Static seals and V-rings: small components, great reliability

When people think of seals, they naturally picture those working on moving rods and pistons. But every hydraulic system also has dozens of static seals: between head and tube, between flanges, under covers, in fittings and valves. Then there are V-rings, small axial seals that protect bearings and oil seals on rotating shafts. Simple components, but decisive for reliability.

Static seals

What they are

A static seal seals two parts that do not move relative to each other. It sounds easy, but the seal must withstand pressure, peaks, vibration, thermal expansion and sometimes small movements caused by parts "breathing" under pressure.

The most common types

• O-rings: the most widespread solution for radial and axial grooves, often combined with back-up rings at high pressure.
• Static seals with support ring: specific profiles, for example for sealing between the head and tube of cylinders, designed to better resist extrusion and pressure pulsation.
• Bonded seals (metal washer with elastomer lip) for screws and fittings.
• Flat gaskets for flanges and covers.

In our catalogue, in the static seals category, you will find several dedicated profiles as well as the wide range of O-rings.

How to choose them

1. Type of groove: radial (on a diameter) or axial (on a face), groove dimensions.
2. Pressure and pulsation: high or variable pressures require anti-extrusion profiles.
3. Temperature and fluid: the material must be compatible.
4. Surface finish: even a static seal leaks if the surface is scratched or corroded.

V-rings

How they work

A V-ring is an elastomer ring fitted on the shaft that rotates with it. Its conical lip rests axially against a surface perpendicular to the shaft (for example the face of a bearing or housing). Thanks to centrifugal force, when the shaft turns the lip throws off dirt, dust and water splashes.

Where they are used

• As additional protection in front of an oil seal in very dirty environments;
• As the main seal against dust and splashes for grease-lubricated bearings;
• In electric motors, gearboxes, agricultural machinery, conveyors, industrial washing machines.

Profiles and selection

There are several V-ring shapes (standard, compact, wide section or with a stepped fit) suited to different spaces and speeds. To choose one you need the shaft diameter, the available axial space and the distance from the counterface. The V-ring is fitted with some stretch on the shaft and positioned so that the lip is slightly compressed.

Mistakes to avoid

• Reusing O-rings and static seals after dismantling: a compressed seal has lost its initial elasticity.
• Tightening flanges unevenly: the seal is squeezed irregularly.
• Fitting a V-ring without respecting the installation distance: too compressed, it wears; too far, it does not seal.
• Ignoring chemical compatibility because "it is only a static seal": an incompatible material swells or hardens even without movement.

Static seals, O-rings and V-rings are available in our catalogue in a huge range of sizes. With the search by dimensions you will quickly find the right spare part; for special profiles or doubts about the material, contact our technical support.

Frequently asked questions

Do static seals need lubricating too?

Yes, during assembly: a film of compatible lubricant prevents the O-ring or seal from twisting or being cut as it enters the groove.

How do I choose a V-ring size?

The main reference is the shaft diameter; then check the available axial space. Each V-ring size covers a small range of shaft diameters.

Can bonded seals be reused?

Better not: after the first tightening the elastomer has conformed to the surfaces and may no longer seal reliably.