The unpredictable nature of injectable pharmaceutical powders makes it imperative for the packaging sector to use machines that deliver tight dose control. For this particularly volatile—and understandably stringently-controlled—subset of the greater pharmaceutical industry, machines need to provide not only strict dosage accuracy and repeatability, but also tight precision and communication between metering devices, efficient yet effective sampling, and precise check-weighing for proper dose verification. Adjustability and adaptability are also key machine features in an industry where smaller batch runs favor the most versatile equipment.
In order to accurately fill any given powder, its flowability and bulk density must be understood and its propensities properly managed. Being the “self-weight” of powder, bulk density in particular is a crucial predicator of the powder’s behavioural tendencies in both compressed and uncompressed states. And once these parameters are defined, manufacturers must then translate that “weight” into the main concern of a filling system: volume.
Considering this challenge, a strong case can be made for utilizing vacuum-pressure powder dosing machines, based on the effectiveness of this technology when it comes to high-accuracy dosing requirements in high-speed line configurations.
Vacuum-Pressure Powder Dosing Machines
A brief overview of machine components using vacuum-pressure dosing disc systems can be helpful in the understanding of the vacuum-pressure dosing process.
A main hopper with an agitator that helps the powder flow downwards.
An intermediate hopper equipped with:
- An internal stirrer assigned to keep the powder in continuous movement in order to maintain product characteristics (flowability, grade of agglomeration, homogeneity) and allow an easy feeding of the underneath chambers.
- A see-through window allowing the operator to ascertain powder state and quantity.
- A minimum-level sensor to manage the powder flow coming from the main hopper.
- A dosing disc composed of 12 chambers. Each chamber is:
- Vacuum assisted. Once the powder flows inside the chamber, a depression is generated that lasts until the chamber is on top of the vial. This depression is then turned into a sterile air-blow to foster the ejection of the slug of powder into the vial. The sterile air-flow in charge of this suction/expulsion momentum passes through a filter that is specially conceived and dedicated to the characteristics of the type of powder to be handled.
- Adjustable in depth. The fixed diameter is determined by taking into account both the requested filling amount and internal diameter of the vial’s neck. The depth of the chambers, however, can be adjusted to cover a broad range of dosages. The ratio between the chamber diameter and its depth has to respect specific rules to assure dosing accuracy.
- Piston regulated. One sliding piston is present in each chamber, and equipped at the top with a filter through which the sterile air-flow passes for powder compression/slug ejection. It is this regulation, performed before starting production and therefore preventing any possible particle contamination, which allows infinitesimal perfection in the volume of powder that the chambers can host to reach the ideal result.
A purge station. After the discharge of the product into the vial, the empty chamber continues its rotation. The chamber is then cleaned via high-pressure sterile air blow, assuring that any residual powder is removed before refilling. A dedicated dedusting system takes care of any possible powder loss that may occur during this process.
Advantages of Vacuum-Pressure Dosing Machines
For addressing the specific complexities of filling injectable powders, then, it is no surprise that vacuum-pressure dosing machines have proven to be efficient and reliable when it comes to assuring consistently accurate dosing. We can say that vacuum-pressure dosing system simply has tools perfectly designed for filling such an exacting format.
By and large, vacuum-pressure dosing machines also are quite user-friendly, with its primary complexity—disc assembly and disassembly—fairly straightforward and easy to learn. It is the reason why many of today’s fully validated production lines are equipped with vacuum-pressure dosing discs, and new generations of these machines are continually being developed and introduced.