ISO 12917-2:2002 pdf download

ISO 12917-2:2002 pdf download.Petroleum and liquid petroleum products一 Calibration of horizontal cylindrical tanks一 Part 2: Internal electro-optical distance-ranging method.
5.4 Stadia
A rigid bar, usually 2 m long, such that the graduated length between the two stadia marks remains constant to
within ± 0,02 mm.
5.5 Auxiliary equipment
Auxiliary equipment includes
a) magnets or other equipment to steady the unit, and
b) lighting within the tank, if required.
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.
6.5 The tank shall be free from vibration and airborne dust particles.
NOTE The floor of the tank 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.
7 EODR instrument set up within the tank
7.1 The number and locations of the instrument stations shall be determined in order not to exceed incidence-angle limitations of equipment (see normative annex A). A typical minimum angle may be 10 gon.
If more than one station is necessary, survey traverse techniques should be used to move from one station to the other and the procedure in this subclause repeated.
7.2 The instrument shall be set up with care, particularly in the horizontal and vertical axes and according to the procedure and instructions given by the manufacturer.
7.3 The instrument shall be set up so as to be stable and free from external vibrations.
If necessary, the tank shell, in the vicinity of the instrument, shall be made firm and steady by placing heavy weights in the area.
The legs of the tripod on which the instrument is mounted may be steadied using suitable devices, such as magnetic bearers, to prevent slippage on the tank bottom.
8.2 Location of target points — General principle
Target points shall be located on each surface, randomly but distributed over the entire surface. No target points shall be positioned within 300 mm of a welded seam or stiffener.
NOTE It is not a requirement of this method that any particular point be used as a target point
8.3 Cylindrical courses
A minimum of 16 target points per course in tanks of diameter less than 3 m, and a minimum of 24 target points per course in tanks of diameter 3 m or greater, shall be sighted. The uncertainty of calibration will be reduced if the number of target points is greater than the minimum specified.
8.4 Heads
8.4.1 Flat end, elliptical, spherical head, conical head
A minimum of 50 target points, randomly but evenly distributed over the surface, shall be sighted. The uncertainty
of the calibration will be reduced if a greater number of target points is used.
8.4.2 Knuckle-dished end (head)
A minimum of 16 target points, randomly but evenly distributed over the surface, shall be sighted. The uncertainty of the calibration will be reduced if a greater number of target points is used.
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.