Ultrasonic Screen Cleaning in Gas-Ex Zones
Washing and classifying please!
Hole to hole and straight through! The demands placed on screening technology used in potentially explosive atmospheres, particularly the food and pharmaceutical industries, are enormous. High demands for compliant performance and cost-effectiveness must be fulfilled. In addition, there are specific demands concerning the uses and products to be screened. Using the example of a Ludwigshafen-based bulk solids specialist’s project shows how gas-proof classifying in gas-ex zones with product spraying and ultrasonic cleaning can increase productivity in the long term.
It is not always the big things that make the difference. This is the case with the delivery of two JEL Vibspeed vibration screening systems to a well-known pharmaceutical manufacturer. As a protective, control and classifying screen for free-flowing, dry bulk goods, the screening machine is used in all sectors of the chemistry, pharmaceuticals, food and plastics industries due to its wide range of uses and user-friendliness. The flexibility and simple handling are mainly due to the hinged cover of the machine: this saves the user a considerable amount of assembly and cleaning effort. Its curved form reduces noise emissions during operation to as low as 3 dB(A). The pharmaceutical customer had a cover such as this in mind and wanted to use two machines straight away to classify a new suspension. But first it was necessary for the machine suppliers to fulfil the complex demands of the client.
Product spraying during the screening process
Both screening machines had to be able to spray liquid during the continuous screening process in order to screen the suspension. Because various water volumes are released during the screening process, both vibration screening systems have three different water cycles which can be adjusted separately. To do this, there are nozzles inside the cover, which each spray the complete screening surface with water. Divided into three sections, it is possible to supply three different water volumes.
If the screening machines are used in the production sector, it is important that they can be accessed easily as they must often be cleaned after a change in product or a different batch. The simple dismantling of the screening machine helps here: the user can remove the detachable sieve from the top of the machine quickly and easily after opening the cover and loosening the clamping device on the front. In addition, the machines are equipped with an ultrasonic cleaning system, which keeps the sieve fabric open during the screening process and protects it from becoming clogged with product. It means the machine can be used for screening processes up to a grain size of 40 µm, even under Atex conditions.
Ultrasonic cleaning - even in gas-ex zones
As both vibration screening machines will be used in potentially explosive areas at the customer’s premises, they must be suitable for the Atex zone 1 gas (internal and external) temperature class T4. This requirement alone shows the complexity of the job specification, as ultrasonic cleaning is normally only used in dust-ex zones, meaning many suppliers only manufacture dust-ex protected systems.
In general, the vibration screening machine from Ludwigshafen can also be delivered with other cleaning systems, such as the spherical or triangular cleaning device. With the newly developed CIP cleaning (Cleaning in Place), the screening machine can be cleaned on-site and does not need removing from its location. With the CIP screen cleaner, the machine is equipped with cleaning nozzles in the cover and the outlets. If required, the manufacturer will also fit extendible nozzles, which only come into the product space when the machine is being cleaned.
Gas-proof and designed to meet GMP
Both screening machines are gas-proof (20 mbar) and all seals are designed to conform to FDA regulations. They were manufactured in line with GMP with ground and electropolished (Ra < 0.8 µm) internal surfaces. The construction of the screening machine, which requires little space due to its compact structure, provides the customer with a high degree of flexibility. It can be adapted quickly and without any major effort to changed requirements, e.g. different screening products. With help from an adjustable inclination, the user can modify the speed of the product and therefore its retention time on the sieve fabric by changing the angle of inclination of the sieve deck.
The vibration screening machine has an inclination angle of 5° when delivered. This angle can be adjusted by ± 2° at any time. The trajectory parabola of the screened product can be modified by changing the excitation of the sieve fabric. The direction of the vibration can be changed by the layout of the vibrators. The settings can be adjusted in intervals of 15° between 0° and 90°. The series is available up to a maximum screening surface of 7.5 m². The spectrum of the single-deck design is from 0.24 to 3.75 m², while the double-deck design ranges from 0.48 to 7.5 m². If needed, the screening machine can be supplied with a stationary or mobile undercarriage in ten different sizes. Depending on the size of the screening machine, the sieves have a width of 250 to 1,250 mm with a consistent length of 500 mm.
Decisive facts for operators
- The screening machine sprays various volumes of liquids over the entire screening surface during the continuous screening process using three cycles that can be adjusted individually.
- The cover of the screening machine can be opened, reducing the assembly and cleaning effort.
- The curved form of the cover reduces noise emissions during operation to as low as 3 dB(A).
- The machines are available with different cleaning systems, such as ultrasonic cleaning, spherical or triangular cleaning and CIP cleaning with the help of integrated nozzles.