Dry chemicals systems

Dry chemical systems (e g., sodimn bicarbonate). These are not toxic and do not conduct electricity or freeze. 

Fixed systems may be fixed nozzles or hand hose line systems. They usually range in capacity from 68 to 1,360 kgs (150 to 3,000 lbs.). Most use a high pressure nitrogen cylinder bank to fluidize and expel the dry chemical from a master storage tank. Where immediate water supplies are unavailable, fixed dry chemical systems may be a suitable alternative. 

Dry Chemical Systems Kitchens Loading or Unloading Racks (mostly when water system is uneconomical or unavailable)... 

These agents are effective on small spill fires. If there is risk of re-ignition from embers or hot surfaces, these ignition sources should be quenched or cooled with water and secured with foam, or the source of fuel should be shut off before attempting extinguishment. An example of a dry chemical system is shown in Figure 7-36. 

All dry chemical systems should be tested, which should include the operation of the detection system, signals and releasing devices, including manual stations and other associated equipment. A discharge of the dry chemical normally is not part of this test. 

Each dry chemical system should have a tag or label indicating the month and year the maintenance is performed and identifying the person performing the service. Only the current tag or label should remain in place. 

Dry chemical systems are well known for being an effective means of fire extinguishment of flammable and combustible liquid fires however, certain types also have application as neutralizing and solidifying agents for liquid spills. Products are available for treating both acids and caustics. 

Locations where flammable liquids are loaded or unloaded should have adequate fire protection. A water spray system operated manually and automatically is the most economical and best for most materials. Where water supply is inadequate or unavailable, a dry chemical system can be engineered. Ultraviolet ray detectors are recommended for speed of operation and automatic discharge of the agent. 

Fire protection is another critical safety concern. Automatic fire detectors are located throughout the plant. Sprinkler systems supplied from a large storage tank come on automatically in the event of a fire in the unloading and unpack areas. In other areas, dry chemical systems are deployed. Halon systems protect the control room and power supply room. 

All dip tanks exceeding 150 gallons of flammable liquid capacity or having a liquid surface area exceeding 4 square feet must be protected with at least one of the following automatic extinguishing facilities water spray system, foam system, carbon dioxide system, dry chemical system, or automatic dip tank cover. 

Dry-chemical extinguishing systems are used to protect flammable-liquid storage rooms, dip tanks, kitchen range hoods, deep-fat fryers, and similar hazardous areas and appliances. Because dry chemical is nonconductive, these systems are useful in the protection of oil-filled transformers and circuit breakers. Dry-chemical systems are not recommended for tele-phone-switchboard or computer protection. Dry chemicals are also widely used in portable fire extinguishers. 

Most dry chemical systems use sodium bicarbonate. This dry chemical agent works best to extinguish flammable liquids, but also works on electrical fires. One problem with this agent is that it is corrosive and can damage the finely polished metal surfaces found in electrical equipment. 

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