Investigations of flame front propagation between interconnected
process vessels. Development of a new flame front propagation time
prediction model
Journal of Loss Prevention in the Process Industries, 12 (5):
421--436 (September 1999)DOI: http://dx.doi.org/10.1016/S0950-4230(99)00013-3
Abstract
For the case where a dust or gas explosion can occur in a connected
process vessel, it would be useful, for the purpose of designing
protection measures and also for assessing the existing protection
measures such as the correct placement, to have a tool to estimate
the time for flame front propagation along the connecting pipe. Measurements
of data from large-scale explosion tests in industrially relevant
process vessels are reported. To determine the flame front propagation
time, either a 1 m3 or a 4.25 m3 primary process vessel was connected
via a pipe to a mechanically or pneumatically fed 9.4 m3 secondary
silo. The explosion propagation started after ignition of a maize
starch/air mixture in the primary vessel. No additional dust was
present along the connecting pipe. Systematic investigations of the
explosion data have shown a relationship between the flame front
propagating time and the reduced explosion over-pressure of the primary
explosion vessel for both vessel volumes. Furthermore, it was possible
to validate this theory by using explosion data from previous investigations.
Using the data, a flame front propagation time prediction model was
developed which is applicable for: - gas and dust explosions up to
a K value of 100 and 200 bar m s-1, respectively, and a maximum reduced
explosion over-pressure of up to 7 bar; - explosion vessel volumes
of 0.5, 1, 4.25 and 9.4 m3, independent of whether they are closed
or vented; - connecting pipes of pneumatic systems with diameters
of 100-200 mm and an air velocity up to 30 m s-1; - open ended pipes
and pipes of interconnected vessels with a diameter equal to or greater
than 100 mm; - lengths of connecting pipe of at least 2.5-7 m.