This reference page provides dimension and drafting information for a Weld Neck Flange 3/4 Inch Class 900. Use the source data below to check flange geometry, bolt-hole details, weight, and the connection information needed for piping layout or fabrication review.
For accurate selection, compare the flange dimensions with the mating flange, pipe outside diameter, pipe schedule, gasket arrangement, and project material requirements. The bore is not a universal value because it must correspond with the selected pipe wall thickness and schedule.
Weld Neck Flange 3/4″ Class 900
Weld Neck Flange 3/4″ Class 900 is widely used in piping systems that require strong, leak-resistant flange connections under high-pressure service. It features a long tapered hub that provides excellent stress distribution and is commonly applied in process piping, utility lines, refineries, power plants, and industrial systems where welding strength and reliability are essential.
This dimension data is based on ANSI / ASME B16.5-2020.
Weld Neck Flange 3/4″ Class 900 Dimensions
- Reference Standard: ANSI / ASME B16.5
- Nominal Pipe Size (NPS):3/4″
- DN Size: DN20
- Outside Diameter:130mm
- Flange Thickness:25.4mm
- Hub Diameter:44mm
- Bore Diameter: varies depending on pipe schedule and pipe wall thickness
- Raised Face Diameter:42.9mm
- Weight: 2.7kg
- Number of Bolts:4
- Stud Bolt Size: 3/4″ UNC (or M20) x 115 Long
- Hole Diameter: 7/8″ (22.225mm)
What Is a Weld Neck Flange?
A weld neck flange is a type of pipe flange designed with a long tapered hub that is welded directly to the pipe. This design helps reduce stress concentration at the flange base and provides better strength under pressure, temperature fluctuation, and cyclic loading.
Common Applications
Weld Neck Flange 3/4″ Class 900 is commonly used for:
- Process piping systems
- Oil and gas lines
- Refinery and petrochemical piping
- Very high-pressure service
- Pressure piping connections
- Industrial fabrication and maintenance work
CAD Drawing Download
This page includes the CAD drawing file for Weld Neck Flange 3/4″ Class 900, which can be used for drafting, detailing, piping layout coordination, and fabrication reference.
Available Weld Neck Flange Class 900 Sizes
This size is part of the Weld Neck Flange Class 900 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, pipe schedule, bore size, gasket type, bolt length, and applicable pressure-temperature rating.
How to Use This Weld Neck Flange Reference
A weld neck flange is aligned with the pipe and joined through its tapered hub. The hub provides a gradual transition between the pipe and flange, which is one reason this flange type is commonly considered for demanding piping service. The weld connection, pipe fit-up, welding procedure, and inspection requirements still need to be established by the applicable project documents and qualified personnel.
Dimension and bore coordination
The listed outside diameter, thickness, hub diameter, raised-face diameter, bolt-hole diameter, and bolt count describe the flange geometry. The bore diameter must be checked separately against the pipe schedule and wall thickness. Do not select a bore from the flange size alone.
Bolt and gasket checks
Before ordering or installation, confirm the bolt-hole pattern, thread system, bolt length, washer requirements, gasket type, and facing arrangement with the mating flange. The source lists the stud-bolt designation as 3/4" UNC (or M20) x 115 Long; the project should identify which fastener system applies rather than mixing designations without verification.
CAD and related references
The downloadable DWG can support preliminary drafting, piping layout coordination, and fabrication reference. It should be used alongside the dimension list and checked against the selected pipe and mating components. Related PipeSTD references for pipe schedules, flange dimensions, piping terminology, and CAD/DWG resources can help complete the surrounding design review.
Before fabrication
- Match the flange to the pipe outside diameter and selected bore.
- Check the mating flange class, facing, gasket, and bolt-hole alignment.
- Confirm material, welding, inspection, and pressure-temperature requirements.
- Verify the applicable project specification and current engineering approval before fabrication or installation.
Frequently Asked Questions
What is the bore diameter of this flange?
The bore varies with the pipe schedule and wall thickness. Confirm the required bore from the pipe specification before selecting or fabricating the flange.
How many bolts are listed for this flange?
The source data lists four bolt holes. Confirm the complete pattern and alignment against the mating Class 900 flange.
What stud-bolt information is provided?
The listed stud-bolt detail is 3/4" UNC (or M20) x 115 Long. The applicable thread system, material, length, and washer arrangement should be confirmed against the project specification.
What is the DWG file used for?
The DWG may be used as a drafting, detailing, piping-layout, and fabrication reference. Check it against the authoritative dimension data and the actual pipe and mating components.
Does Class 900 alone determine the flange’s allowable service?
No. Pressure-temperature applicability depends on factors such as material, temperature, governing requirements, and project design conditions. Verify the complete rating basis before use.