Reliable sealing
of the machine
Trouble-free operation
of the system
Low wear and long
service life
Plannable maintenance intervals
and minimisation of downtime
Increasing the energy
efficiency of the plant
Extensive tests in our
in-house technical centre
Protection of the product
from contamination
Easy installation and
cleaning
Reduction of
emissions
The task of a seal in these machines is to reliably seal the agitator shaft, minimize mixing losses and protect the mixing material from contamination. It should also prevent medium from entering the bearings and causing damage there. In summary, the aim is to ensure trouble-free operation of the plant and thus of the entire process.
This is exactly what the new SDF Series was designed for.
Until now, standard seals have been used in the aforementioned plants, which usually cannot fulfil all requirements at 100%. Stuffing boxes, for example, are simple in design, but react sensitively to shaft impacts and misalignments and thus have a very limited service life.
Mechanical seals provide low leakage due to their axially aligned sealing surfaces. They have a significantly long service life in normal operation, but noncircular running of the shaft can severely impair the function. However, depending on their complexity and type, mechanical seals are also expensive.
Gas-locked floating ring seals, on the other hand, can compensate for an a noncircular shaft and run very well. If designed correctly they can reach a long service life. however seals of this type are prone to seal gas leakage.
The STASSKOL DynamicSeal Faceseal combines the advantages of the known shaft seals without compromising on functionality. The axially contacting sealing surface minimizes leakage on the one hand through direct contact and on the other hand through the redirection of the material flow from the axial to the radial direction.
The large radial clearance in the sealing chamber makes it possible, similar to a floating ring seal, to maintain the sealing function even if the shaft runs highly out of round by up to 4 mm. The bearing of the sealing rings on the elastic inner component, made of STASSKOL’s own material SK5102, ensures contact at the dynamic sealing surfaces even in the case of misalignment between shaft and housing, effectively preventing leakage.
The use of sealing gas also ensures that if particles unexpectedly enter the sealing gap, they are blown out again. This greatly extends the service life of the STASSKOL DynamicSeal Faceseal.
In order to obtain optimum properties with regards to temperature development, wear and strength in the area of application, STASSKOL developed the new material SK933 especially for the sealing rings. In the first step, the material properties were determined on the in-house tribometer. Subsequent in-depth numerical studies were validated with the help of experimental studies on the seal test bed. This calculation model is now used to quickly estimate the function of the seal under changed operating conditions.
The minimalist design with few components enables easy assembly and disassembly at the point of use. All sealing elements and the housing are axially separable so that the seal can be mounted around the shaft without having to remove bearings and other attachments. In addition, the elastic inner component has a specially designed puzzle joint. The sealing rings can also be manufactured in this special design, so that the assembly can be carried out almost without tools.
The simple design of the seal also makes it possible to clean the components quickly and safely. The materials used are food-compliant and can also be used under extreme conditions of pH values between 2 and 11.
The new SDF has already proven its excellent performance in a twin-shaft horizontal mixer for animal feed. In the batch process, several barrels of cereal flour were mixed with various abrasive fillers such as stones and minerals per mixing process.
With a shaft diameter of 200 mm and a speed of 50 min-1, a noncircular run of 0.7 mm was found. With the conventional seal originally used, a product leakage of 25 kg per day was recorded. After replacing it with the new SDF, which occupies exactly the same space as the previous seal, the leakage was zero.
At the same time, the consumption of sealing air was minimized, thus increasing the energy efficiency of the plant.
