Overview
A DN80 flange is a flange for the DN80 nominal piping size. DN80 is a designation, not a statement that every bore or outside diameter measures exactly 80 mm. The actual dimensions depend on the flange standard, PN or Class, type, facing, bore, and edition.
DN80 is commonly associated with NPS 3 in cross-reference usage, but the two descriptions should not be used to assume drilling compatibility across EN, ASME, JIS, or other systems.
Why It Matters for Pipe Components
A DN80 PN16 flange can differ from a DN80 flange in another PN rating, and an NPS 3 Class 150 flange belongs to a different dimensional system. Bolt holes may not align even when the nominal line size appears equivalent.
The flange type changes bore and welding. Weld-neck, slip-on, threaded, socket-weld, blind, and lap-joint products are not interchangeable.
Procurement should therefore avoid “DN80 flange” as a complete line item. The supplier needs all joint and material details.
Methods, Parameters, or Process
Complete the DN80 designation with the following fields.
| Field | Required information | Why it matters |
|---|---|---|
| Standard | EN, ASME, JIS, project drawing, or other | Controls dimensions and ratings |
| Rating | PN, Class, or system-specific rating | Selects drilling and thickness |
| Type | WN, SO, blind, threaded, socket, lap joint | Defines connection geometry |
| Facing | RF, FF, RTJ, Type B, or specified face | Matches gasket and mating flange |
| Material | Exact specification and grade | Controls properties and service |
| Bore/pipe | Pipe OD, wall, or schedule where needed | Controls fit and weld transition |
Supplier and Inspection Checklist
- State the flange standard and edition.
- State DN80 plus PN or the applicable rating class.
- Name the exact flange type and facing.
- Specify material and product form.
- Provide bore or connected pipe details.
- Verify drilling and gasket dimensions.
- Check certificate and product markings.
- Do not mix EN and ASME flanges based only on nominal size.
- Request a dimensional drawing when replacing existing equipment.
Application to Pipe Fittings, Valves, and Flanges
DN80 flanges are used on pumps, valves, pipe spools, tanks, instruments, and utility systems. The mating equipment can use a regional or proprietary flange pattern, so replacement work should start with the equipment drawing.
For lined or plastic piping, DN80 may refer to the system nominal size while the flange adapter and backing ring have manufacturer-specific dimensions.
FAQ
Is DN80 the same as 80 mm bore?
No. DN80 is a nominal designation. Actual bore depends on pipe wall, flange type, and standard.
Is DN80 the same as NPS 3?
They are commonly corresponding nominal sizes, but dimensional compatibility must be verified.
What is the bolt pattern for DN80?
It depends on the standard and rating. Do not use a generic pattern.
Can DN80 PN16 connect to NPS 3 Class 150?
Do not assume so. Compare the complete dimensions, facing, ratings, and obtain approval.
What should be on a DN80 RFQ?
Standard, rating, type, facing, material, bore, quantity, coating, tests, certificates, gasket, and bolting.
Next Steps
Convert DN80 into a complete flange description before quotation. Include the mating component drawing when the standard or rating is uncertain.
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