To tell you about the silicone-filled gaskets, In this section, we will give an introduction to the complexity of fluid sealing.
In the food, pharmaceutical and fine chemical industries, among others, the management of their fluids is not easy.
And it gets more complicated when the fluids have a certain viscosity or involve suspended particles. We are referring to slurries, syrups, slurries, leachates, molasses and food fluids, among others.
On this occasion, we are going to see how these fluids condition the design of the dynamic seals to be installed in the rotating equipment involved in their handling: pumps, mixers, valves, dosing units, rotary evaporators, agitators, reactors, etc.
We also discussed why silicone-filled gaskets are a very good solution.
Index
Difficulties in sealing inherent to the type of fluids
A pharmaceutical laboratory or a tomato juice plant, to cite two examples, may have in common that the nature of some of their process fluids is determined by their chemical aggressiveness.
Consequently, the seals chosen for dynamic sealing of the equipment must be made of materials resistant to chemical attack. The best performers are PTFE formulations with fillers, ultra high molecular weight polyethylene (UHMW-PE) and even polyetheretheretherketone (PEEK).
On the other hand, both PTFE collars with UHMW-PE or PEEK fillers need a spring to keep the sealing lips separated from each other, since these materials have no elastic memory.
Adding the spring is what we know as “energizing the joint”.
At this point, it is clear that to avoid leaks in our equipment, we will need an energized lip seal, based on a formulation with sufficient chemical resistance.
The problem arises, what can happen to our gasket if the fluid is loaded with grit or if it brings with it the remains of the crushed tomato?
What most probably happens is that the fluid or foreign bodies affect the proper functioning of the spring, blocking its coils, thus reducing the tension it exerts.
Then, the seal lip loses the force that holds it in position and gives way due to interference with the shaft. The conclusion is that the probability of the seal suddenly leaking is very high.
We may also find that the spring is a niche for bacteriological growth, which is a situation to be avoided in food and pharmaceutical applications.
Silicone-filled gaskets: a suitable solution
The solution to this problem is to inject silicone that fills the cavity and plugs all the gaps between the spring and the lips of the sealing gasket, thus creating the necessary cavities. silicone-filled energized gaskets.
In this way, the filler will prevent foreign bodies, which may be contained in the process fluid, from affecting the tension of the seal lips.
The following image corresponds to a rotary joint model DR 117 energized by a «U» spring and with an immobilization flange. And the same piece with silicone filling.
It is a clean design, without dead zones and suitable for CIP cleaning, as long as the chemical resistance of the silicone to the chemical agents to be used is verified.
In addition, silicone filler is used in collars made from silicone. If the fluid permits, the use of these collars has two advantages:- - No spring
- - Design of housings without the radial section and part height restrictions imposed by the spring.
The silicone filling prevents, as an example, the remains of the crushed tomato from accumulating between the lips of the collar, rotting and damaging the juice being processed. Collar without dead volume between the lips.
Characteristics of the silicone filler
The use of silicones in sealing applications is well known.
The silicone in question is a polymer, consisting of a backbone of alternating silicon and oxygen atoms, to which methyl and vinyl groups are attached to the silicon atom.
The filler material is usually a one or two-component liquid silicone, with the particularity that it polymerizes and vulcanizes at room temperature (RTV - Room Temperature Vulcanizing), in the hollow of the pier.
In specific cases, vulcanization can be accelerated by heating the part. The silicone can be white or red.
What do we achieve with silicone-filled gaskets?
Thanks to the silicone-filled gaskets, In case of contamination of the process fluid with small particles, these will not be deposited between the lips of the seal and therefore, the tightness will not be altered.
Thus, we present you a solution for dynamic sealing radial very suitable for those industries that work with corrosive fluids and at the same time, contaminated with particles in suspension, or with a need of design without dead zones.
As a complement to this article, you can read the blog post describing the CIP cleaning / SIC, The company's products are widely used in the food and pharmaceutical industries.
We hope that this blog has helped you to learn more about the functionalities of the silicone-filled energized gaskets.
If you still have any doubts, contact our specialist sealing department. In case you want more related information, visit our website.