Designation: D 5421 – 00

Standard Specification for

Contact Molded “Fiberglass” (Glass-Fiber-Reinforced
Thermosetting Resin) Flanges1
This standard is issued under the fixed designation D 5421; 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
1.1 This specification covers circular contact-molded fiber-
glass reinforced-thermosetting-resin flanges for use in pipe
systems and tank nozzles. Included are requirements for
materials, workmanship, performance, and dimensions.
1.2 Flanges (see Fig. 1) may be produced as integral flanges,
Type A, or flange-on-pipe, Type B.
1.3 This specification is based on flange performance and
does not cover design.
1.4 These flanges are designed for use with pipe and tanks
that are manufactured to Specifications D 2996, D 2997,
D 3262, D 3299, D 3517, D 3754, D 3982, and D 4097. FIG. 1 Flange Types
1.5 Selection of gaskets is not covered in this specification,
refer to the manufacturer’s recommendation. D 2996 Specification for Filament Wound “Fiberglass”
NOTE 1—ISO Equivalent—There is no similar or equivalent ISO (Glass-Fiber-Reinforced Thermosetting Resin Pipe)2
standard. D 2997 Specification for Centrifugally Cast “Fiberglass”
1.6 The values stated in inch-pound units are to be regarded (Glass-Fiber-Reinforced Thermosetting Resin Pipe)2
as the standard. The SI units given in parentheses are for D 3262 Specification for Reinforced Plastic Mortar Sewer
information only. Pipe2
1.7 The following precautionary caveat pertains only to the D 3299 Specification for Filament Wound Glass-Fiber-
test methods portion, Section 9, of this specification: This Reinforced Thermoset Resin Chemical-Resistant Tanks2
standard does not purport to address the safety problems, if D 3517 Specification for “Fiberglass” (Glass-Fiber-
any, associated with its use. It is the responsibility of the user Reinforced Thermosetting Resin) Pressure Pipe2
of this standard to establish appropriate safety and health D 3754 Specification for Fiberglass Sewer and Industrial
practices and determine the applicability of regulatory limita- Pressure Pipe2
tions prior to use. D 3982 Specification for Custom Contact-PressureMolded-
Glass-Fiber-Reinforced Thermosetting Resin Hoods2
2. Referenced Documents D 4097 Specification for Contact Molded Glass-Fiber-
2.1 ASTM Standards: Reinforced Thermoset Resin Chemical Resistant Tanks2
C 582 Specification for Contact-Molded Reinforced Ther- F 412 Terminology Relating to Plastic Piping Systems2
mosetting Plastic (RTP) Laminates for Corrosion Resistant F 436 Specification for Hardened Steel Washers4
Equipment2 2.2 ANSI Standards:
D 883 Terminology Relating to Plastics3 B 16.1 Cast Iron Pipe Flanges and Flanged Fittings5
D 1599 Test Method for Short-Time Hydraulic Failure Pres- B 16.5 Pipe Flanges and Flanged Fittings5
sure of Plastic Pipe, Tubing, and Fittings2 B 27.2 Type “A” Narrow Washers5
D 1600 Terminology Relating to Abbreviated Terms Relat- 3. Terminology
ing to Plastics3
3.1 Definitions:
1 3.1.1 Definitions are in accordance with Terminology
This specification is under the jurisdiction of ASTM Committee D20 on
Plastics and is the direct responsibility of Subcommittee D20.23 on Reinforced D 883. Abbreviations are in accordance with Terminology
Plastic Piping Systems and Chemical Equipment.
Current edition approved Nov. 10, 2000. Published February 2001. Originally
4
published as D 5421 — 93. Last previous edition D 5421 — 93. Annual Book of ASTM Standards, Vol 15.08.
2 5
Annual Book of ASTM Standards, Vol 08.04. Available from American National Standards Institute, 11 West 42nd Street,
3
Annual Book of ASTM Standards, Vol 08.01. 13th Floor, NY, NY 10036.

Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.

