Portable cookstoves are used by caterers and campers to bring the convenience of a “kitchen appliance” to places where such appliances are normally not available. Some cookstoves are fueled with liquefied propane that is supplied in 1-lb canisters (first photo) or 20-lb containers (second photo). Others utilize liquefied butane that is supplied in aerosol-like cans (third photo). While all these systems are equipped with unique safeguards, certain types have failed catastrophically, injuring workers and guests.
Cookstove Safeguards. Butane cookstoves (example in fourth photo) are generally equipped with a multi-function gas safety valve. When the fuel can is installed, a lever must be pressed to latch the can into place so that the gas will begin flowing through the valve to the burner. The valve also has a pressure-safety pin that is designed to trip the latch and disengage the can when the fuel pressure exceeds a safety threshold. However, in some models, the retracting mechanism has been observed to fail intermittently and the can fails to disengage even though the pressure-safety pin performed as it should.
Can Safeguards. Small butane fuel cans are also equipped with certain safety features that are designed to prevent or mitigate catastrophic releases of flammable gas. Because the fuel cans are installed horizontally into the cook-stove chassis, the fuel withdrawal tube is equipped with a right-angle extension to ensure that butane vapor is withdrawn from the headspace, rather than butane liquid from the lower portion of the can. The neck of the can contains a feature that is intended to prevent improper rotation in the stove, but users can unknowingly defeat this safeguard and install the can in the wrong orientation, permitting butane liquid to be withdrawn instead of butane vapor, which is undesirable.
This author has investigated several flash fires involving portable cookstoves and has identified product defects as well as certain ways the products can be misused. In the worst-case scenario, the fuel canister overheats and ruptures, releasing a fireball that causes personal injury and property damage.
The purpose of “Investigation Anecdotes” is to inform our readers about the intriguing field of engineering investigations. We hope you are instructed by this content, and we encourage you to contact us if you seek additional information. Copyright Martin Thermal Engineering, Inc. (2013)