Mechanical problems detected & avoided using ultrasound

Ultrasonic scanning instruments are fast becoming standard tools for preventative maintenance programs in the food processing industry.   The ability to use ultrasound tools to pinpoint and repair faulty steam traps, bearings, vacuum leaks and electrical problems before they cause serious disruptions is saving food companies thousands of dollars in unscheduled downtime.

Ultrasound scanning tools provide information in two ways:  They let the operator hear ultrasounds qualitatively through a noise-isolating headphone that blocks out plant noise and they display quantitative, incremental readings on a meter.   The sensitivity of the scanning instrument can be adjusted to seek out particular sounds. Used with a hyper-sensitive, scanning microphone, the detector can even record the sound of an eye blinking from several feet away.  (A blink creates a popping sound, caused by the break of the seal formed by fluid that bathes the eye.)

Avoiding costly bearing failures
Inland Empire Foods in Riverside, CA, pre-cooks, dehydrates and packages a wide variety of beans for resale to other food processing companies. As part of Inland's preventative maintenance program, it uses a lightweight Ultraprobe 2000 manufactured by UE Systems to make monthly inspections of bearings throughout the plant.

Ultrasound scanning allows operators to hear sounds the human ear cannot detect under normal conditions.  All operating equipment and most leakage problems produce a broad range of sounds.  The high-frequency, ultrasonic components of these sounds have extremely short wave lengths and tend to be directional.  By pointing the ultrasonic instrument in the direction of the object to be tested, the signal is isolated from background plant noises and its location easily detected.  As subtle changes occur in mechanical equipment, the directional nature of ultrasound permits potential warning signals to be detected before actual equipment failure.

According to plant manager Perry Stemer, "using ultrasound, we have the choice of testing for bearing wear either during actual production or when the plant is shut down.  Wherever there is evidence of a problem," says Stemer, we use the ultrasonic detector to provide confirmation of our vibration readings and replace the faulty bearing.

"One of our biggest problems is dry bearings.   Using the ultrasonic detector, we can hear if the bearing is running dry or if there is a small particle of dirt on the ball.  If there is a flat spot on the ball hitting the raceway of the bearing, we'll hear it randomly as the ball rotates."

Sterner schedules periodic greasing of the bearings and can listen with the ultrasonic equipment as he pushes grease into the raceway.  The meter readings are recorded monthly and are used to indicate when the bearings need to be replaced.

In addition to using the ultrasonic detector for predicting and preventing bearing failure, Inland Empire Foods periodically checks for leaks in steam traps, inspects motors for phasing problems, and checks starters for arcing with the sensitive listening equipment.

Recently, Sterner discovered another use for his ultrasonic detector.  "Our QC department had placed a load of black-eyed peas on hold for possible infestation and disposal. I was curious to know if the ultrasonic device could detect the presence of insects in the tote bags.  I put on the headphones and placed the ultrasonic detector near the sack.  It was amazing.   You could actually hear the insects crunching on the peas!"

Joe Coencas is a free-lance writer specializing in
applied technology for the food processing industry.