Bill: I'll post this on the Q&A page, but suspect Heinz
Baumann <baumann@sc3101.med.buffalo.edu> or John Claypole
<Lightinter@aol.com> will have some thoughts thereon!
Fil Graff, Secretary
Heinz wrote:
In 1815, Humphry Davy (see picture attached) studied the
explosion process caused by methane gas (or
"firedamp") commonly encountered in coal mines. He
recognized that methane gas ignites at high temperature, e.g.,
at the temperature produced by open flame lamps. To prevent
that heating to occur, he constructed a lamp with a two-layer
metal gauze chimney. The principle function of the metal mesh
is to dissipate the heat of the flame and thus to maintain a
temperature outside of the lamp below a critical level. While
it is correct that under normal burner settings the flame is
confined within the gauze chimney, a passage of the flame
through the wire mesh or heating to ignition point of gas
outside of the chimney could in principle occur at extremely
high setting of the flame within the lamp or at high air draft
condition. The Davy lamp also indicates the presence of methane
in the air. By drawing methane-containing air into the Davy
lamp, the flame become larger (extended). Hence, the change in
flame size serves as marker for the presence of significant
amounts of combustible gas.
