ASTM A688/A688M-00
(Specification)Standard Specification for Welded Austenitic Stainless Steel Feedwater Heater Tubes
Standard Specification for Welded Austenitic Stainless Steel Feedwater Heater Tubes
SCOPE
1.1 This specification covers welded austenitic stainless steel feedwater heater tubes including those bent, if specified, into the form of U-tubes for application in tubular feed-water heaters.
1.2 The tubing sizes covered shall be 5/8 to 1 in. [15.9 to 25.4 mm] inclusive outside diameter, and average or minimum wall thicknesses of 0.028 in. [0.7 mm] and heavier.
1.3 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 shall be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.
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Designation: A 688/A 688M – 00 An American National Standard
Standard Specification for
Welded Austenitic Stainless Steel Feedwater Heater Tubes
This standard is issued under the fixed designation A 688/A 688M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope the following as required to adequately describe the desired
material:
1.1 This specification covers welded austenitic stainless
4.1.1 Quantity (length or number of pieces),
steel feedwater heater tubes including those bent, if specified,
4.1.2 Material description,
into the form of U-tubes for application in tubular feed-water
4.1.3 Dimensions—Outside diameter, wall thickness (mini-
heaters.
5 mum or average wall), and length,
1.2 The tubing sizes covered shall be ⁄8 to 1 in. [15.9 to
4.1.4 Grade (chemical composition) (Table 1),
25.4 mm] inclusive outside diameter, and average or minimum
4.1.5 U-bend requirements, if order specifies bending,
wall thicknesses of 0.028 in. [0.7 mm] and heavier.
U-bend schedules or drawings shall accompany the order,
1.3 The values stated in either inch-pound units or SI units
4.1.6 Optional requirements—Purchaser shall specify if an-
are to be regarded separately as standard. Within the text, the
nealing of the U-bends is required or whether tubes are to be
SI units are shown in brackets. The values stated in each
hydrotested or air tested (see 11.6)
system are not exact equivalents; therefore, each system shall
4.1.7 Supplementary requirements—Purchaser shall
be used independently of the other. Combining values from the
specify on the purchase order if material is to be eddy current
two systems may result in nonconformance with the specifi-
tested in accordance with Supplementary Requirements S1 or
cation.
S2, and if special test reports are required under Supplementary
2. Referenced Documents
Requirement S3.
2.1 ASTM Standards:
5. General Requirements
A 262 Practices for Detecting Susceptibility to Intergranu-
5.1 Material furnished to this specification shall conform to
lar Attack in Austenitic Stainless Steels
the applicable requirements of the latest published edition of
A 370 Test Methods and Definitions for Mechanical Testing
Specification A 450/A 450M unless otherwise provided herein.
of Steel Products
A 450/A 450M Specification for General Requirements for
6. Materials and Manufacture
Carbon, Ferritic Alloy, and Austenitic Alloy Steel Tubes
6.1 The tube shall be made from flat-rolled steel by an
A 480/A 480M Specification for General Requirements for
automatic welding process with no addition of filler metal.
Flat-Rolled Stainless and Heat-Resisting Steel Plate,
6.2 Subsequent to welding and prior to final heat treatment,
Sheet, and Strip
the tubes shall be cold worked either in both the weld and base
A 941 Terminology Relating to Steel, Stainless Steel, Re-
metal, or in the weld metal only. The method of cold work may
lated Alloys, and Ferroalloys
4 be specified by the purchaser. When cold drawn, the purchaser
E 527 Practice for Numbering Metals and Alloys (UNS)
may specify the minimum amount of reduction in cross-
3. Terminology sectional area or wall thickness, or both.
6.3 Many surface contaminants may have detrimental ef-
3.1 Definitions Of Terms—For definitions of terms used in
fects on high temperature properties or corrosion resistance of
this specification, refer to terminology A 941.
tubing. Contamination by copper, lead, mercury, zinc, chlo-
4. Ordering Information
rides, or sulfur may be detrimental to stainless steels. The
manufacturer shall employ techniques that minimize surface
4.1 Orders for material to this specification should include
contamination by these elements.
7. Cleaning Before Annealing
This specification is under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel, and Related Alloys and is the direct responsibility of Subcommittee
7.1 All lubricants of coatings used in the manufacture of
A01.10 on Steel Tubing.
straight-length tube or in the bending shall be removed from all
Current edition approved March 10, 2000. Published June 2000. Originally
published as A 688 – 73. Last previous edition A 688M – 98.
surfaces prior to any annealing treatments. U-bends on which
For ASME Boiler and Pressure Vessel Code applications see related Specifi-
a lubricant had been applied to the inside surface during
cation SA-688 in Section II of that Code.
bending shall have the cleanness of their inside surface
Annual Book of ASTM Standards, Vol 01.03.
Annual Book of ASTM Standards, Vol 01.01. confirmed by blowing close fitting acetone-soaked felt plugs
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A 688/A 688M
TABLE 1 Chemical Requirements
Grade. TP 304 TP 304L TP 304LN TP 316 TP 316L TP 316LN TP XM-29 TP 304N TP 316N . . . . . . . . . . . .
