ASME B16.21 pdf download Nonmetallic Flat Gaskets for Pipe Flanges
1 SCOPE This Standard covers types, sizes, materials, dimen- sions, tolerances, and markings for nonmetallic flat gas- kets. These gaskets are dimensionally suitable for use with flanges described in the referenced flange standards.
2.1 Relevant Units This Standard states values both in SI (metric) and U.S. Customary units. As an exception, diameter ofbolts and flange bolt holes are expressed in inch units only. These systems of units are to be regarded separately as standard. Within the text, the U.S. Customary units are shown in parentheses or in separate tables. The values statedineachsystemarenotexactequivalents;therefore, it is required that each system of units be used indepen- dently of the other. Except for diameter of bolts and flange bolt holes, combining values from the two sys- tems constitutes nonconformance with the Standard.
2.2 Quality Systems Requirements relating to the product manufacturers’ quality system programs are described in Nonmandatory Appendix A.
2.3 References Standards and specifications adopted by reference in this Standard are shown in Mandatory Appendix II.
2.4 Flanged Joints A flanged joint is composed of separate and indepen- dent, although interrelated, components: the flanges, gasket, and bolting, which are assembled by another influence, the assembler. Proper controls must be exer- cised in the selection and application for all these ele- ments to attain a joint that has acceptable leak tightness. Additional guidelines for flange assembly can be found in ASME PCC-1 (see Nonmandatory Appendix B).
2.5 Types Dimensions are provided for the following types of gaskets, which are suitable for use with the flange faces indicated:
2.6 Size NPS, followed by a dimensionless number, is the des- ignation for nominal pipe size, as described in ASME B36.10M and is related to the reference nominal diameter, DN, used in international standards. The rela- tionship is as follows:
GENERAL NOTE: For NPS ≥ 4, the related DN p 25 NPS
2.7 Pressure Class Designation Class, followed by a dimensionless number, is the designation for common flange pressure-temperature ratings as given by the referenced flange standards.
3.1 Composition Gaskets shall be made of resilient or pliable materials. Metal or nonmetal composites may be incorporated as reinforcement or filler material.
3.2 Service Requirements Selection of a material suitable for a given service application is the responsibility of the user subject to the requirements of any applicable code or government regulation. The material selected shall be compatible with the fluid and suitable for the pressure-temperature conditions of the service.
4 DIMENSIONS AND TOLERANCES
4.1 Dimensions Gasket dimensions shall be in accordance with Tables 1 through 9 (Tables I-1 through I-9 of Mandatory Appendix I) for the flanges’ standards, sizes, and classes indicated. Selection of gasket thickness is the responsi- bility ofthe user, considering the properties ofthe gasket material as well as the intended service application.
(a) Outside diameter for
(1) NPS 12 and smaller:
+0.0, −1.5 mm (+0.0, −0.06 in.)
(2) NPS 14 and larger:
+0.0, −3.0 mm (+0.0, −0.12 in.)
(b) Inside diameter for
(1) NPS 12 and smaller, ±1.5 mm (±0.06 in.)
(2) NPS 14 and larger, ±3.0 mm (±0.12 in.)
(3) bolt circle diameter, ±1.5 mm (±0.06 in.)
(4) center to center of adjacent bolt holes, ±1.0 mm (±0.03 in.)
5.1 Material Marking
Unless otherwise specified by the purchaser, gasket material shall be marked with the material manufacturer’s name or trademark and material designation.
5.2 Gasket Marking
Gaskets shall be packaged with NPS, class, gasket manufacturer’s name, material designation, thickness,and ASME B16.21 marked or tagged on the package or gasket. At the option of the manufacturer, the DN designation may be included.