In case this is the first time you’re hearing the phrase, ANSI flanges simply refers to flanges whose construction meets ANSI (American National Standards Institute) specifications.
Large diameter flanges
These may be either smaller or large diameter flanges and as you would expect, there are a variety of different styles of ANSI flanges used by process engineers across a wide range of industries. Keep reading for brief descriptions of the most common types of ANSI-compliant flanges.
Threaded Flanges
Threaded flanges are a very popular choice, since they can be easily integrated into an assembly without requiring welding. Their threaded design also allows for flanges to be salvaged and reused when an assembly is dismantled, provided the flange is otherwise in good condition.
Standards, Dimensions & Weight of Threaded flanges
Threaded Flanges can be used in very high pressure services and their major advantage is that they can be assembled without welding.- ASME/ANSI B16.5 Class 150 TH
- ASME/ANSI B16.5 Class 300 TH
- ASME/ANSI B16.5 Class 600 TH
- ASME/ANSI B16.5 Class 900 TH
- DIN 2565 PN6
- DIN 2566 PN10
Slip On Flanges
These flanges are often chosen for applications where no disassembly is anticipated, since these ANSI flanges are welded into place. Despite the fact that welding is required, they are considered to be one of the easier types of flanges to properly fit and align.
Standards, Dimensions & Weight of Slip on flanges
The Slip-on flange has a low hub because the pipe slips into the flange prior to welding.
- ASME/ANSI B16.5 Class 150 SO
- ASME/ANSI B16.5 Class 300 SO
- ASME/ANSI B16.5 Class 600 SO
- ASME/ANSI B16.5 Class 900 SO
- BS 3293 Class 150 SO
- BS 3293 Class 300 SO
- BS 3293 Class 600 SO
- DIN 86029 PN 10
Blind Flanges
A blind flange is most often used in applications, which require stopping up the end of a flanged pipe, pressure vessel or valve. As the name implies, these ANSI flanges do not feature an outlet.
Standards, Dimensions & Weight of Blind flanges
- ASME B16.47 Series A/MSS SP-44 Class 150 BL
- ASME B16.47 Series A/MSS SP-44 Class 300 BL
- ASME B16.47 Series A/MSS SP-44 Class 600 BL
- ASME B16.47 Series A/MSS SP-44 Class 900 BL
- ASME B16.47 Series B/API 605 Class 75 BL
- ASME B16.47 Series B/API 605 Class 150 BL
- ASME B16.47 Series B/API 605 Class 300 BL
- ASME B16.47 Series B/API 605 Class 600 BL
- ASME B16.47 Series B/API 605 Class 900 BL
Lap Joint Flanges
These ANSI flanges differ from other styles in that their use requires an end connector; the pipe, valve or other product to be connected with the flange does not come into physical contact with it. However, this type of flange assembly allows for the rotation of the flange and makes it well suited for applications where the assembly may need to be dismantled relatively frequently for cleaning and maintenance.
Standards, Dimensions & Weight of Lap joint flange
Lap joint flange is having two components, a stub end, and a loose backing flange. 
