Industry Blog

Achieving a Dust-Free Milling Process

Modern processes often use high potency APIs and other ingredients, which are potentially dangerous if mishandled - this is a particular concern during milling, a process which is notorious for generating dust. Hence, in order to protect both the operator and the process environment, it is important to consider various methods which could be used to help minimise this problem.

There are a number of ways to contain dust during cone milling, this article shall focus primarily on three methods; in-line vacuum transfer, container-to-container milling and milling inside an isolator. All three techniques offer an efficient and effective way to achieve dust-free milling.

 

In-line Vacuum Transfer

Feeding and discharging from a cone mill using a vacuum is a particularly effective method for achieving dust-free milling. This process not only contains the dust, but also automates the process and minimises waste - helping customers make efficiency savings.

Using an in-line vacuum transfer system (such as the Hanningfield Uni-Vac), material is automatically fed into the inlet chute, and is also automatically drawn from the outlet of the mill. This process ensures that from pick-up to discharge, the system is fully enclosed, preventing the escape of dust.

 

Container-to-Container Milling

This solution uses the principle of gravity to feed product through the mill. By positioning a bin above the mill, and another bin below the mill, product is released from the top IBC, milled, and then passes directly into the bottom IBC.

This creates a totally contained, in-line solution for milling. Not only does this contain the product during the milling phase, but this is also a simple and effective method for transferring product from bin-to-bin, and cone milling the product en-route.

 

Isolator Milling

One suggested method for the containment of such fine powder during milling, is the use of an isolator or ‘glove-box’ to ensure all excess material remains contained, ensuring the fine dust particles are not exposed to either atmosphere or operator.

Cone mill integration within the isolator is performed by means of through the wall fixing flange. This fixing flange and particular configuration of the cone mill allow for a physical division of the cone mill head by the technical area that is left outside the isolator. Thanks to this special configuration all cone mill cleaning operations are performed within the isolator by means of gloves or half-suit, reducing any risk of exposure for the operator and avoiding any transport to cleaning room.

Another benefit of isolator milling is for achieving a zoned area such as ATEX. The isolator itself creates an ATEX environment for milling, ensuring the entire process environment (including motors and controls) do not need to be changed to comply with the necessary requirements. Learn more about milling in an isolator here.

 

Conclusions

In a modern process, containing dust is extremely important.  This can be easily achieved during the cone milling stage, simply by employing one of the methods listed above.  Each solution will be more or less suited to any particular application.

For more information on how to contain dust during processing, please just contact us.

High Containment Transfer Systems

The need for containment is greater than ever, given the increasing potency of processing ingredients and API’s.

Improving containment is often the main driver for specifying new process equipment in the pharmaceutical and associated industries. Current expectations of levels of containment often far exceed the capabilities of equipment designed and manufactured only a few years ago. There are many ways of improving process containment.

There are a number of reliable high integrity methods for ensuring containment during transfer;


Gravity Transfer using a Hoist

Gravity Transfer typically uses a combination of gravity feed and flexible silicone sealing interfaces. Lift systems are often a main component in gravity transfer for accurate docking of process equipment such as IBC’s and valves. High containment lift systems use intelligent positioning sensors to ensure outlets and inlets are precisely aligned, allowing the fast and accurate transfer of powders, granules and liquids etc.

‘Failsafe’ is another important feature of a lift system which is to be used in a high containment application. The security offered by the ‘failsafe’ feature ensures that even in the event of a machine breakdown, the two ports will remained docked, and most importantly, the material will remain contained and uncontaminated.


Flexible Silicone Connections

The connections between each element of the transfer process are the weakest links in the transfer chain. To ensure containment is not compromised at these connecting points, silicone dust caps and flexible sleeves can often be used. These elements provide simple cost effective containment which is very adaptable and easily cleaned.

Another benefit is that some of these components can be translucent of clear, allowing a visual indication of the process condition. Typically these transfer connections take the form of silicone caps and sleeves. Generally the connection parts are moulded in standard sizes so this should be taken into consideration when designing and specify new process equipment installations.


