Flanges - General Information
Specifications
Refer to page 8-1 for a list of flange specifications (with page references) covered in this Section.
Manufacture
Notes
1 MSS SP-44 flanges are designated Series A flanges in ASME B16.47.
2 API 605 has been cancelled. API 605 flanges are designated Series B flanges in ASME B16.47.
3 BS 10, although obsolete, remains in use for light weight economy stainless steel flanges.
4 Within specification ANSI B16.5, plate can only be used to provide blind flanges.
5 Most small BS 10 flanges are made from bar.
6 Castings are not included in this manual.
❍ Materials. Most standards specify the material
from which the flange is produced. The purchaser
should specify the exact requirements.
❍ Flange Sizes. All sizes and grades compatible to
standard pipe ranges and wall thicknesses
(pressure ratings) are available. The table below
provides a summary.
❍ Flange Face. There are various face
configurations for flanges. Typically: flat face,
raised face, tongue and groove, ring joint.
❍ Face Finish. The finish on the face of a flange is
measured as an Arithmetical Average Roughness
Height (AARH). The finish is determined by the
standard used. For example, ANSI B16.5
specifies face finishes within a range 125AARH -
500AARH (3.2 Ra to 12.5 Ra). Other finishes are
available on request, for example 1.6 Ra max,
1.6/3.2 Ra, 3.2/6.3 Ra or 6.3/12.5 Ra. The range
3.2/6.3 Ra is most common.
Notes
1 MSS SP-44 flanges are designated Series A flanges in ASME B16.47. It also covers flanges in the range NPS 12 to 24,
these being equivalent to ASME/ANSI B16.5 flanges in the same range (except for the addition of NPS 22 in MSS SP-44).
2 API 605 has been cancelled. API 605 flanges are designated Series B flanges in ASME B16.47. Ranges quoted are based
on ASME B16.47 Series B.
3 Dimensions not covered in this summary.
Summary of materials used for flanges
ASME/
ANSI
B16.5
ASME B16.47
Series A
(or MSS SP-441)
ASME B16.47
Series B
( or API 6052)
BS
4504
BS
3293 BS 103
Forging (ASTM A 182) ✔ ✔ ✔ ✔ ✔ ✔
Plate (ASTM A 240)4 ✔ ✔ ✔
Bar5 ✔
Casting6 ✔ ✔ ✔
Summary of flange sizes specified by common standards
Flange Type
Specifications
ASME/ANSI
B16.5
ASME B16.47
Series A
(or MSS SP-441)
ASME B16.47
Series B
(or API 6052)
BS 4504
(ISO 7005-1) BS 3293
Nominal Pipe Sizes
< NPS 26 >NPS 26 >NPS 26 DN 10 to
DN 4000 > NPS 26
Nominal Pressure (Class)
Class (lb) Class (lb) Class (lb) PN (bar) Class (lb)
Weld Neck 150-2500 150-900 75-900 2.5-40 150-600
Slip-on 150-1500 - - 2.5-40 150-600
Blind 150-2500 300-900 300-900 2.5-40 -
Lap Joint 150-2500 - - 6-403 -
Socket Weld 150-1500 - - N/A -
Threaded 150-2500 - - 6-40 -
Flat/Raised Facings As above As above As above As above As above
Ring Joint Facings 150-2500 300-900 300-900 2.5-40 300-600
Other Facings 150-25003 - - 2.5-40 -
