Tri Clamp Dimensions & Sizing Guide
Tri Clamp fittings (also known as Tri Clover or sanitary fittings) are widely used in food, beverage, pharmaceutical and biotech applications. This guide explains how Tri Clamp sizing works and shows a dimension table based on the 3-A Sanitary (OD-tube) standard, which is also used by most modern European and Chinese manufacturers.
1. How Tri Clamp Sizes Are Defined
Nominal Tri Clamp sizes are based on the outer diameter (D1) of the tube (for example 1.5" OD tube), not on the clamp or ferrule outside diameter.
2. What Makes a Complete Tri Clamp Connection?
A complete Tri Clamp connection consists of:
- Two ferrules (welded or otherwise attached to the tubing)
- One clamp (that closes around the ferrule flanges)
- One gasket (between the ferrules, providing the seal)
All parts must be the same Tri Clamp size (for example 2") so that the ferrule OD, clamp and gasket match.
3. How to Measure Tri Clamp Components
- Tube (D1, D2): D1 is the tube outer diameter (nominal size). D2 is the typical tube inner diameter for the given wall thickness.
- Ferrule: Measure the ferrule outside diameter (clamp flange). This tells you which clamp and gasket series you need (25.4 mm, 34 mm, 50.5 mm, 64 mm, 77.5 mm, 91 mm, 106 mm, 119 mm, 167 mm, 217.7 mm, etc.).
- Clamp: The clamp is selected by the ferrule OD, not by tube size directly.
- Gasket: Choose the gasket by the same ferrule OD. For hygienic processes it is good practice to select a gasket whose inner diameter is close to the tube ID (D2), especially for sizes that are used with several tube wall thicknesses.
4. Tri Clamp Size Chart (3-A Based)
The image below shows how the dimensions correspond to the Tri Clamp ferrule.
The table below lists common Tri Clamp sizes and typical dimensions. Ferrule OD values follow the 3-A / ASTM A270 Tri Clamp connection standard; tube IDs (D2) are typical values and may vary slightly between manufacturers. In our internet shop you also mainly will find fittings based on 3-A / ASTM A270 standart.
| Nominal size in inches | Nominal size in mm | Ferrule OD | D1 | D2 |
|---|---|---|---|---|
| 1/2" | 12.7mm | 25.4mm | 12.7mm | 9.7mm |
| 3/4" | 19mm | 25.4mm | 19mm | 16mm |
| 3/4" | 19mm | 34mm | 19mm | 16mm |
| 1/2" | 12.7mm | 50.5mm | 12.7mm | 9.7mm |
| 3/4" | 19mm | 50.5mm | 19mm | 16mm |
| 1" | 25mm | 50.5mm | 25.4mm | 22.4mm |
| 1 1/4" | 32mm | 50.5mm | 31.8mm | 28.8mm |
| 1 1/2" | 38mm | 50.5mm | 38.1mm | 35.1mm |
| 1 3/4" | 45mm | 64mm | 45mm | 42mm |
| 2" | 51mm | 64mm | 50.8mm | 47.8mm |
| 2 1/2" | 63mm | 77.5mm | 63.5mm | 59.5mm |
| 3" | 76mm | 91mm | 76.2mm | 72.2mm |
| 4" | 102mm | 119mm | 101.6mm | 97.6mm |
| 5" | 127mm | 144.5mm | 127mm | 120mm |
| 6" | 152mm | 166.7mm | 152.4mm | 147.4mm |
| 6 1/2" | 159mm | 183mm | 159mm | 153mm |
| 8" | 204mm | 217.7mm | 203.2mm | 196.7mm |
| 10" | 254mm | 268mm | 254mm | 250mm |
Note: 1/2" and 3/4" tube sizes appear with several ferrule ODs (25.4 mm, 34 mm, 50.5 mm). Choose the version that matches the clamp size already used in your system.
5. Practical Sizing Tips
- Always confirm the ferrule OD with a caliper before ordering new clamps or gaskets.
- When mixing components from different suppliers (EU, US, China), use 3-A based dimensions (as in this table) as the reference.
- Use reducers if you need to connect different tube sizes but want to keep the same clamp size.
- For hygienic applications, match gasket ID as closely as practical to tube ID to minimise dead zones.