- 1. What is NPS and How Does It Differ from OD?
- 2. Why Convert Flange NPS to OD?
- 3. General Rule: How to Convert NPS to OD
- 4. How Does This Apply to Flanges?
- 5. Practical Steps to Convert Flange NPS to OD
- 6. Factors That Influence Flange OD
- 7. Common Mistakes to Avoid
- 8. Tools for NPS to OD Conversion
- 9. When to Contact Sunjin Metals Vina
- Conclusion: NPS and OD—Know the Difference, Choose the Right Flange
In the realm of piping and flange systems, understanding Nominal Pipe Size (NPS) and Outer Diameter (OD) is essential for engineers, technicians, and procurement professionals. However, confusion often arises when converting between NPS and OD, particularly when dealing with international standards, technical drawings, or flange selection.
This comprehensive article explains how to convert flange NPS to OD, why it matters, and how to avoid errors during flange sourcing and installation. Sunjin Metals Vina (SJM Vina) supports global customers with accurate flange dimensioning, custom manufacturing, and expert technical consultation.
1. What is NPS and How Does It Differ from OD?
1.1 What is NPS?
NPS, or Nominal Pipe Size, is a standard used in North America to define the diameter of pipes and their corresponding flanges. The term “nominal” indicates that the size is not an exact measurement but a standardized reference.
-
NPS is expressed in inches (e.g., NPS 2, NPS 6, NPS 10).
-
It does not always correspond to the actual outer diameter, especially for smaller sizes.
1.2 What is OD?
OD, or Outer Diameter, is the actual external diameter of a pipe or flange. OD is critical for ensuring proper fitment, alignment, and sealing in piping systems.
For example, NPS 6 does not equal an OD of 6 inches. Instead, NPS 6 has an OD of 6.625 inches. This discrepancy is where confusion begins and why accurate conversion is vital.
2. Why Convert Flange NPS to OD?
Knowing the OD from a given NPS is essential for:
-
Ensuring proper pipe-flange fitment.
-
Interpreting engineering drawings accurately.
-
Ordering flanges that match existing pipes.
-
Avoiding mismatched connections.
-
Complying with standards such as ASME B16.5, B16.47, DIN, or JIS.
Many engineers and buyers mistakenly assume NPS equals OD, which can lead to procurement errors. SJM Vina assists customers in verifying all dimensional parameters before finalizing orders.
3. General Rule: How to Convert NPS to OD
Follow this simple rule:
-
For NPS ≤ 12: OD is greater than NPS (based on ASME B36.10 or B36.19 standards).
-
For NPS ≥ 14: OD approximates NPS (nominal equals actual).
Some common sizes:
-
NPS 1 = OD 1.315 inches
-
NPS 2 = OD 2.375 inches
-
NPS 4 = OD 4.5 inches
-
NPS 6 = OD 6.625 inches
-
NPS 8 = OD 8.625 inches
-
NPS 10 = OD 10.75 inches
-
NPS 12 = OD 12.75 inches
-
NPS 14 = OD 14.00 inches
From NPS 14 and above, the OD equals the nominal size.
4. How Does This Apply to Flanges?
Flanges are matched to pipe size using NPS, but their outer diameter (flange OD) varies depending on:
-
NPS size.
-
Pressure class (150, 300, 600, etc.).
-
Standard used (ASME, DIN, JIS, etc.).
For example, an NPS 6 flange, Class 150, has:
-
Pipe OD = 6.625 inches.
-
Flange OD = 10.62 inches (per ASME B16.5).
Thus, converting NPS to flange OD must consider the flange type and pressure class.
5. Practical Steps to Convert Flange NPS to OD
Follow these steps:
Step 1: Identify the NPS Size
Determine the nominal pipe size from documentation or pipe markings.
Step 2: Refer to Flange Standard
Identify which standard the flange follows:
-
ASME B16.5 (for sizes up to 24 inches).
-
ASME B16.47 (for sizes above 24 inches).
-
DIN EN 1092-1.
-
JIS B2220.
-
GOST or BS standards.
