FAQ >> Gin Pole Derrick

Gin Pole Derrick

Agirrlwle is the most elemental form of derrick-it could be described as primitive--essentially a leaning mast incapable of swinging and held in place by guys. With no boom, lifting is done from a load fall at the tip of the mast. Large and small gin poles find roles quite distinct from one another. In the middle range alternative lifting devices are more practical, and so middle-sized poles are a rarity. Long heavy-duty gin poles operate at fixed radii with a lean of only 50 or 100 from the vertical. They are primarily used for rigging work, raising heavy machinery, vessels, or structural components into place. Poles of 250 ft (76 m) or more are available with capacities ranging to about 300 tons (270 t). The practical limit to the size results from the need to use other lifting equipment for assembly. At a refinery or chemical plant, large gin poles are sometimes paired and used to erect vessels, as shown in Fgure 2.4. The derrick hooks are made fast to the vessel at a point above the center of gravity. As the derricks lift, the bottom end of the vessel rotates and must be moved laterally toward the derrick bases. To accommodate those movements, a tailing crane lifts the vessel bottom and leads it in toward the poles. Tailing cranes are discussed in detail in Chap. 5. A small gin pole fitted with a topping lift and side guys can luff in and out. A pole of 30 ft (9 m) or so with capacity of about 5 tons (4.5 t) is often used for raising loads to the roof of an existing building or for erecting a larger derrick. Though simple in form, a lufTing pole requires a skilled rigger to operate it safely as it can easily become unstable. As other types of lifting equipment have replaced them, the requisite skill needed to operate these rigs is increasingly difficult to find in the labor force.

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