1
COPYRIGHT ASTM International
Licensed by Information Handling Services
 D 5421
D 1600, unless otherwise indicated. The abbreviation for limits shall be categorized by single arabic number designa-
reinforced-thermosetting-resin pipe is RTRP. tions as indicated by the cell classification system of Table 2.
3.2 Definitions of Terms Specific to This Standard: Descrip- 4.2 Designation Code—The flange-designation code shall
tions of Terms Specific to This Standard: consist of the abbreviation for contact molded (CM) followed
3.2.1 contact molding (CM)—a method of fabrication by the type as a capital letter, grade as an Arabic numeral, class
wherein the glass fiber reinforcement is applied to the mold in as a Roman numeral, and the pressure-rating category as a
the form of all chopped-strand mat, or chopped-strand mat and capital letter and two Arabic numbers identifying the cell-
woven roving, in alternate plies by hand with the resin matrix classification designations of the short-term rupture pressure
applied by brush or roller and the laminate consolidated by a and sealing-test pressure, respectively. Thus, a complete
roller. flange-designation code shall consist of three letters, one
3.2.2 fiberglass pipe—a tubular product containing glass- Arabic numeral, one Roman numeral, one letter and two
fiber reinforcements embedded in or surrounded by cured numerals.
thermosetting resin; the composite structure may contain 4.2.1 Example—Contact molded fiberglass is CM-AlID-46.
aggregate, granular or platelet fillers, thixotropic agents, pig- This designation described a stub flange, made using glass-
ments or dyes; thermoplastic or thermosetting liners or coat- fiber-reinforced polyester resin for full-axial pressure thrust.
ings may be included. The flange has a 100-psi (0.69-MPa) pressure rating, a short-
term rupture pressure of 400-psi (2.1-MPa), and a sealing-test
4. Classification pressure of 225-psi (1.6-MPa).
4.1 General—This specification covers reinforced- 4.3 Attachment of Flanges to Pipe, Pipe Fittings, or Tanks:
thermosetting-resin flanges defined by type (method of manu- 4.3.1 Type “A” flanges are to be butt and strap welded to
facture), grade (generic type of resin), class (pressure end pipe described in Specifications D 2996, D 2997, D 3262,
thrust capability), and pressure rating. Flanges complying with D 3517, D 3754, and D 3982 or using overlay joint into a tank
this specification are also given numerical classifications relat- as described in Specifications D 3299 and D 4097.
ing to rupture pressure and sealing test pressure. 4.3.2 Type “B” flanges are built onto elbows, reducers, or
4.1.1 Types: other parts where the use of an integral flange (Type “A”) is not
4.1.1.1 Type A—Integral flange, contact molded with the practical or required.
stub integral with the flange.
4.1.1.2 Type B—Flange on pipe, contact molded onto an 5. Materials and Manufacture
existing pipe or fitting. 5.1 Flanges manufactured in accordance with this specifi-
4.1.2 Grades: cation shall be composed of reinforcement embedded in or
4.1.2.1 Grade 1—Epoxy resin. surrounded by cured thermosetting resin.
4.1.2.2 Grade 2—Polyester resin. 5.2 The resins, reinforcements, and other materials, when
4.1.2.3 Grade 3—Furan resin. combined into composite structure, shall produce a flange that
4.1.2.4 Grade 4—Vinylester resin. will meet the performance requirements of this specification.
4.1.2.5 Grade 5—Phenolic resin.
NOTE 3—The term “other materials” does not include recycled or
4.1.3 Classes: reprocessed thermosetting plastics which might otherwise be added as
4.1.3.1 Class I—Hoop and axial-pressure. fillers.
4.1.3.2 Class II—Hoop pressure only.
5.3 Flanges manufactured in accordance with this specifi-
NOTE 2—All combinations of type, liner, grade, and class may not be cation shall have an inner corrosion barrier fabricated with the
commercially available. Additional type, liner, grade, and class may be same resin, reinforcement, ply sequence, and nominal glass/
added as they become commercially available. The purchaser should resin ratio as required in the applicable ASTM standard for the
solely determine or consult with the manufacturer for the proper class,
type, liner, and grade to be used under the installation and operating
tank or pipe on which the flange will be used.
conditions that will exist for the project in which the flange is to be used.
6. Performance Requirements
4.1.4 Pressure Rating—Pressure rating shall be categorized 6.1 The following performance requirements are intended to
by single-letter designation. Pressure designations are shown in provide classification and performance criteria for the purpose
Table 1. of qualification testing and rating of prototype constructions
4.1.5 Short-term rupture pressure and sealing-test pressure and periodic reevaluation of the manufacturer’s stated ratings.
They are not intended as routine quality assurance require-
TABLE 1 Pressure Categories
ments for production runs of rated flanges:
Pressure RatingA
Designation
psi MPa TABLE 2 Short-Term Rupture Pressure and Sealing-Test
A 25 0.173 PressureA
B 50 0.345
Property/Cell Classification 1 2 3 4 5 6
C 75 0.517
D 100 0.690 Short-Term Rupture 100 200 300 400 500 600
E 125 0.862 Pressure, psi (MPa) (0.69) (1.38) (2.07) (2.76) (3.45) (4.14)
F 150 1.034 Sealing-test pressure, psi 37.5 75 112.5 150 187.5 225
A (MPa) (0.26) (0.52) (0.78) (1.03) (1.29) (1.55)
Flanges with higher pressure ratings are available by agreement between the
A
purchaser and the manufacturer. Refer to Test Method D 1599 for explanation of failure.

