Cyclone Screener for APIs Screening API Without Exposure: How to Ensure Containment in Screening and Maintenance

Author / Editor: Frank Pahl* / Manja Wühr

New containment cyclone screener — Screening products under containment conditions is one matter. Maintaining and inspecting cyclone screeners without exposure is another. Now Azo has designed a new real containment solution that utilise a flexible film liner technology.

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Inspecting the screen cylinder using the maintenance hatch
Inspecting the screen cylinder using the maintenance hatch
(Pictures: Azo)

Containment has been a core issue for years in the pharmaceuticals industry particularly. Low occupational exposure limits and complex toxicological evaluations pose special challenges for processors and manufacturers of highly active substances with regard to process safety. On top of this, there are new regulations, such as the modified EU GMP directives, which came into force on 1 March 2015.

Thanks to engineering design solutions, today’s plants now generate so little dust in regular operations that it is possible to rule out any threat to the health of plant operating staff from harmful dust. The situation is far more critical when maintenance or cleaning work has to be carried out.


Inspection hatches have to be opened in order to inspect working parts in machinery and plants. In the case of maintenance activities, maintenance staff have to remove worn components and install new replacement parts. In the past, this was only possible within isolators when smaller plants and machines were concerned or, when larger machines were concerned, by wearing full body protection. Installation in an isolator is not possible in the case of cyclone screeners for reasons of handling and space, which is why Azo has developed the type DA … Vario Containment screener.

Containment cyclone screener

With its newly designed DA … Vario Containment screener, Azo provides an entirely new solution to satisfy the above-mentioned requirements: Based on the DA screener, tried and tested in actual practice for years, and on the widespread practice of using flexible containment systems in the pharmaceuticals industry, it is now feasible to open the familiar inspection hatch and to inspect the screen in this way without any dust escaping. In addition, it is possible to replace the screen basket and exchange the dosing screw under containment conditions.

Additional Information
Interview with Frank Pahl, Head of Development, Azo
Screening Ignitable Bulk Materials

? Frank Pahl, is the cyclone screener suitable for use in production in zones where there is the potential for explosion? Can the machine be used to screen ignitable bulk materials?

Pahl: It is indeed correct to consider use in defined zones separately to the actual interior of the machine. The electrical components, as regards drives and sensors, are defined according to zones in the relevant requirement in conformance with Atex. Typically, on the inside of the machine zone 20 prevails with combustible products. Azo has a type examination in place for all its screeners for this use in compliance with EC directive 94/9/EC. This type examination specifies that products with a minimum ignition energy of MIE ≥3mJ may be screened.

? The regulations for explosion protection are subject to constant change.

Pahl: My colleagues and I follow amendments to the legislative framework for explosion protection very closely. The type examination therefore already satisfies the requirements of directive 2014/34/EU that comes into force in April 2016.

? It is also possible to screen products and dusts with lower minimum ignition energy using this cyclone screener?

Pahl: The figures from the type examination are to be observed with no exceptions. If the product’s properties are unfavourable, this may necessitate installing additional protection in and on the machine. In this case, we use inertisation of the internal chamber as an example.

? What assistance do you offer your customers when they put concepts like this into practice?

Pahl: Azo already offers expert consulting in the initial discussions about choosing and dimensioning potential systems for protection. This is how we were able in the past to plan alternative solutions for rendering hybrid mixtures inert (when combustible dusts and potentially explosive dust/gas mixes are present at the same time) in collaboration with our customers.

What is special about the DA machine type is that there is no need for an upstream dosing unit thanks to self-dosing. It is possible to adjust the integrated dosing screw’s dosing rate to match the specifications for the specific product using frequency converters. With the DA … Vario, the screeners throughput can be adjusted using a combination of different dosing screws with the screen module in order to accommodate very diverse products, screen capacity or mesh sizes.

Screen inspection

The inspection hatch for checking the screen cylinder can be opened using a glove integrated in the flexible liner. The screen cylinder can be rotated manually by almost 360° and, thanks to the built-in light, it can be inspected for damage or contamination through the film. Once inspection has been completed, the inspection hatch can be closed again using the film gauntlet. Using this procedure means that the operator has no contact with the high-risk substance in the machine at any time whatsoever.

Replacing the screen

If any damage to the screen fabric is found during the screen inspection, this will necessitate replacing the damaged screen. This procedure can also be carried out using liner technology without any contact with the screened product. If the machine has stopped, the drive unit for the screen rotor is removed from the housing lengthwise together with the screen cylinder. The weight of this unit is supported by an extraction device. The plastic film system that was attached when the machine was fitted is deployed in this process; it forms a tubular working space, in which the screen cylinder and the screener rotor are located.

Additional Information
After-Sales Service
Ensuring Reliable and Safe Operation

In addition to the quality of the machinery and plant, being able to rely on customer service is a decisive criterion for every customer. This applies to both installation and commissioning as well as to inspections and maintenance or the supply of spare parts.

Azo provides rapid delivery and extended availability of quality-controlled original spare parts. If orders are placed before 2 pm, available items can be shipped the same day. Azo works with all reputable parcel services and, if required, can arrange for express or special delivery.

Online spare parts catalogues for specific plants make it possible to identify spare parts reliably. The customer is also given suggestions for keeping a supply in stock. This includes not only all wear parts and consumables but also the spare parts required to maintain fault-free operation. Examples for this cyclone screener would be:

  • wear parts: gaskets, screen mesh, bearing seals ...
  • consumables: foil liners for screen replacement, foil liners for supplying and evacuating cleaning materials, foil hood with integral gauntlet for screen inspection
  • spare parts: screen basket, bearing assembly, rotor ...

Azo employs a team of permanent staff who are highly qualified and who have cross-cultural skills and international experience. The aim is to ensure that Azo’s plants and machinery provide reliable and safe operation, downtimes are kept to a minimum and procedures are optimised. For that reason, Azo offers comprehensive after-sales services, which also include:

  • hotline for specific customers and plants,
  • advice and assistance on any questions relating to service,
  • customer or user training,
  • inspection and/or maintenance contracts,
  • remote maintenance,
  • retrofitting.

By using appropriate double-crimp-and-cut techniques, it is then possible for the operator to remove the used or damaged screen inside the plastic liner and to install the new screen while using a new liner, also within a protected environment. The use of a new liner prepares the machine for further operation and for the next screen replacement.

Replacing the dosing screw

The dosing screw conveys the product to the screen cylinder in a continuous process. The speed and thus the dosing rate can be adjusted using a frequency converter, depending on the particular product characteristics. To make adjustments to the range of dosing rates, it is possible to change the dosing screw geometry or to vary the speed with the frequency converter. The machine also allows for the dosing screw to be exchanged under containment conditions. The machine is opened using an extraction device in the same manner as for screen replacement. A film liner provides reliable protection to stop dust from escaping.

Cleaning the machine

A washing system is used to clean the inside of the machine with water. Dust particles are flushed out; any remaining particles in the machine are wetted with water and thus bound inside the machine. After dismantling the screw, the built-in glove system can be used to clean the contaminated inner walls of the machine with appropriate cleaning instruments.


Thanks to the DA … Vario Containment cyclone screener, the familiar advantages of Azo’s patented screener with separate drives for the rotor and dosing sides are combined with film liner technology from flexible containment systems. The outlay for wearing full body protection can be reduced for plant operators. Dust is reliably prevented from escaping during maintenance and inspection work. This means containment for operation as well as maintenance.

* * The author is Head of Development at Azo, Osterburken/Germany.