SDT170-MTT | SDT Hear More | Ultrasound Detectors for Condition Based Maintenance (CBM) and Predictive Maintenance (PdM)

Ultrasonic Tightness Control of Underground Tanks

Around the globe the problem of soil pollution has become a priority

For some time now the majority of countries have created a legislative framework for this, aiming to identify and assess risks connected with historical soil pollution and avoid any new pollution. In view of possible pollution of soils or groundwater, the storage of vehicle fuels, heating oil or dangerous liquids in underground tanks is more and more subject to strict operating conditions. Rigorous, periodical tank leak-tightness monitoring is imposed in order to guarantee incident-free operation.

The aim is to be able to identify any leak rapidly so as to limit all risk of pollution as far as possible. In the event of major leaks it may be necessary subsequently to clean up the surrounding sub-soil, which usually leads to relatively costly treatments and work.

The controller is rendered liable through the services provided:

So it is easy to understand that the risk of a wrong diagnosis renders the controller liable when a tank is downgraded or approved. The latest SDT TankTEST system was designed with this technician's responsibility in mind. The SDT170MTT is the most reliable, the most comprehensive and the most accurate available for checking the tightness of underground flammable liquid tanks and their associated pipe work by introducing a vacuum and listening to the ultrasounds. With the SDT's "Graphs & Measurements" software for the automatic creation of authenticated reports all data and test measurements are stored in the detector. They can be transferred to a PC. They provide evidence of testing, measurement readings and graphics and archiving of the performances

The control principle:

The use of ultrasonic frequencies means a far higher level of sensitivity than is possible the audible sound.
The pressure in the tank is reduced, and the ultrasonic vibrations caused by the passage of water, air or other substances through a hole in the tank wall are detected by two sensitive sensors, one in the liquid and the other above the level of the liquid.
The SDT170-MTT detects the typical frequencies of leaks in underground tanks. It measures them and converts them to audible frequencies. These are fed back to the operator in three forms: visually and measured in dBuV on the detector display, and audibly through his headphones.

How Does the SDT170-MTT work?

The vacuum pump creates a gradual vacuum in the tank.
As soon as the vacuum created is greater than the hydrostatic pressure (max. 250mbar) due the the height of the liquid, any leaks generate ultrasonic signals.
The 2 sensitive sensors placed in the tank ( one above, the other in the liquid ) detect even the tiniest leaks, thus allowing the checking of flammible liquid tanks or tanks containing products harmful to the environment.

A widely recognized and approved method.

The SDT TankTEST for testing underground tanks was developed by SDT.

Belgian accreditation

The SDT TankTEST method has been tested and approved since 1995 by various authorities, including AIB Vincotte and Lloyd's Register in Antwerp. It meets the criteria of Walloon Government decrees of 3 July 1997 and 30 November 2000. It has also been approved by the Ministry for the Flemish Community (Animal, number AMV/30.06.95/1).

French accreditation

In 1998, Cetim in Senlis tested the ultrasonic SDT TankTEST method on behalf of the French Ministry for Town and Country Planning and the Environment; it was approved. Compared with the hydraulic method (pressurizing the tank after filling it with water), the SDT TankTEST has been recognized as being more sensitive in its detection, easier to implement, faster and more economical.

US accreditation

The SDT TankTEST method has been tested successfully by Ken Wilcox Ass., an American company licensed by the EPA, the only organization in the world to have defined the minimum level sensitivity to be met by a technique destined for use in the American market.

See their website for details on Underground Storage Tanks - http://www.epa.gov/OUST/cmplastc/