CDEM1000 Coal Dust Explosibility Meter Coal Dust Explosions

CDEM-1000 Coal Dust Explosibility Meter

Coal Dust Explosions • Natural occurring methane in coal mines causes frequent explosions, which alone may not pose a major hazard. • When a methane explosion prompts a coal dust explosion, the intensity is far greater. • Coal dust explosions can cause deaths both directly and by trapping miners through mine cave-ins.

Rock Dusting in Coal Mines • Coal dust explosions are averted in coal mines by applying layers of inert rock dust over the coal dust. • The inert rock dust used in the US is commonly limestone, although marble dust may be used as well. • MSHA may levy fines against coal companies that don’t maintain enough rock dust in their mines, based on a lab analysis.

CDEM-1000 • The CDEM-1000 uses reflectivity of rock dust/coal dust mixtures to determine the % rock dust in the mixture. • This works, because coal dust is black and the rock dust is white. The lighter color the mix, the more rock dust it contains. • MSHA requires a rock dust/coal dust mix of at least 80% rock dust. • The CDEM-1000 is a go/no-go meter that produces a green indication for % RD above 80.

CDEM-1000 • The CDEM 1000 was developed by NIOSH at the Pittsburgh Research Laboratory. • It is produced solely by Sensidyne, LP. • It has an MSHA approval for intrinsic safety. • It has been thoroughly field tested by both MSHA and NIOSH.

CDEM-1000 Kit • The CDEM-1000 kit comes with all accessories required for field sampling.

Accessories • • • A) CDEM-1000 B) PPC Samples C) Molecular sieves D) Calibration vials E) Calibration funnels F) Spatula and brush G) Sample vials H) Sample funnels I) Sample cups B E G A H C D I F

Collecting a Sample • A sample of the mine’s coal dust/rock dust mixture is taken from the mine floor and walls according to an MSHA procedure. • It is transferred to a sample vial.

Preparing a Sample • The sample vial contains activated molecular sieves, small beads that absorb moisture. • The beads are removed by a funnel with a small screen inside, as the sample is transferred to a sample cup.

Sample Size • The dried sample is transferred to a sample cup, observing the cup’s fill line. • The cup is placed against the CDEM 1000’s lens. A spillover is expected.

Red/Green Indication • The CDEM unit is a go-nogo meter. It is not an analytical tool. • A green indication means that the rock dust is present in the sample mixture at 80% or more. • A red indication means that more rock dust must be applied. • An extended red function allows the user to see a range that represents how close the mix is to green (e. g. 75 to 78%).

Methane Consideration • The CDEM will ask the user to input a methane value for the area. This value is read from a separate methane meter. • The user can input methane values from 0. 0 to 2. 0% methane in 0. 1% increments as read from the methane meter. • For each 0. 1% of methane, the CDEM-1000 will slide the green criteria upward by 0. 4% rock dust. For example, a reading of 0. 5% methane inputted into the CDEM-1000 will raise the green indication from 80% to 82% (i. e. , 5 x 0. 4% = 2%).

Calibration • The unit is calibrated by exposing the lens in turn to 100% PPC. 100% RD and an 80% mixture of the mine’s rock dust and the PPC provided. • The CDEM-1000 walks the user through the calibration steps through the LCD display. • A calibration is required every field 200 samples.

Pittsburgh Pulverized Coal • Calibration must be conducted using the PPC samples provided. They represent the coal dust particle size range that is most dangerous in mine explosions.

Rock Dust • Rock dust used in the calibration procedure must come from the mine. The rock dust used by the mine must meet the correct size distribution specified by MSHA.

Reflectivity Check • A reflectivity check is required after every 1000 field samples. • The CDEM-1000 will prompt the user when the reflectivity check is due. • To conduct this check, a special sample cup with a color standard permanently placed inside is exposed to the lens. • This cup is matched to the CDEM-1000 unit by serial number. • The unit will display a pass or fail based on its agreement with the standard’s % RD value, which is stored in the CDEM 1000’s memory. • The reflectivity sample cup doubles as a protective cup for shipping. It attaches to the unit bayonet style.

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