---
title: What Is the Difference Between ANSI and PN Flanges?
date: 2025-06-22T15:59:43Z
modified: 2026-07-16T08:09:13Z
permalink: "https://www.longanflange.com/blog/what-is-the-difference-between-ansi-and-pn-flanges/"
type: post
status: publish
excerpt: ""
wpid: 2834
categories:
  - Blog
featured_image: "https://www.longanflange.com/wp-content/uploads/2024/10/7a9abd5a00d19f531a47.jpg"
featured_image_alt: different flange
timestamp: 2026-07-16T08:09:13Z
tags:
  - Blog
---

If you’re specifying piping components for international projects, you’ve probably asked: _what is the difference between ANSI and PN flanges?_

Understanding this can help avoid mismatched parts, project delays, and installation headaches.

## **Different Systems, Different Measures**

To understand the difference between an ANSI flange and a PN flange, you first need to look at the measurement systems behind them. Each follows a different set of global standards—and those differences affect everything from pressure ratings to bolt alignment.

- **ANSI flanges** (also called ASME) use an imperial-based pressure class system (e.g., Class 150, 300, 600), defined in ASME B16.5/B16.47. These classes are not direct pressure values in psi, though commonly associated with them.
- **PN flanges** come from the metric DIN/EN system (e.g., PN10, PN16, PN25), where PN indicates nominal pressure in bars (such as 10 bar for PN10).

## **Size and Compatibility Issues**

ANSI and PN flanges are **not interchangeable**. Flange bolt patterns, thicknesses, and diameters differ across these standards. Even so, some cross-referencing tables exist:



| **ANSI Class** | **Approx. PN Equivalent** |
| --- | --- |
| Class 150 | PN20 |
| Class 300 | PN50 |
| Class 600 | PN100 |
| Class 900 | PN150 |
| Class 1500 | PN250 |
| Class 2500 | PN420 |

Despite these mappings, they should never be directly mixed on the same piping system.

## **Choosing the Right Flange Standard**

Use **ANSI flanges** when:

- Projects adhere to ASME or API standards
- Materials are in imperial units (inches, psi)
- Your pipeline specs reference Class 150, 300, or higher

Use **PN flanges** when:

- Working with European or ISO-based specs
- Measuring pressure in bar and dimensions in metric
- Projects call for PN16, PN25, etc., commonly in water and chemical plants

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## **Impact on Procurement and Installation**

Mixing flange standards can lead to misaligned bolt holes, sealing failures, and safety issues.

For seamless supply chains, it’s wise to stick with one system—either ANSI **or** PN—and ensure all components, including stainless steel or other ASME-compliant options, match that standard.

It’s also smart to verify that flanges like those from Longan Flange meet your chosen system specs, whether you’re sourcing[ stainless steel flanges](https://www.longanflange.com/wp-content/uploads/wp-mfa-exports/page/stainless-steel-flange.md) or[ ASME flange](https://www.longanflange.com/wp-content/uploads/wp-mfa-exports/page/asme-flange.md) types.

## **What is the difference between ANSI and PN flanges? Final Take**

What is the difference between ANSI and PN flanges?

It boils down to standards:

- ANSI = imperial, class‑based;
- PN = metric, bar‑based.

They differ in dimensions, bolt layouts, and ratings. Staying consistent with the correct system ensures compatibility, reduces risk, and simplifies procurement.Need help aligning flange standards with your project specs? [Longan Flange](https://www.longanflange.com/wp-content/uploads/wp-mfa-exports/page/about.md) can guide you to the right ANSI or PN-compliant solutions, making sure your systems fit and perform. [Contact us](https://www.longanflange.com/wp-content/uploads/wp-mfa-exports/page/contact.md) today!