Cold Applied Anticorrosive Grease for Overhead Conductors
Cablegard Corrosion Resistance and Corrosion Protection
Most overhead power cables/conductors consist of aluminium strands, sometimes reinforced by central strands of galvanised steel – Aluminium Conductor Steel Reinforced (ACSRs).
Although aluminium is generally considered to be fairly corrosion resistant, it is prone to crevice corrosion. A stranded conductor inevitably presents many crevices, as each strand is in contact with its neighbours. Importantly, the zinc of the reinforcing strands of ACSRs is also prone to crevice corrosion.
The most corrosive atmospheres are generally encountered in salt-laden coastal regions and in industrial areas with their atmospheric pollutants such as sulphur dioxide. Given that much of the world’s population and its accompanying industry is concentrated in coastal regions, both salt and acid pollutants are frequently found together. Clearly the life of a conductor is determined by the degree to which it can withstand this corrosive cocktail.
The traditional method of combatting corrosion has involved the application of molten grease during the manufacture of the conductor. This entails maintaining a fairly large thermally insulated reservoir of permanently molten grease and pumping it into the point(s) of application. The process is somewhat hit-or-miss and generally fails to completely fill the crevices between conductor strands. In fact, specifications call for only a 65% minimum of the theoretical fill – leaving as much as 35% of the length of the conductor unprotected. A chain is only as strong as its weakest link!
At least as important as filling the conductor is that the grease should be an effective corrosion protective for aluminium, zinc and steel, both individually and also in mutual contact, to prevent galvanic and differential aeration (crevice) corrosion. In tests – and in practice – most widely used hot applied greases fail to come up to the highest standards in this respect.
Cablegard is the easily applied anticorrosive that reaches where others cannot and performs where others fail. By this means it extends conductor life, thereby offering the world’s power generators and distributors major cost savings.
UNIQUE PATENTED FORMULATION
Cablegard consists of a synergistic blend of corrosion inhibitors, penetrating aids, metals’ deactivators and age resistors in a highly refined, gelled mineral oil. It protects all major metals and alloys and is especially effective on steel, aluminium and zinc.
Cablegard is applied during manufacture of the conductor at room temperature – straight from the drum as received. The need for the melting, storing, pumping and application of a molten grease is entirely eliminated. Cold application makes for a much cleaner operation than that of a molten grease where strict temperature control – and therefore viscosity – is very hard to achieve, making the operation both messy and difficult to control.
STAYS IN PLACE
Cablegard’s unique rheological (flow) characteristics enable it to be easily pumped at room temperature straight from the drum onto the conductor during the stranding operation. However, once applied it immediately re-sets & stiffens to resume its grease-like consistency and remain firmly in place.
FILLS THE CONDUCTOR COMPLETELY
Unlike hot-applied greases, Cablegard’s unique viscosity and flow characteristics enable the entire conductor to be 100% filled to ensure complete protection. In this way, the crevice corrosion, which is the main cause of failure, is eliminated.
WILL NOT MELT OR DRAIN AWAY
Cablegard does not have a melting point, it stays where it is put, regardless of the highest temperatures likely to be encountered. The drop point of Cablegard is in excess of 300 degress Celsius.
Naturally, the cost of the high performance Cablegard anti corrosive is initially more than that of the relatively crude hot-applied greases. However, this is largely offset by the savings due to:
Ease of application
No trace-heated pipework to install and maintain
Elimination of heating and capital costs associated with storing and pumping molten grease
Improved safety compared to the handling of hot molten grease.
Cleaner, less messy operation
LONG TERM – “THE BOTTOM LINE”
The greatly superior protective properties of Cablegard compared to conventional lubricating greases based on lithium or sodium soaps, will considerably extend the useful life of conductors. This, allied with reduced maintenance, offers long-term savings many orders of magnitude greater than the (relatively tiny) extra cost of the Cablegard which is infinitesimal when overall costs are taken into account:
The cost of pylons
The cost of conductors themselves
Greatest cost of all…replacement of corroded conductors