All rusted up?

Buying a new anchor chain is a big expense for any yacht and there are many factors to take into consideration before laying out the cash.

How to tell if chain is damaged or stretched?

As the old saying goes “A chain is only as strong as its weakest link“   then potential disaster.  So how do you check for damage? This could be corrosion, faulty links or stretched chains. What signs should you be looking out for? It goes without saying that each time you let out the chain or pull it in you would keep an eye out for any damage, corrosion or pitting but every year it is worth giving it a thorough check.To add longevity to the chain the first action to take would be to end for end the chain.

Corrosion

On stainless steel anchor chains corrosion will show up around the weld and if you have what looks like worm holes these are normally the result of an earth link.It is important to bear in mind that if the boat has any sort of earth leak – when the anchor is on the ground it will act as an earth point – and stainless is extremely susceptible to electrolysis. The same will happen if you have a steel chain with a stainless anchor – corrosion will appear on the swivel pin, shackle and flukes of the anchor where it digs into the sand.  If there is an earth leak corrosion can weaken and eat an anchor chain extremely quickly in the worst case scenarios within a couple of months.

On steel chains it is always good to keep an eye on the Kenter links as these are generally not galvanized and tend to rust quite quickly.

Bent or stretched links

On marine stud link cable – (this is a strong chain and has a stud across the middle which gives extra rigidity and helps prevent any link distortion under extreme loads)– Check if any of the studs are disconnected or not sitting square in the links. They should be at an angle of 90 degrees.

Stretch– According to LLoyds the maximum acceptable wastage is between 10-12%.  So how should you measure this?  You will need to measure stretch over at least 5 links  (If you only measure one link you will not get an accurate result as a single link  may have slight distortions.)   Lay out a length of chain and measure theoverall full length of five links and compare it against the tables available for that size of chain,with maximum allowable tolerance of 2.5%.

Re-galvanising – pros and cons

Often a chain will be fine but just corroded – bleeding rust onto your scrubbed decks and freshly polished paint work.  Re-galvanising can be a cost effective option and but there are a couple of points to take into consideration.

Before re-galvanising the chain needs to stripped and cleaned, chain has so many nooks and crannies and areas where the links are touching each other it is hard to effectively clean it.  This means that the galvanising can’t properly adhere to these areas and once the chain has gone round a couple of times it will start to come off – leading once again to rusty paint work.  .

It is also worth noting that the chemical process of re-galvanising can have a detrimental effect on higher strength chain Grade 40 and above eventually weakening it.  “Hydrogen embrittlement” is the problem causing the metal to become brittle but unevenly (perhaps just one or two links in the chain.) 

So you are probably fine re-galavanising lower grade chains a couple of times but if you do it anymore than this it would be highly advisable to get the whole length of chain (not just a section) pull tested to at least twice its working load.  The reason being the chain is a series of interconnected links – any part of which could be weak through general wear or through hydrogen embrittlement.

New Chain

Once you have established that the chain needs to be replaced for one reason or another.  What do you need to bear in mind?

The first thing to check is the Gypsy.  Unfortunately if the chain has been damaged that might mean that accumulated wear and tear will have built up on the gypsy causing teeth to wear out etc so it is always best to have a good look at this as well.

Marine stud link chain cable is normally produced in lengths of 15 fathoms (27.5 metre) but can be made to measureas a single lengthand certified and connected to your anchors.

For connecting your lengths of chain to each other kenter links are used but be awarethatthey are very slightly wider than the standard chain links and these can bind up in the gypsy and get jammed in the spurling pipes.

When we are asked to supply new chain we need to know the length and size of chain needed and the grade of steel required (which can be seen from the previous test certificate. The Test Certificate will show the approved classification society from Lloyds Register and other class societies to be either grade U2 or U3.We also need to know what extras are required such shackles and swivelforerunners.

It is in measuring the size of chain where mistakes are generally made and we often have to go down to the boat to double check. 

The size of chain should be in the ship’s papers and the gypsy will be marked to a chain sizebut if you can’t find it there then you will need to measure up

When taking a measurement it is best to check several links but make sure they are not next to each other as one link might give a rogue measurement.  Before you measure you should scrap off rust and salt build up. The same for any thick areas of galvanising – look for the thinnest areas to measure from.   A common link is measured by wire size (diameter of material), internal length and the outside width.  Stud links are measured in the same way.

What measurements are we looking for?

Wire size




This is the diametre of the wire that was bent to make the chain links. This should be measured away from the weld.

The internal link length 

 

The Width 

If you need a new chain, anchor or want to re-galvanise existing chain give us a call and we can come down to the boat and discuss your requirements.   Call Jason +34 609 639 687 or Cphir  +34 636 974 404 or email us info@linksmarine.es

The Links Marine team provide a complete marine welding, fabrication and machining service, with over 15 years of experience working within the super yacht industry in Mallorca.  They are also one of the leading suppliers of anchors, chains and swivels on the island.

This article first appeared in the Islander Magazine in May 2019