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Keeping Drums at Arms Length
July 29, 2021
We were approached by a Global Healthcare company in need of a very specific product. They were looking for a simple stainless steel vessel out of 316L material, crevice free, to sit on a Mettler KA15 balance. The vessel was needed to weigh up to 4 kg bags of powder with a diameter of 270mm and height 230mm. An important requirement was that it sat flat on the balance.
The drum was to be used inside an isolator and would be wiped with IMS between batches. Sharp edges needed to be avoided to reduce the likelihood of inadvertently making a hole in the bag whilst using a metal scoop. However there also needed to be no powder/IMS traps present.
The important thing to know was that the operator would be in a half-suit inside a metal box.
Quantities of powder were to be weighed inside a bag inside the vessel. The vessel was required simply to keep the bag on the balance – a weigh pot. The operator needed to scoop powder from one bag into the weigh pot achieving a target weight of 3 to 4 kg. This bag would then be sealed and removed from the isolator.
Ideally the operators needed to be able to lift the weigh pot and bag towards them rather than stretching in the half-suit to remove the bag and powder out of the pot. So if the drum weighed no more than 3 kg and the dispensed qt weighed 4 kg there would be a total weight of up to 7kg being moved whilst stretching.
The wider the weigh pot the better. Too high would pose an ergonomic risk scooping the powder in.
Due to the unique way the vessel was to be used, it was clear the two main issues we needed to address with our drum was weight and a flat bottom.
As we already offer a flat bottom option with our stainless steel vessels, this did not pose a problem. Producing a vessel light enough and robust enough would present a challenge though.
Early considerations of cutting circular discs out of the drum body were quickly dismissed as we felt this would produce potentially sharp edges and pose a risk of the operator cutting themselves or piercing the bag.
An obvious place to start was thickness of material. 1.2mm was selected rather than 1mm to maintain rigidity. A Pressed neck rather than solid would reduce weight further but also provide a product trap so that was ruled out. A folded safety edge, however, would substantially reduce weight whilst providing the rigidity.
We worked closely with the customer to provide a prototype flat bottomed open top vessel. Produced in 1.2mm 316L grade stainless steel with a folded safety edge. The weight of each vessel was 2.1kg and FDA compliant.
Feedback from both operators and Environmental Health and Safety was “Excellent”, and further vessels were ordered.