Instrumentation in petrochemical industries
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The measurement of temperature is a vital part of instrumentation in petrochemical industries. Platinum Resistance Temperature Detectors (RTD's) are often used for their excellent temperature response. Thermocouples are used in locations that need a more durable sensor. Thermocouples come in many types.
A pressure to current converter (P/I converter) in petrochemical industries is used to measure the pressure developed by liquified petroleum gas (LPG), crude oil, petrol, and various other petroleum byproducts. In the P/I converter, the indicated pressure can be a digital or an analog form. The main advantage is that it can be directly shown on the control panel in the control room. This is true for temperature measurement also.
Because refined oil is volatile, it is important to know the quantity of oil being transported at numerous points along the pipeline. This requirement also holds for natural gas. Flowmeters are generally of vortex, positive displacement (PD), differential pressure (DP), coriolis, and ultrasonic varieties.
Petroleum and natural gas industries need very accurate level measurement. Besides traditional technologies like differential pressure level meters, radar, magnetostrictive, and magnetic float are also used extensively.
One of the problems with a significant number of technologies is that they are installed through a nozzle and are exposed to products. This can create several problems, especially when retrofitting new equipment to vessels that have already been stress relieved, as it may not be possible to fit the instrument at the location required. Also, as the measuring element is exposed to the contents within the vessel, it may either attack or coat the instrument causing it to fail in service. One of the most reliable methods for measuring level is using a Nuclear gauge, as it is installed outside the vessel and doesn't normally require a nozzle for bulk level measurement. The measuring element is installed outside the process and can be maintained in normal operation without taking a shutdown. Shutdown is only required for an accurate calibration.
- William Bolton (6 August 2015). Instrumentation and Control Systems. Elsevier Science. pp. 54–. ISBN 978-0-08-100621-4.
- Alan S Morris (9 March 2001). Measurement and Instrumentation Principles. Butterworth-Heinemann. pp. 328–. ISBN 978-0-08-049648-1.
- Roger C. Baker (9 August 2002). An Introductory Guide to Flow Measurement. John Wiley & Sons. pp. 52–. ISBN 978-1-86058-348-3.
- Lipták, Béla G. Instrument Engineers' Handbook: Process measurement and analysis. Taylor & Francis, Inc. pp. 151 (Chapter 2). ISBN 978-0-8493-1083-6.