The machine whisperer

by World Grain Staff
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by Elfi Braun

Dieter-Otto Gräf, owner of the "Neumühle" in Lahnau-Dorlar, Hessen, Germany, is a master miller, qualified engineer and innovator. In his mill, he has developed an award winning range of unusual and innovative measures for the prevention of dust fires and explosions.

"In the past, millers used their hands to monitor their machines," Gräf said.

"They used to touch the roller surface in order to check the temperature and thoroughly ‘listened’ to their machines. These days of course, in the era of state-of-theart safety technology and strict hygiene requirements, this is no longer possible. Today we need reliable safety throughout the whole process: smooth workflows,
top product quality and effective fire and explosion protection. To achieve this, we have to make use of electronics."


There is plenty of "listening" and "feeling" still going on today in Gräf’s "Neumühle," but the miller’s hands are no longer needed — thanks to the automation Dieter-Otto Gräf developed for his mill. The "listening" is taken over by microphones, while the "feeling" is carried out by means of an infrared temperature measurement system for the rollers.

Using microphones, Gräf monitors the noise level of the system. "A change in the noise level can point to worn bearings, damaged suspension elements, imbalance or off-track running," Gräf said. Long before a damaged bearing overheats and becomes a possible source of ignition, the monitoring equipment ‘hears’ that something is wrong and switches the system off."

To prevent sources of ignition, Gräf uses infrared sensors to monitor the surface temperature of the rollers. If the preset roller temperature is exceeded, an alarm is triggered and the milling process is switched off automatically.

"These days, those who want to survive in business have to come up with
new ideas. The important thing is to see today’s extremely demanding product hygiene and product quality requirements not as a burden, but rather as a challenge. And that’s all I have done."

Today’s miller has all the vital information he needs about the system and processes visualized on a computer screen or display with the aid of electronics.

Even vibrations in the product flow above the roller mills are made "visible" in Gräf’s mill, enabling safety-related process problems to be spotted at an early stage. Here, Gräf makes use of the latest radar technology, which he saw at the aircraft manufacturer Boeing and has since adapted for his own purposes. Changes in the vibration characteristics, for example, are an indication of foreign particles or a blockage somewhere in the flow.

Light barriers on all the mill floors "see" immediately and reliably if flour or cereal dust is escaping from the system anywhere. The milling process is shut down immediately as soon as the light beam of the barriers is broken.

Gräf refers to his approach to electronic monitoring of his mill as "Preventive maintenance." This preventive maintenance also includes further measures, including spark detection in the product conveyor lines and monitoring of the temperature of bearings on fast-running machines. But for Gräf the businessman, the term "maintenance" also includes proper machine care. "My machines work best when they are running smoothly and when the machines are running trouble free and reliably, so is my business." WG

Elfi Braun is editor of Occupational Safety, Wiesbaden, Germany. Braun may be contacted at el .