UNS S30400 S30403 S30453 S31600 S31603 S31653 S24000 S30451 S31651 N08367 N08926 S31254 S32654
Element
A
Designation .
Composition, %
Carbon, max 0.08 0.035 0.035 0.08 0.035 0.035 0.060 0.08 0.08 0.030 0.020 0.020 0.020
B
Manganese, max 2.00 2.00 2.00 2.00 2.00 2.00 11.50– 2.00 2.00 2.00 2.00 1.00 2.0–4.0
14.50
Phosphorus, max 0.040 0.040 0.040 0.040 0.040 0.040 0.060 0.040 0.040 0.040 0.03 0.030 0.030
Sulfur, max 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.030 0.01 0.010 0.005
Silicon, max 0.75 0.75 0.75 0.75 0.75 0.75 1.00 0.75 0.75 1.00 0.5 0.80 0.50
Nickel 8.00– 8.00– 8.00– 10.00– 10.00– 10.00– 2.25– 8.00– 10.00– 23.50– 24.00– 17.5– 21.0–
11.00 13.00 13.00 14.00 15.00 15.00 3.75 11.0 14.00 25.50 26.00 18.5 23.0
Chromium 18.00– 18.00– 18.00– 16.00– 16.00– 16.00– 17.00– 18.0– 16.0– 20.00– 19.00– 19.5– 24.0–
20.00 20.00 20.00 18.00 18.00 18.00 19.00 20.0 18.0 22.00 21.00 20.5 25.0
Molybdenum . . . 2.00– 2.00– 2.00– . . 2.00– 6.00– 6.0– 6.0– 7.0–
3.00 3.00 3.00 3.00 7.00 7.0 6.5 8.0
C
Nitrogen . . 0.10– . . 0.10– 0.20– 0.10– 0.10– 0.18– 0.15– 0.18– 0.45–
0.16 0.16 0.40 0.16 0.16 0.25 0.25 0.22 0.55
Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75 max 0.5–1.5 0.50–1.00 0.30–0.60
A
New designation established in accordance with Practice E 527 and SAE J1086, Practice for Numbering Metals and Alloys (UNS).
B
Maximum, unless otherwise noted.
C
The method of analysis for nitrogen shall be a matter of agreement between the purchaser and manufacturer.
through 10 % of the tubes of each bend radius. Dry, oil-free, air 8.3.4 The inside of the tube shall be purged with a protective
or inert gas shall be used to blow the plugs through the tubes. or an inert gas atmosphere during heating and cooling to below
If the plugs blown through any tube shows more than a light 700°F [370°C] to prevent scaling of the inside surface. The
gray discoloration, all tubes that have had a lubricant applied to atmosphere should be noncarburizing.
the inside surface during bending shall be recleaned. After
9. Surface Condition
recleaning 10 % of the tubes of each bend radius whose inside
surface had been subjected to bending lubricants shall be
9.1 The straight tubes, after final annealing, shall be pickled
retested.
using a solution of nitric and hydrofluoric acids followed by
flushing and rinsing in water. If bright annealing is performed,
8. Heat Treatment
this requirement does not apply.
8.1 All finished straight tubing or straight tubing ready for
9.2 A light oxide scale on the outside surface of U-bend area
U-bending shall be furnished in the solution-annealed condi-
shall be permitted for tubes which have been electric-resistance
tion. The annealing procedure, except for N08367 and N08926,
heat treated after bending.
shall consist of heating the material to a minimum temperature
of 1900°F [1040°C] followed by a rapid cooling to below
10. Chemical Composition
700°F [370°C]. The cooling rate shall be sufficiently rapid to
10.1 Product Analysis:
prevent harmful carbide precipitation as determined in Section
10.1.1 When requested in the purchase order, a product
13. UNS N08367 should be solution annealed from 2025°F
analysis shall be made by the supplier from one tube or coil of
[1107°C] minimum followed by rapid quenching.
steel per heat. The chemical composition shall conform to the
8.2 N08926 shall be heat-treated to a minimum temperature
requirements shown in Table 1.
of 2010°F [1100°C] followed by quenching in water or rapidly
10.1.2 A product analysis tolerance of Specification A 480/
cooling by other means.
A 480M shall apply. The product analysis tolerance is not
8.3 If heat treatment of U-bends is specified, it shall satisfy
applicable to the carbon content for material with a specified
the annealing procedure described in 8.1 and 8.2, and shall be
maximum carbon of 0.04 % or less.
done as follows:
10.1.3 If the original test for product analysis fails, retests of
8.3.1 The heat treatment shall be applied to the U-bend area
two additional lengths of flat-rolled stock or tubes shall be
plus approximately 6 in. [150 mm] of each leg beyond the
made. Both retests, for the elements in question, shall meet the
tangent point of the U-bend.
requirements of this specification; otherwise all remaining
8.3.2 If the heat treatment specified in 8.3 is accomplished
material in the heat or lot (Note 1) shall be rejected, or at the
by resistance-heating methods wherein electrodes are clamped
option of the producer, each length of flat-rolled stock or tube
to the tubes, the clamped areas shall be visually examined for
may be individually tested for acceptance. Lengths of flat-
arc burns. Burn indications shall be cause for rejection unless
rolled stock or tubes that do not meet the requirements of this
they can be removed by local polishing without encroaching
specification shall be rejected.
upon minimum wall thickness.
