Jim Kline: The forgotten factor
July 1, 2014
It’s part of your infrastructure that is easily ignored, particularly in older bakeries. It is likely to be unbalanced; many times its maintenance is forgotten, yet its performance is key to the efficiency of your process and the productivity of your people. So what is so easily overlooked that can have such a significant impact on your bakery’s operation? Your ventilation system.
We all can agree that process variation contributes to product defects and affects equipment performance. In fact, to avoid process variation, we go to great lengths to control our dough temperature; our fermentation, proofing and retarding temperatures and humidity; and our baking time and temperature. Yet the environment that the doughs and batters are exposed to, where production equipment resides and where we work remains, for the most part, as-is.
Think about it: Our doughs and batters have surface exposure to ambient conditions for more than 20 minutes on average. Granted, the inner mass of the dough or batter may not be affected in those 20 minutes, but the outer layer certainly is. Ever look at a tray of product and wonder why you see size variations? Ever wonder why on a sheeting line you suddenly start to get dough sticking? Ever notice your batter donut size varies from the start of a batch to its end? Well, perhaps you need to look no further than your environment.
And don’t neglect to look at the effect of the ambient temperature on equipment performance. Sheeting equipment is gaining in use for various bakery processes. If the sheeting equipment is sitting in a 90°F ambient temperature, what temperature will the sheeting rollers be? Ever notice that in warmer months the use of dusting flour increases, as does operational and mechanical downtime? Care to guess the probable cause?
Do you realize that your coolers are likely to be the single greatest source of heat in the bakery? Let’s take a bakery that is producing 9,000 24-oz loaves of bread an hour. Cooling the bread releases 1.1 million Btu per hour into the air; that is equivalent to a 329-kW electric heater or a 35-bhp boiler dumping heat, non-stop, into the room.
Am I suggesting that every bakery be air conditioned? Certainly not — it would not be the most practical solution, and for some products and processes, it would even be detrimental. What I am suggesting is that the environment be considered and evaluated to identify cost-effective improvements.
Here are some initial checks before you get started on your evaluation. Is all the ventilation equipment turned on and operating as designed? Are the fans rotating the proper direction, including oven exhausts? Scoff at this question, but we find it frequently. Have the intake filters been changed recently? Blocked filters will reduce the fresh air intake. Are oven stacks located away from the air intakes or sufficiently elevated to prevent exhaust from being drawn back into the bakery?
Is the bakery either at neutral or slightly positive air pressure when compared with outside conditions? If not, you are drawing in unfiltered air from the outside and likely affecting temperature control of your oven. If the oven’s low-pressure gas regulator has a vent on it, unless piped to the outside (some are), interior air pressure fluctuations will affect your fuel-to-air ratio.
After the initial checks, look at the air flow patterns within the bakery. You want to exhaust heat near the sources and keep it from migrating. Are you bringing the fresh air into your makeup and packaging areas and exhausting above your main heat sources (being the oven[s] and cooler[s])? If not, this offers a real opportunity for significant improvement.
How and where is your fresh air intake distributed? Bring it in where the most people are working so they get the best air movement. Consider directing the air toward fixed worked positions in mixing, makeup and packaging. Spot cooling is a great way to improve the environment in these work areas, as well as aid the process environment where temperature control is important but general air conditioning is not practical.
Lastly, on the roof, where you draw in the makeup air, is the surface in the immediate area of the air intakes either white or silver? If not, give it a coating to reflect rather than absorb the sun’s rays — it will translate to a reduced intake temperature.