WINCHES

Winches are frequently used as a source of power for operating hoisting rigs, particularly gin poles, heavy-duty derricks, and light-hoisting equipment, such as pole derricks. A WINCH, generally speaking, is a device having one or more drums on which fiber line or wire rope is wound. Winches are used for hoisting or hauling of materials or objects. Both hand-operated and engine-driven winches of various types are available.

Figure 6-15.\Differential chain hoist.

A single-drum, hand-operated winch similar to the one shown in figure 6-17 is suitable for lifting light loads. Single-drum hand winches are available in various capacities, including capacities of 2, 5, 6, and 15 tons (1.8, 4.5, 5.4, 12.5 metric tons).

Hand-operated winches are generally mounted near the foot of the rig, where they can be operated efficiently. Notice the location of the winch on the pole derrick shown in figure 6-13.

In hoisting and moving heavy objects in the field, engine-driven winches may be used with tackle. Vehicular-mounted winches are also widely used (fig. 6-18). Sources of power for power-driven winches include diesel, gasoline, compressed air, or steam engines as well as electric motors. When vehicular-mounted winches are used, the vehicle should be placed so that the operator can keep a close watch over the load during hoisting.

When setting up a power-driven winch to operate hoisting equipment, make sure you give careful consideration to these two factors: (1) the angle with the ground that the hoisting line makes at the drum of the hoist and (2) the fleet angle of the hoisting line winding on the drum.

In considering the ground angle, remember that if the hoisting line leaves the drum at an angle upward from the ground, the resulting pull on the winch will tend to lift it clear of the ground. In this case, a leading block should be placed in the system at some distance from the drum to change the direction of the hoisting line to a horizontal or downward pull. The hoisting line has to be overwound or underwound on the drum, as may be necessary, to prevent a reverse bend.

As for the fleet angle, bear in mind that the distance from the drum to the first sheave of the system is the controlling factor. Place the drum of the winch so that a line from the last block

Figure 6-17.\Single-drum hand winch.

Figure 6-18.\Using a vehicular winch for hoisting.

passing through the center of the drum is at right angles to the axis of the drum. The angle between this line and the hoisting line as it winds on the drum is referred to as the FLEET ANGLE.

As the hoisting line is wound in on the drum, it moves from one flange to the other, causing the fleet angle to change during the hoisting process. See that the fleet angle does NOT exceed 2; and, where possible, keep it below this. A 1 1/2 maximum angle is satisfactory and will be obtained if the distance from the drum to the first sheave is 40 inches (100 centimeters) for each inch (2.5 centimeters) from the center of the drum to the flange. The wider the drum of the hoist, the greater the lead distance has to be when the winch is placed.

Most winches, even those made by the same manufacturer, differ from each other in their operation. If you are not familiar with the operation of a winch to be used on a job, study the operating procedure described in the manufacturer's manual beforehand. The fundamentals of winch operation must be understood to ensure safe, efficient handling of materials. The use of hand signals in giving directions to operators of winches is especially important to the safety of both the crew member and the material being hoisted.

CRANES

The crane is one of the most useful pieces of construction equipment. It is also one of the most versatile. For instance, by rigging the crane chassis with a boom and lifting hook, you have an excellent device for lifting and moving heavy materials, machinery, and other objects. (See fig. 6-19.) The capacity of the crane for lifting depends on the boom length and angle. The capacity will be noted inside the cab of the crane, and this capacity should NOT be exceeded. You will not be required to operate the crane; that is the job of the Equipment Operator. But there are other important jobs, such as that of hook-on man or signalman, and you have to be able to handle either of these.