Step 3: Look Up Pipe OD
Use ASME B36.10/36.19 charts or online references to find the actual pipe OD for the given NPS.
Step 4: Check Flange OD Based on Class
Use a flange dimension chart to match NPS and pressure class to the flange OD.
Tip from SJM Vina: We provide detailed dimensional drawings with each quotation to help customers avoid confusion and mismatched selections.
6. Factors That Influence Flange OD
When converting flange NPS to OD, consider:
-
Pressure Class: Higher pressure results in a larger flange OD.
-
Flange Type: Weld neck, blind, or slip-on flanges have different dimensions.
-
Standard: ASME and DIN flanges have different OD values.
-
Material: Some materials may require design adjustments (e.g., for stress or sealing).
7. Common Mistakes to Avoid
-
Assuming NPS = OD: Only true for NPS 14 and above.
-
Ignoring Pressure Class: Significantly affects OD.
-
Using the Wrong Standard: ASME and DIN can differ by several inches.
-
Overlooking Flange Type: Each type has unique dimensions.
Ensure accuracy by double-checking with a trusted supplier like SJM Vina.
8. Tools for NPS to OD Conversion
-
ASME B16.5/16.47 flange charts.
-
Digital caliper or tape measure for field measurements.
-
Online calculators or flange dimension apps.
-
3D CAD models or technical drawings.
-
Technical support from SJM Vina.
We recommend verifying with official standards or the manufacturer’s technical sheet before finalizing orders.
9. When to Contact Sunjin Metals Vina
If you need assistance converting NPS to OD or selecting the correct flange, SJM Vina’s technical team is ready to help. We offer:
-
Comprehensive flange dimension charts in PDF or CAD.
-
Custom flanges for specialized piping systems.
-
Support for ASME, DIN, EN, and GOST standards.
-
Professional advice for international projects.
-
Marked drawings and certificates with every order.
Conclusion: NPS and OD—Know the Difference, Choose the Right Flange
Understanding the difference between NPS and OD is crucial for anyone involved in piping systems. While NPS serves as a nominal reference, OD is the actual measurement that determines fit, sealing, and system integrity.
By mastering how to convert flange NPS to OD, you can:
-
Select the correct flange every time.
-
Avoid costly rework or installation issues.
-
Enhance procurement efficiency.
-
Ensure system safety and compliance.
When in doubt, rely on experts like SJM Vina to guide you to the right choice. Contact us at +84 33 4233 127 or via email at sjmvina@sunjinmetal.com. Visit www.sjmvina.com.vn for more information and to place your order today!
Số lần xem: 19
In industrial piping systems, flanges play a critical role by securely connecting pipes, valves, pumps, and other equipment. They ensure tight sealing, mechanical stability, and easy disassembly for maintenance.
To guarantee proper identification and compliance with international standards, every flange is marked with detailed information, including standard, pressure rating, material, and manufacturing data. These markings are not just identification codes – they are essential for quality control, traceability, and system safety.
In modern hydraulic systems, where fluids are transmitted under extreme pressure, every component plays a vital role in ensuring overall performance and safety. Among these components, steel flanges are indispensable. They are used to connect pipes, valves, pumps, and other equipment, creating a secure and leak-proof joint that withstands both high pressure and temperature.
Today, Korean steel flanges have gained strong recognition in the industrial market thanks to their superior quality, durability, and compliance with strict international standards. Their exceptional ability to endure high pressure makes them an ideal solution for hydraulic systems and other demanding industrial applications.
In industries operating in marine and coastal environments, the durability and resistance of materials to corrosion are critical factors in ensuring safety and long-term performance. Among the most essential components in pipeline systems for marine applications are steel flanges, which connect pipes, valves, and fittings. For environments exposed to seawater, Korean steel flanges have proven to be an optimal solution due to their superior quality, corrosion resistance, and compliance with international standards.
In modern industries, pipeline systems are required to operate under increasingly complex and demanding conditions. From oil and gas, petrochemicals, power plants, to marine engineering, the performance and safety of pipeline connections play a critical role in ensuring stability and minimizing risks. Among the essential components of these systems, Korean steel flanges stand out for their superior leak-proof properties in high-pressure environments, helping businesses optimize operations while ensuring compliance with safety standards.
