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.