AHT Tugs

 

The Anchor handling vessels developed by the Royal Navy to lay moorings for the Naval Fleet changed over the years as the ship sizes increased. The largest Admiralty mooring required increasingly large vessels. As the sizes increased, so the vessels build costs increased and these vessels were then required to cover additional work like fuelling, storing, victualling, watering etc. 

 

The early anchor-handlers were pontoon barge type vessels with large bow rollers on A-frames and large crane facilities to lift anchors and chain onto the barge decks. It was soon found that these vessels with small modification were very useful in the constructuon industry, but had poor seagoing qualities. 

 

With the new requirement for towage of oil rigs and anchoring of other large structures in ever increasing water depths, in areas further and further from the ports and safe havens, designs had to follow. 

The anchor handling tug today is required to have the following attributes:- 

 

- Sea going (100A1 notation) 

- Powerful (50 ton bollard pull upwards) 

- Multifunctional 

 

Able to steam and operate world-wide under an IACS Classification Society member (BV, GL, DNV etc.). 

 

Able to have adequate power to tow structure to their designated positions and then ensure they are able to maintain position to lay the structures, securing anchors. On completion have adequate power within the winches in slow speed to break the anchors and chanis from the sea bed. Have adequate craneage to lift anchors and chains from stowed positions. 

 

To offer fire protection. Usually FiFi minimum of 2,400m3 / hr jet and spray with accommodation cooling. Oil recovery into ships holding tanks, cranage, large open deck for storage and hauling anchors, Stern roller in order to enable rolling of structures, chain and anchors onto the deck. Work or DOTI (rescue) boat service. Good / high forecastle structure. Low speed multifunctional waterfall winch to enable controlled winch movements. 

 

The AHT is generally a powerful twin screw fixed or Azumuthing thrusters with bow and sometimes stern thrusting units, able to work offshore. 

 

The inshore works in still covered by 'Shoalbuster' vessels, multi role tugs with AHT characteristics and 'Multicat' self-propelled pontoons.