Rotary valves with new rotor geometry
Whether for discharging and metering or as a protective system in a potentially explosive zone - rotary valves are used in all kinds of industrial processes. Naturally, it is very important to use equipment that conveys the product gently, and which can also be retrofitted to requirements at a later date. The new EZS series of rotary valves fulfils these requirements.
Today pellets, tomorrow powders - industry must continually adapt its production and modify its products to the demands of the market, and at an ever faster pace. Those entrepreneurs who can employ their machine parks flexibly can consider themselves lucky. So it makes all the more sense for production plants to be relatively easily adaptable to changing conditions, by retrofitting for example. Engelsmann kept this ideology in mind while developing a new rotary valve, and offers a varied range of auxiliary equipment.
The quintessence of the EZS series of rotary valves, patent pending, is the unconventional rotor geometry. Their skewed chambers present a number of advantages over conventional types. One of these advantages, for example, is gentler conveying of the product. During an endurance test with polyethylene granulate, this new rotor geometry reduced the dust fraction by about 20 % compared to conventional rotor geometries. There is also less squeaking noise generated when conveying fine-grained products such as sugar. Measurements confirmed 2 to 3 dB(A) lower noise emission. And yet these rotary valves not only produce less noise, they also have lower torque requirements thanks to optimized shear edges. That means drives of lower power can be used, thereby reducing energy costs. A fourth advantage is the option for drill holes in the housing of the new series of valves, which allows leakage air to escape. This option can even be added at a later date after purchasing.
Safe in hazardous situations:
Many operators produce their goods within a potentially explosive zone. For this reason, special attention was given in the development of the new rotary valves to the concepts of explosion protection and a protective system (for dusts). The valves prevent flashback in both directions. This flashback safety has been tested by a certified body, meaning the rotary valves are employable as protective systems. They have also undergone type approval, which means it is assured that the valves can be employed for zones 0/1/2 and 20/21/22 (internal) as well as for zones 1 and 2, and also 21 and 22 (external). As a protective system, the new series can be employed for the following parameters:
- Flashback resistant in conveying and opposite direction,
- Minimum ignition energy (MIE) > 3 mJ,
- Ignition temperature (ZT)M 360 °C,
- Dust explosion class ST1 (organic dusts).
The manufacturer is Atex-certified by an accredited body, and as such authorized to market equipment and protective systems with the corresponding Atex indication. The accredited body regularly controls that the valves are tested and at consistent quality as they leave the factory.
Extra features make it easier to remove rotors
Another essential property of rotary valves is that they must be easy to clean. Many operators are obliged to clean the valves after a change of product or even after individual batches. As such, they must be easy to dismount. Even that has been taken into account in the new series: there is a removable version in which the rotor can be taken out entirely, including the face plate with bearing and seal, with little expenditure of time. That way, the interior of the housing is very easily accessible and accordingly the rotor can be easily cleaned.
As yet another innovation, the operator can equip the valve with a pull-out fixture and/or a draw-out mechanism. Thus the operator is given the option of first buying the retractable model on its own and then upgrading to these options when convenient. There is no need to make any further modifications to the rotary valve. The operator need only buy the appropriate retrofitting kits, which he can then install with relative ease. The pull-out fixture was developed because in some cases the rotor can only be unstuck from the housing with difficulty. The reason for this is most commonly deposits of product. The pull-out fixture can be mounted relatively effortlessly. By pressing onto the pin, the rotor can be easily loosened from the housing and then manually removed completely.
The draw-out mechanism is especially useful when the rotors need to be cleaned frequently. But it is also helpful when there is only very slight radial play in the rotor, such as in the flashback-resistant models. The mechanism can also be mounted onto the valve very quickly. Once the screws on the face plate have been loosened, the entire rotor can be drawn out from the housing. Since the rotor is held on guide rods, it is very easy for the operator to handle. When developing this draw-out mechanism, particular importance was given to compact design. That keeps the space requirements within limits.
Two installation sizes available first
The new series of valves will first be offered in two sizes. The smaller valve (EZS 200) has an installation height of 300 mm and an inlet/outlet flange of DN 150. The conveying volume is 3.0 l per revolution. The larger valve (EZS 250) of installation height 400 mm has an inlet/outlet flange of DN 250 and a conveying volume of 10.6 l per revolution. Other installation sizes shall follow.
The rotary valves are available in grey cast iron, cast V2A and cast V4A. Special materials such as Hastelloy will also be available upon request.
Conclusion: Even though there are many valve variants available on the market, there is plenty of room for improvement. The new rotary valves of the EZS type series have been developed for diverse applications. If necessary, they can be easily retrofitted, such as with a draw-out mechanism that makes cleaning of the rotors easier. New rotor geometry conveys the product more gently and quietly. These rotary valves can also be employed in potentially explosive zones and as a protective system. The new series of valves are anticipated to be available from late summer 2008.