This reference is for engineers, designers, fabricators, estimators, and CAD drafters checking 18 inch Schedule 120 pipe data. It brings together the NPS designation, DN equivalent, outside diameter, wall thickness, inside diameter, and linear weight in one place.
Use the dimension table when developing layouts, checking clearances, preparing material takeoffs, or coordinating pipe supports. For broader comparison work, it can also be reviewed alongside related pipe schedule references, pipe weight tables, flange dimensions, and CAD/DWG resources.
Schedule 120 pipe 18 inch (DN450) is a heavy-wall steel pipe size commonly used in piping design, fabrication, drafting, and engineering estimation work. This page provides the standard dimensions, wall thickness, inside diameter, and weight per meter for NPS 18 Schedule 120 pipe based on ASME B36.10.
18 Inch Schedule 120 Pipe Dimensions
- Nominal Pipe Size (NPS): 18 inch
- Diameter Nominal (DN): DN450
- Outside Diameter (OD): 457 mm
- Wall Thickness: 34.93 mm
- Inside Diameter (ID): 387.14 mm
- Pipe Weight: 363.58 kg/m
- Pipe Weight Filled With Water: 481.23 kg/m
- Reference Standard: ASME B36.10
- Pipe Type: Steel Pipe
Schedule 120 Pipe 18 Inch Data Table
| Pipe Size | DN | OD (mm) | Wall Thickness (mm) | ID (mm) | Weight (kg/m) |
|---|---|---|---|---|---|
| 18 inch | 450 | 457 | 34.93 | 387.14 | 363.58 |
What Does Schedule 120 Mean?
Schedule 120 refers to a heavy wall thickness series used for steel pipe under ASME B36.10. For the same nominal pipe size, the outside diameter remains fixed while the wall thickness increases according to the schedule. A thicker wall reduces the inside diameter and significantly increases pipe weight.
Typical Uses of 18 Inch Schedule 120 Pipe
NPS 18 Schedule 120 pipe is commonly referenced for heavy-duty industrial piping systems where high wall thickness is required. It may be used in process piping, plant utility systems, structural loading checks, fabrication work, and engineering applications where pipe strength and wall thickness are more critical than maximum flow area.
Why Pipe Weight Matters
Pipe weight per meter is essential for transport planning, crane lifting studies, support design, structural loading, fabrication estimates, and installation planning. For an 18 inch Schedule 120 pipe, the heavy wall thickness results in much higher installed weight than lighter schedules, so accurate weight data is important for engineering and construction work.
18 Inch Schedule 120 Pipe Calculation Notes
The listed weight is based on standard steel pipe dimensions using the outside diameter and wall thickness of the pipe. Actual product weight may vary slightly depending on manufacturing tolerance, material specification, and supplier standard.
Frequently Asked Questions
What is the outside diameter of 18 inch Schedule 120 pipe?
The outside diameter is 457 mm.
What is the wall thickness of DN450 Schedule 120 pipe?
The wall thickness is 34.93 mm.
What is the inside diameter of NPS 18 Schedule 120 pipe?
The inside diameter is 387.14 mm.
How much does 18 inch Schedule 120 pipe weigh?
The approximate weight is 363.58 kg/m.
Which standard covers this pipe size?
This dimension data is based on ASME B36.10 for steel pipe.
Conclusion
Schedule 120 pipe 18 inch (DN450) has an outside diameter of 457 mm, wall thickness of 34.93 mm, inside diameter of 387.14 mm, and a weight of 363.58 kg/m. It is a useful reference for piping design, fabrication, estimating, and heavy-duty industrial engineering work.
How to Use This Pipe Reference
The nominal size identifies the pipe designation rather than serving as a direct measurement of the inside diameter. For this entry, NPS 18 corresponds to DN450, while the listed outside diameter and wall thickness define the actual pipe geometry used for drafting and engineering checks.
Schedule selection affects more than wall thickness. Because the outside diameter remains associated with the nominal size while the wall becomes heavier, the available inside diameter decreases and the pipe mass increases. These changes can affect routing space, connected-component alignment, support loads, lifting plans, and transportation arrangements.
Design and Drafting Checks
- Confirm that the selected schedule matches the project piping specification and material requirements.
- Use the listed outside diameter for layout, clearance, clamp, and support coordination.
- Use the listed inside diameter when reviewing flow-area assumptions or connecting components.
- Use the linear weight for preliminary takeoffs and load checks, then verify the purchased product data before fabrication or installation.
- Review the downloadable DWG together with the dimension table so that drawing geometry and written specifications remain consistent.
The published weight is a reference value. Actual delivered pipe can differ because of manufacturing tolerances, material requirements, coating, end preparation, and supplier practices. A pressure rating should not be inferred from the schedule designation alone; pressure design also requires the applicable material, temperature, code, fabrication, and project criteria.
Related Reference Topics
Readers comparing alternatives may also need the site’s references for other pipe schedules, nominal pipe size and DN terminology, pipe fittings, flange dimensions, support design considerations, and DWG-based piping details. These related topics help connect dimensional data with practical layout and fabrication work.
Additional Questions About NPS 18 Schedule 120 Pipe
Is NPS 18 the same designation as DN450?
For this reference, yes. The page identifies the pipe as NPS 18 and DN450, which are the inch-based and metric nominal designations used for the same pipe size.
Does Schedule 120 define the pressure rating?
No. Schedule 120 describes a wall-thickness series for steel pipe dimensions. Pressure suitability must be evaluated using the applicable material specification, design conditions, governing code, manufacturing requirements, and project engineering criteria.
Why is the inside diameter smaller than the nominal pipe size?
Nominal pipe size is a designation, not a direct inside-diameter measurement. The inside diameter is determined by the outside diameter and the specified wall thickness.
Can this information be used for a CAD drawing?
Yes, the dimensional data can support preliminary drafting and coordination, and the page includes a downloadable DWG reference. Before issue for construction, compare the drawing with the project specification, connected components, and supplier documentation.
Why should the filled-pipe weight be considered separately?
A pipe-support or lifting review may need to consider the pipe itself and the contents it carries. The source data lists a separate weight for the pipe filled with water, which is useful for preliminary load-awareness checks; the governing design case may require a different operating, test, or contents condition.