impeller.net The Online Pump Magazine

28.08.2017

Retrofitting Anode Blocks by Tsurumi

As soon as water is involved, corrosion is an issue that needs to be addressed: The service life of many pumps and aggregates is shortened if they are exposed to aggressive media such as saltwater. One remedy is to retrofit anode blocks and replace parts.

What many users do not know: Even ‘rustproof’ pumps made of stainless steel are not completely immune to corrosion. The destructive reaction starts when the thin passive layer on the surface is damaged. A sharp impact on the casing is all it takes.

More frequently though, it is elements made of cast metals that are susceptible to corrosion, whilst parts made of titanium are most resistant. The general rule is: The more aggressive the medium, the more reactive the metal; and rust will appear quickly afterwards. Even salty water has a huge potential to cause contact corrosion, if it connects different metals – basically always. And all manufacturers face this problem.

This is why the construction pump market leader Tsurumi now supplies retrofittable sacrificial anodes. The solid plates made of aluminium or zinc are simply screwed to the casing. The complete set, which is available in retail stores, contains all the necessary material. Two plates are required per pump. They specifically start a bimetal corrosion process: The corrosion always attacks the less noble metal, i.e. the anodes. These become rusty whilst the bodies of the pump made of the more noble metal remain practically unscathed. The local effect stops when the material of the sacrificial anode has been spent by corrosion. This galvanisation ‘trick’ significantly prolongs the service life of the pumps. The cycle starts over again when the spent anodes are replaced with new ones.

However, this principle does not work on rotating parts such as the impeller on the intake opening of the pump. For this reason, Tsurumi has developed customized replacement impellers. The corrosive wear on these parts is reduced by around 90 percent, so that the service lives are also extended here. The user can replace these parts easily by simply unscrewing some screws.

Retrofitting is an investment that pays off: Unscheduled pump stops could be more expensive, and purchasing a new pump is always more expensive. By comparison, anyone who bought pumps made of titanium and glass fibre reinforced plastic, for instance Tsurumi’s TM series, is always on the safe side.

Source: Tsurumi (Europe) GmbH

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