New approach sees iicorr save Mallaig Harbour £100,000

Aberdeen based integrity, inspection and corrosion specialist iicorr successfully completed the £500,000 project for Mallaig Harbour Authority in the northwest of Scotland. The company was appointed to implement a corrosion protection system which would prolong the life of the harbour and minimise the effects of corrosion on the steel work.

The solution devised by the iicorr team involved securing the needed standoff bar anodes onto the harbour’s steel work wall by using bespoke cantilever brackets designed specifically for this project.

Gordon McKinnell, cathodic protection services business unit manager at iicorr explained, ‘The way the anodes have been attached in the past is totally through the efforts of a team of subsea welders. Two difficulties arise from this. One is that since the anodes are an elongated U shape, it means two individual welds (top and bottom) underwater per unit, taking up more divers and putting a strain on diving times.’

This is especially true when the harbour wall in question needs as many anodes as the Mallaig construction, some 850 in all.

Mr McKinnell continued, ‘The second difficulty is that divers usually have to precisely position and hold these large and very heavy anodes, which are lowered by crane or winch, against the piling at the same time as carrying out the weld.’ This is not easy, since each of them weighs in at between 155 kg to 170 kg.

The solution was putting in place brackets that would be tacked on attached at low water by conventional (dry) welds. When the anode was lifted into place (hanging down from below the bracket) it was already held against the wall, needing much less manhandling and just a single full subsea weld to fasten it.

‘This makes life much easier because you are not having to spend so much time in the water, and further you can go along and visually inspect the placing of the anodes, taking the time pressures and technical problems away from the dive teams’, added Mr McKinnell.

By using the bracket, iicorr was able to save approximately eight weeks of diving time, valued at around £100,000.

Mr McKinnell concluded, ‘Corrosion in structures submerged in seawater is a recurring problem for ports and harbours around the world. At iicorr we have developed a low cost solution which gives port authorities the piece of mind that their structures are protected and regularly monitored so that any necessary repairs can be budgeted for.’

The products have been designed to protect the steel work and piles of the harbour for approximately 25 years.