Soil side corrosion, a major cause of tank bottom failures, is typically caused by the ingress of external contaminants and moisture through gaps and spaces around the annular chime space. Filling and emptying of the stored product cause the bottom plates to flex drawing in more moisture and external contaminants.
This mix of corrosive contaminants and moisture creates pitting corrosion that can cause tank bottom failures well short of the design life of the asset. Tank bottom plate inspections show that significant corrosion tends to occur around the tank chime.
But how do you provide corrosion protection for this vulnerable chime area while the tank is in service?
Zerust Oil & Gas has developed the innovative Chime Ring – Dry Sleeve system that allows for the introduction of corrosion inhibitors while the tank is in service.
A system of perforated PVC pipes is installed around the entire annular chime area and sealed in place.
Sleeves of proprietary Zerion inhibitor formulation are installed into the PVC chime ring and the system is closed.
Vapor Corrosion Inhibitors or VCIs typically have vapor pressures higher than air. As they are released from the sleeves, they enter the tank underside space through the same paths that allow ingress of contaminants and moisture.
The VCIs rise to the metal surface and neutralize contaminants. The flexing of the bottom plates during tank operations provides a further mechanism for the propagation of the inhibitors.
The diffusion of the VCIs provides protection against corrosion in the vulnerable 3-4 meters from the annular chime ring.
The Zerust inhibitor delivery system remains in place and the Zerion inhibitor sleeves can be periodically replaced, even while the tank is in service.