Frewitt: High-Tech Solution down Pat

| By | Frewitt

When planning complex systems these days, you can’t ignore the specifications. But our recent experience with a pharmaceutical contractor from the United Kingdom demonstrates that under certain circumstances, “thinking out-of-the box” has it’s benefits.

The project manager of the afore-mentioned subcontractor, accompanied by the end-ser, requested a meeting with Frewitt at the Interphex NYC trade fair  seeking out a new milling and powder-handling solution At the time, neither the project manager, nor  his company had had no experience with the milling enterprise from Fribourg, Switzerland. Up to that point, they had been working for many years with mills from competiting companies.

Restructuring the production areas with the aim of enabling the process of heterogeneous solids, notably active pharmaceutical ingredients, often referred as API’s using a single, innovative, multi-purpose system compelled them to look around a proven innovator active in this sector.

Convinced beyond words

Easier said than done to convince a trade fair contact only using words; it was quickly agreed thatthat only a milling test at the Contract Manufacturing Organisation (CMO) plant site  could lead to a conclusive decision. Frewitt went from word to action. As a first step, two Frewitt machines were shipped to the customer site in England. One unit was a FreDrive-Lab laboratory mill, with a hammer milling head, as well as conical grinding head, and the other was a FreDrive-System designed for production quantities with a HammerWitt-3-type grinding head, along with an interchangeable ConiWitt-200-type grinding head.

Now, let’s take a quick look at how we scale up the modular FreDrive-System: The milling tests using a small amount of product on the lab machine serves as a reference for scaling up in order to be able to achieve the same results on the Production scale mills.

The results of the product tests brought clarity. After successful and significantly better results of the test series with all variants, the subcontractor quickly decided to purchase HammerWitt-3 which was already under rental at the end-users site.

This decision also meant that the large future production system was potentially in the cards: Frewitt was tasked with bringing a turn-key solution life. The decision was justified by the simplicity of the milling head, product change-over, as well as the ease of cleaning and general handling of the mills.

Offer as a specification

Since the subcontractor did not  know in advance about the product characteristics of the products, and whether they would be required to process hard, crystalline, soft, fibrous, toxic, or even potentially explosive product. Therefore the system had to be conceived in a modular structure and product changes were required to be seamless. After multiple rounds of discussion, the processes were defined; therefore providing the basis for drafting the system concept, and the submission of an offer to the customer.

The system offered was equipped at the start with a conical and cylindrical hammer mill-grinding head (sifter) in order to be able to pulverize, dis-agglomerate, homogenise, grind and fine-grind products with various material characteristics.. The ATEX Directive was followed to ensure a safe process whenever the customer was required to mill potentially explosive products.

No Ifs, Ands or Buts

As always, a rigid inspection of the process parameters is necessary for API production on account of the high occupational exposure band level and ATEX zone classification.

Therefore, hardly an element or part of the system exists, that isn’t controlled and monitored by probes, sensors or sensing devices. For example, fill level sensors prevent product clogs, oxygen sensors measure the oxygen content, pressure sensors monitor the nitrogen pressure, and temperature sensors measure the temperature at sensitive locations on the machine, protecting both the process and the products.

The two buffer tanks alone – one located at the inlet and the other in the middle part of the system – are equipped with a total of eight sensors in order to be able to measure products levels, pressures and oxygen contents. In addition, the two 500 l tanks each have a viewing window, which also permits a visual inspection.

When processing potentially explosive products, a monitoring system constantly measures the oxygen content at the ProFi-Clean’s dust removal system outlet. Two measuring sensors are installed here for safety. The arrangement of sensors at this location ensures that the entire system is filled with nitrogen and that the grinding process begins only after sufficiently low oxygen levels are detected at the ProFi-Clean outlet.

A Critical Element

What requirements does the system need to meet in order to mill potentially explosive products (Ea ≤ 1 mJ)? Let’s take a look at the process.

The product is fed into the first buffer tank until the specified product quantity has been reached. The valve on the container inlet closes, and the buffer tank is rendered inert while the oxygen content is monitored. The same thing happens with all other parts of the system. As soon as the oxygen content reaches 3% in the entire system, the dosing system and the mill start. Production can then begin in the closed system. If the oxygen content rises in the system, nitrogen is automatically injected until the oxygen content falls below the prescribed, critical level. However, if the prescribed, maximum oxygen content of 5% is exceeded, the machine stops immediately. Due the constant monitoring of the system, the critical risk factor of oxygen is always under control therefore there is protection against explosions.

Integrated Insulators 

Three large insulators are combined with the Frewitt milling system altogether.

Installed over three levels; the first insulator is installed at the inlet to the buffer tank, the second is in the area around the milling head, and the third is around the dosing, weighing and filling system at the system outlet.

The operator can input parameters, set and query values, evaluate alarm messages and perform many other process-relevant functions via a central human–machine interface (HMI).

Conclusion: What began with a question, and an idea developed at a trade show in the USA, ultimately led to the installation of a high-tech system, which today manufactures products with very different characteristics according to the highest standards.

Using his system, a new Frewitt customer isn’t only optimally equipped; today, he has offered himself a great deal of possibilities others can only dream of. It’s a leap forward that the latest version of modular milling technology from Frewitt made happen.


Frewitt fabrique de machines SA
Route du Coteau 7
1763 Granges-Paccot / Suisse
Tel.: +41 (0) 26 460 74 00


Matthias Honisch,
Regional Sales Manager


GMP news
Pharmaceutical industry News and events. Technology transfer and contract manufacturing of medicines.