In one part of a waste water plant in Germany, three Archimedes pumps are connected to the secondary settlement basin at the sludge recirculation pumping station. They continuously take the biological sludge back into the aeration basins, where the micro-organisms break down dissolved and fine particulate organic pollutants.

In the space of about a year each of the three spiral pumps failed due to the design. Due to the extensive mechanical damage it was the gear block was literally torn apart and had to be completely replaced, but the cause was not easily identified.

It was suspected that over time, other gearwheels become wedged into one another. Once this happens total failure follows within a few days. Vibration changes are often the first sign that something is amiss.

Condition monitoring system

To prevent future damage to the sludge recirculation pumping system, the local system integrator and Mitsubishi Electric proposed a reference application to the plant operator.  A condition monitoring system consisting of a Mitsubishi System Q PLCs linked to three Schaeffler FAG SmartCheck vibration sensors was suggested for monitoring the condition of the gears using vibration monitors. The system supplies early information on deviations from the normal value which could lead to possible damage to the machine.

An FAG SmartCheck sensor was attached to each of the three drives, allowing their condition to be precisely monitored. Vibration due to a defective gear operation and not perceptible to humans is detected by the sensor.  The MELSEC System Q compares the measured data with the normal value. If a deviation is detected, a specific error message is created to inform the operator, so that the problem can quickly be targeted and corrected. The reference project in Germany identified a gearbox failed completely within four months of the initial advance warning.

Increased overall reliability of the plant

Targeted correction of the faults can be carried out based on specific error messages, without the whole gear block having to be taken apart into its smallest components looking for the cause. The microprocessor integrated in the sensor stores all the values long term to be evaluated later and viewed via a web server.

The controller can pass the data on to higher level systems directly or via remote control technology. Condition monitoring contributes to preventing unplanned down-times and expensive consequential damage – and thus increases the overall efficiency of the plant.

Go to 999 Automation for Mitsubishi System Q at discounted prices