This reference page provides the dimensional data and practical context needed to review Schedule 80 Pipe 18 Inch DN450 for piping layouts, fabrication, estimating, and procurement. Use the table below as the local dimensional reference, then confirm material, service conditions, end preparation, and project code requirements before final selection.
For related design work, compare this entry with the site’s pipe schedule references, nominal pipe size guidance, pipe weight resources, and flange-dimension pages. These references help connect dimensional data with supports, fittings, valves, joining details, and drawing coordination.
Schedule 80 Pipe 18 Inch (DN450 mm) is a heavy-wall steel pipe size commonly used in industrial piping systems where higher wall thickness and stronger pressure-related performance are required. This pipe size is referenced from ANSI/ASME B36.10 and is widely used in oil and gas, water treatment, process piping, utility lines, and general mechanical applications. The current page data lists this size with an outside diameter of 457 mm, inside diameter of 409.34 mm, wall thickness of 23.83 mm, and pipe weight of 254.57 kg/m.
In pipe sizing, NPS 18 corresponds to DN450 as a nominal reference size. The schedule number indicates wall thickness. For the same nominal pipe size, a higher schedule generally means a thicker wall and a smaller inside diameter, while the outside diameter remains standardized. This is why Schedule 80 pipe is often selected when additional strength, durability, or corrosion allowance is needed in the design.
Schedule 80 Pipe 18 Inch DN450 Dimensions
- Pipe Standard: ANSI/ASME B36.10
- Nominal Pipe Size: 18 inch
- DN Size: DN450
- Outside Diameter (OD): 457 mm
- Inside Diameter (ID): 409.34 mm
- Wall Thickness: 23.83 mm
- Pipe Weight: 254.57 kg/m
- Pipe Weight Including Water: 386.1 kg/m
What Does Schedule 80 Mean?
Schedule 80 refers to a pipe wall thickness classification. It does not directly describe the outside diameter. In standardized steel pipe systems, the outside diameter stays fixed for a given NPS size, while the wall thickness changes by schedule. Because of this, Schedule 80 pipe provides a thicker wall than lighter schedules and reduces the internal flow diameter compared with lower schedules of the same nominal size.
Where Is 18 Inch DN450 Schedule 80 Pipe Used?
This pipe size is often used in larger industrial systems where mechanical strength and long service life are important. Typical applications include:
- Process piping in factories and plants
- Water transmission and utility piping
- Oil and gas pipeline systems
- Fire protection and heavy-duty service lines
- Pump stations and treatment facilities
Why These Dimensions Matter
Understanding pipe dimensions is important for engineering design, fabrication, and installation. The outside diameter is needed for clamps, supports, and flange compatibility. The inside diameter affects flow capacity and pressure drop. The wall thickness influences strength and allowable service conditions, while the weight per meter is useful for transport planning, structural support design, and lifting calculations.
18 Inch Schedule 80 Pipe Dimension Table
| NPS | DN | OD (mm) | ID (mm) | Wall Thickness (mm) | Weight (kg/m) |
|---|---|---|---|---|---|
| 18 inch | 450 | 457 | 409.34 | 23.83 | 254.57 |
Additional Reference for Designers and Buyers
Before selecting this pipe for a project, engineers usually also review the pipe material specification, end type, corrosion allowance, operating temperature, design pressure, and applicable code requirements. While Schedule 80 gives the dimensional wall category, the final pipe selection should always match the full project specification and service condition.
Note: NPS is the nominal pipe size in inches, while DN is the nominal diameter reference in metric format. These are standardized naming systems used for piping identification and are not always equal to the exact measured internal diameter.
How to Use This Schedule 80 Pipe Reference
Start with the nominal designation to identify the intended pipe size in specifications, bills of material, and drawings. The listed outside diameter is generally the key interface dimension for supports, clamps, sleeves, fittings, and flange selection. The listed inside diameter is more relevant to hydraulic review, flow-area checks, velocity assessment, and pressure-drop calculations.
Schedule should be read as a wall-thickness designation rather than as a direct pressure rating. A complete engineering review also considers material grade, manufacturing specification, corrosion or erosion allowance, operating temperature, design pressure, joining method, and the governing piping code. The schedule value alone cannot establish allowable service conditions.
Design and Drafting Checks
- Use the outside diameter when coordinating supports, penetrations, insulation clearances, clamps, and compatible components.
- Use the inside diameter when preparing flow calculations or checking the effect of wall thickness on hydraulic performance.
- Use the listed mass per unit length when reviewing transport, lifting, rack loading, and support reactions.
- Confirm whether the project requires seamless or welded pipe, a particular material specification, a defined end type, or additional inspection requirements.
- Check that connected flanges, fittings, valves, gaskets, and branch components match the selected piping specification.
Related Pipe References
For a broader piping review, pair this page with references for pipe schedules, NPS and DN terminology, pipe fittings, flange dimensions, and pipe support design. A CAD or DWG reference can also help drafters coordinate the nominal size and outside profile in plant layouts, fabrication drawings, and equipment connections.
Important Selection Note
The dimensional table is useful for identification and preliminary coordination, but it is not a substitute for a project piping specification or engineering design calculation. Verify the full service and material requirements before ordering, fabricating, or approving the pipe.
Frequently Asked Questions
What does Schedule 80 mean for this pipe?
Schedule 80 identifies the pipe wall-thickness category. It is not the outside diameter and does not, by itself, define a complete pressure rating or allowable service condition.
What is the relationship between NPS 18 and DN450?
NPS 18 and DN450 are nominal identification systems used to describe the same referenced pipe size. Neither designation should be treated as the exact measured inside diameter.
Which dimension is used for pipe supports and clamps?
The outside diameter is normally the starting dimension for supports, clamps, sleeves, and external clearances. Final component compatibility should still be checked against the applicable product and project specifications.
Why is the inside diameter important?
The inside diameter affects available flow area and is used in hydraulic calculations such as flow capacity and pressure-drop review. Actual performance also depends on the fluid, operating conditions, fittings, and system arrangement.
Does Schedule 80 alone determine whether the pipe is suitable?
No. Selection also requires review of material specification, corrosion allowance, temperature, design pressure, end type, joining details, code requirements, and the intended service.
Where can the DWG reference be used?
The accompanying DWG resource can support drafting and layout coordination. Designers should verify project-specific dimensions, connection details, tolerances, and fabrication requirements before using CAD data for construction.