Flared and Flareless Tube Connections: How They Seal
Jul 21st 2022
Hydraulic tube connections are commonly built around either a flared tube end or a flareless compression design. Both styles can create a dependable seal, but they do it in very different ways.
The right choice depends on the system pressure, the available installation space, vibration, and how often the line may need to be serviced.
How Flared Tube Connections Work
A flared connection starts by forming the tube end into a cone. In many hydraulic applications this is a 37 degree flare that seals against a matching fitting nose.
When the nut is tightened, the flared tube is clamped between the fitting seat and the sleeve or nut assembly. The seal is made by the shaped metal surfaces, so the tube flare, fitting angle, and mating surface condition all matter.
Flared fittings are often selected for rugged hydraulic circuits, higher pressure service, and applications where vibration resistance is important. JIC-style 37 degree connections are one of the most familiar examples.
How Flareless Connections Work
A flareless connection does not require the tube end to be flared. The tube is inserted into the fitting body, and a sleeve, ferrule, or bite ring grips the tube as the nut is tightened.
This can make installation faster because the tube end does not need a flaring operation. It can also help in tight spaces where forming or positioning a flare is difficult.
Because the ferrule or sleeve does the holding work, tube size, tube hardness, wall thickness, and tightening method have to match the fitting series.
Where Each Style Fits
Flared tube connections are a strong choice when the system needs a proven metal-to-metal hydraulic seal and the tube can be prepared correctly. Flareless fittings can be useful when repeatable assembly and compact installation are more important.
Neither style should be chosen by appearance alone. The fitting family, tube preparation, pressure rating, and maintenance plan should all match the same connection standard.