Time is money in a bakery, and 15 minutes can feel like a lifetime and look like lost profit, but it could also mean avoiding a catastrophic event caused by a leaky gas valve. This need for uptime can introduce a variety of risks, especially during a purge. It is a practice that bakers simply must not shortcut.
Before lighting the burners, the purge cycle will run the machine’s fan to remove any combustible gas that happens to be left in the baking chamber.
“Sometimes it will get maladjusted — or purposely readjusted — so 10 minutes will turn into just a couple minutes,” said Damian Morabito, president and chief executive officer, Topos Mondial. “And that’s fine … until there’s a leaky gas valve. If that happens, and then overnight the oven chamber was filled up with gas and then the purge time was shortened, you could light the oven and cause an explosion.”
This is especially important in a propane-fired oven because propane is heavier than air and sits lower in the chamber, Mr. Morabito explained. In this case, the purge cycle must be longer because it must draw air from the bottom of the chamber, the oven and the fire box.
“It definitely gets all the gas out of the combustion area when it draws from the bottom of these chambers, so it doesn’t cause a problem,” Mr. Morabito said.
For the purge cycle, Auto-Bake offers an exhaust stack thermal mass flow sensor.
“It replaces the traditional pressure switch and totalizes the amount of actual air being removed from the baking chamber prior to ignition,” said Scott McCally, president, Auto-Bake, part of the Middleby Bakery Group. “This system greatly reduces that potential of residual gas within the system and improves ignition safety.”
Take the time to make sure mechanical components remain covered. Exposed external burner linkages could inadvertently get bumped, broken or maladjusted, and that could result in a burner safety hazard.
“If a linkage or control device is out in the open and you bump them, it could adjust the air-fuel mixture, and then you’re running rich,” Mr. Morabito warned. “If you run rich in a car, it backfires; in an oven, there could be an explosion.”
He suggested that sophisticated burners, such as Weishaupt burners used in J4 ovens, are designed with reliable protection around them, and they eliminate the possibility for linkages and components to be easily damaged in a bakery environment during both operation and clean-up.
This article is an excerpt from the October 2018 issue of Baking & Snack. To read the entire feature on ovens, click here.