What is a rod seal?
There are so many different types of seals out there that it might be hard to understand all the different terminologies and functions. In this article, we give you our guide to what rod seals are, how they are manufactured and why you should choose rod seals from Martin’s Rubber.
Rod seals are often the decisive factor in ensuring that a hydraulic cylinder operates at peak performance. Leakage through the rod seal can lead to environmental damage and accidents, which is why it’s crucially important to select the correct seal for your application. While leakage past a piston seal will affect its efficiency, the system fluid or gas remains contained in the system. With a rod seal, failure will allow external leakage, and it should be paired with an appropriate wiper and gland housing design to ensure correct operation.
How do rod seals work?
Rod seals perform the difficult balancing act of creating a seal at both high and low pressure. This is often in combination with alternating high and low temperatures. As such, they need to leave an oil film, thin enough to return into the cylinder, after having passed an effective wiper seal. When selecting a piston rod seals, it is important to define your area of application and provide carefully defined specifications. Martin’s Rubber can then give you our recommendations for an appropriate rod seal to match your specific operating conditions.
The key element of the buffer seal is the lubrication film thickness which passes the sealing edge. It is responsible for the performance of the entire rod sealing system. Different pressure and speed conditions during the in- and outstroke of the piston rod are typical for heavy-duty hydraulic cylinders and result in different oil film thickness. Therefore, the buffer seal needs to be designed to ensure a hydraulic cylinder rod step seals and absorb pressure peaks during operation.
An additional advantage of this type of seal is that the primary cylinder rod seals SPNO gets better lubrication, leading to smooth running equipment. If the buffer and primary rod seal work together correctly (as described above), friction in the entire rod sealing system can be similar to that of a single rod seal component. Reducing friction extends the life of the rod seal and the entire hydraulic cylinder.
The influence of different in- and outstroke velocities has already been analyzed for a common U Cup rod seals ISI (see above graph). The results show that if outstroke velocity is much higher than instroke velocity, the likelihood of leaks increases. On the other hand, if instroke velocity is much higher than outstroke velocity, it is more likely the low-level of lubrication will increase friction on the instroke.