SAIMC Secunda’s March technology evening was hosted by Endress+Hauser. Alwin Lutchman gave a presentation on automatic tank gauging. This is the generic name for the static quantity assessment of liquid products in bulk storage tanks. Whatever method is used, a high degree of reliability and accuracy is of paramount importance when the data is used for inventory control or custody transfer purposes. Two methods for accurate tank gauging are:
• Servo gauges.
• RADAR gauging.
Servo tank gauges operate on the principle of displacement measurement. A small displacer on a measuring wire is unwound from a drum and accurately positioned in the liquid medium using a servo motor. The weight of the displacer is precisely balanced against a magnetic coupling and the wire drum. When the displacer is lowered and touches the liquid, the weight of the displacer is reduced because of the buoyant force of the liquid. As a result, the torque in the magnetic coupling is changed and this change is measured.
Radio Detection and Ranging (RADAR) works on the principle of time of flight – the time taken to send and receive a signal divided by two. The time measured will represent a distance and that distance will be translated into the level of the tank. For expensive products it is advisable to install an expensive gauging system that is very reliable and accurate, to give a higher return on investment.
According to the International Organisation Of Legal Metrology (OIML) R85 and the American Petroleum Institute (API), the accuracy of factory calibration should be ±1 mm and the accuracy for the instrument after installation should be ±3 mm. This gives a total allowable fault tolerance of ±4 mm when in service. To conclude, when it comes to tank gauging for product inventory, investing in an expensive level instrument that is designed according to OIML R85 and API will give a highly accurate measurement of inventory and ensure a higher return on investment.
All instrumentation and control mechanicians, technicians and/or engineers are welcome to attend our monthly technology events in 2017. The planned dates for the rest of the year are:
06 April 2017
11 May 2017
01 June 2017
06 July 2017
03 August 2017
07 September 2017
12 October 2017
02 November 2017
All the presentations will earn CPD points for ECSA registered persons and any enquiries can be directed to the branch chairman, Johan Maritz at [email protected] or 082 856 3865.
| Tel: | +27 11 312 2445 |
| Email: | [email protected] |
| www: | www.saimc.co.za |
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