Centrifuges are commonly used in the food and beverage industry for beer, wine, milk, water and juice. Internally the centrifuge has many layers of plates (or discs) stacked closely together so the speed of the liquid changes where different products are driven out of solution into solids and liquids. As an example, milk is heavier than cream, so the cream is driven by centrifugal force to the surface of the milk. The cream in turn flows off into a channel which leads to a collection vessel. The milk is forced out to the periphery of the drum and is collected in another channel into a separate vessel.
One is commonly called a basket centrifuge, normally a vertical machine used for smaller continuous processes, and the other is called a separator which is normally horizontally mounted and used for larger flow rates. Other uses for centrifuges are in sewage, wastewater, tallow, pathology, grinding machining coolant, oil industry to remove solids from the drilling fluid and the list goes on.
Centrifuges work at a relatively high speed and can have issues with imbalance and overall vibration. Pumps operate at rotational speeds between 1000 and 3000 rpm but frequently reach in excess of 6000 rpm.
All it takes is for the centrifuge to be out by 500g and the centrifugal forces will create up to 500kg of imbalance which can be extremely destructive. The more imbalance, the worse the final result and damage. Initially it could just be damage to bearings and fatigue to the machine and pipework in particular. In the worst case, it could be a total and catastrophic failure of the machine.
An important factor that is often overlooked is the impact to production. If a machine is off-line, production is lost. If a machine completely destroyed, there could be no product produced for weeks while awaiting repair or replacement.
ifm has been involved with vibration analysis for almost 20 years with sensing technology to determine the level of machine wear and imbalance. In the simplest form, a single sensor is mounted on the centrifuge to detect the imbalance to give a warning to the operator or automatically turn the machine off if a critical imbalance is detected.
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