Tri Clamp Gaskets
Clamp and Gasket Sizing
Tri Clamp flanges of the same size use the same size clamp. We sell 1/2″ and 1.5″ clamps in our shop for use in any fitting advertised as 1/2″ or 1.5″ Tri Clamp respectively.
However you may wish to give special consideration to the gasket size. Tri Clamp Gaskets are sized for both the outer diameter of the flange and the inner diameter of the tube.
For example a 1.5″ gasket has an OD of 50.4 mm and ID of 34.8mm, matching the BS standard for 1.5″ tubing. A DN40 gasket has an OD of 50.4 mm and an ID of 38mm. This leads us to the following considerations:
- If you connect two DN40 Ferrules with a 1.5″ standard gasket, the gasket will create a slight obstruction of flow in your application.
- If you connect two 1.5″ Ferrules with DN40 gasket, there will be a brief increase in diameter between your two fittings at the gasket
Case 1 should be avoided. Case 2 is acceptable, as long as you are not concerned with the flow dynamics and are not designing a critical CIP (Clean in Place) System. In CIP systems this change in inner diameter between fittings becomes a critical factor, because you do not want any obstruction in the flow path where dirt and bacteria can collect. For homebrew applications, it is generally fine to use a gasket with a larger ID than your two fittings. Just remember to regularly disassemble your parts for cleaning.
What about connecting two parts of completely different ID? For example a DN15 Valve with a DN40 ferrule? This is a pretty common application. In this case, pretty much any 50.4 mm gasket with an ID > 15mm is fine. Yes a 40mm ID gasket might be slightly better because the entirety of the gasket will be clamped tightly between the two parts. A 15mm gasket will sit “loose” between the two fittings and theoretically could trap particles at that location. In practice I don’t see this as being a big concern.
When connecting two Tri Clamp parts together, make sure your gasket ID is larger than the smallest ID of your two parts! Otherwise the gasket can restrict your flow.
But if you want to get it perfect, you should always try to choose the inside diameter of the gasket to fit the largest inside diameter tube that will be connected.
Many of our valves, connectors, and adapters use a ISO 11850 DN15 tube size with an OD/ID of 18mm/15mm. When connecting two such components, you can still use a DN40 gasket (ID = 38mm). This will leave a small bit of dead space between the two fittings, and if you want to eliminate this space you should choose the DN15 (ID = 16 mm) gasket.
We make every effort to provide specific information about which gaskets and clamps should be used for every fitting we sell in our shop. If you are still unsure, feel free to ask us before your purchase!