Sizing and selection of explosion vent panels is critical to the safety of plant and personnel. Calculations are in accordance with general guidelines from standards such as NFPA-68 or VDI 3673. Baum Pneumatics CFD calculations on dust explosion can show the effectiveness of such calculations and provide alternative ways of achieving higher safety based on specific scenarios.
Baum Pneumatics propitiatory CFD code solves explosion using input variables such as dust particle distribution, pressure, temperature and velocity values and solves the motion and chemistry equations for small time steps (1e-7 sec) and provides output at desired time intervals. The chemistry part of calculation is verified based on experimental values of dust explosion acquired from laboratory testing on given dust samples compliant to NFPA 69 and ASTM E1226 standards.
Above animation shows the results of a CFD calculation of dust explosion of following size distribution inside a cyclone:
3.0 micron 10%
25.4 micron 45%
81.3 micron 45%
Note that the sample is a very fine dust (ground sample for explosion testing)
The Kst and Pmax of the sample are 205 and 10.5 bar (as per NFPA guide the combustible dust for wood flour) respectively.
An ignition source was placed at the center of cyclone which ignites the dust/air mixture at t=0 (sec).
ps1 and ps2 represent pressure sensors located at the designed venting panels.
Above plot shows pressure rise due to explosion on ps1 sensor up to t = 12 (ms) where venting area is open to atmosphere and flame can exit.
Utilizing Baum Pneumatics CFD calculations for explosion venting advantages:
- The desired Pred (reduced explosion pressure generated by an explosion in a vented vessel) can be achieved based on hazard scenarios
- Multiple scenarios can be studied for interconnected vessels of any shape and volume
- CFD results can show parameters that are not measurable by NFPA standard formulas such as the venting time, or optimum location for venting