Tank & Vessel Calibration

Tank and vessel calibration in Dubai, Abu Dhabi and Fujairah — capacity table production to API MPMS Chapter 2 and ISO 7507 using manual strapping, EODR and 3D laser scanning for shore tanks, ship tanks, LPG vessels and process equipment. ISO 17020 accredited, ADNOC approved. Last reviewed: August 2026.

A tank capacity table converts a measured level into a quantity, and that quantity is what gets bought, sold, taxed and reconciled. An error of a fraction of a percent on a large storage tank is a commercially significant quantity of product on every transfer — which is why capacity tables are produced to defined standards and recalibrated at defined intervals rather than treated as permanent.

Calibration methods

• Manual strappingDirect circumference measurement with a calibrated steel tape at each shell course to API MPMS 2.2A. The reference method, still specified by many operators and terminal agreements, and the one against which other methods are validated. Requires access to the external shell.
• EODR — electro-optical distance rangingInternal measurement from a single instrument position using laser distance ranging to API MPMS 2.2D, producing a full shell geometry without external access or scaffolding. Suited to tanks where the shell cannot be strapped safely or where out-of-service time is limited.
• 3D laser scanningDense point cloud capture of the full internal geometry, producing a capacity table and a permanent digital record of the tank — including deformation, out-of-roundness and settlement — against which future surveys can be compared.
• Liquid calibrationVolumetric calibration by measured transfer of liquid through a certified meter, used for smaller and irregular vessels where geometric methods are impractical and where the highest accuracy is required.

Tanks and vessels covered

• Vertical cylindrical shore tanks, fixed and floating roof
• Horizontal cylindrical tanks
• Ship and barge cargo tanks
• Pressurised vessels, LPG and LNG
• Bullets, spheres and process vessels
• Road and rail tankers
• Wet and dry bulk cargo compartments

What the capacity table accounts for

A calibration is not simply a measurement of the shell. The table has to account for everything that displaces or affects volume at a given level:

• Shell course dimensions, plate thickness and out-of-roundness
• Tank tilt and floor deformation, and their effect on volume at low levels
• Floating roof mass and displacement, and the critical zone where the roof lands
• Internal structures, heating coils, columns and mixers as deadwood deductions
• Bottom profile and dead stock below the outlet
• Reference height and datum plate condition — where discrepancies in reconciliation usually originate
• Temperature correction for the shell material

Standards applied

• API MPMS Chapter 2 — tank calibration: 2.2A manual strapping, 2.2B optical reference line, 2.2C optical triangulation, 2.2D EODR
• ISO 7507 series — calibration of vertical cylindrical tanks for petroleum and liquid petroleum products
• ISO 8311 for refrigerated and non-refrigerated tanks where applicable
• API MPMS Chapter 3 for tank gauging where level measurement is verified alongside calibration
• Client, terminal and custody transfer agreement requirements where more stringent

Recalibration intervals

Capacity tables are not permanent. Tanks settle, floors deform, shells distort under repeated loading, and repairs change the geometry. API and ISO practice sets recalibration intervals — commonly five to fifteen years depending on tank type, service and construction — and recalibration is also required after any repair or modification affecting the shell or bottom, after significant settlement, and where reconciliation discrepancies suggest the table no longer reflects the tank.

When calibration is commissioned

• On commissioning of a new tank, before first custody transfer
• At the recalibration interval set by the standard or the terminal's procedures
• After repair, plate replacement or modification of the shell or bottom
• Following measurable settlement or tilt
• Where stock reconciliation shows persistent unexplained variance
• On change of ownership or operator of a terminal
• Before a tank enters custody transfer service

Accreditation and coverage

ITMAD is accredited to ISO/IEC 17020 as an inspection body and is an ADNOC approved inspection contractor. Tank and vessel calibration is carried out at terminals, refineries, tank farms and alongside vessels across Abu Dhabi, Dubai, Sharjah and Fujairah, scheduled around tank out-of-service windows and vessel movements.

What you receive

• Capacity tables in the increments and units your operation uses
• The calibration method applied and the standard followed
• Raw measurement data supporting the table
• Deadwood schedule showing every deduction and addition applied
• Reference height, datum and tilt measurements
• Point cloud data where laser scanning was used
• Certificate of calibration with validity period and next due date