ISO 12917-2:2002

Overview

ISO 12917-2:2002 specifies the internal electro-optical distance-ranging (EODR) method for calibration of horizontal cylindrical tanks used for petroleum and liquid petroleum products. It applies to tanks with diameters greater than 2 m and covers internal measurement procedures, equipment requirements, data recording and the compilation of tank-capacity tables. The method is applicable to tanks inclined up to 10 % from horizontal (with a correction for measured tilt).

Key topics and technical requirements

• Measurement method: Internal electro-optical distance-ranging (EODR) using an electro-optical distance-ranging instrument to record slope distance, horizontal and vertical angles to target points.
• Equipment specifications:
  • Angle measurement: resolution/gradation ≤ 0.002 gon; repeatability ≤ ±0.005 gon.
  • Distance measurement: resolution ≤ ±1 mm; repeatability ≤ ±2 mm.
  • Low-power laser emitter compliant with IEC 60825-1 for target positioning.
  • Stadia bar (typically 2 m) with dimensional stability within ±0.02 mm.
  • Stable tripod and auxiliary steadying devices (e.g., magnetic bearers).
• Target point selection:
  • No target points within 300 mm of weld seams or stiffeners.
  • Cylindrical courses: minimum 16 points per course for tanks < 3 m diameter; minimum 24 for ≥ 3 m.
  • Heads: minimum 50 points for flat/elliptical/spherical/conical heads; 16 for knuckle-dished ends.
• Measurement procedure:
  • Use reference target points (≈100 gon apart) and repeat measurements to verify stability.
  • Slope distances to reference points must agree within ±2 mm between start and end measurements.
  • Carry out calibration without interruption; verify instrument performance before use.
• Safety and environment:
  • Follow IEC 60079-10 for hazardous area classification and IEC 60825-1 for laser safety.
  • Tank must be free of vibration and excessive dust; lighting should not interfere with the EODR instrument.
• Documentation:
  • Procedures for data collection, drawings, and capacity table calculation; Annex A (limiting angle) is normative and Annex B contains an example.

Applications and users

• Primary applications:
  • Generating accurate tank-capacity tables for inventory control and custody transfer.
  • Verifying tank geometry for leak detection, regulatory compliance and asset management.
• Who uses this standard:
  • Petroleum storage operators, calibration laboratories, surveyors and metrology teams.
  • Inspection bodies, tank fabricators and maintenance contractors involved in tank gauging and certification.

Related standards

• ISO 12917-1 (Manual methods for horizontal tanks)
• ISO 7507-1 and ISO 7507-4 (vertical tank calibration and EODR methods)
• IEC 60825-1 (laser safety), IEC 60079-10 (hazardous area classification)
• ISO 1998 (petroleum industry terminology)

Keywords: ISO 12917-2:2002, horizontal cylindrical tanks, tank calibration, electro-optical distance-ranging, EODR, tank-capacity tables, petroleum tank gauging, laser distance measurement.