Manufacturing
The Effects of Heat from Electro-mechanical Components in Critical Instrumentation Heat in electronic and fluidic control systems such as those seen in analytical, scientific and medical instruments will in many cases be an unwanted byproduct of the excessive power required to initially operate electro-magnetic devices such as solenoid valves and electro-mechanical devices. Although the initial power is unavoidable, the need to maintain full power when the device has been energised becomes excess to requirement in many instances. In the majority of cases, it is possible to reduce the power to a level that maintains the required function but reduces the excessive currents being drawn, and in doing so there is less heat and a lower overall power requirement that can be considerable, depending on the number of devices present. Reducing power consumption is both cost-effective and desirable in this day and age of carbon-footprint awareness. Solenoid valves in particular are a source of localised heat which, if unchecked, can transfer to the media passing through them and in doing so can elevate the temperature beyond the desired limits, and can be a particular problem if the media is a physiological fluid or is heat-sensitive. However, any electro-magnetic device can emit heat and draw higher than necessary current if not intelligently controlled. Such devices can be as simple as electromagnetic clamps, locks and sorting devices.
Figure 1. Typical solenoid valve
Figure 2. Sample electro-magnet
One of the many laws of physics states that energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object. Energy is a conserved quantity; the law of conservation of energy states that energy can be converted in form, but not created or destroyed.
Simplistically speaking, that is all there is to it; however, each time there is a transfer from one form of power/energy to another, there will be some losses that are inherent in the device. The most wasteful phase is after the mechanical movement has been achieved and the magnetic circuit has been completed, the power to hold the device in position is considerably reduced. Assuming that the instrument’s design allows the same power to flow through the device, the excess power is liberated as heat and it is this heat build-up that should be addressed.
In the real world, we are more likely to think of the concept of power rather than pure energy as it is more relative to the tasks we need to perform. For electro-magnetic devices, the subject of this editorial, the principle is simple: Electricity In = Electro-Magnetic Field = Magnetic Attraction = Mechanical Movement.
Wasting power may not appear to be a major consideration for mains-powered
Figure 4. Sample power savings
equipment, but what if there is need for a battery-operated instrument with a long field life? Even mains-operated instruments can benefit from power reduction, savings on the cost of electronic power supplies and reduction in physical size and weight of the final instrument.
Figure 3. Temperature traces for a high-pressure solenoid valve 84 INTERNATIONAL PHARMACEUTICAL INDUSTRY
Electro-mechanical devices are designated to have specific duty ratings which will greatly affect their potential to generate excessive heat, and particular care needs to be taken when selecting such devices to match the application in hand. A 100% Spring 2021 Volume 13 Issue 1
