Tri-Clamp Size Chart Australia: Ferrule Sizing Guide

Ordering the wrong tri-clamp size is easier than it should be, because the nominal size on the label refers to the tube, not to the part of the fitting that actually determines your clamp and gasket. To get the right components, you need to measure the outside diameter of the ferrule flange (the flat sealing face), not the tube. 

That single measurement drives everything else, and this guide shows you what the numbers look like under ASME BPE and DIN 32676.

How Tri-Clamp Sizing Works

A tri-clamp connection has three measurable dimensions: the tube OD (the pipe it is welded to), the ferrule bore (the internal flow diameter), and the ferrule flange OD (the wide circular sealing face that the clamp grips). Only the ferrule flange OD is shared between two mating ferrules, and it is the only dimension that matters when selecting a clamp or gasket.

The nominal size, whether expressed in inches or as a DN designation, is a catalogue reference that corresponds to the tube, not to the flange. A 1" ASME BPE ferrule sits on a 25.40mm tube but presents a 50.5mm sealing face. This explains why the nominal size printed in a catalogue rarely matches the flange measurement taken on site.

ASME BPE Tri-Clamp Size Chart

ASME BPE (Bioprocessing Equipment) is the standard used on pharmaceutical-grade, biotech, and high-purity process systems, particularly those of US design. Its nominal inch sizes correspond to actual tube OD: a 1" ASME BPE ferrule welds directly to 25.40mm OD tube.

Inox Fittings Australia stocks the DT22B standard-length ASME BPE ferrule: 28.6mm leg, 316L stainless, SF1 surface finish 0.51Ra µm max, available from 1/2" through 4".

Important note: Ferrule flange measurements are not unique to one nominal size. For example, ASME BPE 1/2" and 3/4" ferrules both have a 25.4 mm flange, while DIN DN10, DN15 and DN20 ferrules all have a 34.0 mm flange. Record both the tube OD and ferrule flange OD before ordering.

DIN 32676 Tri-Clamp Size Chart

DIN 32676 is the European standard for food and beverage, dairy, and chemical processing systems designed in Europe. It uses DN (nominal diameter) designations that describe the approximate bore, not the tube OD. A DN25 ferrule fits a 28mm OD tube, and the two figures do not match, which is a common source of confusion when ordering.

The table below covers DIN 32676 Series 1, the most widely used variant for food and beverage applications. Inox Fittings Australia stocks the full DIN 32676-A metric range from DN6 through DN125; sizes outside this table should be confirmed against the product page before ordering.

The Shared-Flange Trap

Measuring the ferrule flange OD is the right starting point, but the same measurement can correspond to more than one nominal size. This is the most common source of ordering errors in tri-clamp systems.

In the ASME BPE range, 1/2" and 3/4" both produce a 25.4mm ferrule flange reading. If you put a calliper on either of them, you’ll get the same number. A 1" and a 1 1/2" ferrule both measure 50.5mm across the sealing face. 

Because the flange ODs are identical, the same clamp can fit both ferrules. A gasket with the same outer profile may also sit inside the clamp, but its internal bore must still suit the tube or ferrule size. Choosing the wrong bore can create a step or gap in the flow path.

A similar overlap occurs in DIN 32676. DN10, DN15 and DN20 all have a 34.0mm flange, while DN25, DN32 and DN40 all measure 50.5mm.

The safe approach is to always record both measurements, ferrule flange OD and tube OD, before placing an order. The ferrule flange OD selects the clamp and gasket series; the tube OD confirms which nominal size within that series you actually have.

Gaskets and Clamps Follow the Ferrule, Not the Tube

Clamps and gaskets are specified by ferrule flange OD, not by tube size or DN designation. A clamp listed as "1 1/2" works on any ferrule with a 50.5mm flange, whether that is an ASME BPE 1" or 1 1/2", or a DIN DN25, DN32, or DN40 ferrule.

When sourcing tri-clamp fittings from Inox Fittings Australia, products are listed by nominal tube size. Locate your tube OD in the relevant table above, confirm the matching ferrule flange OD, and use that flange OD to select your clamp and gasket. If you need a full-bore gasket with an inner diameter closely matching the tube ID, confirm both the ferrule flange OD and the tube ID before ordering, as bore sizes vary between ASME BPE and DIN components.

Which Standard Do I Have? ASME BPE vs DIN 32676 vs ISO 2037

If you are working with an existing system and need to identify the standard, tube OD is the most reliable distinguishing measurement.

ASME BPE

The tube OD matches the nominal inch designation exactly. A 1" nominal line measures 25.40mm OD. ASME BPE is common on US-designed pharmaceutical, biotech, and high-purity process systems, often specified with SF1 or SF4 internal surface finishes.

DIN 32676

The tube OD is a round metric figure that does not correspond to an inch designation. A fitting that looks like a 1" nominal but measures 28mm tube OD is almost certainly DIN DN25. DIN ferrules are standard on European-built food and beverage, dairy, and brewing equipment.

ISO 2037 

A third standard you may encounter, particularly on older European systems. It uses inch nominal sizes but metric tube ODs. ISO 2037 specifies 25mm OD for a 1" nominal, against ASME BPE's 25.40mm. The 0.40mm difference matters at the weld and for full-bore gasket selection, so it is worth confirming if you cannot trace the original equipment documentation.

When in doubt, contact the Inox Fittings team on 1300 017 018 with both your tube OD and ferrule flange OD measurements, and we can confirm the standard and matching components.

FAQs

How do I measure a tri-clamp fitting?

Measure across the flat sealing face of the ferrule flange with a vernier calliper. This flange OD determines the clamp series. You should also measure the tube OD, as several nominal sizes share the same flange measurement, and the tube OD helps identify the exact fitting size and standard.

Why doesn't my ferrule measurement match the nominal size?

Tri-clamp nominal sizes refer to the tube the ferrule welds to, not to the ferrule flange itself. A 1" ASME BPE ferrule sits on a 25.40mm tube but has a 50.5mm sealing flange. The nominal size is a catalogue designation, not a measurement you will find directly on the fitting. Because each standard follows its own sizing system, the tables above provide a more reliable reference than the component’s stamped size.

Are DIN 32676 and ASME BPE tri-clamps interchangeable?

At the clamp-and-gasket level, sometimes. Several sizes share the same ferrule flange OD across both standards. ASME BPE 1" and 1 1/2", and DIN DN25, DN32, and DN40 all use a 50.5mm clamp and gasket, so they will physically connect. However, the tube ODs differ, meaning a DIN ferrule cannot be butt-welded to an ASME BPE tube without a mismatch at the weld. If you are connecting across standards, do so at the flanged joint using a compatible gasket, and keep the tube and butt-weld sections within a single standard wherever possible.

What size gasket do I need for my clamp?

Find your ferrule flange OD in the table above and order a gasket to match that measurement. A 64mm ferrule flange OD requires a 2" ASME BPE gasket or a DN50 DIN 32676 gasket; both cover the same 64mm flange. For full-bore, hygienic applications, confirm the gasket inner diameter matches your tube ID as closely as possible to avoid a step at the joint that could trap product.