2
COPYRIGHT ASTM International
Licensed by Information Handling Services
 D 5421
6.1.1 Sealing—Flanges shall withstand a pressure of at least especially in high-pressure flanges. The use of ANSI B 27.2 narrow
1.5 times the pressure rating without leakage when tested in washers is suggested because of their smaller outside diameter. The
accordance with 9.4. customer should be notified when these washers with smaller outside
diameter are to be used.
6.1.2 Short-Term Rupture Strength—Flanges shall with- NOTE 5—For special-design large flanges, it may be desirable to
stand a hydrostatic load of at least four times their pressure provide the required bolt area by using smaller bolts spaced closer
rating when tested in accordance with 9.5 using flat-faced steel together than is normally used for steel flanges. The minimum bolt size
closure and using the gasket or “O” ring designated by the shall be 5⁄8 in. (16 mm).
flange manufacturer. 7.1.1 Flange Face for Full-Faced Gaskets— The flange
6.1.3 Bolt Torque—Flanges shall withstand, without visible face shall be perpendicular to the axis of the fitting within 1⁄2 °,
sign of damage, a bolt torque of two times that recommended and shall be flat to 1⁄32 in. (1 mm) for sizes up to and including
by the manufacturer. The use of a non-fluid thread lubricant is 18-in. (457-mm) diameter and 1⁄16 in. (2 mm) for larger
recommended on all bolts. diameters. For other sealing systems the tolerances must be
7. Dimensions and Tolerances established to meet the requirements of 6.1.1.
7.1.2 Washer-Bearing Surface—Washer-bearing surface
7.1 Flange and Bolt Dimensions—Flanges of 24 in. (610
shall be flat and parallel to the flange face within 1°.
mm) or smaller diameter shall conform to the values for bolt
7.1.3 Flange Outside Diameter—Outside diameter of
circle and number and size of bolt holes, for Class-150 cast
flanges is to be at least equal to that of ANSI B 16.5 for up to
iron flanges in ANSI B 16.5. Flanges larger than 24 in. (610
24-in. (610-mm) inside diameter and ANSI B 16.1 for larger
mm) in diameter shall conform to the values for bolt circle,
flanges. It is accepted practice to increase all flange outside
number and size of bolt holes, for Class-125 cast-iron flanges
diameters to provide greater strength at the bolt holes.
in ANSI B 16.1 as shown in Table 3. The tolerance for these
flange dimensions shall be the same as those contained in ANSI 8. Workmanship, Finish, and Appearance
B 16.1 and B 16.5. A flat washer is to be used under all bolt 8.1 Workmanship and appearance shall conform to Table 5
heads and nuts. on visual acceptance criteria of standard C 582 for the process
NOTE 4—Interference between the hub and bolt spot face may occur, side, and shall be as free as commercially practical of defects,
including indentations, delaminations, bubbles, pinholes, for-
TABLE 3 Flange Dimensions eign inclusions, and resin-starved areas in the structural layer
Nominal Outside Drilling and outer surface as agreed upon between the purchaser and the
Pipe Size, Diameter, Bolt Circle Number of Diameter of Diameter of manufacturer.
in.A min, in.A DiameterA Holes HolesA BoltsA
1 4 1⁄4 3 1⁄8 4 ⁄
58 ⁄
12 9. Test Methods
1 1⁄2 5 3 7⁄8 4 ⁄
58 ⁄
12
9.1 Conditioning—When conditioning is required, and in
2 6 43⁄4 4 3⁄4 5⁄8

