Compact Ex Protection

Wilhelm Niemann Maschinenfabrik guarantees the reliable operation of their machines with accurate sensors and fast compact interface devices from Turck

Wilhelm Niemann Maschinenfabrik is a company that manufactures mixers and mills for the paint, varnish and chemical industry. Customers use them almost exclusively in explosion hazardous areas. The manufacturer based in Melle installs space saving isolating switching amplifiers and temperature measuring amplifiers from Turck's IMX12 interface series in the control cabinet. These send the signals of the operator buttons to the field and transfer intrinsically safe digital and analog input signals. Niemann has also relied for many years on the IM36 potentiometer amplifiers for positioning the height of toothed discs. Turck inductive initiators with a Namur output have been even longer in use, and were able to impress Niemann due to their large switching distances.

Niemann equips its machines, like this Kreis dissolver with sensors and interface technology from Turck
IMX12 and IM36 amplifiers guarantee safe signal transmission in the Ex environment
The power bridge system simplifies the power supply of the IMX12 devices
Inductive proximity switches in the machine column query the height of the hydraulic ram
Compact BIM-UNT magnetic field sensors are concealed in the fill openings
During the production process a double suction disc in the container rotates at the set height
Hendrik Werges, workshop and project manager for electrical engineering at Niemann

Streamlined devices

Niemann produces three basic machine types, the dissolver, the basket mill and the “Butterfly” Kreis dissolver. One thing is common to all machines here – their use in explosion hazardous areas. This must also be taken into account in the control cabinet outside of Zone 1. Encapsulated Profinet or Profibus cables can be run from the PLC in the control cabinet to an operating element.

The second variant without PLC technology requires hard wiring. This sends signals from the operator button to the field via IMX12 isolating switching amplifiers from Turck. Devices from the IMX12 interface series are also used if users wish to pass certain digital or analog values from the Ex area. Turck's IMX12 devices were chosen thanks to their narrow width of only 12.5 millimeters, but also due to their power supply via a power bridge.

Three environments, three initiators

Niemann had been using Turck sensor technology for a long time before the interface technology devices. For example, the technicians at Niemann install M18 inductive proximity switches in the columns of its machines in order to query heights. The sensor must detect the cylinder and ring in spite of the distance. This demonstrates the benefit of Turck's NI10-G18 proximity switches.

Anyone wanting to look for the smallest Turck components in a Niemann machine must look really closely. With a housing length of 31 millimeters and a height of six millimeters, the BIM-UNT-AY1X magnetic field sensor is hidden in the cover hinge of a tank fill opening. This detects here whether the cover is open or closed. In addition, a specially designed inductive sensor must withstand wear in the drive. This scans a switch lug in the very demanding atmosphere.

IM36 passes speed test

The position of the toothed disc inside the container is determined by a cable sensor. This supplies resistance values via the contact of the measuring cable, which have to be supplied as analog values. A potentiometer amplifier converts this quickly to an intrinsically safe 4-20 mA value so that connected systems can regulate the height steadily. The process sometimes still caused problems five years ago.

“If the conversion takes too long, the machine misses crucial points by a few centimeters and then continuously oscillates”, explains Hendrik Werges, workshop and project manager for electrical engineering. A transducer with a cycle time of less than 700 milliseconds was required as a solution. Niemann therefore turned at that time to Turck interface technology. To be precise, the IM36 amplifier, which completes a conversion within 30 milliseconds and thus enables the toothed disc to be positioned within the hysteresis range.

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