When Macleod Pharmaceuticals expanded to a new range of antibiotic products, it needed to fit a bulk solids mixer, conveyor and filling machine in a confined area and reserve enough space for boxing, taping and labelling operations.
The company’s antibiotics are typically comprised of seven or eight powdered ingredients that are manually dumped from fibre drums into a 0.71cu-m ribbon blender mounted on load cells. Weight gain information on a display enables operators to dump the required amount of each material.
After a mixing cycle, the powder is gravity discharged into the U-shaped charging adapter of a 76mm diameter flexible screw conveyor manufactured by Flexicon Corporation.
The conveyor consists of a flexible steel screw enclosed in a tube that is driven by an electric motor.
As the screw rotates, it propels material through the tube and self-centres, providing sufficient clearance between the screw and the tube wall to prevent product damage. It transports the powder about 3.5m at a 45° angle, into a surge hopper atop the filling machine that dispenses drugs into a variety of containers.
The screw is the only moving part contacting material and can be removed rapidly between product changeovers for sanitizing of the screw and the tube’s crevice-free interior.
Products are made in campaigns, each of which typically last two weeks and involve the manufacture of several batches of a single product.
Macleod selected a flexible screw conveyor to fit within the limited space and prevent contamination of the product and plant environment.
Macleod Pharmaceuticals r00uled out other types of conveying systems that allowed the escape of dust, which must be avoided in the case of antibiotics, the Flexicon unit is dust tight and allowed them to curve the conveyor tube to fit the restricted space between the blender and filler.
To ensure the conveyor would transport Macleod’s antibiotic powders efficiently, Flexicon ran them in its test laboratory on a full size flexible screw conveyor configured to simulate Macleod’s application.
Flexicon engineers also solved design problems specific to his application by orienting the charging adapter horizontally instead of at an angle and fabricating a flange that attached tightly to the blender’s valve to discharge powder directly into the charging adapter with no exposure to the atmosphere.
Due to a ceiling height restriction, the conveyor’s discharge adapter also needed to be oriented as close to horizontal as the curvature of the conveyor tube would allow.
While Macleod was suspending the discharge adapter, complete with its 87kg motor, from the ceiling, it had one of the Flexicon engineers on the speakerphone. He entered the data into his AutoCAD and calculated the adapter angle that corresponded to the curvature of the conveyor.
Because this is a new manufacturing site for products that will be packaged in a new container size, U.S. Food and Drug Administration (FDA) approval is required before commercial products can be produced, as is also the case with drugs for humans. In anticipation, Macleod has been running pilot batches and practice runs to validate the system.