hole— The reference standard shall contain three or more holes equally spaced circumferentially around the pipe and longitudinally separated by a sufficient distance to allow distinct identification of the signal from each hole. The holes shall be drilled radially and completely through the pipe wall, with care being taken to avoid distortion of the pipe while drilling. One hole shall be drilled in the weld, if visible.Alternately, the producer of welded pipe may choose to drill one hole in the weld and run the calibration standard through the test coils three times with the weld turned at 120° on each pass. The hole diameter shall vary with NPS as follows:
| NPS Designator | Hole Diameter |
| 0.039 in. [1 mm] | |
|
above 1 ⁄ 2 to 1 1 ⁄ 4
|
0.055 in. [1.4 mm] |
| above 1 1 ⁄ 4 to 2 | 0.071 in. [1.8 mm] |
| above 2 to 5 | 0.087 in. [2.2 mm] |
| above 5 | 0.106 in. [2.7 mm] |
14.9.2.2 Transverse Tangential Notch—Using a round tool or file with a 1 ⁄ 4 -in. [6.4-mm] diameter, a notch shall be filed or milled tangential to the surface and transverse to the longitudinal axis of the pipe. Said notch shall have a depth not
exceeding 12 1 ⁄ 2 % of the specified nominal wall thickness of the pipe or 0.004 in. [0.102 mm], whichever is greater.
14.9.2.3 Longitudinal Notch—A notch 0.031 in. or less in width shall be machined in a radial plane parallel to the tube axis on the outside surface of the pipe to have a depth not exceeding 12 1 ⁄ 2 % of the specified wall thickness of the pipe or 0.004 in., whichever is greater. The length of the notch shall be compatible with the testing method. More or smaller reference discontinuities, or both, may be used by agreement between the purchaser and the manufacturer.
14.10 Standardization Procedure:
14.10.1 The test apparatus shall be standardized at the beginning and end of each series of pipes of the same size (NPS or diameter and schedule or wall thickness, grade, and heat treatment condition), and at intervals not exceeding 4 h. More frequent standardization may be performed at the manufacturer’s option or may be required upon agreement between the purchaser and the manufacturer.
14.10.2 The test apparatus shall also be standardized after any change in test system settings, change of operator, equipment repair, or interruption due to power loss, process shutdown, or when a problem is suspected.
14.10.3 The reference standard shall be passed through the test apparatus at the same speed and test system settings as the pipe to be tested.
14.10.4 The signal-to-noise ratio for the reference standard
shall be 2 1 ⁄ 2 to 1 or greater. Extraneous signals caused by identifiable causes such as dings, scratches, dents,straightener
marks, and so forth shall not be considered noise. The rejection amplitude shall be adjusted to be at least 50 % of full scale of the readout display.
14.10.5 If upon any standardization, the rejection amplitude has decreased by 29 % (3 dB) of peak height from the last standardization, the pipe since the last calibration shall be rejected. The test system settings may be changed or the transducer(s), coil(s), or sensor(s) adjusted and the unit restandardized. But all pipe tested since the last acceptable standardization must be retested for acceptance.
14.11 Evaluation of Imperfections:
14.11.1 Pipes producing a signal equal to or greater than the lowest signal produced by the reference standard(s) shall be identified and separated from the acceptable pipes. The area producing the signal may be reexamined.
14.11.2 Such pipes shall be rejected if the test signal was produced by imperfections that cannot be identified or was produced by cracks or crack-like imperfections. These pipes may be repaired per Sections 12 and 13. To be accepted, a repaired pipe must pass the same non-destructive test by which it was rejected, and it must meet the minimum wall thickness requirements of this specification.
14.11.3 If the test signals were produced by visual imperfections such as: (1) scratches, (2) surface roughness, (3) dings,(4) straightener marks, (5) cutting chips, (6) steel die stamps,(7) stop marks, or (8) pipe reducer ripple. The pipe may be accepted based on visual examination, provided the imperfection is less than 0.004 in. [0.1 mm] or 12 1 ⁄ 2 % of the specified wall thickness (whichever is greater).
14.11.4 Rejected pipe may be reconditioned and retested providing the wall thickness is not decreased to less than that required by this or the product specification. The outside diameter at the point of grinding may be reduced by the amount so removed. To be accepted, retested pipe shall meet the test requirement.
14.11.5 If the imperfection is explored to the extent that it can be identified as non-rejectable, the pipe may be accepted without further test providing the imperfection does not encroach on the minimum wall thickness.
15. Repair by Welding
15.1 For welded pipe of size NPS 6 or larger with a specified wall thickness of 0.188 in. [4.8 mm] or more, weld repairs made with the addition of compatible filler metal may be made to the weld seam with the same procedures specified for plate defects in the section on Repair by Welding of Specification A 999/A 999M.
15.2 Weld repairs of the weld seam shall not exceed 20 % of the seam length.
15.3 Except as allowed by 15.3.1, weld repairs shall be made only with the gas tungsten-arc welding process using the same classification of bare filter rod qualified to the most current AWS Specification A5.9 as the grade of pipe being repaired as given in Table 4.
15.3.1 Subject to approval by the purchaser, it shall be permissible for weld repairs to be made with the gas tungstenarc welding process using a filler metal more highly alloyed than the base metal, if needed for corrosion resistance or other properties.
15.4 Pipes that have had weld seam repairs with filler metal shall be identified with the symbol “WR” and shall be so stated and identified on the certificate of tests. If filler metal other than that listed in Table 4 is used, the filler metal shall be identified on the certificate of tests.
15.5 Weld repairs shall be completed prior to any heat treatment.
TABLE 4 Pipe and Filler Metal Specification
| Pipe | Filler Metal | |
| UNS Designation | AWS A5.9 Class | UNS Designation |
| S31803 | ER2209 | S39209 |
| S32205 | ER2209 | S39209 |
| S31200 | ER2553 | S39553 |
16. Product Marking
16.1 In addition to the marking prescribed in Specification A 999/A 999M, the marking shall include the manufacturer’s private identifying mark and whether the pipe is seamless or welded. If specified in the purchase order, the marking for pipe larger than NPS 4 shall include the weight.
17. Keywords
17.1 duplex stainless steel; ferritic/austenitic stainless steel; seamless steel pipe; stainless steel pipe; steel pipe; welded steel pipe