Electricity + Control October 2019

COVER ARTICLE

FEATURES: · Control systems+ automation · Cables+ accessories · Earthing+ lightning protection · Pressure+ levelmeasurement+ instrumentation · Analytical instrumentation

R eplace parts before they fail, avoid unplanned downtime – these are the promises of predictive maintenance. But how do we determine the aging of a cable and predict when it will fail? LAPP has developed a solution for Ethernet cables that does not require any changes to the cable. Predictive maintenance is one of the most promising benefits of digitalisation in factories. It is based on sensor data that is supposed to enable conclusions to be drawn about the aging and required replacement of the monitored parts. Predictive maintenance also concerns connection systems. Even if cables usually last for many years, failure cannot be ruled out, and cable failure can paralyse an entire production line – causing unplanned downtime with its associated high costs. "That's why we wanted to develop a solution that will sound the alarm before a cable fails," says Guido Ege, Head of Product Development and Management at LAPP. Focus on Ethernet cables Ethernet cables, particularly when laid in energy chains, are more prone to failure than current- carrying cables due to their complex structure and the necessary high-frequency characteristics. For instance, broken shielding leads to increased EMC interference. If strands of wire break, attenuation increases and the data rate drops. If a strand breaks, communication fails completely. Ege's team therefore focused on developing a predictive maintenance solution for Ethernet cables. The aim was to be able to predict the remaining lifetime of a cable and plan replacement in a way that would guarantee minimum disruption to machine operation. For this purpose, the transmission characteristics of data cables are monitored and changes in those characteristics are used to calculate the expected service life. One of the requirements was to develop a measuring principle that works without changing the cable – without additional ‘sacrificial wires’ in the cable. (Additional wires mean additional installation work.) The solution was to be based only on a protocol and a special algorithm. This means it can be used with standard Ethernet cables and standard connectors such as RJ45 or M12.The installer connects the cables as usual and does not have to connect any additional sacrificial

wires. This approach also has the advantage that it allows for retrofitting to existing systems. LAPP’s Predictive Monitoring Box, the PMBX, has two Ethernet ports and is simply inserted at the start of the Ethernet cable to be monitored.The data packets are transmitted transparently from one Ethernet port to the other, almost instantly. For a connected PLC, the PMBX is not visible and it has no influence on the data transmission. It can therefore be used on existing systems without necessitating any changes to the PLC software. The failure prognosis is based on up to four transmission-relevant parameters which are used to calculate the LAPP Predictive Indicator. Plausibility checks can also be done to minimise potential misinterpretations of measured values. The predictive maintenance system uses a deep learning approach. For LAPP drag chain cables, for example, millions of measured values have been collected in-house and analysed usingmathematical algorithms. The more data available, the more accurate the prediction. The system is self-learning. After just a few weeks of data collection at LAPP's own test centre, cable failure was predicted with notice from a few hours to several days. Such predictability means replacement can be planned and carried out at a suitable time.

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For more information visit: www.lappgroup.co.za

The LAPP Predictive Maintenance Box is being further developed and refined in the LAPP Test Centre.

The ETHERLINE ® TORSION Cat.7 is a high-performance cable for industrial Ethernet.

Electricity + Control

OCTOBER 2019

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