Case study – Nutsche filter dryer inside a glove box

Summary

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 totally included inside the isolator, allowing for complete Nutsche filter dryer management in contained conditions.

Problem

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, and it is expected to grow at a rate of 8.7% from 2019 to 2027.

The ability to manage the production of these molecules is the result of the combination of the design of the plant 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 like:

reasonably not expensive, as the machine is quite similar to a standard Nutsche filter dryer and the additional cost is associated with the glove box
compact, as the coupling machine + isolator results in a footprint only slightly larger than the machine itself

There are, however, some disadvantages:

access to the machine body in a contained environment is only provided by the discharge nozzle, which in the case of pilot units can be small (e.g. 4-5 inches), making it difficult for total product recovery
the bottom, which is where the filtering sheet is located, cannot be lowered and inspected without a prior machine deep cleaning. This increases the time that the filter dryer is out of service, especially in the event of a rupture or necessary maintenance .

Solution

Using a customer’s specific needs as a starting point, Delta Costruzioni Meccaniche and Food and Pharma Systems developed a totally different approach, which has addressed all of the aforementioned issues.

The glove box, which is normally externally connected to the Nutsche filter dryer, is totally incorporated into the lower part of the machine body.

This special design allows for the standard discharge procedure of a Nutsche filter dryer in a contained environment, but also allows for complete access to the internal parts of the machine. Since the lower part of the machine is in a contained environment, it is possible to lower the bottom and totally 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 cylindrical body. This component has two tasks:

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

The design allows for a double barrier for each coupling. As such, failure is completely avoided:

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

The proposed design has a further advantage: since the hydraulic driving systems are totally outside the isolator, process contamination with oil is avoided.

Highlights

The filter dryer is made of a special alloy, based on nickel, which is frequently used for APIs. Consequently, the machine is extremely specialized.
It is equipped with a dry running double mechanical seal with a sanitary design for minimizing dead areas where product can remain.
The filtering sheet is made of 5 layers of metal sintered grid.
It is equipped with a specially designed sampling device developed by Delta, which makes it possible to take a sample 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