Seals

What is a seal and what does it actually do?

A seal is a small part with a big job. Its role is simple: keep fluids in, keep contaminants out, and make sure two components work together without leaks. When it’s doing its job properly, you don’t even notice it. When it fails, you notice immediately.

Most seals are made from materials like NBR, FPM (Viton®), EPDM, polyurethane, or silicone. The material matters just as much as the shape. Temperature, pressure, movement, and the type of fluid involved all influence the choice. Whether you’re installing new equipment or replacing a worn-out seal, selecting the right one isn’t optional — it’s critical. The wrong seal won’t last.

At CSB, we offer a wide range of seals in different materials and profiles to match real-world operating conditions. Every application is different, and the seal must match the job.

The main types of seals

Here are the most common categories you’ll come across:

Rotary Shaft Seal (SPI Seal)

Often called an SPI seal, this type is essential for rotating equipment. It prevents oil or grease from leaking along a spinning shaft. You’ll find them in gearboxes, crankshafts, and clutches – especially in automotive applications.

They’re available in single-lip or double-lip versions, depending on whether you need extra protection against dust or contaminants.

Hydraulic Seals

Hydraulic seals are built to handle pressure — sometimes extreme pressure. They seal moving components such as pistons and cylinders in hydraulic systems. The material you choose determines how much pressure and wear the seal can withstand. In hydraulic applications, durability isn’t a luxury – it’s a necessity.

O-Rings

The O-ring is one of the simplest and most versatile seals. Shaped like a torus, it works in both static and dynamic applications. You’ll see them everywhere: in hydraulic systems, pneumatic systems, and countless industrial assemblies. When sized and selected correctly, they provide reliable, cost-effective sealing.

Wiper Seals

Wiper seals are installed on moving shafts, such as hydraulic cylinders. Their job is to keep dirt, dust, and moisture from entering the system. They protect internal components and extend equipment life. Without a proper wiper seal, contamination quickly becomes a problem.

When should you replace a seal?

If you see a leak, the answer is obvious — replace it.

But even without visible failure, seals shouldn’t automatically be reused after disassembly. Once installed, a seal conforms to its housing. Removing it changes its geometry, and refitting it rarely guarantees the same performance.

If the seal hasn’t been removed, replacement depends on operating conditions, wear, and exposure. In demanding environments, preventive replacement often saves far more than it costs.

How to identify the right seal

Unlike bearings, seals aren’t standardised by universal part numbers. The same application from two manufacturers can use completely different profiles. That’s why measurement is essential.

For rotary shaft seals, hydraulic seals, or wiper seals, you’ll need:

For O-rings, you’ll need:

Why order your seals from CSB?

At CSB, we don’t just ship parts – we help you get it right.

Not sure which material suits your application? Need help identifying the correct profile? Our team works with sealing solutions every day and can guide you quickly and clearly.

And when it comes to value, we combine quality products with competitive pricing, which is why professionals trust us as a long-term partner, not just a supplier.