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JUL-AUG 2018

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External floating roof tank with still pipes: Internal floating roof tank without still pipes: Fixed roof tank: 8" stilling pipe Floating roof Floating roof 36 INTECH JULY/AUGUST 2018 WWW.ISA.ORG SPECIAL SECTION l GWR has different and open com- munication protocols, such as ana- log 4–20 mA, Foundation fieldbus, and wireless. l GWR can have an intrinsic lab accu- racy between 2 mm and 3 mm, and a 25 mm installed accuracy depend - ing on the vendor and measuring distance. l GWR vendors can provide five-point calibration for each GWR. l The technology is in compliance with all API MPMS chapter 3.1B require - ments highlighted above. l GWR will eliminate the conventional RTG proprietary hardware and sys - tem component. l Due to its simplicity, a FAT is not necessary. l GWR can be installed with or without stilling piping. GWR piloting and test results A plan was set to pilot four GWR level instruments from two different manu- facturers on different types of tanks with different refinery products, and to monitor the performance over one year. Over this period, the operation team conducted frequent manual gauging (three times per test) to check the installed accuracy of the GWR. Before proceeding with the field test, the selected vendors were asked: l to confirm that the intrinsic accuracy of their GWR is within ±3 mm (±1/8 inch). Also, every vendor had to pro- vide five-point calibration of each GWR to confirm the said accuracy. Both vendors provided the confirma- tion and data required. l to provide a certificate of the refer- ence-certified instrument, illus trat- ing traceability to national or in- ternational standards. The vendors provided certificates for traceabil - ity to German accreditation body DAkkS. l to confirm that the GWR transmit- ters have write protection. Both ven- dors confirmed and illustrated this feature for their GWR instruments. It was also mutually agreed with the two GWR vendors to check and con- firm the following after the installation and commissioning: l the overall accuracy of the GWR, which should be within ±25 mm (±1 inch) l the reading difference between the local transmitter display and remote DCS reading, which should be within 1 mm Accordingly, four tanks were selected to proceed with the field trial. The fig- ure 7 table highlights the data. The sketches in figure 8 represent the installation setup for the GWR instru- ments on the three types of tanks (from the left: external roof, internal roof, and cone roof ). After commissioning, the echo curve was collected for each transmitter to confirm a strong echo for each GWR, with no loss of signal and no interfer- ence (figures 10 and 11). Over one year, the refinery opera- tion team conducted manual dip- ping to check the reading accuracy of the installed GWR instruments. The data over the year has clearly demon - strated that the accuracy is within the required ±25 mm for inventory tank gauging applications. A sample of the data collected is in figure 12. Project scope revision The successful results of piloting GWR for the inventory tank gauging applica- tion revealed a new and suitable solu- tion for Saudi Aramco's Riyadh Refinery project. The project scope was revised to mandate GWR for the project and eliminate all the complexity and con- Figure 7. Pilot installation for GWR Figure 9. Installed GWR for piloting Tank # Transmitter tag Product Tank construction Gauge hatch size Manufac- turer R-Y-T72 Z41-LI-3333 MTBE External floating roof/12 meter 8 inch + stilling pipe E+H 1Z0-D- 006 Z41-LI-2222 Jet fuel Internal floating roof/15 meter 8 inch + stilling pipe VEGA 945-V6 Z41-LI-4444 Crude oil Internal floating roof/18 meter 8 inch E+H R-Y-T70 Z41-LI-1111 MTBE External floating roof/12 meter 8 inch + stilling pipe VEGA Figure 8. GWR installation options on different types of tanks

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