Why Temperature Is A Key For Condition Monitoring

Temperature is a very common and easy to measure physical property.
So, no wonder that all smart sensors of our Smart Automation and Monitoring System SAMS do have temperature measurement on board. But why you should utilize this particular smart sensor function in your application, I will try to explain in this post.

Smart Sensor Features of SAMS components

Temperature measurement is made in almost every industrial automation application.
There are many common and inexpensive sensors, typically resistance thermometer types such as PT100 or PT1000.
And they are widely used for control of the temperature of oil, cooling-water and many other liquids, cabinet temparature of machines. Of course paticularly different process temperatures in manufacturing processes are monitored and controlled very precisely, in order to get the production process at its optimum condition.

In the context of condition monitoring temperature can give you a lot of information on the status of your machines and equipment.
You can detect annomalies like worn out or overloaded parts of the machine, since the temperature of machine components like ball-bearings heat up if they do not run propperly. This could be caused by wear & tear or impropper maintenance i.e. missing lubrication.

Motors and drives which are running under overload will show increased energy consumption and thus higher temperatures.

Inside hydraulic power units the temperature is usually monitored, but will all the oil circulate through the whole piping circuit?
If you have very long piping and hoses in your hydraulic system with cylinders moving barely during the process, the temperature should be monitored close to the actors as well. In steel industry for example, the cylinders in coke plants are exposed to high temperatures, while they are moving just 5 or 6 times during an hour. The hydraulic fluid doesn’t arrive to the cooler just because of the small volume pumped in the system.

Therefore, despite central oil cooling, the hydraulic oil in the area of actuators (and thus the sensors or displacement transducers) may reach high oil temperatures. A temperature measurement integrated in the sensor system can reliably detect this.

Temperature control in plastic manufacturing

In plastic manufacturing you have a huge amount of temperature controls in injection molding machines. From material drying for the granulate to the plastification process with the screw in the injection unit the temperature has to be contolled accurately.

In the main step of injecting the plastic into the mold cavities there are many temperature sensors built inside the mold tool. Here the exact tempering is crucial for the product quality.

Very often this kind of production is running 24/7 to minimize cost. Every stop of a machine requires a re-start with heating up the often big and heavy tools. Heating up molds with several tons will take hours to get to a stable process. Therefore unplanned downtime is costly and time consuming.

Troubleshooting in Plastic Injection Molding Manufacturing

Still sometimes it happens that production gets unstable during the day or during night shift for a certain period. Typically this happens while the maintenance team is not on site…

Then troubleshooting is often difficult, when the equipment is back running normal.

According my experience it turned out in some cases as very simple thermal interference. In one case, the sun was shining through a window in the ceiling in summer during noon time, while the operator was at lunch break. The small temperatur drift caused a quality issue on the final product.

In another case, there had been quality issues during night shift. None of the standard machine parameters did show significant annomalies. The problem occured often in a similar period of time.
One day the maintenance guy stayed for a night shift, to see if something happens in or around the machine.

Finally, the cleaning staff entered the site and opened some doors of the production hall and blocked them in order to get their equipment in and out easily.
During the winter period cold air was blown through the shopfloor and the properly tempered mold got additonal cooling from the outside air. Of course the sensors inside the massive steel mold will detect this temperature drift, but with some significant delay. Therefor the time to re-heat the cavities and channels lagged behind and product quality suffered.

Imagine if some of the sensors mounted on the machine outside the mold or at auxilliary equipment would have had internal temperature sensors and the data collected would have been used for condition monitoring.
Beside the sensors main purpose, which might have nothing to do with the actual molding process, they could recognize changes in ambient conditions much quicker as they are not incorporated in massive metal. Such data could be collected from sensors mounted anyway at or around the machine. The cost of such smart sensors today is not significant higher and installation isn’t different versus a standard sensor.

Condition Monitoring Sensor

Of course it is also possilble to place additional sensors like this BCM condition monitoring sensor at a machine. This will enable you to benefit from even more information like relative humidity, ambient pressure, vibration and alignment, but with no other function for the process.