Selecting the right Sensors for Plant Operations |
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| By Carla Jack |
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Sensors are an essential element for safe and profitable plant operations and are used for both process control and monitoring. Generally speaking, the higher the performance/accuracy requirement the higher the cost of the instrumentation acquisition and maintenance. Finding the right balance between performance and cost should always factor in with the budgeting of a new plant or plant expansion rather than always getting the best performing sensor. The principles of selecting the right sensors for a specific plant application rely on the following needs: > Cost of Sensors This includes both the cost of acquisition and maintenance costs. The cost and estimated frequency of instrument calibrations should also be considered when laying out operations budgets. > Accuracy Accuracy is usually expressed as engineering units or a percentage of the sensor range and ties in with 'reproducibility' which refers to the variance in values measured under the same operating conditions over a period of time. > Range/Span of the Sensor Limit or range over which a process variable can be measured. This range is defined by the lower and upper range values. > Reliability Reliability ties in with the instrument's consistency with the process environment. You will need to assess how a device will perform for a period of time under specified operating conditions. (For example should the sensor be heat resistant?). Some sensors can have direct content with the process materials whilst others need to be protected.) Sensors in direct contact must not be degraded by the process material. > Dynamics The use of the sensor dictates the allowable delay in the sensor response. Some sensors will be required to provide real-time measurements and information outputs whilst others may only need to provide data on a daily or monthly basis. > Safety requirements Compliance to health, safety and environmental regulations should always be considered when selecting instrumentation for your plant. Display Panels, Control Panels, and Control rooms Once the sensor has collected data the next consideration is how the Information displays. Local display refers to display on the instrumentation whilst local panel display refers to control via a panel in the immediate area. A centralized control room is utilised for large plant operation when multiple processes need to be controlled at once. A centralized control system facilitates the analysis and control of the integrated plant. In rare occasions a plant or network of plants can be operated without onsite personnel but from another location. This is called remote monitoring. Smart Sensors and the future of instrumentation Whilst the basic chemistry and physics of sensors are not changing the integration of microprocessors with sensor technology marks exciting possibilities for plant owners. This includes increased data variables direct from the sensor includes the integration of multiple sensors. The digital format allows many sensor values to be sent simultaneously reducing the cost of cabling. Smart sensors can also warn when measurements might not be accurate via advanced diagnostics. 'Noise' reduction and advanced configuration also make smart sensors very accommodating to custom installs. Selecting the right sensors for your plant operations does not have to be a drawn out process. Make a simple list of your requirements and talk to people in the instrumentation industry and with related associations to help narrow down your choices. |
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| Article Source: http://interpret.zar.vg | ||||
| About The Author PJ Boner is an instrumentation company (est. 1978) which provides calibration services, automation technology, plant applications & internationally-sourced instrumentation in Ireland |
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| © 2012 interpret.zar.vg |