Split Butterfly Valves

The integration of a split butterfly or ‘High Containment Valve’ between the inlet and outlet of two process components creates a fully contained method of product transfer, with virtually zero exposure to either the operator or the process environment. This is extremely important when handling potentially hazardous material or material that cannot be exposed to ambient air. Total sealing during emptying and filling operations can be easily achieved with the split valve system and fully automated valves can be specified which allow ease of operation in difficult to access locations such as containment isolators.

The split valve system comprises of an ‘active’ and ‘passive’ half. The active half of the valve has most of the moving parts and is usually static. The passive half is often installed on the moving part of the valve interface any in some cases a large number of passive valves and be docked into the same active half. The split butterfly valve provides the most effective high integrity method of contained transfer.


Vacuum Transfer

Another commonly used method of containment is vacuum or ‘pneumatic’ transfer, which uses contained pipe-work and hoppers to transfer material. The main advantages of vacuum conveying are that it is very flexible if needed to cope with a variety of process duties, has very few moving parts and is easily cleaned. The most common form of vacuum transfer is termed as ‘lean-phase’. The lean-phase method of vacuum transfer uses entrained air to create an air-flow for efficient material conveying.

Vacuum transfer can be used over considerably long distances and has the additional benefit of being very low maintenance. Conveying of materials by vacuum is a well established process in the pharmaceutical industry and rarely has any detrimental effect on the product integrity. There are many different configurations used in vacuum conveying allowing automated material pick-up, level control, multiple integrated systems and other special design to deal with variable material properties.

Vacuum Transfer Systems

Vacuum transfer systems are an excellent method of moving powder, granules, pellets and other materials from ‘Point A’ to ‘Point B’.

Example Uni-Vac Application: Feeding a Tablet Press

The systems use a vacuum to carry the material through the pipework, allowing material to be transferred in a gentle, yet rapid manner. This allows up to 4,000 kgs/hr to be transported, without significant disturbance to the characteristics of the product.

Vacuum Transfer of Pharmaceutical Powders

Vacuum transfer is an automated method of transporting material from Point A to Point B of a process, such as sucking powder directly from an IBC and transporting it to a hopper which will then load a tablet press.

This automated system negates the need for manual handling whilst offering increased throughput and safety.

For more information on vacuum transfer systems, please click here.

Uni Mill: Method

Method of Operation

Unprocessed material is loaded into the product inlet of the Uni-Mill by hand, gravity feed or vacuum transfer.  The material then passes into the milling chamber where a rotating impeller forces the unprocessed material through a stationery cone-shaped screen by a vortex action.  The material is instantly reduced in size as it passes through the holes in the screen.

By changing a combination of screen, impeller shape and speed, the finished milled particle size can be carefully controlled.  Most important for hygienic requirements, such as those in pharmaceutical and food production, there is no metal-to-metal contact between the impeller and screen.

‘Uni-Vac’ Conveyor Systems

Vacuum conveying is one of the most popular methods of material transfer.

The Uni-Vac vacuum conveyor can help automate the transfer of powder, granules, pellets and flakes - eliminating the need for manual handling, whilst dramatically improving productivity.

For more information on the Hanningfield Uni-Vac, please click here.

Powder Transfer Systems

Powder transfer is an excellent method of automating certain aspects of processing to eliminate manual handling and increase efficiency.

Powder transfer can drastically improve every aspect of a process, from hygiene to productivity.

For more information on powder transfer systems, please click here.

Vacuum Transfer Equipment for Food Processing

The food processing industry involves the handling of powders, granules, pellets and other food stuffs.

Vacuum transfer equipment can overcome many of the problems posed by the manual handling of material, such as dust containment and contamination issues.  Moreover, the vacuum transfer of material can vastly improve productivity by significantly increasing throughput.

For more information on Hanningfield’s vacuum transfer equipment, please click here.

Powder Handling Equipment

Powder handling equipment is vital to the productivity and hygiene requirements of the pharmaceutical, food and allied industries.

Powder handling through vacuum transfer can significantly increase productivity through the automation of manual tasks such as IBC loading or tablet press loading.  Meanwhile, the fully contained transfer system helps maintain the integrity of the product, whilst eliminating waste and operator exposure to dust.

Powder handling equipment can significantly improve your process; for more details, please click here.

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