Have you ever wondered what the difference is between static and dynamic seals and their uses in sealing technology?
Seals find their applications in a vast array of sectors. Whether as a simple sealing set in a hydraulic cylinder, as a rotary seal in a mill, in rolling mills or even in domestic households as an O-ring in a faucet, for example. The scope of application is varied, as are the different types of seals. Wipers, rod seals, flat gaskets, O-rings, and much more.
There is a specific type of seal and material for every application. They ensure that machines and equipment operate flawlessly or prevent hazardous substances from leaking. These types of seals are categorized into many subtypes. Among these are static and dynamic seals. But what is the difference between them? In the following blog post, we aim to give you a closer insight into this topic. Read more seal information and explore our application areas for seals.
What is the role of seals?
Seals and gaskets are used to separate two rooms with different contents. This is intended to reduce or even prevent the exchange of solid, liquid or gaseous elements.
They can prevent the escape of hazardous substances, for example, with the help of sealing technology. Toxic, corrosive liquids can otherwise be a danger to the environment and employees. Gaskets can also protect the sensitive inner workings of a machine from contamination. In this way, the penetration of dirt, dust or moisture is inhibited.
In addition, seals play a significant role in the service life of systems. With direct contact of metal parts, the wear would be significantly higher. The interplay of entire sealing sets determines the durability of the devices.
What is a static seal?
A static seal is inserted between two immovable components. Its task is to prevent the transfer of substances. With static seals, the surfaces to be sealed are in constant contact. Therefore, the rate of leakage is relatively low.
Static seals require a minimum necessary clamping force and must not exceed a maximum allowed pressure, aspects that vary depending on the type of seal, material, and manufacturer. Additionally, the pressing forces between the sealing material and the parts to be sealed can be higher as there are no frictional forces like those in dynamic seals.
Static seals can be applied purely by external forces, such as in the case of flat gaskets. In contrast, pressure-activated static seals, like O-rings, experience an increase in sealing pressure proportional to the system pressure
Areas of application of static seals
Typical areas of application for static seals include the sealing of flanges, valves, plates, or closures. Flat gaskets are frequently used for these purposes. Depending on the application, a variety of technical materials are utilized for these seals.
Among the most common are aramid fiber materials from companies like Frenzelit and Klinger, or flat gaskets made from NBR. Flat seals made of FKM, EPDM, polytetrafluoroethylene (PTFE), graphite, or even sealing paper are also employed.
O-rings are also commonly used as static seals. They effectively seal almost all liquid and gaseous substances. They are available in elastomeric and other materials. Depending on the application, support rings are often incorporated with O-rings to enhance their pressure resistance and prevent gap extrusion.
Support rings are primarily made of PTFE or PU. Interestingly, static seals also encompass non-detachable connections such as welded, soldered, glued, or pressed connections. Static seals find applications across various industrial sectors, including turbine construction, hydroelectric power plants, heavy chemistry, and the pharmaceutical industry, among others.
What is a dynamic seal?
Dynamic seals derive their name from the movement to which they are exposed. Their purpose is to seal between two components that move relative to one another, thereby preventing or limiting substance exchange to an acceptable level.
A sealing gap is often inevitable, but it can be advantageously utilized. For instance, lubricant can be introduced into it during operation. The elements to be sealed can come into contact with each other in dynamic seals just as they do in static seals.
However, there are also non-contact seals that operate without the mechanical contact between the two parts and sealing materials. The service life of the seal is notably high – but so is the leakage.
Areas of application of dynamic seals
The use of dynamic seals is dependent on the following factors:
Translational, rotational movement, or a combination of both
Movement speed (rotational speed or stroke speed)
Medium to be sealed (oil, air, water, etc.)
Level of sealing performance required
Temperature differential
Magnitude of pressure differential
Effort required for installation
Costs
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