CHAPTER 3 POWER GENERATION

Generators play an important part in your assignment with the Seabees. Whether operating a generator as a main power source or as standby power or as emergency power, you need a through knowledge of their hookup, operation, and maintenance. At the completion of this chapter, you should know how to install generators of the advanced-base type, stand a generator watch, perform preventive maintenance, and make minor repairs on power generators and control equipment. Theory for both dc and ac generators is included in Navy Electricity and Electronics Training Series (NEETS), Module 5. Generator theory will not be covered in this chapter. Keep in mind that the generator (alternator) in an automobile works on the same principle as does the huge turbine generator used in a nuclear power station.

INSTALLATION AND SERVICING GENERATORS Most of the generators you are likely to work with in the Naval Construction Force (NCF) range in size from 5 kW to 200 kW. Generators in these sizes range in weight from 488 pounds (221.4 kg) to 10,500 pounds (4770 kg). All of these units are mounted on skid bases. Lifting and tie-own attachments are provided. All have provisions for lifting with a forklift of the appropriate capacity (with the exception of the 5-kW gas-driven generator set, which does not include the forklift provision). Several factors should be considered before a final decision is made about where to locate a generator. The noise levels of generators sized from 5 kW to 200 kW range from 77 dBa to 93 dBa (adjusted decibels) at 25 feet. Generator noise is a problem in low-noise level or quiet areas (libraries, offices, hospitals, chapels, etc.).

The operating 60-kW generator, for example, presents a noise hazard (84 dBa to 91 dBa, depending on the model) to all personnel in the immediate area. The noise level near the unit exceeds the allowable limits for unprotected personnel. Therefore, everyone working around the generator needs single (noise < 84 dBa) or double hearing protection (noise > 104 dBa).

Placing a generator set near points of large demand will reduce the size of wire required, hold the line losses to a minimum, and afford adequate voltage control at the remote ends of the lines.

The following points should be considered before an exact site is chosen for a generator set:

1. Generators must not be closer than 25 feet (7.6 meters) to a load because of noise, fire hazard, and air circulation.

2. The set must be placed on a stable, preferably level, foundation. It should not be operated while inclined more than 15 degrees from level.

3. The site must be within 25 feet (7.6 meters) of any paralleled generator set and within 25 feet (7.6 meters) of any auxiliary fuel supply.

4. When preparing a temporary installation, you should move the generator set as close to the jobsite as practical. In an area where the ground is soft, do not remove the wood-skid base if you have not already done so. The wood-skid base will establish a firm foundation on soft ground, mud, or snow; otherwise, use planks, logs, or other material for a base in an area where the ground is soft.

Although advanced-base portable generators are designed to be operated outdoors, prolonged exposure to wind, rain, and other adverse conditions will definitely shorten their lives. When the generators are to remain on the site for any extended period of time, they should be mounted on solid-concrete foundations and should be installed under some type of shelter.

There are no predrawn plans for shelters for a small advanced-base generating station. The shelter will be an on-the-spot affair- the construction of which is determined by the equipment and material on hand plus your ingenuity, common sense, and ability to cooperate with personnel in other ratings. Before a Builder can get started on the shelter, you will have to furnish information, such as the number of generators to be sheltered, the dimensions of the generators, the method of running the generator load cables from the generator to the panelboard and from the panelboard to the feeder

Figure 3-1.- Typical 60-kW generator set.

system outside the building, and the arrangement of the exhaust system. Large generator units may have, connected or attached to them, engine equipment that requires extra space and working area. Included in this equipment are air-intake filters, silencers for air intake and exhaust, fuel and lubricating oil pumps, tanks, filters, and strainers. Also included are starting gear, isochronous regulating governors with over-speed trips, safety alarm and shutdown devices, gauges and thermometers, turning gear, along with platforms, stairs, and railings.

An even larger and more complete power plant may require separate equipment, such as a motor-driven starting air compressor and air storage tanks; motor-driven pumps for jacket water and lubricating oil cooling, or heat exchangers with raw cooling water pumps and lubricating oil coolers; and tanks that include day-fuel storage.

Be sure to provide enough working space around each unit for repairs or disassembly and for easy access to the generator control panels. Installation specifications are available in the manufacturer's instruction manual that accompanies each unit. Be sure to use them. Consulting with the Builder about these specifications may help cut installation costs and solve future problems affecting the shelter of the generator.