Author: John Mulindi
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What are Virtual Instruments?
Virtual instruments (VI) are instruments based on computer software whose controls and displays are presented on a computer screen and whose operation and settings are controlled by the keyboard and mouse. Instead of purchasing a number of expensive, dedicated, standalone instruments, users find it less costly to purchase a computer with a multichannel, analog-to-digital converter…
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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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4 Common Arrangements of Distribution Substations
The general technique of supplying large quantity of power to factories or other complexes is by means of high-voltage (HV) supply, typically at 11 kV, occasionally at 6.6 kV. The installation consists of a main substation at the point of entry, with HV cables to supply subsidiary substations located near load centres. Where necessary, it…
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AC Transmission and Distribution Systems
Electrical energy is generated, transmitted and distributed in the form of AC. Since, alternating voltage can be changed in magnitude by means of a transformer; it is possible to transmit AC power at high voltage which reduces the current in the conductors hence the line losses. The conductors system is the means by which electric…
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What is the Safety Instrumented Function (SIF)?
The safety instrumented function (SIF) is used to monitor a selected process parameter and takes an executive action to make the process safe, if certain limits are exceeded. An illustration of safety instrumented function in a process plant is shown below: The figure above illustrates a gas pipeline which supplies a feed to a power…
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Gunn Diode – Features, Operation & Applications
Features of a Gunn Diode A gunn diode is made up of only N-type semiconductor which is typically sandwiched between two metal conductors. The central section is usually lightly doped N– surrounded by heavily doped N+ layers. The central section is N-gallium arsenide whereas the two outer sections undergo epitaxial growth from GaAs with increased…
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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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How HAZOP Technique is used to identify Hazards in a Process
In functional safety, hazards are events which have the potential to cause harm such as personal injury, damage to the environment or the business. Hazards in the process industry might include: the pressure of liquid in a vessel (high pressure may result in loss of containment, leaks or vessel rupture), the level of liquid in…
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Safety Function in a Machine Control System
A safety function is executed by the safety-related parts of the machine control system to achieve or maintain the equipment under control in a safe state with respect to a specific hazard. A failure of the safety function can result in an immediate increase of the risks of using the equipment; that is, a hazardous…