Rectifiers & deep well anode beds
In order to offer adequate cathodic protection to large pipeline components, a magnesium anode is not sufficient. This is because the small difference of potential between the cathode and the magnesium anode make it impossible to achieve the desired pipeline potentials. With the aid of the impressed current technique using a rectifier and an deep well anode bed, the difference of potential between the cathode and the anode can be configured independently, resulting in a much broader reach.This makes it far easier to monitor the degree of CP-protection. A rectifier system combined with impressed current provides adequate cathodic protection to large pipeline components. Note however, that the reach is dependent on the power demands of the pipeline component that has to be protected, and on the soil resistivity.
Positioning anode bedIn general, the transition resistance of a new deep anode bed has to be below 3 ohm. Before determining the size of the anode column and the depth of the bore hole, Korf KB first conducts on-site tests to confirm the expected soil resistivity. After drilling the bore hole a measuring post is used for establishing the actual soil resistivity at intervals of 5 metres. On the basis of this information we compose the anode bed which consists of anodes and dummies.
During the construction of the anode column, we make sure that the anodes are placed in the soil layer with the lowest soil resistivity. The electrical resistance sustained by the current sent from the rectifier to the anode bed into the ground should be as low as possible. This is why anodes are usually placed at large depths; here the soil resistivity levels are more favourable, enabling the electricity to flow easily from the anode to the cathode that has to be protected. Generally, the head of the anode bed is situated at -40m from the surface level, also to prevent disturbance to systems of other pipeline/cable owners and to minimise the potential gradient located at the surface level.
Korf KB works with hollow silicon iron tube anodes, which are placed in a tube. The tube is subsequently sealed off with backfill. The tube contains a coupling frame, which facilitates the linkage of the tubes in the field. Korf KB builds its rectifiers according to the client’s wishes, often using the Amstel rectifier, which is available in different models. For installing the rectifier system we generally use a double-door polyester cupboard. However, here too is the customer king.
Reasons to opt for Korf KB
- Quick delivery of the anodes and dummies through in-house production
- Every desired cable length is available
- Rectifier is completely tailor-made in accordance with the wishes of the client
- Whole-package project approach! We take care of the:
- assembly of the rectifier (rectifier plate & E-plate)
- assembly of the anode column (anodes & dummies)
- positioning of the rectifier and anode bed in the field
- application of the cathode cables to the pipe
- installation of the LS-connection in the rectifier cupboard
- installation of the system in accordance with the client’s wishes