Pro Tip: Detecting, locating and fixing air leaks can help bakeries save both time and money.

Compressed air is a necessary part of most bakery operations, but it’s probably the most inefficient source of energy in a plant. To operate a 1-hp air motor, you need 7 to 8 hpr of electrical power. At higher than typical pressures, even more power is needed.

For example: 30 scfm at 90 psig is required by the 1-hp air motor; 6 to 7 bhp at compressor shaft is required for 30 scfm; and 7 to 8 hp electrical power is required for 6 to 7 bhp at shaft.

The overall efficiency of a typical compressed air system can be as low as 10% to 15%. Annual energy costs for a 1-hp air motor vs. a 1-hp electric motor for a five-day per week with a three-shift operation is \$0.17/kWh (current national average): \$5,937 (compressed air) vs. \$990 (electric).

How Do You Find Leaks?

At \$0.17 per kWh: A \$340/year leak cannot be felt or heard; a \$1,360/year leak can be felt but not heard; and a \$2,380/year leak can be felt and heard.

The leak cost formula is the number of leaks x leakage rate (CFM) x (kW/CFM) x operating hours per year x (\$/kWh).

For example, let’s say you discover a 1/4-inch circular hole or line in the plant that runs on 90 psig leaking. According to the Department of Energy’s leakage rate chart, your leakage rate is 89.2 CFM. Let’s assume your compressor(s) run year-round (8,736 hours), your energy costs \$0.17 per kWh, and your compressors use is 0.19 kW/CFM. Following the formula, you would calculate 89.2 x 0.19 x 8,736 x \$0.17. In this situation, the energy cost or waste equates to \$25,169.81 per year.

Since air leaks are almost impossible to see, other methods must be used to locate them.

The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high frequency hissing sounds associated with air leaks. These portable units consist of directional microphones, amplifiers and audio filters, and usually have either visual indicators or earphones to detect leaks.

A simpler method is to apply soapy water with a paint brush to suspect areas. Although reliable, this method can be time consuming. Other methods include smoke sticks, candles, foam, manometers and stethoscopes.

Ultrasonic detectors can find mid- to large-sized leaks. The advantages of ultrasonic leak detection include versatility, speed, ease of use, the ability to perform tests while equipment is running and the ability to find a wide variety of leaks. They require only a minimum amount of training; operators often become competent after 15 minutes.

Since ultrasound is directional in transmission, the signal is loudest at its source. By generally scanning around a test area, it is possible to quickly locate a leak and find its location. For this reason, ultrasonic leak detection is not only fast, but also very accurate.

Typical Components of Demand

Demand for compressed air goes beyond what is needed to do work. It includes inappropriate uses, leaks and increased demand due to excessive system pressure. To effectively cut costs in a compressed air system, these demands need to be minimized.

Inappropriate uses are any application that can be done more effectively or more efficiently by a method other than compressed air.

Leaks are an unintended loss of compressed air to ambient conditions.

Increased demand due to excessive system pressure refers to additional compressed air usage due to pressure levels higher than what is necessary to keep equipment operating properly. Reduce overall plant system pressure whenever possible. Reducing the system supply pressure in small increments can determine if a system's pressure is set higher than optimal. For every 2 psig reduction in compressor discharge pressure, compressor energy use can be reduced by 1%. Reducing pressure by 10% can lead to 5% savings in energy.

Use electrical interlocks or photo eyes to turn off compressed air devices when the line is down or not necessary for air to be available.

Replace pan blowers, crumb blowers and bag blowers with electric point-of-use blowers. This can save up to 85% on energy cost and dramatically reduce the induction of mold spores if designed correctly.

Rowdy Brixey is founder and president of Brixey Engineering Inc.

You can connect with him on LinkedIn.