Vacuum works simply by extracting air from a closed container which causes a negative pressure in the container, allowing water to replace it. This movement of air is accomplished by a vacuum pump. There are several types of vacuum pumps. There are rotary vane, piston or displacement pumps. Care should be taken when comparing pumps, to make sure it is done by the same rating standards. Many factors comprise a vacuum system and need to be carefully considered. Another major component of a properly constructed vacuum system is the tank. Remember that marine grade and aircraft grade aluminium corrode the same as any metal. Chlorinated water is highly corrosive and any tank must be coated to protect against this corrosion and rust. The tank on a vacuum tanker should be a round structure with dished heads constructed of strong enough material to withstand the vacuum force placed upon it. The tank must be properly supported and mounted to reduce road stresses from affecting it. Improper supports and lightweight material have been know to cause problems for fire fighting personnel. Baffling within the tank is also a major factor in a vacuum tank. The baffles inside the tank should be able to control the movement of water inside the tank and to also reinforce the tank against the vacuum force placed on it. Flat pieces of metal inside the tank will do very little to prevent water swash or reinforce the tank. Since a vacuum tank must be a totally closed system in order to build vacuum, a venting system must be added in order to fill conventionally from a hydrant. These are all things that should be considered and investigated when looking at a vacuum tanker. |
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- Warranty
- The pump set up
- Pump protection (shut off system)
- Easily serviceable
- Power Source and drive mechanism need to be the proper size
needed for the varied conditions of fire service.
