Large-Scale Explosion Propogation Testing

"LARGE-SCALE EXPLOSION PROPAGATION TESTING" BACKGROUND Traditionally, new safety technologies have been deemed suitable or approved for in-mine use by regulatory authorities with data based on large-scale performance tests in simulated coal mines. This high priority study includes engineered rock dust performance experiments to validate the ability of new and improved anti-caking formulations to prevent propagation of coal dust explosions as well as or better than the current rock dust supply complying with 30 CFR 75.2. An effective rock dust relies on two critical elements to suppress a propagating coal dust explosion: 1) the ability of the rock dust to be lifted and suspended with the coal dust during an explosion and 2) maintaining the correct proportion of rock dust to coal dust within the top 2 - 4 mm depth of the dust layer deposited on mine surfaces. Rock dusts can be treated to resist caking in the presence of moisture. The impact of such treatments on inerting effectiveness is unknown. Previous work at the Lake Lynn Experimental Mine (LLEM) established inerting effectiveness using large-scale explosion tests in A-drift. The cross-sectional area of this drift was roughly 13 m2 with a length of 500 m. Vendor will coordinate with CDC staff regarding any historical work at the LLEM and previous test results, if vendor is determined responsive and considered for possible award. PURPOSE The objective is to conduct large-scale comparison experiments to determine if an anti-caking stearin-treated rock dust is as effective in preventing flame propagation as untreated rock dust, when mixed and layered with coal dust that has physical and combustion properties similar to NIOSH's "medium" Pittsburgh Coal dust. The primary goal of these proposed studies is to compare the relative inerting effectiveness of anti-caking treated and untreated rock dusts under the same test conditions. Performance effectiveness will be based on the extent of flame propagation and flame velocity within the dusted zone. SCOPE OF WORK The vendor will proved all labor, materials and equipment required to complete the tasks outline below. This includes: A. Preparation of the experimental mine test site, B. Coal dust having similar size characteristics to the Medium Pittsburgh coal (d38), C. Stearin-treated rock dust having similar size characteristics to the Reference rock dust, D. Non-stearin treated rock dust having similar size characteristics to the Reference rock dust, E. The labor to acquire, mix, and place the coal dust and rock dusts, F. The methane gas, ignitors, and other miscellaneous materials required for test ignitions, G. The labor to set up each test, H. The labor to conduct each test, I. The calibrated instrumentation to collect data such as temperature, static pressure, dynamic pressure, flame travel, flame velocity, etc. at high speeds (all instrumentation will be calibrated as per manufacturers' specifications), J. The experienced personnel to assess the data for inconsistencies or instrumentation failure, K. The labor to clean the experimental mine entry after each test, and L. The disposal of waste material generated during each test. TASKS TO BE PERFORMED Initial testing will first establish inerting effectiveness (extent of flame propagation and flame velocity) for mixtures of coal and untreated rock dust. This process follows the traditional approach used at the LLEM to establish inerting limits of homogenous (well-mixed) mixtures of coal and rock dust based on average coal particles sizes found at US coal mines. Homogenous mixtures coal dust and untreated rock dust will be created and tested to determine the extent of flame propagation and flame velocity within a dusted zone. Previous LLEM testing used a 350-ft dusted zone. The mixtures will be distributed in the test entry in a manner similar to that used in previous BEM testing: one-third of the material placed on the roof, one-third on the ribs (shelves), and the final third on the floor. A 10% mixture of methane gas in air will be initiated by electric match at the closed end of the test entry. Subsequent tests will then evaluate coal/rock dust mixtures using a treated rock dust in place of the untreated dust. Inerting effectiveness will be measured by the length of flame propagation and flame velocity in the dusted test zone. Once the homogenous mixture determination is made, repeats of the tests will be conducted to compare the relative performance of the same coal dust and rock dusts used in the initial tests except the dusts will be distributed in the gallery in layers. DELIVERABLES For each large-scale test, the vendor shall provide the following: A. The raw test data which includes temperature, static pressure, dynamic pressure, flame velocity and flame travel B. The reduced test data in Excel format which includes temperature, static pressure, dynamic pressure, and flame travel C. Drawing(s) depicting the set of test conditions 1) Ignition zone 2) Dust loading zone 3) Propagation zone D. A summary report of test results MINIMUM VENDOR QUALIFICATIONS The vendor should have the following qualifications: A. The vendor shall have expertise and a proven, documented track record for conducting large-scale underground gas and coal dust explosions in the underground experimental mine. B. The vendor personnel overseeing and conducting such large-scale underground experiments must be well established in the subject as demonstrated by relevant peer reviewed publications. C. An explosion gallery capable of assessing propagating explosions. The entry should have a minimum length 400-m long with a minimum rectangular cross-sectional area of 7.5 m2 and a surface roughness ranging from +15 to -15 cm. D. The underground experimental coal mine must contain flame sensors spaced on regular intervals along the ribs of a 110 m long dust distribution zone that will detect the arrival of combustion flame as a function of time. It must also contain static and dynamic pressures transducers for measuring the static pressures perpendicular to the ribs and dynamic pressures along the centerline to measure the destructive wind pressures as a function of time. E. The underground experimental coal mine must also utilize high speed data acquisition systems that can digitally record data from each sensor at a frequency of at least 2000Hz. F. The vendor shall have facilities and expertise to grind, pulverize and classify coal dust that contains 36% volatility with the particle size distribution that represents the medium Pittsburgh coal dust used in explosion studies conducted at the LLEM. PERIOD OF PERFORMANCE: Effort shall commence upon award and be completed no later than one year after award.