2 1⁄2 7 5 1⁄2 4 3⁄4 5⁄8 all cases of disagreement, condition the test specimens at 73.4
3 7 1⁄2 6 4 3⁄4 5⁄8 6 3.6°F (23 6 2°C) for not less than 40 h prior to test, in
3 1⁄2 8 1⁄2 7 8 3⁄4 5⁄8
accordance with Procedure A of Test Methods D 618.
4 9 7 1⁄2 8 3⁄4 5⁄8

5 10 8 1⁄2 8 7⁄8 3⁄4 9.2 Test Conditions—The tests may be conducted at ambi-
6 11 9 1⁄2 8 7⁄8 3⁄4 ent temperature and humidity conditions. When controlled-
8 13 1⁄2 11 3⁄4 8 7⁄8 3⁄4
environment testing is specified, conduct test at 73.4 6 3.6°F
10 16 14 1⁄4 12 1 7⁄8

12 19 17 12 1 7⁄8 (23 6 2°C). When elevated-temperature testing is specified,

14 21 18 3⁄4 12 1 1⁄8 1 conduct the tests at the design operating temperature, with a
16 23 1⁄2 21 1⁄4 16 1 1⁄8 1 tolerance of 6 3.6°F (2°C).
18 25 22 3⁄4 16 1 1⁄4 1 1⁄8
20 27 1⁄2 25 20 1 1⁄4 1 1⁄8 9.3 Dimensions and Tolerances—Measure flange dimen-
24 32 29 1⁄2 20 1 3⁄8 1 1⁄4 sions with a micrometer, vernier calipers, or other suitable
26 34 1⁄4 31 3⁄4 24 1 3⁄8 1 1⁄4 measuring devices accurate to within 50 % of the required
28 36 1⁄2 34 28 1 3⁄8 1 1⁄4
30 38 3⁄4 36 28 1 3⁄8 1 1⁄4 tolerance. Determine diameters by averaging a minimum of
32 41 3⁄4 38 1⁄2 28 1 5⁄8 1 1⁄2 four measurements, equally spaced circumferentially.
34 43 3⁄4 40 1⁄2 32 1 5⁄8 1 1⁄2
9.4 Sealing—Bolt together flanged components in general
36 46 42 3⁄4 32 1 5⁄8 1 1⁄2
38 48 3⁄4 45 1⁄4 32 1 5⁄8 1 1⁄2 aagreement with Fig. 2 using the gasket and bolt torque
40 50 3⁄4 47 1⁄4 36 1 5⁄8 1 1⁄2 recommended for standard field installation by the flange
42 53 49 1⁄2 36 1 5⁄8 1 1⁄2
44 55 1⁄4 51 3⁄4 40 1 5⁄8 1 1⁄2
manufacturer. Then pressure test the assembly and require it to
46 57 1⁄4 53 3⁄4 40 1 5⁄8 1 1⁄2 hold the test pressure for a period of 168 h without leakage.
48 59 1⁄2 56 44 1 5⁄8 1 1⁄2 Retorquing to the manufacturer’s specified level after initial
50 61 3⁄4 58 1⁄4 44 1 7⁄8 1 3⁄4
52 64 60 1⁄2 44 1 7⁄8 1 3⁄4
pressurization is permitted.
54 66 1⁄4 62 3⁄4 44 1 7⁄8 1 3⁄4 9.5 Short-Term-Rupture Strength—Hydrostatically test
60 73 69 1⁄4 52 1 7⁄8 1 3⁄4 flanged components in accordance with Test Method D 1599
66 80 76 52 1 7⁄8 1 3⁄4
72 86 1⁄2 82 1⁄2 60 1 7⁄8 1 3⁄4
with free-end closure for Class I flanges and fixed-end closure
84 99 3⁄4 95 1⁄2 64 2 1⁄8 2 for Class II flanges except as herein noted. Increase the
96 113 1⁄4 108 1⁄2 68 2 3⁄8 2 1⁄4 pressure in the specimen until failure of the flange occurs.
A
1 in. = 25.4 mm. Pressure testing in an atmospheric environment is permissible.

