Undertank Reference Electrodes
The environmental conditions beneath an aboveground storage tank make it very difficult to obtain potential measurements. The sand is dry when the electrode is first installed. Cathodic protection currents and/or heat from the product further dries out the sand sharply increasing resistivity. A permanently installed reference electrode can completely dry out in this environment and the absence of moisture in the area will prevent it from rewetting. Consequently, electrodes in such locations may last only a few years. Where potential measurements throughout the life of an AST are desired, a preferred solution is to use our Undertank Reference Electrode (Model UT).
The Undertank Reference Electrode is placed in a slotted pipe installed in the sand pad beneath the tank bottom. When bottom potential measurements are needed, the electrode is slowly pulled through the pipe to produce a potential profile. An alternate design with a threaded coupling rather than an eye-bolt can be used in those cases where it is necessary to push the electrode into the pipe. Between measurements, the electrode can be either left at one end of the slotted pipe or used to develop a potential profile in another tank.
Permanently installed references beneath ASTs
Installations which require continuous potential monitoring will use Reduced Diameter Reference Electrodes permanently installed in the sand bed. EDI’s SlimLine™ Reference Electrode (Model US) has a 30 year design life and is considered the premium reference electrode for this application. Choose the Extended Life version (Model US50) with a 50 year design life for projects where a longer service life would be beneficial. Some engineers prefer using our Dual Element Reference Electrode (Model UD) with a 30 year design life Cu/CuSO4 (or Ag/AgCl) gelled element along with an encapsulated zinc element.
Download our paper on Instrumented CP Systems on an AST for additional information on potential measurements beneath an aboveground storage tank.
For More Information
Complete Product Information and Installation Instructions are available for downloading as pdf files. Click on the documents you wish to download.
Undertank Reference Electrode (Model UT).
Installation Instruction for undertank reference electrodes.
EDI products may be purchased from any corrosion control products distributor or directly from EDI.