of the manhole to prevent damage to the cable sheath. A section of an old tire casing can serve as a protective boot for this job.

The boards nailed to the two edges of the reel are called lagging. When the reel is in place, remove the lagging. You must be careful not to damage the cable when you pry the lagging loose. Be sure to remove any projecting nails from the edge of the reel before starting to remove the cable. Next, you must release the end of the cable from the reel, and you will then be ready for the main part of the job.

CABLE INSTALLATION Assume that the winch line has been drawn into the duct, as the test line was pulled out. A basket grip is now attached to the end of the underground cable on the reel. The end of the basket is secured to the cable with a tight wrap of tape or wire. A swivel connection is necessary between the basket and the pulling cable to relieve twisting of the rope.

If the cable reel is within sight of the winch, it will take four people, in addition to the winch operator, to do the job safely. One person attends the reel to see that the cable rolls off the reel properly. Another in the manhole guides the cable into the duct. Both inspect the cable as it unreels and immediately signal "stop pulling" when a defect appears so that a closer inspection can be made for possible damage to the sheath. A third, stationed in the other manhole at the pulling end. signals "stop pulling" when the cable appears. The fourth crew member, aboveground at the pulling-end manhole, relays signals to the winch operator. This procedure enables the winch operator to concentrate on his job of seeing that the winch line is wound onto the reel properly.

The speed for pulling cable into a duct varies with the length of the duct and cable sizes. A single cable can be pulled in successfully at 75 feet per minute in a clear. straight duct. When you are handling more than one cable, reduce the speed to about 20 to 25 feet per minute, so you can prevent the conductors from crossing as they enter the duct.

When the "stop pulling" signal is given, make sure there is sufficient slack in both manholes for splicing or terminating the cable. The slack can be adjusted with the cable basket grip. Exercise care to prevent injury to the cable insulation. Remove the binding tape and the basket grip from the cable. The cable is then cut to the desired length and the cutoff end in the manhole is sealed unless splicing is done immediately. The end of the cable remaining on the reel also must be sealed. In addition, check the seal on the end of the cable that has traveled through the duct, and reseal it if it has been broken from the strain.

DANGEROUS GASES

Gases may be dangerous for several reasons. The gas concentration may be explosive if it is made up of methane, sewer gas, natural gas, concentrations of spilled gasoline, or other liquid fuel vapors. As a general rule, these gases are heavier than air and will concentrate in low areas, such as manholes and ducts. They will remain there until they are dispersed. These gases are toxic as well as explosive. Other toxic gases are chlorine, ammonia, and a variety of the sulfide combinations. Other gases deplete the oxygen in the manholes and duct systems. Lack of oxygen can be as deadly as either the explosives or toxic gases. For these reasons, underground structures must be tested before workers enter them. Figure 4-49 shows two common types of test sets used for identifying carbon monoxide and combustible gases. View A shows a carbon monoxide tester and view B, an explosimeter. Only personnel who are specifically trained and certified may conduct tests for safe entry. Before entering any underground structures the base confined space manager or the assistant must certify the area safe for entry.

MAINTENANCE

Test equipment is essential for satisfactory power system operation. Meters are needed to monitor system operation conditions and also to check equipment before and after placing it in service. Periodic checks are necessary to ensure that the equipment remains in proper operating condition.

BASIC MEASURING INSTRUMENT PRECAUTIONS

When using measuring instruments, you must observe certain precautions. For example, it is especially important to be careful in using an ammeter because of its low internal resistance. If mistakenly placed across a voltage source, the meter can be damaged. Always break the circuit and CONNECT AN AMMETER IN SERIES with one meter lead going to each point of the circuit breaker to measure an unknown quantity. Be sure to de-energize the circuit before making or breaking the connections.