Seamless transition
Docking systems provide virtually dust-free transfer of bulk material

There is increasing interest in the dust-free transfer of bulk material. This is not surprising when you consider the proliferation of high potency substances. Engineers and designers have given a lot of thought to finding ways of nearly eliminating contamination in the surrounding air.

You cannot make an omelet without breaking eggs. This proverb may be a valid basis in all other industries, but it does not apply to filling and dosing of expensive or toxic bulk material. As a general principle, it should not even be apparent that work is ongoing, and sophisticated process technology makes it possible to achieve this.
“Total containment” is the approach used in the chemical and pharmaceutical industries to protect humans and the environment and to prevent cross-contamination. The critical interface is often encountered during transfer from storage containers (containers, drums or big bags) to the processing equipment (mixers, fluidized bed systems, tablet presses, etc.). Handling of primary pharmaceutical products in particular (active pharmaceutical ingredients or API) is becoming increasingly difficult. As the potency of APIs continues to increase, tolerance levels for maximum workplace concentration continue to decrease. In addition to pharmaceutical companies, the special and fine chemicals industry is also on the lookout for new approaches to total containment.
A statement by Andreas Znidar, Product Manager at Glatt Systemtechnik GmbH in Dresden, Germany, illustrates this point: “A benchmark study has shown that nearly 70 systems handling highly active substances have been completed in the past five years or will be completed within the next two years.” Znidar added: “Of these systems, nearly 20% are in the high toxicity range of OEL <1 µg/m3, and on average the ratio of high toxicity applications is on the rise.” OEL stands for operator exposure limit, but the term is not easy to
define.

Dust-free does not really mean dust-free, because particles in the nanogram range can have a toxic effect. Znidar cited a few aspects that must considered when measurements of ambient air are taken:
Where was the measurement taken relative to the source of emissions?
What was the duration of the measurement?
Was chemical product detection or particle count used?
Does the result reflect a momentary concentration or a weighed value over an eight hour period?
What product was used (particle size, type, flowability)?
Was additional local suction removal used?
Is the operator working with a 100% active substance or a “thinned” active substance?
To achieve comparable results, guidelines for test setups were developed during the past two years, which define how to conduct investigations of this type. The SMEPAC is scheduled for publication by the ISPE at the end of 2003.
Dust-free become a reality
Manufacturers have been willing to invest a significant amount of effort, money and development work to come up with a definition of the term “dust-free”. An increasing number of companies have decided to use docking systems in place of costly insulation equipment or expensive clean room suits for their personnel. These systems allow companies to significantly reduce their cleanroom space. Let us now have a look at some docking systems.
Glatt Systemtechnik in Dresden has developed docking systems centered around a patented butterfly valve system. The systems are designed for use by companies that process powder and granulate. The passive half of the flap without actuator is located on the mobile element (container), and the half with the flap and locking actuator is positioned on the docking system from or to the process equipment. In a setup environment conforming to SMEPAC requirements, the momentary concentration of the Glatt SKS butterfly valve system was less than 0.1 µg/m3 measured at a distance of 200 mm from the point of emissions.
GEA Buck Valve’s total containment system features a seal that was developed in collaboration with the seal specialist Precision Polymer Engineering (PPE). The system consists of an active and a passive valve which provide a completely dust-free seal on two containers independently of each other. The active valve, which is located on the production unit, can be activated automatically or manually. The passive valve has no operating mechanism. It is usually located on a warehouse IBC or a mobile IBC. The seals on the two valves are made of an FDA-compliant version of PPE’s Perlast, which is resistant to a wide variety of chemicals over a broad temperature range. Martin Koch, Business Manager at GEA Buck Valve, explained the issues involved in selecting a material: “Our first trials using PTFE seals were a failure because PTFE is too stiff to use in processes where high pressure is present. We decided to use a seal made of Perlast, which combines high chemical resistance with the flexibility of a rubber seal. This solved the pressure problem.” Perlast is a new perfluoroelastomer which uses patented cross-linking. The material features very high chemical resistance over a wide temperature range.
Easy to shoulder
Drums continue to represent an important method of transporting and storing material. However, emptying a drum that has an inner bag is complicated. The powder is often not pourable, and drums often weigh more than 50 kg. To handle situations like this, Dietrich Engineering Consultants located in Ecublens, Switzerland has developed the DCS (Drum Containment System), which is used in combination with the PTS (Powder Transfer System) to empty drums and transfer the powder safely and without contamination directly into a container. The DCS consists of a transparent cylindrical glove box with two lateral openings for the gloves. A stainless steel flange with a flat seal is attached to the lower section of the glove box to ensure that the connection to the drum is properly sealed. A mounting for the inliner is welded to this flange. A moveable suction lance with a bellows seal is introduced from the top. The system is connected to a pneumatic lift system, which allows the glove box to be raised and lowered above the drum.
The Bohle Containment System BCS was also developed to provide dust-free transfer of solids. The docking system is suitable for universal use. It can act as part of a docking station, it can ensure that product flow takes place under containment conditions through a screening machine, or it can be used to fill products which generate dust into equipment such as Bohle process machines. The system features a low profile. The BCS is a so-called split cone system. Vacuum is used to attach the cones to the active and passive elements. The resulting connection is extremely impermeable, and there is no need to rinse the surfaces which are exposed following the docking operation (as is customary on other systems). Due to a rotationally symmetric design, the passive element can be docked from any direction. A quick-fitting coupling is used for media supply on the active element, reducing the need for externally mounted cables and/or tubing.
The BCS can easily maintain total containment conditions (residual dust content less than 1 µg/m3). A cleaning adapter can be used to achieve CIP compliance in conformance with FDA rules
The systems supplier AZO is also focusing on dust-free transfer no matter what type of container is used. A system installed at Hermes Arzneimittel is a good example. A pneumatic suction transport system gently sucks the material from the dosing worm conveyors directly into the dosing containers (dositainers). Each silo has its own transport line, which is designed to accept a screening machine to perform an incoming check. The round dositainers, which act as receiving containers, are vacuum rated and have a generously dimensioned filter to retain dust. When the product or batch is changed, the containers can simply be removed from the filling stations and thoroughly cleaned. After the containers (made of stainless steel or plastic for example) are placed on a floor scale, a dust-proof connection system is docked and dosing into the container can commence.