API MPMS 2.2D:2003(R2021) pdf download.Manual of Petroleum Measurement Standards Chapter 2—Tank Calibration
5 Equipment
5.1 ELECTRO-OPTICAL DISTANCE-RANGING INSTRUMENT 5.1.1 The angular measuring part of the instrument shall have an angular graduation and resolution equal to or better than士0.0002 gon*, a repeatability equal to or better than士 0.0005 gon, and an uncertainty equal to or better than士 0.001 gon. 5.1.2 The distance-measuring part of the instrument, used for direct determination of the distances, shall have a gradua- tion and resolution equal to or better than土1 mm, a repeat- ability equal to or better than +2 mm, and an uncertainty equal to or better than+2 mm. . 5.2 INSTRUMENT MOUNTING consisting of a tripod which is firm and stable. The legs of the tripod shall be held firm, and steadied by suitable devices such as magnetic bearers. 5.3 LASER BEAM EMITTER having a low-power laser beam complying with IEC 825, which is either an integral part of the EODR instrument or a separate device. If the laser beam emitter is a separate device, it may be ftted with a fiber optic light transmitter system and a theodolite telescope eye- piece connection, by which the laser beam may be transmit- ted through a theodolite, or such that it may be fitted to a theodolite with its axis parallel to the axis of the theodolite. The laser beam may be coincident with the optical axis of the telescope Note 1: The laser beam emitter is used to position target points on the tank shell. 5.4 STADIA a rigid bar, usually 2 m long, such that the graduated length between the two stadia marks remains con- stant to within士0.02 mm.
6 General Considerations
6.1 The EODR instrument shall be maintained so that the values of its measurement uncertainty do not exceed the val- ues given in this part of Chapter 2. 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. Note 2: The hydrostatic 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 angular measuring unit shall be verified using the procedures recommended by the manufacturer. The appropriate procedures given in Appendix A shall be used for the verification of equipment in the field. 6.5 The tank shall be free from vibration and airborne dust particles. Note 3: The floor of the tanks should be as free as possible from debris, dust and loose scale. 6.6 Lighting, when required, shall be placed within the tank so as not to interfere with the operation of the EODR instrument.