1st Year, Level 4, Lesson 4

As a rule of thumb, the friction loss for each sheave is approximately ? of the sheave load.

10 percent

A crew has a job assignment to hoist a 3,200-pound bundled conductor in order to change out a string of insulators. The crew will use a four-part block and tackle system to accomplish this task. The sheave is a roller bearing type, with only 10% loss due to friction, threaded with 1/4-inch wire rope. The lead or fall line is threaded through the stationary or top block of the system.The lead line tension needed to lift the conductor bundle with the block friction figured in would be ? .

1120 lbs

A single block hoisting assembly has a fall line pull of 150 pounds. If the lines are parallel to each other and ignoring friction, the load on the block will be ? .

300 lbs

As the angle between the load line and the lead line (fall line) increases, the load of the block ? .

Decreases

A nylon rope cannot be used with a snatch block.

False

As more sheaves reduce the force required to lift a load, the distance the lead line must be pulled decreases.

False

Mechanical advantage means that a load can be lifted by applying a force more than the load weight.

False

The force of two objects resisting movement is ? . Select one:

Friction

When lifting a load with a block and tackle system, part of the lifting force is lost due to ? in the turning of the sheaves.

Friction

The working load limit is determined by the breaking strength of rigging equipment, divided by the ? .

Safety Factor

Before a new wire rope is threaded over a block sheave, a Qualified Electrical Worker should check ? .

That the contour of the sheave matches the rope size

A ? block is the lower movable block in a block and tackle configuration.

Traveling

A sheave is a grooved wheel attached to a frame that supports a rope that is changing directions.

True

Lacing is the simplest method of reeving.

True

The lead line is the part of the rope to which force is applied to hold or move a load.

True

Using an improperly sized block can derate the Working Load Limit of the wire or fiber rope that is used with it.

True

In both figures, the tension on the line is 500 pounds. The hook load for the setup in Figure A is 1,000 pounds. The hook load for at 90 degrees is ? .

less than 1000 lbs

A single block hoisting assembly has a lead line pull of 1,500 pounds. If the lines are perpendicular to each other and friction is ignored, the load on the block is ? .

more than the load by about half (2121 lbs)

The constant force applied to an object to keep that object in place is ? force.

static