8.3.3 Temperature control shall be accomplished through
NOTE 1—For flattening and flange requirements, the term “lot” applies
the use of optical or emission pyrometers, or both. No
to 125 tube groupings, prior to cutting to length, of the same nominal size
temperature-indicating crayons, lacquers, or pellets shall be
and wall thickness, produced from the same heat of steel and annealed in
used. a continuous furnace.
A 688/A 688M
11. Mechanical Requirements tested in accordance with one of the following paragraphs as
specified by the purchaser.
11.1 Tensile Properties:
11.6.1.1 Hydrostatic Test—Each tube shall be given an
11.1.1 The material shall conform to the tensile properties
internal hydrostatic test in accordance with Specification
shown in Table 2.
A 450/A 450M, except that the test pressure and hold time,
11.1.2 One tension test shall be made on a specimen for lots
when other than that stated in Specification A 450/A 450M,
of not more than 50 tubes. Tension tests shall be made on
shall be agreed upon between purchaser and manufacturer.
specimens from two tubes for lots of more than 50 tubes (Note
11.6.1.2 Air Underwater Test—Each tube shall be air un-
2).
derwater tested in accordance with Specification A 450/
11.2 Hardness:
A 450M.
11.2.1 Grade TP XM-29 tubes shall have a hardness number
not exceeding 100 HRB or its equivalent. Tubes of all other
12. Nondestructive Test (Electric Test)
grades shall have a hardness number not exceeding 90 HRB or
its equivalent. This hardness requirement is not to apply to the 12.1 Each straight tube shall be tested after the finish heat
treatment by passing it through a nondestructive tester capable
bend area of U-bend tubes which are not heat treated after
bending. of detecting defects on the entire cross section of the tube, in
accordance with Specification A 450/A 450M.
11.2.2 Brinell or Rockwell hardness tests shall be made on
specimens from two tubes from each lot.
13. Corrosion Resisting Properties
NOTE 2—For tension, hardness, and corrosion test requirements, the
13.1 One full section sample 1 in. [25.4 mm] long from the
term “lot” applies to all tubes prior to cutting to length, of the same
nominal diameter and wall thickness, produced from the same heat of steel
center of a sample tube of the smallest radius bend which is
and annealed in a continuous furnace at the same temperature, time at
heat treated shall be tested in the heat treated condition in
heat, and furnace speed.
accordance with Practices A 262.
13.2 One full-section sample 1 in. [25.4 mm] long from
11.3 Reverse Bend Test:
11.3.1 One reverse bend test shall be made on a specimen each lot (Note 2) of straight tubes shall be tested in the finished
condition in accordance with Practices A 262.
from each 1500 ft [460 m] of finished tubing.
11.3.2 A section 4 in. [100 mm] in length shall be split 13.3 The appearance of any fissures or cracks in the test
specimen when evaluated in accordance with Practices A 262
longitudinally 90° on each side of the weld. The sample shall
then be opened and bent around a mandrel with a diameter four indicating the presence of intergranular attack, shall be cause
times the wall thickness, with the mandrel parallel to the weld for rejection of that lot.
and in contact with the outside surface of the tube. The weld
shall be at the point of maximum bend. There shall be no 14. Permissible Variations in Dimensions (Fig. 1)
evidence of cracks or lack of penetration in the weld or of
14.1 Permissible variations from the specified outside diam-
overlaps resulting from flash removal of the weld.
eter shall be in accordance with Specification A 450/A 450M.
Those tolerances do not apply to the bent portion of the
NOTE 3—The reverse bend test is not applicable when specified wall is
U-tubes. At the bent portion of a U-tube for R 5 2 3 D or
10 % or more of the specified outside diameter, or the wall thickness is
0.134 in. [3.4 mm] or greater, or the outside diameter size is less than greater, neither the major nor minor diameter of the tube shall
0.375 in. [9.5 mm]. Under these conditions, the reverse flattening test of
deviate from the nominal diameter prior to bending by more
Specification A 450/A 450M shall apply.
than 10 %. If less than 2 3 D is specified, tolerances could be
11.4 Flattening Test—Flattening tests shall be made on greater.
specimens from each end of one finished tube, not the one used 14.2 Permissible Variations from the Specified Wall Thick-
for the flange test, from each lot (Note 1). ness:
11.5 Flange Test—Flange tests shall be made on specimens 14.2.1 Permissible variations from the specified minimum
from each end of one finished tube, not the one used for the wall thickness shall not exceed +20 % − 0.
flattening te
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