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African Petrochemicals Jan/Feb Edition 15_1

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6 Continued from page 5

6 Continued from page 5 When the echo curves of a 26-GHz sensor and a VEGAPULS 64 are compared in the same application, even experts are impressed. And with smaller, horizontal LPG tanks, there is a further advantage: bypass tubes are often used in these round tanks. VEGAPULS 64 can be installed directly on the tank without a bypass tube. This saves additional costs. VEGASWING 66 is a universal vibrating level switch for all liquids and appropriate for extreme process temperatures and pressures. Better utilization of tank volume 80 GHz has a positive effect, especially when measuring liquids with low dielectric values at the bottom of the vessel. Normally, radar signals are reflected at the surface of the medium. In the case of media with small dielectric values, however, some of the signals penetrate the medium and are then reflected by the underlying container bottom. As a consequence, two signals are received: one from the liquid surface and one from the tank bottom. The lower the dielectric value of the medium and the lower the level, the larger the signals from the tank bottom. With the previous 26-GHz sensors, these two signals overlapped and mixed together, especially at low levels (only a few cm of filling height). The smaller level signal was practically swallowed by the larger bottom signal. For the radar sensor, the level signal was no longer visible. Due to the significantly shorter wavelength of the 80-GHz signals from VEGAPULS 64, the signals that pass through the medium are more strongly attenuated by the medium than those emitted by 26-GHz sensors. As a result, the reflection from the bottom of the vessel is significantly weaker. Even at low levels, the level signal is much stronger than the bottom signal. The result is that even the lowest filling levels (a few mm) can still be measured reliably and accurately. Processes can thus be further optimized and liquids reliably measured even at the bottom of large-volume containers. In other words, the tank volume can be utilized even better. Different antenna systems in different sizes are available for VEGAPULS 64. At the moment, the thread sizes on offer are ¾” (beam angle 14°), 1½” (7°), DN50 (6°) and DN80 (3°). Until now, VEGAPULS 64 was only approved for temperatures down to -40° C, but from the middle of 2017 onwards it will be possible to use the sensor in applications down to -196° C. Intelligent solutions for processes at sea If the storage tanks are on a ship, one of the first questions a user asks is where can the sensor be installed, in view of the many internal installations in the tanks. In a typical tank there are pumps that require a pipe for the hydraulic feed, another pipe for the return feed and a pipe for the conveyed product. Often there are two pumps, one for the large quantities, one for the residual liquid. All internal fixtures and equipment (the pumps alone have six pipes) generate interfering signals. Trying to get a good, clean measuring signal here is a difficult undertaking. Nevertheless, radar level transmitters are the right choice because they are robust and measure contactlessly. Measurement inside a standpipe is usually preferred for this application. In times past, six-meter long pipes (maximum available length) were welded together to make a standpipe; however, the welding seams disturbed the measuring signal again and again. VEGA was able to drastically reduce these interfering reflections with its special patented weld for such pipes. Difficult ambient conditions Level measurement is necessary not only in the storage and cargo tanks, but in the liquefaction and regasification plants as well. Some liquefaction plants are located at sea and VEGA sensors are deployed there as well. These plants are relatively complex and extend over multiple process stages. In each stage, the level is an important variable playing a major role in protecting the compressors. Measuring instruments control the level and have to function reliably at high pressures (16-18 bar) and very low temperatures (-163° C) in heavy seas. Since the tanks used here are usually smaller and have extremely fast filling or emptying operations, the surface of the product is often quite turbulent. Differential pressure measurement, for example, could be The radar sensor for liquids VEGAPULS 64 (flange version) is appropriate for badly reflecting media, such as low-dielectric liquids. used here, but because of the low temperatures it is extremely difficult in practice: the pressure detecting elements, the diaphragm seals, get covered with layers of ice. Vegaflex 86 is being used more and more for this particular application, the continuous measurement of levels in the various process stages of the liquefaction plants. This robust guided radar sensor is ideal for the task because it measures without being affected by media properties such as density or dielectric constant. Its rugged mechanical construction and second process seal, the so-called “second line of defense”, protect the sensor. It measures down to -196° C and is not bothered at all by turbulent surfaces. However, installing the sensor on board a ship requires a lot of experience. Whereas in applications on land the sensor can simply be mounted in the intended tank opening or bypass and measurement started more or less immediately, on ships the sensor has to be installed in a special way, in order to compensate for heeling movement in heavy seas. Reliable limit level detection LNG processes, whether on land or on ships, require not only continuous level measurement but also point level detection at many points. VEGASWING 66 is often chosen for this task. In general, vibrating level switches are very popular among users in the chemical and petrochemical industry as well as in refineries because they are extremely easy to operate and ensure safe, reliable measurement. In contrast to float systems, VEGASWING 66 offers a much higher level of security, as the sensor constantly performs self-diagnosis and monitors the sensing element. That’s why VEGASWING 66 is preferred over flotation devices in safety-critical applications. However, until two years ago it wasn’t possible to use these devices at very low temperatures. For these applications VEGA developed a patented inductive drive that excites the tuning fork effortlessly even under extreme temperature conditions. The user benefits greatly from the simple handling of this vibrating level switch and its extended application range down to -196° C (normal temperature in the LNG environment) and pressure range of -1 to +160 bar. Because the sensor measures so reliably irrespective of density, no matter what the product, it is perfect for high and high-high alarms in various stations on the ship as well as on land. It is used, for example, in the pump pit of a liquefaction terminal. To keep the pump from running dry, it must always be covered with liquid (LNG). VEGASWING 66 takes over level control here, ensuring reliable pump operation. Conclusion: Whether on land or at sea – there is hardly any process in the LNG/LPG industry that does not require pressure measurement, continuous level measurement or point level detection. Thanks to the plics® concept, VEGA sensors have the advantage that the user interface is the same for every measuring instrument, regardless of the measuring method. Even users with little experience in instrumentation can quickly find their way around. The sensors have become even easier to operate through the combination of Plicscom and Bluetooth. Their wireless Bluetooth communication is particularly useful for hard-to-reach areas, harsh industrial environments and Ex hazardous areas. The modular plics® concept, which VEGA introduced more than 14 years ago, really shows its strengths here. Plicscom is backward compatible and can be used for the entire installed base of plics® sensors – in pressure and level applications, with 70 different types of instruments and the serviceproven adjustment structure, with no software update required. This allows the user to configure and parameterize plics® sensors conveniently from a safe distance with a smartphone or tablet.

