Ventilación

Finding the effect of ventilation on conveyor belt fire suppression systems
by NIOSH’s James Rowland and Alex Smith and MSHA’s Harry Verakis and Michael Hockenberry

The Fire Suppression Facility (FSF) at Lake Lynn. On June 1, 2004, the underground coal mine ventilation safety standards under the Code of Federal Regulations (Title 30, Part 75) became effective for the use of a conveyor beltentry as an intake air course to ventilate working sections. These standards, also known as the Belt Air Rule, contained a section which limited the air velocity in the conveyor belt entry to no greater than 500 feet per minute unless otherwise approved by the US Mine Safety and Health Administration in the fire suppression system section of a mine’s ventilation plan. The Belt Air Rule included arequirement dictating compatibility of air velocity with fire suppression systems. The final rule of limiting air velocity in the belt entry was challenged in the Court of Appeals for the District of Columbia Circuit. The court granted that petition and vacated the requirement on the air velocity cap, according to MSHA. The removal of the air velocity cap from the final rule, paired with thecompatibility requirement, led to a need for research on high air velocity’s influence on fire suppression system performance in belt entries. Test data was needed that illustrated the relationship between fire suppression system performance and air velocity, especially with the increased use of wider belts in underground coal mines, so National Institute for Occupational Safety and Health and MSHAcollaborated to obtain the data. However, this work was initiated before the revised Belt Air Rule was promulgated on December 31, 2008, when 1000 fpm air velocity became a requirement. Four different

types of fire suppression systems were evaluated in a large-scale fire tunnel: a water sprinkler, deluge-type water spray and two different types of dry chemical fire suppression systems. Thesuppression systems are representative of the types used in underground coal mines in the United States, and the large-scale fire tests were conducted using fireresistant rubber belt at a width of 72 inches meeting the outlines of Title 30, Code of Regulations, Part 18, section 18.65. Each fire suppression system was tested at air velocities of 500-550 fpm and 13501500 fpm. A minimum of two tests wereconducted at both air velocities for each system. All experiments were conducted at one location, the NIOSH Fire Suppression Facility – a full-scale, state-of-the-art fire test facility located on the surface of the Lake Lynn Laboratory just southeast of Pittsburgh, Pennsylvania. The fire tunnel was T-shaped to simulate a main entry and crosscut. The former was 153 ft long and the crosscut was 40 ftlong. Each entry was 18 ft wide and 7 ft high, with the roof constructed of corrugated steel bridge planks, and the roof interior was coated with 2 in-thick fire-resistant material. The ribs at the test site consisted of 8 in-thick solid concrete blocks coated with 1 in fireresistant material, and the floor of the facility was made of reinforced concrete. A variable speed axial vane fan measuring6 ft in diameter was installed at one end of the tunnel to provide ventilation. The fan featured a pneumatic controller to adjust the fan blades in order to increase or decrease the air velocity, and produced an air velocity over the cross-section of the entry of 1500fpm.

Groups go to work
A 6 ft-wide fire-resistant rubber belt meeting 30 CFR Part 18.65 requirements was installed on theconveyor belt structure. Typically, the length of the belt ranged from 140-165 ft. Thermocouples were then placed on the sensors used to detect the fire. For example, the dry chemical fire suppression system A used three point-type heat sensors to detect the fire, so thermocouples were placed on the end of each point-type heat sensor to determine which sensor activated the suppression system and at...