In most hydraulic systems, the rod moves a lot—back and forth, under pressure, and often in dirty, demanding environments. The seal on that rod has to do two things at once: hold back pressurized fluid from leaking out and stop dirt or moisture from getting in. It sounds simple until the pressure goes up, temperatures fluctuate, and everything is expected to work smoothly for thousands of cycles.
That’s where UN rod seals come in. They’ve been designed with these real-life challenges in mind. These seals aren’t just thrown into a system—they’re selected carefully depending on the materials involved and the working conditions.
Material Choice: PU or FKM?
Most of the time, we choose between Polyurethane (PU) and Fluoroelastomer (FKM), depending on what the job demands.
Let’s start with PU. This stuff is sometimes called the “fifth plastic”—for good reason. It's somewhere between rubber and plastic in behavior. If you've ever dealt with rubber that breaks down after being exposed to oil or acid, PU gives you a better shot. It handles wear better, doesn’t deform as easily, and takes abuse from hydraulic fluids without swelling or cracking. In field terms, it just lasts longer under tough conditions.
FKM, on the other hand, is the go-to when you're up against extreme heat or aggressive chemicals. It holds up when regular elastomers would melt or dissolve. In hot environments—say, engine compartments or high-performance pumps—FKM gives you confidence. Sure, it might cost a bit more, but when downtime is expensive, it pays for itself.
What Makes UN Seals Stand Out
People often ask, “Aren’t all rod seals basically the same?” Not quite.
The UN seal structure is particularly good at handling both pressure and motion. Its lip design provides just enough flexibility to adjust as pressure rises. That means when the hydraulic pressure increases, the seal doesn’t just hold—it tightens. And because of the material resilience, whether it's PU or FKM, the shape comes back after every stroke.
Temperature range? For PU, it's around -20°C to 120°C, which covers a good chunk of typical environments. FKM stretches it even further, sometimes well over 200°C.
We’ve seen UN rod seals used in all sorts of setups. Some recent ones include:
· Hydraulic cylinders in excavators—where pressure spikes are common.
· Automotive steering systems—especially in heavy trucks and buses.
· Industrial robotic arms—where precise movement and clean operation matter.
· Machine tools and presses—especially where oil leakage would be
disastrous.
They also show up in agricultural machinery, like in the arms of a sprayer system. These aren’t lab conditions; these are dirty, humid fields, and yet the seals keep doing their job.
We team can help you choose the right material based on your actual use case, not just a catalog number. They stock thousands of sizes, so urgent orders don’t sit in limbo. And if you need something custom—say, a seal that fits a non-standard groove or works with a unique oil type—they’ll design, prototype, and test it.
They’ve shipped to over 80 countries, support both large manufacturers and smaller workshops, and operate their own facilities—not just resellers.
UN rod seals might not be the flashiest part of your system, but they’re one of the most important. Choosing the wrong material, or a poor-quality seal, usually leads to leaks, downtime, and messy maintenance. On the other hand, getting it right means longer machine life, fewer failures, and smoother operation.
So, next time you’re reviewing a hydraulic setup—whether it’s in a piece of machinery or part of a new automation line—pay attention to the seal on the rod. It’s doing more than you think.
And if you’re unsure about the best fit, someone at DEDE has probably seen
your problem before. It’s worth asking.
