distance. There are a number of different styles of jacks available; however, only heavy-duty hydraulic jacks or screw jacks should be used. The number of jacks used is determined by the weight of the load and the rated capacity of the jacks. Ensure the jacks have a solid footing and are not susceptible to slipping.

Jacks are available in capacities from 5 to 100 tons. Small capacity jacks are normally operated through a rack bar or screw, and large capacity jacks are usually operated hydraulically (fig. 6-34).

The types of jacks used by Steelworkers are as follows:

1. Ratchet lever jacks are rack bar jacks having a rated capacity of 15 tons. These jacks have a foot lift by which loads close to the base of the jack can be engaged (fig. 6-34, view A).

2. Steamboat ratchets (often referred to as pushing and pulling jacks) are ratchet screw jacks of 10-ton-rated capacity with end fittings that permit pulling parts together or pulling them apart. They are primarily used for tightening lines or lashings and for spreading or bracing parts in bridge construction (fig. 6-34, view B).

3. Screw jacks have a rated capacity of 12 tons. They are approximately 13 inches high when closed and have a safe rise of 7 inches. These jacks are used for general purposes, including steel erection (fig. 6-34, view C).

Figure 6-35. - Use of planks and rollers.

4. Hydraulic jacks are available in many different capacities and are used for general purposes (fig. 6-34, view D).

PLANKS AND ROLLERS

Planks and rollers provide you with an excellent means of moving heavy loads across the ground on a jobsite or the floor of a shop (fig. 6-35).

Oak planks are appropriate for most operations involving plank skids. Planks 15 feet long and 2 to 3 inches thick should be suitable. They distribute the weight of a load and also provide a smooth runway surface in which to skid the load along or in which to use rollers to ease the effort required to move the load.

Figure 6-34. - Mechanical and hydraulic jacks: A. Ratchet lever jack with foot lift; B. Steamboat ratchet; C. Screw Jack; D. Hydraulic jack.