Providing the correct selection and orientation of a dust collector for pharmaceutical installations must consider both current and future application, location, combustible dust standards’ provisions, and most importantly plant and personnel safety. Below are the TOP 10 questions needing to be answered before properly selecting your next dust collector.
1. Is the dust combustible and dangerous to personnel? Both combustibility and toxicity must be considered first and foremost. If the dust is toxic, obviously containment of this dust is key and most important. If it is both toxic and combustible, then extra upfront consideration must be taken to protect plant personnel. Before any system design or equipment purchases are made, make certain that you have the proper dust tests performed to help in making the best decision. Also, do not believe the myth that the MSDS sheet will provide all of the necessary information on a product or the dust generated. Most MSDS sheets do not provide enough information to evaluate the explosive nature of dust.
2. Where will the dust collector be installed? Before answering this question, some of the other questions listed here may need to be answered and considered. If dust is toxic, keeping the collector indoors is generally preferred to avoid potential exposure to people in the area. If the dust is combustible, the best answer is ALWAYS outside!
3. What is the best media for the dust and best air-to-media ratio for my dust? To “BAG” or “NOT TO BAG”, that is the question (Forgive me, Shakespeare). Bag media is always best for the toughest dust, so it certainly works best for easier dust. Air-to-media ratios can run much higher for bag-type dust collectors; however, they are usually taller and more expensive. Additionally, there are many more options with bags than cartridges with regard to temperature and corrosiveness. While speaking of bags, the toxicity may require BAG-IN/BAG-OUT which is accomplished much easier with cartridge-type collectors.
4. Bag-In/Bag-Out – Filter house and Hopper? BIBO is not just for the filters, but in many cases, it is needed with the hopper. There are several ways to effectively achieve BIBO and consideration must be given to location and methods of doing such. There is no easy BIBO!
5. Are there any special considerations for getting the dust to the collector? No filtration system is complete without the proper transportation system; however, when dealing with pharma dust, some extra care and consideration must be taken. Leakage on a negative system is NOT ACCEPTABLE, especially when outside. Since most pharma dust is hygroscopic or has an affinity for moisture, consideration of the smallest amount of moisture entrainment and possible internal condensation can have devastating impacts on the collector and its effectiveness. There are special coatings that can be provided on dust collectors to prevent condensation from occurring in the filter house, should the collector be installed outdoors.
6. When can I use explosion venting and save money by not having to provide chemical suppression? OSHA NEP and NFPA directives dictate when, where, and how you can protect dust collectors with explosion venting. There are multiple solutions whether the DC is indoors or outdoors; however, there are other considerations to be made before deciding on just protecting the DC with less expensive membrane venting. It is better to prevent and suppress an explosion than vent the pressure after the fact. Also, shock waves from a dust collector explosion have caused secondary dust explosions within facilities.
7. Why do I have to use expensive chemical suppression systems? Some dust in the pharma industry has such high KSTs that explosion venting is not enough to protect the system. Additionally, location dictates the use of suppression 9 out of 10 times in pharma applications. In many retrofit applications, due to the back pressure caused by explosion relief stacks, suppression has to be added in order to obtain a valid Pred.
8. Why do I need isolation? The flame front from an explosion is going to take the paths of least resistance and include the explosion vent, outlet, and inlet ductwork. The flame front can travel down the inlet ductwork back to the processing area potentially causing a fire or secondary explosion. Mechanical isolators or valves will stop the flame front and direct the pressure from the explosion through the vent. Chemical isolation will not stop the pressure but will extinguish the flame front. Most tablet coater, pill coater, and fluidized bed dryer suppliers are using the proper techniques outlined in NFPA; however, there are some older systems out there that may not. It only takes one accident to bankrupt a company and destroy a life of valuable plant personnel!
9. How do I get the right equipment for present and future dust applications? There are several important questions that need to be addressed in both present and future applications. Should dedicated dust collectors be provided to a specific piece of equipment or can a centralized dust collection system be used with multiple dusts? If a central system is to be used, how do the various dusts interact? Will dust mixtures create a toxic combination? When different dusts are combined, does the mixed dust produce a different or higher KST than the individual dusts? When sizing the equipment, getting the “smallest” and most affordable collector to justify a project, can significantly “corner” a company when a future change comes up. A collector should be sized for media that is middle of the road in terms of the amount of media that can be put in the collector.
10. Are all my components associated with the collector the right selection to meet standards and practices? Maintaining records of how the equipment was selected including the dust parameters is necessary in the event of an agency audit. Having the right media, grounding, housing construction, coatings, rotary valves, double dump valves, fans, fan controls, etc., is key to making sure you can pass commissioning and validation for your system. Teaming up with the right companies (dust collector, fans, venting, suppression, and/or isolation) that know all the components and how they work best together can save valuable time during design and implementation.
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