Nutsche Filter Dryer Inside a Glove Box

The Challenge

High-potency active pharmaceutical ingredients (HPAPIs) are a growing area within the pharmaceutical industry. According to the European Pharmaceutical Review, this segment represented 16.6 billion USD in the 2019 global market. It is expected to grow at a rate of 8.7% from 2019 to 2027.

The ability to manage the production of these molecules results from the combination of the plant’s design and specific operating procedures. Process machines face high-containment issues when dry product is outside the main chamber.

This usually happens during:

dry product loading
product discharge and post-discharge treatment like milling, weighing, and packaging
sampling
venting and dust filter replacement

The standard solution for HPAPI product sampling and discharging necessitates the installation of a glove box at the discharge nozzle on pilot-sized solid-liquid separation and vacuum drying machines, like the Nutsche filter dryer. Depending on the requested containment level, the isolator can have different features:

equipped or not with an automatic ventilation system
based on a single or multiple chamber(s)
provided with packing devices like RTPs or continuous liners

This offers multiple advantages, such as:

Reasonably inexpensive. The machine is quite similar to a standard Nutsche filter dryer and the additional cost is associated with the glove box
Compact. The coupling machine and isolator result in a footprint only slightly larger than the machine itself

There are, however, some disadvantages:

The discharge nozzle is the only means to access the machine body in a contained environment. This makes the total product recovery difficult, especially for pilot units where the nozzle size can be small (e.g., 4-5 inches).
The filtering sheet at the bottom can only be lowered and inspected with a prior machine deep cleaning. This increases the time the filter dryer is out of service, especially in the event of a rupture or necessary maintenance.

Our Solution

Delta Costruzioni Meccaniche S.r.l. and Food and Pharma Systems S.r.l. combined their expertise to develop a totally new approach for pilot-sized Nutsche filter dryer containment. Instead of installing a glove box at the discharge nozzle, the two technical teams designed and built a system where the machine body is wholly included inside the isolator, allowing for complete Nutsche filter dryer management in contained conditions.

Specifics

This unique design allows for the standard discharge procedure of a Nutsche filter dryer in a contained environment and complete access to the machine’s internal parts. Since the lower part of the machine is in a contained environment, it is possible to lower the bottom and completely recover the product. Additionally, if a problem arises that requires machine repair, it is possible to do minor maintenance without cleaning and breaking the containment.

The core of the new technical solution is the custom flange located on the machine’s cylindrical body. This component has two tasks:

supporting the body inside the glove box
allowing the hydraulic cylinder stem to enter the isolator to lower the machine bottom

Each coupling has a double barrier in the design, completely avoiding any chance of failure:

two o-rings ensure the tightness between the glove box and the machine body
if the stem gasket fails, the PTFE bellows ensure containment preservation

Also, by placing the hydraulic driving systems outside the isolator, the proposed design avoids process contamination with oil.

The Results

The filter dryer’s extreme specialization comes from being made of a special alloy, based on nickel, which is frequently used for APIs.It features a dry-running double mechanical seal with a sanitary design to minimize dead areas where product can remain. The filtering sheet consists of 54 layers of metal sintered grid. In addition, Delta designed a specialized sampling device for taking samples even when the machine body is under vacuum or pressurized.

Filter dryer main features:

internal diameter: 500 mm
working volume: 100 liters
wetted material: C-22 (UNS N06022 or 2.4602)
seal: dry running double nitrogen, fluxed with sanitary design
filtering sheet: 5 layers of sintered grid welded on the machine bottom
sampling valve: piston type for vessel under vacuum or pressurized