API MPMS 2.2F:2004 pdf download.Petroleum and Liquid Petroleum Products—Calibration of Horizontal Cylindrical Tanks
3 Terms and definitions
For the purposes of this part of ISO 12917, the terms and definitions given in ISO 1998, ISO 7507-1 and the following apply. 3.1 reference target point fixed point clearly marked on the inside surface of the tank shell or a prism mounted on a tripod or stadia 3.2 slope distance distance measured from the electro-optical distance-ranging instrument to a target point on any given course of the tank shell 3.3 target point one of a series of points on the inside surface of the tank shell to which the slope distance, vertical angles and horizontal angles are measured by use of the electro-optical ranging instrument
4 Precautions
The general and safety precautions given in ISO 7507-1 shall apply to this part of ISO 12917. In addition, the laser beam fitted to the EODR instrument shall be operated in conformity with IEC 60825-1. The hazards, if any, in the area in which the calibration is to be carried out shall be assessed in accordance with IEC 60079-10. The equipment to be used in the calibration shall be certified as being safe for use in the area of operation.
5 Equipment
5.1 Electro-optical distance-ranging instrument 5.1.1 The angle-measuring part of the instrument shall have an angular graduation and resolution equal to or better than 0,002 gon. This part of the instrument shall have a repeatability equal to or better than ± 0,005 gon. 5.1.2 The distance-measuring part of the instrument, used for direct determination of distances, shall have a graduation and resolution equal to or better than ± 1 mm. This part of the instrument shall have a repeatability equal to or better than ± 2 mm. 5.2 Instrument mounting A tripod which is firm and stable. The legs of the tripod may be held firm, and steadied, by suitable devices such as magnetic bearers. 5.3 Laser-beam emitter A low-power laser beam complying with IEC 60825-1, which is either an integral part of the EODR instrument or a separate device.
9 Procedure for calibration
9.1 Measure and record the horizontal angle, the vertical angle and the slope distance to each reference target point. Two successive readings, at each point, shall be taken and they shall agree within the tolerance given in clause 10. Compute and record the average angles and distance to each point. 9.2 Measure the horizontal and vertical angles and the slope distance to each target point on a surface. See Figure 2. 9.3 If more than one measurement station is required, move the instrument from station to station, taking sufficient measurements at each station to ensure a proper traverse. 9.4 After all measurements from one measurement station are completed, repeat the measurements to the reference target points. 9.5 If the repeated horizontal and vertical angles and slope distances to each reference target point do not agree with the measurements taken in 9.1, within the tolerances given in clause 10, determine the reasons for such disagreement, eliminate the cause and repeat the calibration procedure. 9.6 Commence measurements at one head and progress through the tank to the other head. 9.7 Carry out all measurements without interruption.