Annex to ISO / IEC 17020:2012 accreditation certificate number 231 I, Type A
From  TankTech B.V.
This annex is valid from 12-04-2018 till 22-12-2018 
No. Working Field Type and Scope Method and Procedures

Ship tanks

calibration of ship tanks

Schip tanks directive 71/349/EEG

unit verification


(initial verification)

measuring tanks by means of Total Station




measuring tanks by means of FARO Focus 3D 

laser scanner


This annex has been approved by:
Mr. J.A.W.M. de Haas
Operationeel Director

When ships are built, structural defects, welding stress etc. may cause deviations from respective construction drawings. Suchlike deviations are generally accepted by the Classification Society, since they are within the standards required. However, respective deformations may significantly affect the tank's volume.


According to the drawing, the dimensions of a hull integrated tank are 30,000 x 15,000 x 8,000 mm.

Maximum deviation according to classification requirements

                                                         →  nominal volume

                                                         →  maximum volume

                                                         →  minimum volume

• In the course of gauging, TankTech will measure the tank's actual shape and dimensions.

  The risk of constructional inaccuracy can thus be excluded.  

Yes, TankTech has been certified by the RVA (no. I231).

The RvA is the only Dutch signatory to the MLA, which means that the conformity-statements (certificates, tests and reports) from RvA-accredited bodies are accepted worldwide.

The international standards used in accreditation guarantee that a product, service or organisation are evaluated or tested on the same basis throughout the world.This gives confidence in the equivalence of certificates and reports in the Netherlands and abroad. National accreditation bodies within Europe are affiliated to the EA.

This is not always feasible. Even tanks, which were declared to feature an explosion-proof atmosphere, might still contain gas concentrations harmful to human beings. This depends on the most recently transported cargos.                                                                           

Prior to the measurements the maximum permissible VOC* value will be determined. This value will be submitted to the client in order to take the necesaary precautions before the start of the measurement.

Our staff is equipped with multi-gas meters, which serve to continuously monitor the actual VOC value. If actual VOC values exceed the maximum, the measurement will have to be interrupted.     

*Volitale Organic gas Concentration                                                      

No, this is not necessarily required. If a tank cannot be cleared, measurements can be made by deploying respiratory protective equipment. However, the costs for suchlike gauging will exceed those of standard measurements.    

In all cases a third party must have declared the tank to be explosion proof!

The accuracy depends on the shape on the size of the tanks. For inlandvessel an accuracy of 0,3% at a level difference of 500 mm is guranteed.

 Practical tests proved that in most of the cases the tables deviate by less than 0.1% from reality.

Even the most advanced measuring devices show inaccuracies. These inaccuracies are defined in the manufacturer's factory specifications. The affect of all inaccuracies on the final measuring results, are subject to the determination of the total uncertainty. Calibrationprocedures are performed in a way, which ensures achieving at least the in the certificate mentioned accuracy.                          

No, TankTech deploys 3D laser devices, which facilitate measurement across wide distances. Scaffolds do thus not need to be erected. On the contrary: the less obstacles are present inside of the tanks the better!                 

Self-evidently, this is the ideal case. Nevertheless, The calibration of tanks with residual cargo is feasible. However, additional supporting equipment is needed. Consequently the measurment requires more time, and thus causes extra costs.