This article describes about basic information of jack up legs – Cylindrical Legs vs Trussed Legs, Three-Legged Jack Up vs Four-Legged Jack Up and Three-Chorded Legs vs Four-Chorded Legs.
Cylindrical Legs vs Trussed Legs
Since the hull needs to stay above the storm wave crest, withstand certain pressures, and transmit different loads between the footing and hull, every Jack Up unit will have legs of some sort. Similar to the footings, there are two different types in trussed legs and cylindrical legs.
Cylindrical Legs
Cylindrical legs can vary slightly but the basic premise involves hollow steel tubes. However, some units will have internal stiffening and others may have rack teeth or small holes to allow the hull to move up and down the legs. Generally, these cylindrical legs are used on units that stay shallower than 300 feet of water depth. With the newer units that are designed to work in environment deeper than 300 feet, they tend to use trussed legs and this is because trussed legs require less steel for the same resistance and same elevated response.
Figure 1 – Cylindrical Leg Jack up (dsboffshore.com, 2018)
