Whether as powder or granular material: certain properties of plastic make efficient screening complicated. An experience with which a well-known chemical company approached Engelsmann.
The existing screening technology was to be brought up to date step by step. The company was looking for a solution for classifying S-PVC that would meet the highest demands in terms of throughput, safety and economic machine use.
S-PVC (polyvinyl chloride resin) is produced by suspension polymerisation. Suspension PVC has a wide range of applications. It is used for rigid PVC applications such as pipes, profiles, rigid films and so on. With additional components, it is also used in cable insulation, flexible films, medical products and much more. The end product of the suspension process is S-PVC in various grain sizes, which is characterised by high purity. The screening or flow properties of S-PVC are largely determined by the respective grain size. Sometimes the material also tends to form agglomerates.
New screening technology was needed to separate oversized particles with a mesh size of 400 µm. Any agglomerates in the S-PVC and other oversized particles must be separated dust-tight. The good grain, on the other hand, has to pass through the mesh of the screen mesh and be processed further as homogeneously screened raw material in the appropriate grain size.
Replacing old screening technology is worthwhile in many respects
A dust-tight, product-friendly oversize screening system for S-PVC was implemented, which significantly reduces downtimes for set-up, cleaning and maintenance work and thus ensures high productivity and machine availability.
Thanks to an energy-efficient drive of the four JEL Freischwinger, energy consumption and all costs related to maintenance and spare parts were significantly reduced. The total operating costs were halved.
Engelsmann’s linear stroke screening machines enabled S-PVC production on 360 days p.a. in three-shift operation. Once a year, they undergo intensive maintenance – to benefit from a longer screen life.
With the previously used, outdated screening technology, reliable, safe and economical screening processes were no longer feasible.
A particularly important requirement criterion was the implementation of a dust-tight classifying screening system that protects the environment from excessive dust pollution. Higher productivity and economical machine use were also at the top of the wish list. Spare parts wear, energy consumption and handling during maintenance or cleaning of the linear stroke screening machines were also closely analysed.
In particular, the gearbox of the old screening machines caused problems, as recurring gearbox oil contaminated the production environment and the failure-prone plain bearings drove up the need for spare parts. In addition, the running gears caused enormous noise pollution. After tests with the original product, the Engelsmann designers were quickly certain: the JEL Freischwinger linear stroke screening machine met the specified requirements – with a few adjustments to the basic model.
Low energy consumption
Dust-tight sieve trough
Minimum set-up times
Low maintenance, few spare parts required
High selectivity (up to 98.5%)
Low noise pollution
Sieve inserter with high fabric durability
Basic model JEL Freischwinger: Linear stroke screening machine for classifying dry and free-flowing bulk materials – with throughputs of up to 250 t/h and gentle product classification with up to 99% selectivity. For chemicals, plastics, pharmaceuticals, food – and your industry.
Complex screening task
Target throughput: 12.5 t/h. Dust-tight operation. And economical at the same time.
To achieve the required throughput, each linear stroke screening machine is equipped with six screen inserts arranged one behind the other. This corresponds to a total screening surface of 3m2 per screening machine. For the permanent permeability of the meshes, a cleaning system is installed below the screen mesh. Impact balls lie on a corrugated screen and are set in motion by the vibrations of the screening machine. They hit the screen mesh from below, remove entangled particles of plastic from the meshes of the screen mesh and thus keep the screen layers constantly permeable during the screening process.
JEL Freischwinger: In the end, the customer was so convinced that he ordered four machines with which he can now also produce S-PVC in three-shift operation 360 days a year.
View inside the linear stroke screening machine: impact balls keep the screen mesh free mechanically. For high throughput – even with mesh sizes of 400 µm.
Equipped with adjustable screen inclination, the flow rate of the PVC product and thus its dwell time on the screen mesh can be influenced. The standard preset inclination angle of 5° can be readjusted by ± 2° at any time. In this way, each of the four Freischwinger screens can be individually adjusted for each batch.
Heavyweights with energy-saving drive
For a low-energy operation, each of the 850 kg screening machines is equipped with a specially developed, energy-efficient flywheel drive.
After approx. 15 seconds of drive acceleration, full thrust is reached. After that, the linear stroke screening machine is only operated with 10-20% of the nominal current. This adds up and is worthwhile, especially with heavyweights such as these JEL Freischwinger for screening PVC. Engelsmann technology is also convincing in terms of wear and maintenance. The low-wear concept minimises necessary maintenance cycles: once a year, each screening machine is given a general overhaul. For the rest of the year, S-PVC is screened in the most homogeneous quality.
The JEL Freischwinger is driven by an electric motor that transmits its power by means of a V-belt to a flywheel mass equipped with push rods. The flywheel mass is exactly matched to the mass of the sieve trough. The drive train (shaft and flywheel) is approximately as heavy as the screening trough including the product to be screened.
More efficiency – even when changing the sieve inserter
To ensure that the screen inserts can be changed as quickly as possible and with as little dust as possible, the machines have a special quick-change system and easy-open cover parts that protect the plant environment from excessive dust exposure during the screening process.
The cover of the sieve trough is made of lightweight aluminium and divided into different segments. They can be lifted individually and very easily by hand – without additional lifting tools. This has extremely shortened the time required for changing the sieve inserts. With the predecessor machines, a heavy, continuous cover had to be dismantled laboriously and with a lot of equipment.
Once the cover parts are lifted off, the interior of the screening machine is freely accessible. To change the sieve inserts, only few quick-release clamps have to be loosened. This also saves time – when changing the screen inserts as well as during cleaning work. If spare parts need to be replaced inside the machines, they are also easily accessible.
With the help of quick-release clamps, the sieve trough is closed dust-tight with the cover parts and the emission of dust particles during the sieving process is prevented. The cover clamps adjust automatically if the seals become seated.
Replacing old screening technology reduces operating costs by almost half, increases product quality and sustainably improves working conditions at the installation site.