ATEX vibrating feeders in use

When processing polyimide, the necessary use of solvents for cleaning the systems leads to classification in ATEX zone 2 (gas). The associated requirements include the conveying of the powder.

The task

Polyimide powder is to be transferred in batches from a centrifuge to two-metre-high feeders that convey it to subsequent process steps. A large number of specifications must be taken into account in the production plant and in the processes in order to guarantee efficiency and safety at all times. As the centrifuge undergoes regular self-cleaning with solvents, the polyimide powder also contains residual solvent, which harbours the risk of gassing. Even liquid solvent could get into the feeder trough if the cleaning system malfunctions. Therefore, ATEX zone 2 (gas) with its high requirements applies to the entire process. All materials and equipment used must be selected and designed accordingly. A drainage system for solvent residues must be provided.

The solution

The feeders are made of corrosion-resistant stainless steel and equipped with closed troughs within which the risk of explosion can be eliminated by inertisation. Inertisation is the introduction of inert gas (nitrogen), which prevents the formation of an explosive mixture. The nitrogen introduced prevents potential explosions. There is a permanent monitored pressure of 200 mbar in the trough, which places high demands on the design.

In addition to appropriate seals, the engineers at NetterVibration used finite element calculations (FEM) to ensure that the troughs were suitably and very strongly reinforced. FEM is a computer-aided process for calculating the strength and deformation of components, for example. A professional simulation clearly demonstrated how quickly and drastically the system could have deformed and inflated if not planned properly. A 5-degree gradient in the system prevents solvent from flowing into subsequent process steps, while a corresponding sieve retains residual polyimide powder before the solvent drains off. The powder itself is always conveyed ‘uphill’ against the gradient during operation.

The feeders are each powered by two counter-rotating, ATEX-certified NEG 16410 E external electric vibrators from NetterVibration. For many years, the company has offered a wide range of corresponding vibrators that fulfil the requirements of the current ATEX directives. 

CONCLUSION

Conveying polyimide polymer in potentially explosive environments requires the use of specialised feeders, ATEX vibrators and inertisation, which together minimise the risk of explosion and ensure maximum operational safety. The engineers at NetterVibration proved once again in the previously discussed application that comprehensive expertise and a wealth of experience are essential in order to meet complex requirements for the development, design and optimisation of vibrating feeder construction. The specialists in the technical department have mastered aspects such as vibration behaviour, throughput and abrasion resistance, including detailed calculations, in order to design even special ATEX conveyor troughs according to the respective operational requirements.

Read the full article (in German) here - published in SCHÜTTGUT & PROZESS 06/2024.

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