Use this page as a quick reference for 18 inch Schedule 5 pipe dimensions in large-diameter steel piping work. It brings together the NPS designation, DN equivalent, outside and inside diameters, wall thickness, and pipe weight so designers, drafters, fabricators, and buyers can check the key data before coordinating fittings, supports, layouts, or material takeoffs.
The dimension table below is the primary lookup section. The explanatory notes that follow clarify how NPS 18 and DN450 relate, where the listed measurements are used, and why the pipe’s mass should be considered separately from pressure, material, and design-code requirements.
Schedule 5 Pipe 18 Inch (DN450) is a large steel pipe size commonly used in industrial piping systems that require high flow capacity with a relatively light wall thickness. This pipe size is often used in utility piping, water transfer systems, low-pressure industrial service, and general steel pipe fabrication work.
This dimension data is based on ANSI/ASME B36.10, which is the standard commonly used for carbon steel pipe dimensions.
18 Inch Schedule 5 Pipe Dimensions
- Pipe Schedule: 5
- Nominal Pipe Size: 18 Inch
- DN Size: DN450
- Outside Diameter (OD): 457 mm
- Inside Diameter (ID): 448.62 mm
- Wall Thickness: 4.19 mm
- Pipe Weight: 46.79 kg/m
- Pipe Weight Including Water: 204.77 kg/m
- Standard: ANSI/ASME B36.10
Schedule 5 Pipe 18 Inch Dimension Table
| Pipe Schedule | NPS (Inch) | DN (mm) | OD (mm) | ID (mm) | Wall Thickness (mm) | Weight (kg/m) |
|---|---|---|---|---|---|---|
| 5 | 18 | 450 | 457 | 448.62 | 4.19 | 46.79 |
What Is 18 Inch Schedule 5 Pipe?
A 18 inch Schedule 5 pipe is a steel pipe with a nominal size of 18 inches and a relatively thin wall thickness compared with heavier schedules. For this size, the outside diameter is fixed at 457 mm, while the inside diameter is 448.62 mm based on a wall thickness of 4.19 mm.
Schedule 5 pipe is often selected when a project needs large flow capacity, reduced pipe weight, and easier handling compared with thicker wall pipes. It is commonly referenced in steel piping design, drafting, fabrication, and material takeoff work.
Where Is Schedule 5 Pipe 18 Inch Used?
This pipe size is commonly used in applications that need large flow capacity with relatively light wall thickness. Typical uses include:
- Water transfer and distribution systems
- Utility and low-pressure industrial piping
- Large process and service lines
- Pipe spool fabrication and layout work
- General steel piping projects
Why Pipe Dimensions Matter
Accurate 18 inch Schedule 5 pipe dimensions are important for piping layout, fabrication, transport planning, support design, and installation work. Engineers and designers often check OD, ID, wall thickness, and weight before selecting supports, fittings, welding details, and handling methods.
The outside diameter is important for matching supports, clamps, and pipe accessories. The inside diameter helps estimate internal flow area and system capacity. The wall thickness affects mechanical strength and specification compliance, while the pipe weight per meter is useful for lifting plans, transport, and structural loading calculations.
18 Inch Schedule 5 Pipe Weight Information
The nominal weight of this pipe size is 46.79 kg/m. When filled with water, the combined weight becomes approximately 204.77 kg/m. This information is useful for pipe support design, structural coordination, and lifting preparation in large piping systems.
Difference Between NPS 18 and DN450
NPS 18 is the inch-based nominal pipe size, while DN450 is the metric designation used in international drawings and specifications. Both terms refer to the same nominal pipe size, and users may search by either inch size or DN format depending on project standards.
Common Search Terms for This Pipe Size
Users may also search for this pipe using related keywords such as 18 inch Schedule 5 pipe dimensions, DN450 Schedule 5 pipe dimensions, 18 inch pipe weight per meter, DN450 pipe dimensions, or DN450 sch 5 pipe dimensions.
Conclusion
Schedule 5 Pipe 18 Inch (DN450) has an outside diameter of 457 mm, an inside diameter of 448.62 mm, a wall thickness of 4.19 mm, and a weight of 46.79 kg/m. It is a useful steel pipe reference size for design, drafting, fabrication, and procurement work.
This page provides a quick reference for engineers, drafters, fabricators, and buyers who need reliable 18 inch Schedule 5 pipe dimensions and DN450 pipe dimensions in one place.
How to Use This 18 Inch Schedule 5 Pipe Reference
Start with the dimensional entries when checking a drawing, bill of materials, or fabrication sketch. The outside diameter is the key interface dimension for supports, clamps, sleeves, and many external accessories. The inside diameter is useful for estimating the available flow passage, while the listed wall thickness helps identify the schedule entry and coordinate fabrication information.
For installation planning, use the stated pipe weight per meter as a line-load input only after confirming the project basis. A filled line can impose a substantially different support and handling demand than an empty pipe, so the water-filled value should not be treated as a universal operating load. Actual design checks may also need contents, insulation, valves, fittings, test conditions, support spacing, seismic effects, and applicable project requirements.
Important Checks Before Procurement or Fabrication
- Confirm that the required nominal size is NPS 18 and that the project uses DN450 as its corresponding metric designation.
- Check the listed outside diameter against mating components, supports, clamps, sleeves, and layout clearances.
- Confirm the material specification, manufacturing requirements, end preparation, corrosion allowance, and inspection requirements separately from the dimensional schedule.
- Verify that connected fittings and flanges use compatible dimensions and pressure-class requirements; the schedule entry alone does not define the complete piping design.
- Use the downloadable DWG as a drafting aid, then verify scale, units, tolerances, and project-specific details before issuing fabrication documents.
Related Pipe Reference Topics
This page works well alongside references for pipe schedules, NPS and DN designations, pipe flange dimensions, steel pipe fittings, pipe support design, and DWG pipe details. Cross-linking these topics helps readers move from a dimensional lookup to the connection, drafting, and installation information needed for a complete piping review.
Where a project requires flow, pressure, stress, or structural verification, treat the values on this page as dimensional reference data and confirm the final selection against the governing specification and engineering calculations.
Frequently Asked Questions
What is the DN equivalent of 18 inch Schedule 5 pipe?
The page identifies NPS 18 as DN450. NPS is the inch-based nominal designation, while DN is the metric nominal designation used on many international drawings and specifications.
What are the listed dimensions for 18 inch Schedule 5 pipe?
The source data lists an outside diameter of 457 mm, an inside diameter of 448.62 mm, and a wall thickness of 4.19 mm. Use the table as the local dimensional reference for this page.
What is the listed weight of 18 inch Schedule 5 pipe?
The listed pipe weight is 46.79 kg/m. The listed value including water is 204.77 kg/m. For support and structural work, confirm the load case and project assumptions before using either value.
Does Schedule 5 by itself determine whether the pipe is suitable for a service?
No. The schedule identifies a dimensional wall-thickness entry, but service suitability also depends on material, design pressure and temperature, corrosion allowance, joining method, code requirements, and engineering verification. Confirm those requirements before procurement or design approval.
Where can the CAD reference be used?
The attached DWG can support preliminary drafting and layout coordination. Review its units, scale, interfaces, and project-specific requirements before using it for fabrication or issued-for-construction documentation.