29.06.2009
The International Workshop "Calibration of storage tanks by optical scanning", which took place in Hamburg on June 17 and 18, 2009 and constituted, for the present, the conclusion of a very successful cooperation between PTB, the Verification Authority North and the Trimble Holdings GmbH (formerly CALLIDUS precision systems GmbH) in the development of a novel procedure for the laser-optical measurement of large storage tanks, met with unexpectedly great response.
Storage tanks play an important role wherever large quantities of liquids are handled. In addition to being used for storing liquids, they are, for the most part, also used as volume meters. If they are used for business transactions (e.g. for the purchasing or sale of the liquids) or for official inventories of the quantities stored (to determine, for example, the tax), they are, in Germany, subject to legal control.
Figure 1: Typical storage tanks in the area of the free port in Hamburg
PTB, the Verification Authority North and the Trimble Holdings GmbH had invited to Hamburg to participate in a workshop where a joint development was to be presented to interested technical experts – a new laser scanning procedure for the geometric measurement of such storage tanks.
Figure 2: Participants in the workshop
In addition to the description and presentation of the procedure, especially the aspects of legal metrology - i.e. traceability of the measurements of the laser scanner and determination of the measurement uncertainty for the respective liquid volume in the tank, as well as the repeatability, reproducibility and comparability of the respective measurement results - were addressed. Also discussed in detail was the PTB's approach to prove compliance with the respective legal requirements and thus, the applicability of the laser scanning procedure in transactions under verification law.
The response to the invitation to the workshop was astounding. More than 60 participants from 16 countries accepted the invitation. In addition to our European neighbours, technical experts from - for example - Tanzania, Brazil, China and Uzbekistan came to Hamburg. Far more than half of the participants were representatives of governmental institutions and authorities who are responsible for compliance with the respective legal regulations in their countries.
Figure 3: Photos of the interior of a storage tank during presentation of the newly developed laser scanning procedure
The second day of the workshop was dedicated, above all, to practical presentations. For this purpose, the Holborn Europa Raffinerie GmbH had made a storage tank available which was measured by means of the laser scanner, jointly with the participants.
The workshop in Hamburg has shown very clearly that there is a great demand not only for modern, efficient measuring techniques for storage tanks, but also for communication possibilities and an exchange of experience between the respective technical experts both at the national and international level. Clearly emphasised was the enormous economic importance of exact volume measurements in storage tanks - both in the mineral oil industry (e.g. for the measurement of crude oil and its products) and also, to an increasing extent, for alternative liquid energy sources and combustibles and – last but not least – for liquid food.
In the next step, the verification authorities and PTB will extend the valid GM-P4.2 "Legal Metrology – Testing instructions for storage tanks in the form of vertical cylinders” by including the new laser scanning procedure. This has already been prepared in the "Storage Tanks” Working Committee. In addition, scanning procedures for the calibration of storage tanks shall also be included in general in the international regulations, preferably within the scope of the OIML in the TC8/SC1 "Static volume and mass measurement”, whose next meeting will take place in Vienna in October 2009.
Contact person:
Gudrun Wendt, Department 1.5, E-mail: gudrun.wendt@ptb.de