CHAPTER 10 



SAFETY; TEST EQUIPMENT; TEST METHODS 



Sonar Technicians must assist in the upkeep 

 and repair of the sonar equipment aboard their 

 ship or station. Consequently, you must become 

 familiar with the types of test equipment, test 

 methods, and safety precautions to be observed 

 when using or working on electronic equipment. 

 Naturally, a knowledge of electronics is required 

 also. Information related to the electronics field 

 can be found in Introdu ction t o Electronics, 

 NavPers 10084; Basic Electronics, "NaYPers 10087 

 and Basic Electricity, NavPers 10086. Informa- 

 tion on the selection, care, and use of hand and 

 portable power tools is contained In Basic Hand- 

 tools, NavPers 10085. 



SAFETY 



Maintaining electrical and electronic equipmsnt 

 is a dangerous business. Every year, lives are 

 lost aboard ship due to electric shock. Several 

 cases of fatal shock have been recorded from 

 using such equipment as portable drills and 

 grinders, fans, movie projectors, and even coffee 

 pots. In most instances, death would have been 

 avoided by observing appropriate safety precau- 

 tions. Most men will treat with extreme caution 

 a circuit containing several thousand volts, but 

 will act with indifference toward the common 

 household variety. Yet, 115 volts a-c is the prime 

 source of death from electric shock. You must 

 continually be alert when working with electricity, 

 and you must adhere strictly to all pertinent 

 safety precautions. 



Although some safety practices are given in 

 this chapter, you should become familiar with 

 the safety instructions contained in the following 

 publications: Naval Ships Technical Manual, chap- 

 ter 9670; Han dbook of Test Methods and Practices , 

 NavShips 0967-000-0130; and Safet y Precautions 

 for Shore Activities , NavSO P-2455. An index of 

 Navy Department documents containing safety 

 precautions applicable to the operating forces is 

 contained in OpNav Notice 5100. 



GENERAL SAFETY PRECAUTIONS 



Whenever possible, deenergize the main power 

 input to any equipment before you work on it. 

 Remember, though, that there still may be power 

 in the equipment from such external sources as 

 synchros, remote indicator circuits, and stable 

 elements. When you open the switch in the main 

 supply line (or any other power switch), indicate 

 the switch is open by attaching to it a tag reading; 

 "This circuit was ordered open for repairs and 

 shall not be closed except by direct order of (your 

 name, or name of person in charge of repairs)." 



If you must work on an energized circuit, 

 observe the following safety precautions. 



1. Never work alone. Have another man, 

 qualified in first aid for electric shock, present 

 at all times. He should also be instructed In how 

 to secure the power. 



2. Use insulating rubber matting. The matt- 

 ing must be kept clean and dry. Wear rubber 

 gloves, if possible, and use insulated tools. Re- 

 move rings and watches. 



3. Use only one hand whenever possible. Keep 

 the other hand behind you or in your pocket. 



4. Do not indiscriminately stick your hand into 

 an enclosure. 



5. Have ample illumination. 



6. Never short out, tamper with, or bypass an 

 interlock. 



Before working on a deenergized component, 

 discharge all capacitors in the unit. A capacitor 

 is a device for temporarily storing electrical 

 energy. Successive small charges are built up 

 in the capacitor for later release. Sonar trans- 

 mitting equipments utilize this feature by building 

 up electrical energy in the equipment's capacitor 

 bank between each ping. A trigger pulse then 

 releases the energy in a single high-powered 

 pulse. Nearly all types of electronic equipment 

 use capacitors of varying sizes and types. 

 Normally, the larger the capacitor, the higher the 

 electrical charge it will hold for a greater length 



154 



