API MPMS 2.2D pdf download.Manual of Petroleum Measurements Standards
For the purposes of this part of Chapter 2 the deÞnitions given in API MPMS Chapter 2.2A and the following deÞni- tions apply. 3.1 reference target point: Fixed point clearly marked on the inside surface of the tank shell wall. 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 wall. 3.3 target point: One of a series of points on the inside surface of the tank shell wall to which slope distance, vertical and horizontal angles are measured by use of the electro-opti- cal ranging instrument.
The general and safety precautions contained in API MPMS Chapter 2.2A shall apply to this standard. In addition, the laser beam emitted by the distance-ranging unit shall conform to IEC 825 for a class 1 laser.
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 ± 0.0002 gon*, a repeatability equal to or better than ± 0.0005 gon, and an uncertainty equal to or better than ± 0.001 gon. 2 . 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 ± 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 Þrm and stable. The legs of the tripod shall be held Þrm, 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 Þtted with a Þber 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 Þtted 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 ± 0.02 mm. 5.5 EQUIPMENT FOR BOTTOM CALIBRATION (see 11.1) 5.6 AUXILIARY EQUIPMENT including: a. heavy weights to be set around the instrument to steady the unit; b. lighting within the tank, if required.
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 Þlled 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 veriÞed prior to calibration. The accuracy of the distance-measuring unit as well as the angular measuring unit shall be veriÞed using the procedures recommended by the manufacturer. The appropriate procedures given in Appendix A shall be used for the veriÞcation of equipment in the Þeld. 6.5 The tank shall be free from vibration and airborne dust particles. Note 3: The ßoor 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.