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There are two basic categories of vacuum tubes: (1) electron tubes, and (2) cathode-ray tubes. As for other hazardous materials, you must follow certain safety precautions when you work with or handle vacuum tubes.

Electron Tubes

Electron tubes are fairly rugged devices. Most of them can handle the shocks and knocks of everyday use. However, they are not indestructible. Most electron tubes contain a near vacuum enclosed by glass.

Any excessive stress, like dropping the tube, may cause the glass to shatter, causing an implosion (burst inward). An implosion is the opposite of an explosion. When the glass shatters, the outside air rushes into the tube to fill the vacuum. As the air rushes into the tube, it carries the glass fragments with it, right on through the center of the tube and out the other side. If you are in the path of these flying fragments, you may be injured seriously. So, handle all electron tubes with care.

Some electron tubes contain radioactive material to aid ionization. These must be handled with extra care. Unbroken, the radioactive tubes are as safe as other electron tubes because the radioactive material in the tube emits slow-moving particles that are contained within the tube's thick glass envelope. However, breaking the tube will expose the hazardous radioactive material.

To avoid injuring yourself or others, observe the following safety precautions when you handle either regular or radioactive tubes:

Handle all electron tubes, whether radioactive or not, with extreme care.

Immediately place any electron tube that you remove, whether radioactive or not, into a protective container, such as its shipping container.

Inform your supervisor immediately if you break a radioactive electron tube.

Seal off a radioactive-contaminated area immediately to avoid exposing other personnel to the radioactive material.

Treat all bad or damaged radioactive electron tubes as radioactive waste and dispose of them accordingly.

NEVER remove a radioactive tube from its shipping container until you are ready to install it.

NEVER touch any radioactive fragments. If you do, wash yourself thoroughly with soap and water and get medical attention.

Cathode-Ray Tubes

Cathode-ray tubes (CRTs) are everywhere: in televisions, desktop computers, radars, and electronic warfare systems. As a Fire Controlman, you will probably maintain electronic systems that use CRTs. Therefore, you must know about their hazards, handling, and disposition.

CRT HAZARDS. Working with CRTs can be extremely hazardous. A CRT consists of a large glass envelope that maintains a high internal vacuum. It also has a toxic phosphor coating on its face. CRTs are under great pressure; for example, a 10-inch CRT is subject to nearly 2,000 pounds of force. Of that, 1,000 pounds is impressed on the face of the tube alone. Therefore, breaking the glass envelope will cause a violent implosion. During the implosion, all the glass fragments, metal parts, and toxic phosphor will be expelled violently. Because a CRT carries a very high voltage and emits x-rays, it can also be hazardous when it's energized.

CRT HANDLING. To protect yourself from serious injury when you handle CRTs, follow these precautions:

Follow the manufacturer's handling instructions.

Keep a new CRT in its shipping carton until you are ready to use it.

Place a defective CRT in its shipping carton immediately after you remove it from the equipment.

Wear gloves and goggles.

NEVER remove a CRT until you have discharged its high-voltage anode.

NEVER strike or scratch the surface of a CRT's glass envelope.

NEVER stand in front of a CRT when you install it. If the CRT should implode, the electron gun in its neck could be propelled at a very high

NEVER carry a CRT by its neck.

NEVER touch a CRT's phosphor coating; it is extremely toxic. If you break a CRT, clean up the glass fragments very carefully. If you touch the phosphor, seek medical attention immediately.

CRT DISPOSAL. CRTs are disposed of either by shipping them back to the manufacturer or by discarding them locally. If you ship a CRT back to the manufacturer, put it in the shipping container intact. If you dispose of a CRT locally, follow the procedure prescribed by your safety officer.

Q3.     What are PCBs normally used for on board a ship?

Q4. What are two hazards associated with an energized CRT?


Proper stowage of hazardous materials is essential to ship and personnel safety. Supply department and individual work-center personnel are responsible for the proper stowage of hazardous materials in areas under their control. For answers to your questions concerning hazardous material stowage, consult your supervisor, supply officer, or hazardous material/ hazardous waste coordinator.

Hazardous materials aboard ship are typically packaged in cases or allotments of individual containers. Do not store hazardous materials in heat-producing areas or near heat-producing items. Shield hazardous materials stored on a weather deck or in exposed areas from direct sunlight.

Temporary storage of hazardous material in workspaces is limited to the amount necessary for the operation and maintenance of assigned equipment. If a HAZMINCEN is in operation, no more than a 7-day supply of common-use HM may be kept in workcenter spaces.

Study the Naval Ships' Technical Manual, Chapter 670, Stowage, Handling, and Disposal of General Use Consumables, NAVSEA S9086-WK-STM-010, and become familiar with its contents. You can find additional information in the NAVOSH Program Manual for Forces Afloat, OPNAVINST 5100.19 (Series), NAVOSH Program Manual, OPNAVINST 5100.23 (Series), and the Environmental and Natural Resources Program Manual, OPNAVINST 5090.1 (Series).


In your normal working environment you will be surrounded by hazardous materials. Whether that means greases, oils, paints, primers, or cleaners and detergents, you will be in daily contact with materials that are hazardous to you. Material Safety Data Sheets (MSDSs) give safety information for materials you use in doing preventive maintenance. The Hazardous Material User's Guide (HMUG) gives general guidelines for all types of hazardous materials. Many of these materials have long-lasting consequences that can effect your health even after many years. The Navy is making great strides in using less toxic materials for doing routine maintenance, but there are some materials in use that will always be hazardous to humans. Because of this, you should learn all you can about all of the materials you use. Educate yourself and your fellow FCs concerning the specific hazardous materials you use and know the safety precautions, first-aid procedures, and stowage requirements that are associated with each type of material.


Al.      (I) the name of the material, (2) the name and address of the manufacturer, and (3) the nature of the hazard, including the target organ affected by the material.

A2. Compatibility information, control measures, safety precautions, health hazards, spill control, and disposal guidelines for 22 hazardous material groups.

A3.     Insulators and coolants in electrical equipment.

A4.     A very high voltage and x-ray emissions.


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