Guidance on Mooring Maintenance

The general procedures for the inspection and maintenance of moorings will vary depending on a number of factors including the type of mooring, its location on the Thames and the frequency of usage.  This section is intended to provide guidance to berth operators on the maintenance of midstream buoy moorings and “holding in” moorings attached to anchors embedded in the river.

Moorings typically found on the Thames include:

• Spread moorings consisting of one or more anchor points connected by steel chain to a mooring buoy.  When a single mooring point is provided, the mooring will be fitted with a swivel which allows the moored vessel to move with the tide.  These moorings are known as “swing moorings”.  When a buoy is provided at each end of the vessel these moorings are referred to as “Tiers”.  Sometimes a barge known as a collar barge is moored between the two sets of moorings to make it easier for vessels to tie up.
• Holding in moorings consisting of one or more anchor points connected by chain to a buoy or pick up wire.
• Small vessel moorings such as trot moorings consisting of a ground chain with risers and buoys.

Moorings in the river are constantly being picked up and placed back on the river bed by the action of the tide and waves and or by the action of the vessel moored to them.  The part of the mooring which suffer most from this action is the part that rises aMoorings typically found on the Thames include:immediately under the buoy are also likely to suffer accelerated wear.  In addition, the components of the mooring are prone to wastage due to the corrosive nature of seawater as well as being prone to mechanical damage from collision with vessels or overloading and misuse.  None of this wear is easily visible to the casual observer.

The Port of London Authority recommends that owners and or operators of moorings should check the condition of moorings on a regular basis.  The Authority uses a period of one year, eighteen months, two years or three years depending on the type and location of moorings.  Further guidance can be obtained from the British Standard BS 6349 Part 6 1989.

The Authority’s own moorings are maintained on the following intervals:

A typical inspection requires the removal of the buoy and breaking down of the mooring into its component legs.  The chain is then hove to the surface where it can be inspected for damage and measured for wastage.  The Authority uses divers to inspect the parts of the mooring that cannot be hove to the surface for inspection in the dry.  These inspections are carried out every other year on small moorings and on every other leg every year on the larger moorings.  Divers also check that the anchors are still properly embedded and that the underwater parts of the mooring are not fouled or disconnected.

A Top End inspection includes the upper mooring elements only down to three way or four way plates and main thrash area of the mooring.

Mooring buoys are inspected for damage at each overhaul and replaced if required.  Damaged buoys or those requiring repairs or repainting should be removed and landed ashore for full inspection.