Did you know non standard moorings are more expensive to maintain?

Non standard mooring systems are significantly more expensive to maintain than a standard mooring system. They are also less effective as a mooring system.

Most non standard moorings are made up of several components consisting of large lengths of chain and shackles and numerous metal objects.

All these materials contribute to ongoing and expensive maintenance of your mooring.

For example, electrolysis is created by a reaction between different metals such as mild steel, cast iron and other ferrous/non ferrous metals. The electrolysis then reacts on the least noble metals (usually the chain and shackles) causing accelerated metal wastage. As a result chain and shackles have to be replaced more regularly when their wear exceeds the minimum standards.

Untangling, removing and replacing parts on a non standard mooring takes considerable time and money. Further, this type of mooring due to its makeup usually requires more chain and shackles than a standard mooring. The photo to the right is an example of how uneven wastage can occur to chain.

Less Effective
Not only is a non standard mooring more expensive to maintain, it is also less effective than a single mooring block system. Multiple blocks are prone to entanglement with chain or head rope, they have less lateral and vertical drag resistance compared to a standard 2 or 4 tonne block and generally are light in weight as cast wheels weigh approximately 250 kg each.

Electrolysis issues in Russell, Bay of Islands

While servicing moorings in the Russell area we have identified a ‘high electrolysis activity zone’ in the northern end of the Russell mooring area.

Environmentally occurring electrolysis zones are known to occur in random locations along the Northland coast. There are also areas where human induced electrolysis occurs in varying degrees.

The jury is out as to whether the increased level of electrolysis is environmental or human induced – it may be a combination of both. The current levels of electrolysis are causing accelerated wastage to mooring components – particularly top chain and shackles.

In recent months four moorings have failed due to accelerated steel wastage caused through electrolysis and corrosion. In the last year there have been over eight mooring failures due to electrolysis.

To identify whether there has been an ongoing issue with electrolysis in this area we discussed the issue with the Maritime Section of the Northland Regional Council including one of their staff who previously worked with the Harbour Board. He recalls high base levels of electrolysis in the bay which suggests that it’s presence isn’t recent, but its affects appears to have increased .

What you can do?

Given the increased levels of electrolysis and recent history of mooring failures, it would appear that the three yearly service regime is too long for this particular location. After discussions with the NRC we recommend that all mooring owners consider adopting a two yearly service regime for their mooring as a precautionary approach to protecting your boat.

What Moorings Northland is doing?

Given the implications of these issues, Moorings Northland has changed it’s work practices to protect your asset and our reputation by:-

· Using 20mm certified chain, instead of the minimum 16mm certified chain. Using the larger chain provides greater mass and thus safer margins against wastage.

· Using 26mm shackles instead of the minimum 22 mm shackles. One of our findings revealed that the smaller shackles failed. Particularly shackles that were only ‘tack welded’.

· Fully welding the pin on all shackles with an ‘electrically natural’ electrode. Moorings Northland never ‘tack welds’ as this form of securing shackles is known to fail.

If you have any queries or would like to alter your service regime to two yearly please contact us on 09 4026939 or email mooringsnorthland@xtra.co.nz and we will alter our records accordingly.