DIN Flanges vs ANSI Flange: ANSI Class 150, PN Rating and Selection Guide

DIN flanges and ANSI flanges both connect pipe, valves, pumps and industrial equipment, but they are built on different engineering systems. A DIN flange normally follows metric DN and PN sizing, while an ANSI flange or ASME flange normally follows inch-based NPS and Class pressure ratings such as ANSI Class 150.

For global projects, this difference matters. Two flanges may look similar on a drawing, yet they may not share the same bolt circle, number of holes, thickness, facing or pressure-temperature rating. This guide explains how DIN flanges compare with ANSI/ASME flanges, what whats PN means in practical purchasing language, and how to avoid wrong flange matching.

DIN Flanges and ANSI Flanges: The Basic Difference

DIN stands for Deutsches Institut fur Normung, the German standards organization. In flange purchasing, DIN is often used broadly to describe metric European-style flanges, even though many modern projects may reference EN standards as well. DIN flanges are usually described by DN size and PN pressure rating.

ANSI stands for American National Standards Institute. In current industrial flange work, many buyers say ANSI flange when they are actually referring to ASME B16.5 or ASME B16.47 flange dimensions. The phrase ANSI standard for flanges is therefore often used in the market as shorthand for ASME/ANSI flange standards.

Item	DIN / EN Style	ANSI / ASME Style
Size system	DN, millimeters	NPS, inches
Pressure system	PN, usually expressed in bar-based classes	Class 150, 300, 600, 900, 1500, 2500
Common markets	Europe, parts of Asia, metric engineering projects	U.S., Canada, Middle East, oil and gas, ASME projects
Dimension reference	DIN, EN 1092-1 or project metric standard	ASME B16.5 or ASME B16.47
Interchangeability	Not directly interchangeable with ANSI	Not directly interchangeable with DIN

Whats PN?

Whats PN? PN means nominal pressure. It is a pressure class designation used in metric flange systems, such as PN10, PN16, PN25 and PN40. A PN number is often associated with pressure in bar at a reference temperature, but real allowable pressure changes with material and temperature.

For example, a PN16 flange is not automatically the same as an ANSI Class 150 flange. They may be used in similar general-pressure ranges in some systems, but their dimensions, bolt patterns, gaskets and pressure-temperature tables are not identical. Always confirm the exact standard before replacing or mating flanges.

ANSI Class 150 and ANSI 150 Flange Meaning

ANSI Class 150 is one of the most common pressure classes for ASME-style pipe flanges. Buyers may write it as Class 150, 150 LB, 150#, ANSI 150 flange or ASME B16.5 Class 150. These phrases usually refer to a pressure class, not a simple 150 psi limit.

The actual pressure rating ANSI 150 depends on material and temperature. A carbon steel Class 150 flange at room temperature has a different allowable pressure from the same class at elevated temperature. This is why engineering teams use ASME pressure-temperature rating tables instead of treating the class number as the working pressure.

Term	What It Means	Buyer Note
ANSI Class 150	ASME-style pressure class commonly used for pipe flanges	Confirm ASME B16.5 or ASME B16.47 and material group
ANSI 150 flange	Market wording for Class 150 ANSI/ASME flange	Specify NPS, face type, material and schedule bore
Flange rating ANSI	Pressure-temperature class system such as 150, 300 or 600	Do not convert directly to PN by number only
PN16	Metric nominal pressure class used with DIN/EN flanges	Check EN/DIN dimensions, bolt holes and facing

Why DIN and ANSI Flanges Are Not Directly Interchangeable

A DIN flange and an ANSI flange may have the same nominal pipe size range, but the details often differ. The most common mismatch is the bolt pattern. Bolt circle diameter, hole diameter and number of holes may not align. Even if the bolts pass through, the sealing face and gasket dimensions may still be wrong.

Important differences include:

• DN vs NPS size naming.
• PN vs Class pressure designation.
• Bolt hole quantity and bolt circle diameter.
• Flange outside diameter and thickness.
• Raised face, flat face or other facing dimensions.
• Gasket dimensions and compression area.
• Pressure-temperature rating tables.

