Ring-Joint Gaskets and Grooves for Steel Pipe Flanges

Introductory Notes

1.  Scope
    1.1  This standard for ring-joint gaskets and grooves covers:
        a)  Types and sizes.
        b)  Material
        c)  Dimensions, tolerances, and finish
        d)  Identification numbers
        e)  Marking

2.  Types
    2.1  The types of gaskets provided for herein are octagonal and oval in cross section.
    2.2  The types of grooves provided for herein are flat bottom.

3.  Sizes
    3.1  The gasket and groove sizes for which dimensions are included cover all the sizes in the following flange, flange fitting, and valve standards:
        a)  Steel Pipe Flanges and Flanged Fittings (ASA B16.5)
        b)  Ring-Joint Flanges (API 6B)
        c)  Valves:  Flanged Steel Gate and Plug Valves for Drilling and Production Service.  (API 6C) Iron and Steel Gate, Plug, and Check Valves for Pipe-Line Service (API 6D) Flanged and Welding-End Steel Wedge Gate and Plug Valves for Refinery Service (API 600)
        d)  Wellhead Equipment (API 6E)
        e)  Special Purpose Flanges

4.  Material
    4.1  Ring gaskets shall be of material suitable for the service conditions encountered.  Although it is recommended that the rings be of a hardness lower than the flanges to assure tight joints when gaskets are replaced or renewed, this feature may not be possible to obtain in the case of various alloys.  For example, stainless steel alloy flanges heat-treated for optimum corrosion resistance will have the same range of hardness as the ring gaskets of the same material annealed to minimum hardness. 
    4.2  Ring gaskets of materials listed below shall be furnished with a hardness equal to, or less, than that shown.

5.  Dimensions
    5.1  Dimensions are covered in Tables 1 and 2 for:
        a)  Octagonal Gaskets
        b)  Oval Gaskets
        c)  Flat Bottom Grooves
    5.2  In the early application of these grooves and gaskets, dimensions were established for round bottom grooves and oval gaskets only.  Later developments resulted in the use also of octagonal gaskets and flat bottom grooves for which dimensions were established.  This standard now shows only flat bottom grooves because both oval and octagonal rings may be used therein.  The former round bottom grooves requires the use of an oval gasket.  Purchaser should specify oval or octagonal rings as desired where both types are shown.
    5.3  Dimensions of grooves and gaskets are such that when joints are assembled flanges are apart, the distance depending upon the pressure class of flanges.  The approximate distances which flanges are apart for the various pressure classes are listed in the standards and specifications referred to in Introductory Note 3.

6.  Tolerances
    6.1  Tolerances have been established for both grooves and gaskets.  For convenient use they are shown on the tables of dimensions.

7.  Finish
    7.1  The sides (contact surfaces) of the grooves and gaskets shall be free from objectionable ridges, tool or chatter marks which may cause or contribute to the possibility of joint leakage.

8.  Identification Number
    8.1  For convenience in ordering and referring to these grooves and gaskets, numbers are assigned and prefixed by the letter "R" as shown in tables.

9.  Marking
    9.1  Flanges.  The edge of each ring joint flange shall carry the groove number of prefixed by the letter "R".
    9.2  Gaskets.  The outer surface of each gasket shall carry the manufacturer's trademark, gasket number prefixed by the letter "R", and followed by the material identification.  The application of marking shall be done so as not to injure the contact faces nor to harmfully distort the gasket.  Material identification shall conform the following standards unless otherwise specified on the purchase order.