API MPMS 3.6:2001 pdf download
API MPMS 3.6:2001 pdf download.Manual of Petroleum Measurement Standards Chapter 3- Tank Gauging.
6 Selection and Installation of Hybrid
Tank Measurement System Equipment
6.1 GENERAL
A Hybrid Tank Measurement System (HTMS) consists of four major components: an automatic tank gauge (ATG), an automatic tank thermometer (ATT). one or more pressure sensors, and a hybrid processor which stores the tank parameters and performs calculations. The requirements of these individual components are described below.
The user should define whether the HTMS is to be used primarily for standard volume or mass measurements (or both), whether the measurements are to be used for custody transfer or inventory control application, arid the corresponding degree of measurement accuracy desired.
The user or manufacturer should select the HTMS components and configure the system appropriately to meet the application requirements. The accuracy requirements of the user’s application determines the individual accuracy requirements of the HTMS components. Section 7 and Appendix B provide guidance and methods to estimate the effects on overall HTMS accuracy of the individual component selection.
To achieve standard volume custody transfer accuracy, the ATG and AT1’ components should be selected to meet the applicable custody transfer requirements defined in MPMS Chapters 3.1 B and 7. To achieve mass custody transfer accuracy, the pressure sensors should meet the applicable custody transfer requirements defined in MPMS Chapter 16.2.
If the HTMS is to he customized for a specific application where high accuracy is required for some parameters but not all, refer to Section 7 for additional guidance. Accuracy prediction equations with examples are given in Appendix B to assist users in selection of individual component accuracy requirements.
6.2 AUTOMATIC TANK GAUGE (ATG)
The automatic tank gauge (ATG) component and its installation and mounting should meet the requirements described in MPMS Chapter 3.1 B, where applicable. Note that Chapter 3.1 B defines different levels of accuracy for ATGs used for either custody transfer or inventory control purposes. The ATG accuracy requirements thr HTMS are consistent with Chapter 3.1 B for HTMS systems intended primarily for volumetric measurements. However, the ATG accuracy requirements for mass HTMS applications are somewhat different. Both arc summarized in Table 1, below. The accuracy of the ATG installation will determine the accuracy of the HTMS density and standard vol u me measurements.
The intrinsic accuracy of the ATG, demonstrated by the factory calibration, and the installed accuracy. demonstrated during field verification, should be within the following maximum values:
Note: For mass-based applications (both custody transfer and inventory control), accuracy of the ATG has minimal effect on the mass calculated above the P1 level because of the canceling effect of density/volume errors. However, the uncertainty of calculated density due to errors in the ATG has an effect on heel mass (i.e., at levels below the P1 position). Therefore, the choice of ATG accuracy in Table 1 for mass-based applications is made for the purpose of minimizing error in heel mass. In addition, by minimizing Uncertainty in calculated density. a means is provided to independently monitor the performance of the pressure transmitters.
Where loss control or inventory accounting requirements suggest. maximum inventory control ATG tolerances should be more rigorous (i.e., less than ± 25 mm (I inch)).
6.3 HTMS PRESSURE SENSOR(S)
The HTMS pressure sensor installation should he in accordance with the recommendations given in MPMS Chapter
16.2. The HTMS pressure sensor(s) should he selected in accordance with the accuracy uncertainty calculation for the specific application (See Section 7 and Appendix B). The accuracy requirements of the pressure sensor(s) depends on the HTMS’s intended application (e.g., for volume or mass custody transfer, or volume or mass inventory control). The following maximum values of allowable zero and linearity errors are recommended for various configurations of HTMS.