DIN Flange vs ANSI Flange Comparison Table

Question	DIN Flange Answer	ANSI Flange Answer
How is size written?	DN50, DN100, DN200	NPS 2, NPS 4, NPS 8
How is pressure class written?	PN10, PN16, PN25, PN40	Class 150, 300, 600, 900
What units are common?	Metric dimensions in millimeters	Inch-based nominal pipe sizes with inch or mm drawings
Can it mate with the other standard?	Usually no, unless a proper adapter is engineered	Usually no, unless a proper adapter is engineered
Where is it common?	European and metric-system projects	ASME piping, oil and gas, North American systems

How to Compare PN and ANSI Class 150

Many buyers ask whether PN16 equals ANSI Class 150. The cautious answer is: not exactly. Some project engineers may use PN16 and Class 150 in similar service ranges, but they are different standards with different dimensional rules and rating tables. A simple pressure number comparison is not enough.

Comparison Point	What to Check	Why It Matters
Pressure rating	Material and temperature derating table	Allowable pressure changes as temperature rises
Dimensions	OD, thickness, bore, bolt circle and hole size	Prevents field mismatch
Face type	RF, FF or other face design	Controls gasket selection and sealing
Dichtung	Full face, ring gasket, spiral wound or other type	Wrong gasket can leak or crush
Bolting	Bolt count, diameter, grade and torque practice	Ensures proper assembly load

When to Choose DIN Flanges

DIN flanges are often a good choice when the project is based on metric drawings, DN pipe sizes, PN pressure classes and European-style equipment connections. They are common in water treatment, chemical systems, food equipment, machinery skids and many export projects that specify DIN or EN dimensions.

Before ordering, confirm whether the RFQ requires older DIN dimensions, EN 1092-1 dimensions or a customer drawing. The words DIN flanges may be used broadly, but the exact standard should always be written clearly.

When to Choose ANSI Flanges

Choose ANSI flange or ASME flange products when the piping specification references ASME B16.5, ASME B16.47, NPS pipe sizes and Class pressure ratings. This is common in oil and gas, petrochemical plants, power generation, industrial utilities and North American projects.

For an ANSI Class 150 order, specify the full description, such as ASME B16.5 NPS 4 Class 150 RF ASTM A105 weld neck flange. This avoids confusion between pressure class, material grade, face type and bore.

Ordering Checklist for DIN and ANSI Flanges

Information Needed	DIN Example	ANSI Example
Standard	DIN / EN 1092-1	ASME B16.5 / ASME B16.47
Size	DN100	NPS 4
Pressure class	PN16	Klasse 150
Face type	RF or FF according to standard	RF, FF or RTJ
Material	C22.8, P245GH, stainless steel or drawing material	ASTM A105, A182 F304, A182 F316, alloy steel
Flange type	Plate, weld neck, slip on, blind or threaded	Weld neck, slip on, blind, socket weld or threaded
Documents	MTC, dimensional report, marking photos	MTC, dimensional report, marking photos

FAQ

Is DIN flange the same as ANSI flange?

No. DIN flange systems use metric DN/PN designations, while ANSI or ASME flange systems use NPS/Class designations. Their bolt holes, thickness and face dimensions are usually different.

What is the ANSI standard for flanges?

In today鈥檚 market, the phrase ANSI standard for flanges usually points to ASME B16.5 for common pipe flanges and ASME B16.47 for large diameter steel flanges. The exact project specification should be confirmed.

What is flange rating ANSI?

Flange rating ANSI refers to pressure classes such as Class 150, 300, 600, 900, 1500 and 2500. The actual allowable pressure depends on material and temperature.

Can ANSI 150 flange replace PN16 flange?

Not directly. An ANSI 150 flange and PN16 flange may serve similar general pressure ranges in some cases, but dimensions and bolt patterns often differ. Use an engineered adapter or order the correct standard.

How should I write an RFQ for mixed DIN and ANSI projects?

List each connection separately with standard, size, pressure class, material, face type, flange type, quantity and drawings. Do not rely on approximate conversions alone.

Final Thoughts

The difference between DIN flanges and ANSI flanges is not only language or geography. It includes the whole engineering system: size, pressure class, bolt pattern, face design, gasket practice and pressure-temperature rating. For export projects, Songhai Flange can support DIN flange, ANSI flange, ASME flange and custom transition requirements based on drawings, material grades and inspection documents.