Dry powders, of various types, are an integral ingredient and component of many pharmaceutical products that are manufactured under CGMP operations. Dry powders are clearly the largest component/ingredient of nearly all oral solid dose (OSD) forms. In addition to OSD, powder ingredients are frequently used in the manufacturing of aseptic products, oligonucleotides, mRNA, monoclonal antibodies, vaccines, and cell and gene therapies.
Safe handling of dry powders is an absolute must requirement in all manufacturing operations. Pharma companies need to ensure that both operators and facilities are appropriately protected against the hazards that are present when dealing with powders.
The list of items to consider when handling and processing powders is often quite lengthy and requires significant evaluation and implementation of appropriate engineering controls. This article would like to focus on three key items: dust control and containment; ergonomics and safe handling; and combustibility.
Dust control & containment
One of the biggest challenges faced with the handling and processing of powders is dust generation. Per code, a hazard can occur when one of three conditions are present:
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Significant accumulation of powders on horizontal surfaces (to the point at which the original surface color cannot be discerned)
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A high concentration of powder particulates that have been suspended in air
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Both conditions exist simultaneously
There are many ways to mitigate dust generation and keep fugitive dust emissions to a minimum. Some of those mitigations include:
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Operations below a dust containment system like a downflow booth or isolation booth
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Closed and sealed operations using mechanical connections between powder transfer containers, such as, a split butterfly valve arrangement
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Dust collection equipment with dust collection pickups that can be localized and focused directly on where dusts emissions are generated.
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A well-trained work staff trained on rapid response in the implementation of housekeeping measures — essentially, cleaning as they go
Dust containment has a direct impact on equipment design. Implementation of design features that remove the sources of ignition, the sources of oxygen, or containment or safe directing of an explosion can have significant impact to equipment cost and installation.
A facility designed and constructed for the handling of powders must take into account design features that minimize hazards from the accumulation of powders. The facility could potentially require implementation of electrically classified zones or containment of an explosion. All of these will result in significant impact to cost, construction and schedule for both new and existing facilities. Per code, even existing facilities are required to be evaluated for potential hazards from dusts and powders and mitigations identified and implemented.
Ergonomics & safe handling
When dealing with powders, an immediate key challenge that you are faced with is the wide range of container types that the various dry powders are delivered in, from the raw material supplier. Unfortunately, there is no real industry standardization here and your handling systems will need to accommodate:
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Drums (fiber, plastic, steel, ranging in sizes, with and without liners)
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Bags (paper, plastic and of various size and weight)
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Supersacks/big bags (single trip/multi-trip, single snout/dual snout)
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Other small containers, boxes and just about every other shipping method
From a process design standpoint is important to have a good understanding of the various container types to be handled and implement the necessary equipment and technology to handle all. Know your bulk density ranges and incorporate automated and semi-automated lifting devices to offer ergonomic assist. Understand and apply the appropriate levels of PPE, with considerations as noted above for dust control and containment. Evaluate an understand the flowability of the materials you are handling. (Think about your home sugar bowl left open on a humid day. It certainly isn’t flowing well.)
From a facility design standpoint, it is always important to consider all the locations where powders will be opened and transferred from their source containers to the process. Be sure to provide adequate room space and height, with gravity as the preferred method of transfer. Gravity is your friend and is free. Allow for adequately sized holding and staging areas and always consider a dedicated weigh/dispense area where incoming raw materials can be weighed and subdivided to accurate downstream batching and processing requirements. Use of a common transfer containers that feeds to the process, such as IBCs, single-use bags or appropriately configured transfer containers are a good way to handle process feed standardization.
Combustibility
The realization that a hazard exists when dealing with flammable liquids is straightforward and well established within industry. This is not so much when dealing with combustible dusts. While code provides an easy to implement definition of flammable liquids by flash point and boiling point (data that will be listed on a material’s SDS) this is not the case when classifying combustible dusts. The best, most quantifiable, method for determining the level of combustibility of your powder, or powder blend, is through third party testing. The results from this type of testing are definitive and provide all the necessary data required to do a thorough evaluation of the level of hazard.
Once the combustibility data is obtained the next step in hazard mitigation is to perform a dust hazard analysis (DHA). A DHA is a systematic review of all aspects of your operations that utilize powders to determine where and under what conditions a hazard may exist. The DHA also identifies the necessary mitigations based on the level of hazard. Keep in mind, within North America, a DHA is a code requirement and may be necessary to submit to a local authority as part of the permitting process for your facility.
Conducting a DHA is also necessary from a cost and project controls standpoint. The DHA will not only identify necessary design impacts for your processing equipment it will also define requirements for facility construction. However, the DHA goes beyond immediate capital project needs and defines requirements for long term operations, like, procedural measures for ensuring hazards are mitigated over the life of your facility. The most optimal time to execute a DHA is during the conceptual design phase of a project. The DHA can be used to define additional scope of work that may have significant impact to cost and schedule of your project.
Ensuring the safe handling of dry powders is essential for pharma manufacturers, requiring a comprehensive approach that includes effective dust control, ergonomics and evaluation of combustibility risks — all of which are critical to protecting both operators and facilities.
