Mining Publication: Methods for Evaluating Explosion Resistant Ventilation Structures

• Explosion proof design
• Seals
• Strength of materials

The NIOSH Pittsburgh Research Laboratory (PRL) has conducted full-scale explosion experiments to evaluate the strength characteristics of various seal designs used for safely isolating worked-out areas in underground coal mines. Large-scale explosion tests conducted within the multiple-entry section of PRL's Lake Lynn Experimental Mine (LLEM) are currently the only accepted test method used by the Mine Safety and Health Administration for deeming a seal design suitable for use in U.S. mines. These explosion tests are labor-intensive, expensive to conduct, and can interfere with other critical underground safety and health research programs conducted by NIOSH. PRL has developed an alternative seal evaluation method, based on a hydrostatic pressure-loading concept, that can facilitate the in situ testing of seals in an operating mine. Two chambers within the LLEM and one within PRL's Safety Research Coal Mine were used for hydrostatic pressure loading various seal designs. The results from these chamber tests compare favorably with those from the large-scale explosion tests in the multiple entries. In addition to testing seal designs at the required 20-psi static pressure level, the chamber test approach also allows for the determination of the seal's ultimate design strength. Size-scaling relationships for predicting the strength of seal designs as a function of entry size are also presented.