In industrial systems, especially in the oil and gas, energy, chemical, and construction sectors, steel flanges play a vital role in connecting pipelines, equipment, and valves. To ensure safety and operational efficiency, flange products must strictly comply with national and international quality standards. Among these, the KS (Korean Standards) system stands out as a benchmark widely applied to Korean steel flanges, ensuring stability, safety, and long-term durability.
In industrial systems, boilers play a crucial role in generating steam, heat, and energy for various production processes. These systems operate under extreme conditions, including high temperatures, elevated pressure, and long continuous working hours. Therefore, all piping materials and connection components must meet strict standards of strength, durability, and safety.
In industrial piping systems, pipe fittings play a vital role in connecting pipelines, changing flow direction, branching, or adjusting pressure. To ensure safety, efficiency, and durability, these fittings must comply with strict international and regional standards. Among them, KS (Korean Standards), JIS (Japanese Industrial Standards), and ASTM (American Society for Testing and Materials) are the three most recognized systems applied to Korean pipe fittings.
At Sunjin Metals Vina (SJM Vina), we specialize in supplying Korean steel pipes, Korean steel flanges, and Korean pipe fittings, all manufactured in compliance with these standards to serve key industries such as oil & gas, chemical processing, power generation, and construction.
In the oil & gas sector, steel pipes and pipeline accessories form the foundation of safe, durable, and efficient pipeline systems. Among them, Korean steel flanges are highly valued for their superior quality, precise manufacturing, and ability to meet stringent international standards.
At Sunjin Metals Vina (SJM Vina), we specialize in supplying Korean steel pipes, Korean steel flanges, and Korean pipe fittings, serving industrial projects, especially in the oil & gas industry, with a strong commitment to quality and professional service.
In industrial construction, steel pipes play a vital role in creating durable, stable, and safe structural systems for large-scale projects. With outstanding advantages in quality, load-bearing capacity, and durability in harsh environments, Korean steel pipes have increasingly become the preferred choice for contractors and investors in Vietnam.
At Sunjin Metals Vina (SJM Vina), we specialize in supplying Korean steel pipes, Korean steel flanges, and Korean pipe fittings that fully comply with international standards, providing optimal solutions for industrial construction projects.
In the oil and gas industry, piping systems must operate under extreme conditions with high pressure, fluctuating temperatures, and corrosive environments. To ensure safety and efficiency, high-pressure Korean pipe fittings are considered the optimal choice thanks to superior quality, strict international standards, and long-term reliability.
At Sunjin Metals Vina (SJM Vina), we specialize in supplying Korean steel pipes, Korean steel flanges, and Korean pipe fittings that meet the most demanding requirements of onshore and offshore oil and gas projects.
In modern industries such as oil & gas, petrochemical, power generation, and shipbuilding, Korean steel flanges, pipes, and fittings are trusted for their high precision, durability, and compliance with international standards. Among them, the production technology of Korean steel flanges plays a decisive role in ensuring product quality and operational safety.
At Sunjin Metals Vina (SJM Vina), we specialize in supplying Korean-origin steel pipes, flanges, and fittings, manufactured under strict technological processes that meet global requirements. In this article, we will provide an in-depth look at two primary production methods of steel flanges: forging and casting, highlighting their characteristics and advantages.
Pipe Pressure Calculator (Công cụ tính áp suất ống)
Steel Pipe Weight Calculator
Pipe Wall Thickness Calculator (ASME B31.3)
Flange bolting plays a critical role in ensuring the integrity of piping systems. Improper installation is the most common cause of leaking joints, which can lead to costly downtime, safety risks, and operational inefficiencies. At Sunjin Metals Vina (SJM Vina), we provide Korean-origin steel pipes, flanges, and fittings for industrial projects, and we emphasize that proper flange bolting procedures must always be followed. Below is a comprehensive guide to the correct procedure for flange bolting.
