This reference page summarizes the dimensional and installation-related information for a Blind Flange 3 Inch Class 400. Use it to check the listed flange thickness, weight, stud bolt specification, bolt-hole diameter, and bolt count before coordinating piping layouts, fabrication details, or equipment connections.
The page also provides a CAD drawing resource and explains how the flange data should be reviewed alongside the gasket, material, bolting, and pressure-temperature requirements for the complete connection.
Blind Flange 3″ Class 400
Blind Flange 3″ Class 400 is used to seal the end of a piping system or close off a flange connection in Class 400 service. It is a solid flange without a center bore and is commonly used in industrial piping systems, maintenance isolation points, and future pipeline expansion connections where a higher pressure rating is required.
This dimension data is based on ANSI / ASME B16.5-2020.
Blind Flange 3″ Class 400 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS): 3″
- DN Size: DN80
- Flange Thickness: 31.8mm
- Weight: 9.1kg
- Stud Bolt Size: 3/4″ UNC (or M20) x 125 Long
- Number of Bolts: 8
- Hole Diameter: 7/8″ (22.225mm)
What Is a Blind Flange?
A blind flange is a blank flange used to close the end of a pipeline, vessel nozzle, or equipment connection. It provides a secure shutoff point and is often selected when future maintenance, inspection, or line extension may be required.
Common Applications
Blind Flange 3″ Class 400 is commonly used for:
- Pipe end closure
- Equipment isolation
- Valve and nozzle blanking
- Maintenance shutdown work
- Process and utility piping systems
- Higher pressure piping applications
CAD Drawing Download
This page includes the CAD drawing file for Blind Flange 3″ Class 400, which can be used for drafting, detailing, and piping layout coordination.
Available Blind Flange Class 400 Sizes
This size is part of the Blind Flange Class 400 series. Check other sizes in the same category to find matching dimension data and CAD files for your project.
Notes
Before fabrication or installation, always confirm the latest project requirements, flange material specification, gasket type, bolt length, and applicable pressure-temperature rating.
How to Use This Blind Flange Reference
A blind flange has no center bore. Unlike a flange intended to connect directly to an open pipe bore, it forms a blank closure at a flanged connection. This makes it useful where a line, nozzle, valve connection, or equipment opening must be isolated, closed for maintenance, or reserved for possible future work.
Understanding the Listed Dimensions
- NPS and DN: NPS 3 inches and DN80 identify the nominal connection size. Nominal size is a designation used for piping coordination; it should not be treated as the flange’s measured outside dimension.
- Flange thickness: The listed thickness helps with equipment clearance, gasket positioning, bolt engagement, and drawing details.
- Stud bolts and holes: The stud bolt entry identifies the specified bolting format and length, while the hole diameter describes the flange bolt opening. These items should be checked together with the mating flange and the project bolting specification.
- Weight: The listed weight is useful for handling, support, lifting, and material-takeoff discussions. Confirm the supplied component and any coating or hardware requirements before final handling calculations.
Connection and Drafting Checks
Before using the CAD file in a final drawing, confirm the flange facing, gasket arrangement, mating flange, bolt access, and equipment clearances. A blind flange may be dimensionally compatible with a connection while still requiring a separate review of material compatibility, service conditions, and the applicable pressure-temperature limits.
For related design work, this page can be used alongside references for flange dimensions, pipe schedules, gaskets, stud bolts, and piping CAD blocks. Those related references help keep the blind flange, adjoining pipe, and mating equipment consistent in the piping model.
Blind Flange 3 Inch Class 400 FAQ
What is a Blind Flange 3 Inch Class 400 used for?
It is used to close a flanged piping connection, pipe end, vessel nozzle, valve connection, or equipment opening. Typical uses include isolation, maintenance shutdown work, and connections reserved for future modification.
Does a blind flange have a center bore?
No. A blind flange is a solid blank flange without a center bore. Its purpose is to provide closure rather than to pass fluid through the flange.
What stud bolt information is listed for this flange?
The reference lists 3/4 inch UNC, or M20, stud bolts with a length of 125, together with eight bolts. Confirm the project specification and mating flange before ordering bolting.
Is the listed bolt-hole diameter the same as the stud bolt diameter?
No. The bolt-hole diameter is the opening through the flange, while the stud bolt size identifies the threaded hardware. The two values are related but describe different parts of the connection.
Can the CAD drawing be used directly for fabrication?
The CAD file is intended to support drafting, detailing, and piping layout coordination. Before fabrication, verify the project revision, flange material, facing, gasket, bolting, and applicable service requirements.