Introduction to Dynamic Seals

FIRST IMPRESSIONS ABOUT THE USE OF BLOGGER AS A RESEARCH TOOL

I have just started using this blog to share some of my research about the dynamic sealing problem. It is desirable to share my hypothesis, analyisis, conclusions and impressions with any reader interested in this topic. Internet is a great tool that alllow us researchers to help each other, share articles, papers, or recommend lectures. If this net would have not been stablished, research would be a slower, innefficient task. In the present world, it is a necessary activity for any researcher to use any search and share tool that is available, to contribute to worlwide investigation, both with his own work and supporting other colleagues studies.

INTRODUCTION TO THE DYNAMIC SEALING PROBLEM

Explosion engines, hydraulic pumps, pneumatic pistons,... are some applications that have some features in common: a reciprocating surface that has a relative movement against a fixed surface. Moreover, the three applications involve the fact that both surfaces form a closed volume, where a fluid is pressurized. 

This increase in the pressure of the fluid stablishes a pressure gradient between the fluid that is inside the volume, and any fluid that could be located outside. 

In some cases, it is desirable that this gradient is stablished, as it could be the application aim to pump fluid into a stream, a vessel, or even the final objective could be to accelerate the fluid to very high speeds, like in water-jet cutting.

But, in our field of investigation, the pressure gradient is a non-desired effect, because it stablishes fluid leaks, that reduce the efficiency of the system, or they produce wear on some of the parts that comprise the whole system.

Dynamic seals are parts, or assemblies, that have dual functions. On one side, the must provide low stiffness surface, so the volume that confines the fluid is always closed, even if any of the other parts is too strained. On the other side, they must allow the movable part to exert its reciprocating movement against the fixed surface. This second function can be very affected by the first one, because in order to have every borde surface closed, high contact forces are stablished, and as a cosequence, high wear can occure between the surfaces that move against each other.

Furthermore, if the fluid is very highly pressurized, its temperature is too high, or both pressure and temperature are high, the problem may combine special materials, designs,... as wear may greatly be increased because both high frictional forces, and material properties detrimental because of high temperature.

Finally, it is our objective to desing new seals that can provide a high reliabilty and durability, in order to increase the efficiency of the pumping systems. Efficiency is achieved both by reducing the spare parts cost, and allowing faster reciprocating movement and zero-leak working conditions.

Example: Trelleborg application using both static and dynamic seals.