3
COPYRIGHT ASTM International
Licensed by Information Handling Services
 D 5421
damage (crumbling, flaking, cracking, or other breaking) shall
constitute failure.
NOTE 6—The torque limits determined by 11.6 apply only to flanges
bolted up against a flat sealing surface. Significantly lower bolt-torque
values will normally be allowed when contact-molded flanges are bolted
up against other than flat sealing surfaces. When fiberglass flanges must be
used against other than flat sealing surfaces, the flange manufacturer
should be contacted for his torquing and installation recommendations.
10. Proof of Design
A—End, plate, end cap, or quick closure with coupling for pressure source/vent
line.\ 10.1 Test one each of 150-psi (1.03-MPa) flanges 8, 12, and
B—Reinforced thermosetting resin pipe (RTRP).\ 24 in. (203, 305, and 610 mm) as described in 6.1.2 and 9.5, to
C—Test flange set.\ establish that the design calculations meet the test requirements
D—End plate, end cap, or quick closure.
FIG. 2 Test-Assembly Configuration
and to establish rating data for the particular construction for
all sizes of 150 psi or lower pressure ratings. Any change in
calculation or construction will require retesting.
10.2 For individual orders conduct only those tests specifi-
Minimum-failure time shall be 60 s; no restriction shall be cally agreed upon between the purchaser and the manufacturer
placed on maximum time-to-failure. Leaking past the gasket prior to manufacture of flanges.
interface is permissible during this test. Bolt torque may be
increased as necessary during the test in order to minimize 11. Product Marking
gasket leaking and to achieve the pressure necessary to cause 11.1 Flanges for use or installation by other than the flange
flange failure. The assembly used for the test in 9.4 may be manufacturer shall be marked with the following information:
used for this test. Do not test with air pressure. 11.1.1 The designation “ASTM D 5421” with which the
flange complies,
9.6 Maximum Bolt Torque—Using the gasket and hardware
11.1.2 Identification of the flange in accordance with the
recommended by the flange manufacturer, bolt the flange
designation code in 4.2,
against a flat-face steel flange. Tighten the nuts by hand until
11.1.3 Nominal flange size, and
they are snug. Prior to fit-up, the nuts, bolts and washers should 11.1.4 Manufacturer’s name (or trademark) and product
be well lubricated, using a non-fluid thread lubricant. Establish designation.
uniform pressure over the flange face by tightening bolts in 11.2 Flanges for use and installation by the flange manufac-
10-lb·ft (14-N·m) increments according to the sequence shown turer shall be identified on the fabrication and assembly
in Fig. 3. For flanges with more than 20 bolts, similar drawings with the following information:
alternating bolt-tightening sequences shall be used. Increase 11.2.1 The designation “ASTM D 5421’’, and
the bolt torque uniformly until flange failure occurs, or until all 11.2.2 Pressure rating.
bolts have been torqued to 2 times the level recommended by
NOTE 7—Through a quality-assurance and surveillance program the
the manufacturer for field-installation practice to establish the manufacturer shall ensure that the flanges used are of the designated grade
bolt torque cell classification of the flange. Any sign of flange and pressure rating.
12. Precision and Bias
12.1 No precision and bias statement can be made for the
test methods outline in this standard since controlled round-
robin test programs have not been run. The wide variations in
raw materials and construction between manufacturers make
round-robin testing difficult to apply.
13. Keywords
13.1 butt weld; contact molded; flange on pipe; furan;
integral flange; polyester; vinylester

FIG. 3 Bolt Torquing Sequence

4
COPYRIGHT ASTM International
Licensed by Information Handling Services
 D 5421

SUMMARY OF CHANGES

Committee D20 has identified the location of the following changes to this standard since the last issue
(D 5421-95), which may impact the use of this standard.

1.) Changed punctuation in 1.2 for clarification. 6.) Changed wording in 9.4 for clarity.
2.) Removed reference to ASTM D 2563 in Section 2.1 7.) Added new Note 3.
because of a conflict with C 582. 8.) Changed old Notes 3, 4, 5, 6 to 4, 5, 6, 7.
3.) Added labels to Fig. 1 for clarity. 9.) Corrected long-standing error to bolt tightening sequence
4.) Removed reference to ASTM D 2563 from Section 8.1 on the 8 hole flange in Fig. 3.
5.) Changed wording of temperature tolerance allowance in 9.2 10.) Added Precision and Bias Statement as new Section 12.
for clarity. 11.) Added this “Summary of Changes” section.

The American Society for Testing and Materials takes no position respecting the validity of any patent rights asserted in connection
with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such
patent rights, and the risk of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and
if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards
and should be addressed to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible
technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should make your
views known to the ASTM Committee on Standards, at the address shown below.

This standard is copyrighted by ASTM, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above address or at
610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website (www.astm.org).

5
COPYRIGHT ASTM International
Licensed by Information Handling Services