PILOTAGE PRE-PLANNING GUIDE
Re. 2) Towing of jack-up rigs often involves several tug boats. One of these tug boats
will be called the leading tug. The leading tug will ALWAYS be the tug with the
largest bollard pull and will often be connected to the rig’s tow bridle.
The normal air draught of a jack-up rig will be approx. 165 - 230 metres or more,
and jack-up rigs will normally have a draught of approx. 7 metres and up to 10 metres
if there are spudcans below the hull (typically older rigs).
The towing operation will often be subject to quite strict weather criteria which
must not be derogated from.
Figure 19. Towing of jack-up rigs
Re. 3) Semisub rigs are in ballast during long-distance towing, which gives them an
air draught of up to 130 metres and a draught of approx. 7-8 metres. The weather
criteria may also be quite strict. Sometimes, the rigs are equipped with machinery
and screws, for example azimuth thrusters, which may be used under special
circumstances such as passage of narrow channels or bridges. These are located
under the rig and will increase the draught significantly.