Engen Refinery to undergo planned routine maintenance Engen Refinery, South Africa’s second largest oil refinery, is set to undergo planned maintenance. Starting on 5 February 2018, this scheduled activity forms part of the refinery’s ongoing maintenance programme and will run for 45 days until 30 March 2018. Jehan Zaib, General Manager of the Engen Refinery, explains that routine planned maintenance is essential for the safe and reliable operation of the facility. “The planned outage will primarily focus on essential plant maintenance and inspection activities as well as process regeneration activities,” says Zaib. Additional resources over this period will see the creation of approximately 4 600 temporary positions for skilled workers, and where applicable have been sourced from the local South Durban community. Minimum disruption “To ensure that we complete this planned maintenance outage on time, there will be increased traffic as suppliers and contractors service the refinery,” says Zaib. m3⁄h l/h fact m/s “We will however do our utmost to keep any disruption to a minimum and have detailed planning schedules to mitigate any potential access and capacity issues.” The safety of Engen employees and the neighbouring community is of the highest priority to Engen, adds Zaib. “We want to thank our neighbours in advance for their understanding during this period.” Engen is a leading distributor and marketer of fuels, lubricants and oil-based products. Engen markets approximately one in every four litres of fuel sold in South Africa, while the Engen Refinery produces approximately 17% of South Africa’s refined product. For any queries: Engen Refinery Call Centre: 0800 330099 (toll-free) Liquid flow measurement up to 600 °C or 490 bar OPTISONIC 4400 – technology driven by KROHNE • Ultrasonic flowmeter for high temperature and high pressure liquids, e. g. in vacuum distillation, visbreaking or coker unit • HT version: 45…+600 °C, DN25…1000 • HP version: ≤490 bar, DN25…200 • Flow range 0,5…20 m/s, bi-directional • Communication options with NAMUR NE 107 diagnostics KROHNE South Africa 8 Bushbuck Close, Corporate Park South Randjiespark, Midrand, Tel.: +27 113141391 Fax: +27 113141681, Clayton Duckworth,, 7


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