API MPMS 2.2F:2004(R2014) 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.
6 General considerations
6.1 The EODR instrument shall be maintained so that the values of their measurement specifications do not exceed the values given in this part of ISO 12917. 6.2 Tanks shall only be calibrated after they have been filled at least once with a liquid of density equal to or greater than that of the liquid which they will hold when in use, and at a pressure greater than the pressure at which they will operate when in service. NOTE The hydrostatic or pressure test applied to new tanks will satisfy this requirement in most cases. 6.3 Calibration shall be carried out without interruption. 6.4 The EODR instrument shall be verified prior to calibration. The accuracy of the distance-measuring unit as well as the angle-measuring unit shall be verified using the procedures recommended by the manufacturer (e.g. a stadia or reference laser may be used for distance measurement). The procedures given in ISO 7507-4:1995, annex A should be used for the verification of field equipment.