Tag: Industrial Instrumentation
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Absolute vs. Secondary Instruments
Measuring instruments may be classified as either absolute instruments or secondary instruments. Absolute Instruments This type of instruments gives the value of the measurand in terms of instrument constant and its deflection; this instrument type doesn’t require comparison with any other standard. For instance, the tangent galvanometer gives the value of the current to be…
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How to Measure Pressure using a U-tube Manometer
There are three categories of pressure measurement, namely absolute pressure, gauge pressure and differential pressure. The absolute pressure is the differences between the pressure at a particular point in a fluid and the absolute zero of pressure, that is, a complete vacuum. When the pressure measuring device measures the difference between the unknown pressure and…
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Process Control System Design for a Distillation Unit
The aim of a typical control system is to force a given set of process variables to act in some desired and prescribed way by either fulfilling some requirements of the time or frequency domain or achieving the best performances as expressed by an optimization index. The scope of the control tasks varies widely. The…
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How Capacitive Probes are Used to Measure Level
Capacitive probes can be used to measure the depth of liquids and solids. A rod, normally coated with PVC or PTFE, is inserted into the tank and the capacitance measured to the tank wall. The capacitance has two components C1 above the surface and C2 below the surface. As the level rises C1 will decrease…
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What is the Function of a Steam Desuperheater?
Whereas superheated steam offers an excellent source of energy for mechanical power generation, in most cases, steam at greatly reduced temperatures, near saturation, proves a more desirable commodity especially for most heat-transfer applications. Precise temperature control is required to enhance heating efficiency; eliminate unintentional superheat in throttling processes; or to protect the downstream product or…
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Instrument Piping Systems Installation Guidelines
The right installation ensures the long term instrument system reliability. In this article we look at the general guidelines for the installation of instrument piping systems. Piping Systems/Tubing Runs Before we can proceed, it is important to state the difference between piping and tubing; tubing can be regarded as thin-walled seamless pipe that cannot be…
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What is Calibration of the Sensor?
Calibration of the sensor is the relationship between the physical measurement variable input and the signal variable output for that specific sensor. Typically, a sensor or an entire instrument system is calibrated by providing a known physical input to the system and recording the output. The data is plotted on a calibration curve such as…
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The Operation of a Temperature Control System for lubricating oil
Lubricating oil reduces friction between moving parts and also removes heat from the components. As a result, the oil becomes hot. This heat is removed from the lubricating oil by a cooler to prevent both the breakdown of the oil and damage to the mechanical components it serves. The lubricating oil cooler consists of a…