COAL YARD WATER SPRINKLER SYSTEM
Coal mines often have two potential sources of ignition to consider: coal itself and the material used to transport it. Belt material is typically inert, but when heated by an external source, it can produce carbon monoxide (CO). This can occur from hot burning coal loaded onto the belt or contact with hot metal rollers heated by belt slip or damaged bearings. Coal can ignite by coming into contact with hot surfaces, but it can also self-ignite through the process of spontaneous combustion.
To function effectively, carbon monoxide sensors should be installed in locations and in ways that do not impede the sensor's capabilities to trigger the water sprinkler system.
The temperature must be maintained within upper and lower limits. Since the electrolyte inside the sensor is water-based, the sensor should never be allowed to operate below -20°C. Lower temperatures will render the sensor inactive and may cause permanent damage. The upper-temperature limit for most sensors is +50°C.
The ambient pressure in which the sensor operates should be kept close to normal. The inlet side of dust collection or baghouse fans should be avoided. Typically, the exhaust side is a better choice, since outside pressure is relatively stable.
Moisture can be a problem, particularly if the CO sensor is housed inside an explosion-proof enclosure. Flame arrester elements integrated into the sensor housing can become clogged if water comes into direct contact. In areas of concern, splash guards and/or porous layer filters should be placed before the sensor to prevent the flame arrester from absorbing water.
A sprinkler system consists of lines of pipes along a ground level or ceiling that contain water under pressure, with an additional source of water for a continuous flow. Attached to the lines, automatic sprinklers are positioned at select locations. When a fire occurs, a seal in the sprinkler head breaks at a pre-set temperature, and a continuous flow of water is released.
There are several types of automatic sprinkler systems. Two popular ones are the wet-pipe and the dry-pipe systems. In the wet-pipe system, water is in the lines at all times and is released when heat bursts the seal in the sprinkler head. This is the most common system and is applicable where freezing is not a threat to its operation. Where freezing temperatures and broken lines are a concern, the dry-pipe system is useful. Pneumatic pressure is maintained in the lines until a sprinkler head bursts. Then the air escapes, and water enters the lines and exits through the opened sprinklers. Due to this delay, dry-pipe systems are not as effective as wet-pipe systems during the initial stages of a fire.
Many fire-related accidents can be minimized by improving the reliability of fire suppression equipment. An effective, documented inspection, testing, and maintenance program can help ensure that your system will not fail when you need it most.