API MPMS 3.6:2001(2017) pdf download
API MPMS 3.6:2001(2017) pdf download.Manual of Petroleum Measurement Standards Chapter 3- -Tank Gauging Section 6- -Measurement of Liquid Hydrocarbons by Hybrid Tank Measurement Systems.
Appendix B to assist the user in determining the magnitudes of errors of spot (ie.. static) measurement of observed density. mass, and standard volume due to uncertainty of each of the FfMS system primary neasurements (level, pressure, and temperature,
7.1 ACCURACY EFFECTS OF THE ATG
The accuracy of the ATCJ component and its installation has the most effect on level, observed and reference density, and observed and standard volume.
Refer to MPMS Chapter 3.111 for guidance on the ATG accuracy as related to calibration and installation.
Errors in the measured level have little effect on the cornI iwted mass because of error cancellation in the arithmetical
product of volume and density.
Note; The mass error canccllaiion effect is grcatcc in vciiical cylindrical tanks. In spherical or horizontal cylindrical tanks the mass emw cancellation is somewhat less. The effects of ATG accuracy on mass for various tank geometries can be predicted using the unccrtairny equations in Appendix B, Section 1i2.
If an HTMS is used to determine standard volume for custody transfer or inventory control, then the accuracy of the ATCJ should meet the corresponding requirements set forth in MPMS Chapter 3.18. If the HTMS is used primarily for mass or density determination, then less rigorous requirements of ATG accuracy than those specified in MPMS Chapter 3.1 B for custody transfer may he employed. Refer to Table I for recommended maximum allowable ATG tolerances.
7.2 ACCURACY EFFECTS OF THE PRESSURE SENSOR(S)
The accuracy of the pressire sensors (P1 and P3) directly affect the observed and reference density. and the mass. However, errors in P1 or P3 have no effect on observed volutile, and only a minor eflct on standard volume,
The overall accuracy of the pressure sensoPs will depend on both the eew and linearity crroi-s. The zero error is an absolute error expressed in the pressure unit of measurement (e.g.. Pascal. in-H20. psig. etc.). The linearity error is typically stated in percent of reading. At low levels the zero error is the dominating factor in the uncertainty analysis. The manufacturer should unambiguously state both the zero and linearity errors over the anticipated operating temperature range to allow the end user to verify that the error contribution of the pressure sensor(s) to the overall uncertainty will be acceptable for the required HTMS accuracy (see Appendix 8.). Refer to Table 2 for recommended maximum allowable zero and linearity errors.
The total error in pressure units of a pressure sensor can be calculated by:
9.1 INITIAL PREPARATION
9.1.1 Tank Capacity Table Validation
The hybrid processor will normally store suflicient data to reproduce the tank capacity table, These data should he checked against the Lank capacity table.
9.1.2 EstablIshment of the Hybrid Reference Point
It is essential that the positions of both the P1 transmitter uui ATG arc referenced to the reference datuns/datum plate specified in the tank calibration table. For practical purposes. the hybrid relërencc point is introduced. The hybrid reference point is referenced to the tank datuiwdaturn plate by the dimension H, (Sec Figure A-I).
It is advised that the hybrid reference point be located close to the P1 pressure transmitter’s process connection, and should be clearly and pemianently marked on the tank shell.
The relative position of the hybrid reference point in relation to the lank datum plate (H) should he ace urately measured. recorded. and entered into the hybrid processor. From the hybrid reference point the elevation of the pressure sensor elketive center can he measured (Hh). The pressure sensor position in relation to the tank datum plate (Z = + Hh) can then be calculated by the hybrid processor. Alternately, the value of Z may he entered into the hybrid processor directly. (See Figure A-I.)
