Tubular Anode Guidelines For Use
In groundbed design, it is important to remember that the purpose of the
tubular anode is to provide current to the coke breeze column. Good design
of a groundbed begins with first sizing the diameter and depth of the coke
breeze column (active depth).
Parameters important to consider in the design are:
- Backfill current density. This value is the groundbed current divided
by the surface area of the backfill column that contacts the soil. In
most deep groundbeds, this value should not exceed 100 - 200 mA/ft2.
- Coke breeze resistivity. Use a realistic value based on experience in
the area or obtain advice from the supplier.
- Average soil resistivity
- Soil strata makeup. What is the water table depth?
- Groundbed current.
- Chemical contact of groundwater or moisture. Is chloride salt likely
to be present?
Ventralizers™
For optimum performance, Ventralizers should be used to assure that the
tubular anodes will be located in the center of the groundbed. The
Ventralizer's unique design further allows the operator to attach the anode
to the vent pipe - providing 1" of separation between the anode and vent
pipe. Standard sizes are 6", 8" and 10", suitable for hole sizes ranging
from 6" to 12".
VENT PIPES
Vent pipes should be used in all deep groundbeds. The importance of vent
pipes includes.
- Removal of gases generated downhole.
- Providing a means to water the hole, if necessary.
- Allowing heat to escape from the hole.
It is important to keep the vent pipe clear. Therefore, hole or slit sizes
should be smaller than the smallest particle size of the backfill to keep it
from filling the vent pipe.
BACKFILL
Selection and installation of a high-quality carbonaceous backfill is
critical for proper performance of all types of groundbeds. Backfills should
be pumped from the bottom of the hole and the fill pipe removed.
Backfills for ELTECH LIDA® tubular anodes must have the
following characteristics.
| |
Metallurgical Coke |
Petroleum Calcined Coke |
| Resistivity |
Max. 50 ohm-cm |
Max. 50 ohm-cm |
| Particle Size |
0.1 - 3 mm (150-5 mesh) |
0.1 - 1mm (150-20 mesh) |
| Carbon Content |
Min. 70% |
Min. 90% |
HOLE DRILLING - CLEANING
In all groundbeds, regardless of anode types or bed geometry, the hole
must be cleaned prior to installation of anodes, vent pipe and backfill.
This prevents contamination of the backfill, which can cause high
resistivity and short groundbed life.
