TANK CALIBRATION

From Strapping Tables to Calibration Tables.

Increased accuracy results in reduced product loss, says Hans van den Heijkant of Kalibra International, who talked to Tank Storage magazine about developments in tank calibration, and a method for upgrading accuracy of tank tables, even when the tank remains in operation. As products like mineral oils and chemicals become more expensive, the need for reducing measurement uncertainties grows rapidly, says Hans van den Heijkant.

One of the most important parameters for this measurement uncertainty is based on the storage tank's calibration table, from which transactions and/or inventory measurements are taken, he explains.

The calibration table is known commonly as the strapping table in reference to the first calibration technique for storage tanks, but technology has come a long way since then, says Hans. "Although strapping the tank using measuring tapes has been the method for many years, developments in tank calibration have shown that more accurate methods have become available for calibrating the tank and, from this, more accurate tank tables can be issued."

State-of-the-art Techniques which post-dated the strapping method have included the optical reference line (a trolley that moves along the tank shell) and optical triangulation, both developed in the 1980s.

Since 1995, however, the state-of-the-art technique Electro-Optical-Distance- Ranging (EODR) has become available. "The EODR method is not only much more accurate than the older methods such as strapping, optical reference line and optical triangulation - in fact up to 5 times better - it is also much less time consuming," says Hans. "On top of this, the EODR method can be applied on in-use tanks - the external method - so upgrading the existing tank tables can be done even when the tanks remain in operation."