Do you want to know what is leak tightness and what solutions exist for the operation of equipment and machinery so that they do not leak? In Epidor SRT we are a business dedicated to manufacture and market sealing solutions, so we help you to solve your doubts about the meaning of sealing in the industry and what sealing solutions exist according to the applications or technical needs in your machinery.
If you look up the word “estanqueidad” in the dictionary of the Royal Spanish Academy (RAE), it simply does not appear. You are redirected to “estanquidad” which is defined as “watertight quality”. And, when you look up the word “watertight”, you realize that no definition fits the ability of a part to prevent leaks.
Sealing is defined as the property provided by a part (or several parts) to a piece of equipment so that, once it is in operation, there is no leakage of the fluid it processes and/or the lubricant it needs for its correct operation.
Index
Tightness tests, according to their uses
For sealing purposes, we must distinguish three types of sealing, according to three needs or situations: if the equipment good is a static accessory (flange, cover, cover etc...), if it is a machine with a shaft that is rotating (process pump, agitator, compressor, mixer...) or finally, if it has a piston rod that moves (hydraulic cylinder, pneumatic cylinder, valve or piston pump, among others).
Thus, we are presented with three scenarios that will require different solutions depending on the application. In each of these cases we will need to perform different types of sealing:
- Static tightness.
- Dynamic Radial Sealing.
- Axial dynamic sealing.
Static Tightness
As the adjective indicates, this type of sealing is exclusive for equipment that does not have parts with relative movement between them. A simple example is the flat gasket that is mounted between the faces of a pipe flange to prevent leakage. Another example of static sealing is the rubber profile that is added to the glass of a car and prevents rain or wind water from entering.
The most commonly used solutions in static sealing are, among others: O-rings, profiles and flat seals of any geometry. In order to choose the appropriate material for the static sealing gasket in question, we must basically take into consideration the working temperatures (maximum and minimum), as well as the fluid in contact.
The range of materials for static seals consists of elastomers (EPDM, NBR, FPM, VMQ...), compressed fibers (aramid, carbon, cork, cellulose...), graphites, PTFE's and metal alloys (stainless steel, Monel, Inconel, Hastelloy etc...), among other materials.
Dynamic Radial Sealing
When the shaft of a rotating machine rotates, the sealing system to be implemented in the equipment will consist of a minimum of two components: one will prevent the process fluid from leaking and reaching the shaft bearing; and the second will contain the bearing lubricant and at the same time prevent external contaminants (dust, water, splashes...) from entering the equipment.
Typical seals are grease or oil seals, lip seals, V-rings, labyrinth seals and rotary joints (not to be confused with the equipment good, although they are referred to by the same name).
Usually, seals and flashings are made of elastomers (NBR, FPM, VMQ...); labyrinth seals are usually made of bronze (although stainless steel and PTFE options are also available) and, finally, rotary seals are made of PTFE formulations with fillers.
Each solution has its own characteristics and fields of application, which we will discuss in more detail in other articles. What you should know is that, for the same sealing problem, there is one or even several possible solutions depending on the service requirements.
Axial Dynamic Sealing
The approach to the problem of sealing when dealing with a rod that moves linearly (as is the case of a hydraulic cylinder, a piston of a pressure pump or the shaft of a valve) deserves a separate chapter and has nothing to do with Dynamic Radial Sealing.
Sealing systems for hydraulic cylinders include scrapers, collars for the piston rod and piston, low friction seals for both, compact piston seals and guides. Even in pneumatics, in addition to the parts already mentioned, it is necessary to take into account the so-called cushioning seals, whose function is to prevent a sudden impact of the piston at the end of the stroke.
In hydraulics, the materials commonly used are polyurethane formulations, since they have a very outstanding abrasion resistance. PTFE parts are also manufactured with fillers, which are known as low-friction seals.
In pneumatics, where the working conditions do not have the severity of a hydraulic cylinder, the various parts are manufactured from elastomer (basically NBR) in addition to low hardness polyurethane formulations.
At Epidor Seals and Rubber Technology we are experts in sealing solutions and we have a technical department made up of three applications engineers, a design draughtsman and a quality technician. All this, to advise and recommend the most suitable sealing solution to the needs of your industry. Do not hesitate to contact us and we will help you to solve your sealing problem..