API MPMS 3.1B:2001 pdf download.Manual of Petroleum Measurement Standards Chapter 3- – Tank Gauging Section 1B- Standard Practice for Level Measurement of Liquid Hydrocarbons in Stationary Tanks by Automatic Tank Gauging.
The use of ATGs in custody transfer application requires high accuracy. The use of ATGs for inventory control purposes often permits a lower degree of accuracy.
3.1 B.4.4.1 Use of ATGs for Custody Transfer Purposes
3.1 B.4.4.1 .1 The ATG should meet the fictory calibration tolerances prior to installation (refer to Section 3.lB.4.3.2).
3.1 B.4.4.1 .2 The ATG should meet the field verification tolerance for custody transler (refer to Section 3.113.7.3.3). including the effects of installation methods and changes in operating conditions (refer to Section 3.113.4.3.3).
3.1B.4.4.2 Use of ATGs for Inventory Control Purposes
3.1 B.4.4.2.1 The ATG should meet the factory calibration tolerances prior to installation (refer to Section 3.1 B.4.3.2).
3.1 B.4.4.2.2 The ATG should meet the field verification tolerance for inventory control (refer to Section 3.IB.7.3.3), including the effects of installation methods and changes in operating conditions.
3.1 B.4.4.3 Remote Readout Custody Transfer
The remote readout, if used, should meet the requirements of this standard (refer to Section 3.lB.4.6).
3.18.4.5 INSTALLATION OF ATGs
3.1 B.4.5.1 Manufacturer’s Requirements
The ATG and the associated elecironics should be installed and wired in accordance with the manufacturers’ instructions. NFPA Nusloiwl Fkc;rwui Ccsk and/or local standards.
3.1B.4.5.2 Mounting Location of Ullage-ATGs
The mounting location of an ATG may affect its accuracy after installation. l’he mounting location of the ATG should be such that the ATG may be easily verified by manual gauging from the official gauge hatch.
For custody transfer accuracy. it is essentia] that the mountin location should be stable, with minimal sertical movenwnt with respect to the tank reference (which is typically the joint where the tank shell and bottom meet). If the datum plate is found to be stable. ii may be used to verify the stability of ATO mounting.
The stability of the mounting location is atlected by the changes in liquid head, vapor pressure or loading of the roof or gauging platform.
3.18.4.5.2.1 Top Mounting With a Slotted Still Pipe
Figure I shows an ullage-ATG mounted on a slotted still pipe supported by tank bottom. Figure 2 shows an ullageATO mounted on a slotted still pipe supported by a bracket.
Ullagc-ATGs mounted on properly supported slotted still pipes. as illustrated in Figures 1 and 2. deliver higher accuracy because the slotted still pipe is supported on a stable location and ATG movement is minimized when the tank is tilled or emptied.
3.1 B.4.5.2.2 Top Mounting Without a Slotted Still Pipe
Alternatively, an ullage-ATG may be supported on the roof of a fixcd.roof tank or on a “gallows” on a fixed or Iloating roof tank, as illustrated in Figure 3. This kind of mounting may cause the ATG to move vertically when the tank is filled or emptied. Ullage-ATGs mounted without slo4lcd still pipes can be used for custody transfer or inventory control if the ATG as installed, can be verified to meet the requirements set forth in Section 3.1 B,4.3.4.
API MPMS 3.1B:2001 pdf download
