Breadcrumbs Section. Click here to navigate to respective pages.
Chapter
Chapter
Fig. 14 Scraped-surface anchor agitator with auxiliary crossbar agitator. (From Ref. 20.) have many deleterious effects on it. First, the emulsion may have components that cannot stand the wall temperature, which may be as high as 110-125°C. This is even more important if the dosage has active ingredients that decompose at these temperatures. Second, if the temperature is hot enough, the product may actually stick or burn on the sidewall. Cooling of product through sidewall heat transfer can cause almost as many prob-lems as heating. During cooling, the viscosity of a product almost always increases. A viscous product that is not physically removed from the sidewall builds up and forms an insulating layer than resists efficient heat transfer. Again, once this condition oc-curs, it is very difficult to reverse it. There is a variety of different designs of scraper blades. Some are arranged in rows. Some are offset on either side of the anchor, allowing some overlap as an an-chor makes a complete revolution. Some actually are designed to allow the anchor to revolve in opposite directions, which can prevent the buildup of product on the fol-lowing edge of the anchor. Some designs use a spring to force the blade against the wall. Most modern designs use the force of the liquid flowing into the blade to bring it close to the wall. Scraped-surface agitators are definitely required in emulsification equipment where heat transfers are necessary. These anchor agitators with scraping blades can be just as simple anchors or part of complex multishaft mixers. 5. Counterrotation Anchor-type agitators have a decided weakness when handling high-viscosity products of more than about 75,000-100,000 centipoise. They tend to rotate only the product,
DOI link for Fig. 14 Scraped-surface anchor agitator with auxiliary crossbar agitator. (From Ref. 20.) have many deleterious effects on it. First, the emulsion may have components that cannot stand the wall temperature, which may be as high as 110-125°C. This is even more important if the dosage has active ingredients that decompose at these temperatures. Second, if the temperature is hot enough, the product may actually stick or burn on the sidewall. Cooling of product through sidewall heat transfer can cause almost as many prob-lems as heating. During cooling, the viscosity of a product almost always increases. A viscous product that is not physically removed from the sidewall builds up and forms an insulating layer than resists efficient heat transfer. Again, once this condition oc-curs, it is very difficult to reverse it. There is a variety of different designs of scraper blades. Some are arranged in rows. Some are offset on either side of the anchor, allowing some overlap as an an-chor makes a complete revolution. Some actually are designed to allow the anchor to revolve in opposite directions, which can prevent the buildup of product on the fol-lowing edge of the anchor. Some designs use a spring to force the blade against the wall. Most modern designs use the force of the liquid flowing into the blade to bring it close to the wall. Scraped-surface agitators are definitely required in emulsification equipment where heat transfers are necessary. These anchor agitators with scraping blades can be just as simple anchors or part of complex multishaft mixers. 5. Counterrotation Anchor-type agitators have a decided weakness when handling high-viscosity products of more than about 75,000-100,000 centipoise. They tend to rotate only the product,
Fig. 14 Scraped-surface anchor agitator with auxiliary crossbar agitator. (From Ref. 20.) have many deleterious effects on it. First, the emulsion may have components that cannot stand the wall temperature, which may be as high as 110-125°C. This is even more important if the dosage has active ingredients that decompose at these temperatures. Second, if the temperature is hot enough, the product may actually stick or burn on the sidewall. Cooling of product through sidewall heat transfer can cause almost as many prob-lems as heating. During cooling, the viscosity of a product almost always increases. A viscous product that is not physically removed from the sidewall builds up and forms an insulating layer than resists efficient heat transfer. Again, once this condition oc-curs, it is very difficult to reverse it. There is a variety of different designs of scraper blades. Some are arranged in rows. Some are offset on either side of the anchor, allowing some overlap as an an-chor makes a complete revolution. Some actually are designed to allow the anchor to revolve in opposite directions, which can prevent the buildup of product on the fol-lowing edge of the anchor. Some designs use a spring to force the blade against the wall. Most modern designs use the force of the liquid flowing into the blade to bring it close to the wall. Scraped-surface agitators are definitely required in emulsification equipment where heat transfers are necessary. These anchor agitators with scraping blades can be just as simple anchors or part of complex multishaft mixers. 5. Counterrotation Anchor-type agitators have a decided weakness when handling high-viscosity products of more than about 75,000-100,000 centipoise. They tend to rotate only the product,
ABSTRACT