Sacrificial Anode

This here is a Chlorine Evaporator

Liquid elemental chlorine goes in, gaseous elemental chlorine comes out

The liquid chlorine enters a chamber in the centre of the vessel

Around the outside of this chamber is a water jacket

A heating element keeps the water in that jacket at a temperature around 38℃

The heat from the mass of water conducts through the internal wall of the water jacket and evaporates the liquid chlorine in the centre into it's gaseous form; hence the name

The chlorine gas then flows on through a pipe to the rest of the dosing system

Chlorine is dosed at a low rate into drinking water to disinfect it so it's safe for people to drink and wash with

Today's job was to replace the six sacrificial anodes inside the water jacket on two of the plant's four chlorine evaporators

That's twelve in total

What's a sacrificial anode?

Also known as a galvanic anode; it's a piece of metal that is in effect, subjected to corrosion through electrochemical design so that more important metal parts do not corrode

More on the theory of cathodic protection if you're interested

The more important metals, in this case, are the walls of the inner chlorine chamber and the water jacket

Every 12 months, the anodes in the plant's chlorine evaporators are replaced with new ones

The first step was to find the circuit breakers for the evaporators

Switch them off

Then lock out the switches so the evaporators are de-energised and safe to work on

Here's a box of the shiny new replacement anodes on top of a chlorine drum

And here's a couple of the anodes that were removed from the evaporator

These anodes are made of Magnesium