Condition monitoring is as cost-effective as insurance

Paul Boughton

For a variety of reasonsthis situation is changingso designers need to have an appreciation of what condition monitoring is and the benefits it offersas well as how it can be implemented.

Monitoring the condition of critical power transmission elements enables component degradation to be identified before it causes a failure. Components such as bearings and gears can be monitored using vibration sensors to detect when wear or damage is starting to occur. Brakes and clutcheson the other handmay be better monitored using thermal imaging.

By detecting deterioration earlyunplanned stoppages can be avoided and further damage can be avoided. For examplea seized bearing could cause the shaft it is supporting to stop suddenly; inertia stored in other components could then cause damage to the shaftbearing mounting or other componentsleading to the repairs being far more complex and costly than simply replacing the failed bearing. Condition monitoring can therefore be thought of as a cost-effective insurance policy.

Condition monitoring can also have direct benefits for the machine builderespecially if an extended warranty or service agreement is supplied with the machine. In additionthe conditioning monitoring system can be used to get a ‘signature’ for the machine before it is shippedwhich enables any damage during transportationtrials or commissioning to be identified. Pre-delivery checks can also highlight any components that were either faulty as supplied or damaged during installation.

Although some end user customers are starting to specify that condition monitoring must be installed on new machinerymost still view it as a luxury rather than a sound investment. And very few machine builders incorporate condition monitoring as standard.

Vibration monitoring is the principle form of machine condition monitoring for power transmission systems and today there is a vast range of vibration sensors form which to choose. Hansford Sensors is a relatively young company that has recently introduced a new range of vibration sensors for use on rotating machinery. The HS-130 series sensors are compact deviceshaving a small body diameter and a weight of just 30g. These features make the sensors useful where space is limited or heavier sensors could affect the machinery.

With a robust stainless steel constructionprotection to IP65 standard and non-over-braidedfire-retardanttwin-core screened cablethe sensors are capable of withstanding harsh industrial environments. To complement these 100mV/g accelerometersHansford offers the HS-BE series of sensor connection boxes that are easy to useprotected to IP55 and capable of monitoring up to four sensors via BNC connectors.

In some applications users may prefer 4–20mA sensor outputsso Hansford has also introduced the HS420 series of accelerometers to meet this need. As with the HS-130 sensorsthe HS420 models have a robust stainless steel constructionand the 4–20mA signals can be input directly into analogue modules on programmable logic controllers. To mount the sensordifferent threads are available plus there is a choice of Quick-Fit or adhesive mount studs.

Hansford offers a choice of models with side- or top-entry connector and braided cables; there is also a submersible version that is sealed to IP68 and capable of being totally submerged up to a depth of 100m. In the near future Hansford will launch an Atex and IEC Ex certifiedintrinsically safe version of the HS420 for use in potentially explosive areas.

 

Data collection

 

Installing sensors isof courseonly the first step in condition monitoringas the data must be collected in a way that is convenient and appropriate for the application. One option for data collection is handheld units that gather data from the various sensors located around a machine or plant. SKFfor exampleoffers a Wireless Machine Condition Detector (WMCD) for use with its Marlin handheld data manager. Data is collected from smart studs and temperature magnets that measure and record vibrationenveloped acceleration and temperature.

Being compact and wirelessthe detector is easily portable and therefore extremely versatile. Furthermorethe WMCD avoids the problems associated with conventional wired technology.

By enabling operators to observerecord and monitor machine conditions simply and accuratelycorrective action can be taken in a timely manner to optimise productivity levels and minimise downtime. An ‘alert’ condition provides users with an early warning of impending problemswhile a ‘danger’ alarm is activated if the system identifies issues requiring attention to prevent potentially serious consequences.

SKF’s WMCD uses Bluetooth technology to collect and communicate data quickly and accuratelywhich can then be uploaded to the SKF @ptitude Monitoring Suite for viewing and analysing.

While handheld data collectors are adequate for many applicationsothers require remote data collection and machine monitoring. For theseMonitran offers its Vi-sage combined hardware and web-based monitoring system. Vi-sage can also notify personnel via text messaging and email if user-defined vibration levels are reached.

Employing T-mac Technologies’ range of
GPRS-enabled remote monitoring and control systemsthe Vi-sage hardware is available with either eight or 26 input channels and either four or 16 outputs. Users can log into their accounts from any computer with internet access and check near-real-time dataview historical data and control Vi-sage’s outputs. Neill OvendenMonitran’s sales and marketing directorcomments: "By enabling users to access vibration levels via the web we are making visiblefrom anywhere in the worldthe very information that will help companies realise truly
cost-effective remote monitoring and control. There is no need for expensive cablesbespoke software andif all is wella reduced need for site visits."

Vi-sage hardware can either be connected directly to accelerometers and other sensors or they can interface with one or more networks of sensors via Monitran’s Multiselect products. Data is uploaded to a website with secure user accounts. Vi-sage hardware settings are made on the web site and then automatically downloaded to the unitswhere the new configuration takes effect immediately. In additionthe site’s user interface can be customised to present the most relevant data in the most relevant formatand it is easy to set up additional user accounts with appropriate access rights.

Ovenden adds: "It is easy to imagine a scenario where a maintenance engineer may be at home but on call. Upon receipt of an email or text messagethe engineer could access the asset’s condition monitoring system and decide whether corrective measures can be implemented remotely or if a site visit is necessary."

 

Analysis and reporting

 

National Instruments (NI) is known for its virtual instrumentationbut is also involved in condition monitoring systems. Its systems offer connectivity to vibration sensors such as radial and axial proximity probesIEPE (integrated electronics piezo-electric) accelerometersand speed sensors including laser tachometers and Keyphasorsas well as sensors for variables such as temperature or dynamic pressure.

NI condition monitoring platforms range from portable USB plug-and-play systems to embedded Ethernet data loggers with onboard analysis and controlall with high-speed 24-bit measurements. If detailed signal processing is requiredthe National Instruments Sound and Vibration Measurement Suite with the NI Labview graphical development environment provides hundreds of signal processing functions including spectrum analysis and order trackingplus automated report generation on customisable user interfaces.

One of the latest developments from National Instruments is the NI cRIO-9072 and cRIO-9074 Compactrio systems that enable condition monitoring to be installed cost-effectively on high-volume machines. These Compactrio systems have an integrated hardware architecture that combines an embedded real-time processor and a reconfigurable FPGA within a single chassiswhich therefore lowers the cost of Compactrio for volume applications. Engineers can quickly designprototype and deploy the customisablecommercial off-the-shelf hardware systems for embedded machine control and data acquisition systems using Labviewthereby eliminating the need to spend time and money designing custom embedded hardware.

To reduce the cost of Compactrio for high-volume applicationsNI engineers designed the new cRIO-907x systems as integrated systemswith the embedded
real-time processor and FPGA chip on the same circuit board rather than multiple boards as in traditional Compactrio systems. The cRIO-9072 integrated system combines an industrial 266MHz real-time processor and an eight-slot chassis with an embeddedreconfigurable 1M gate FPGA chipwhile the NIcRIO-9074 integrated system contains a 400MHz real-time processor and an eight-slot chassis with an embeddedreconfigurable 3M gate FPGA chip.

National Instruments has also worked with FAGpart of the Schaeffler Groupto develop the hardware for the FAG Procheck condition monitoring system. FAG Procheck is described as intelligenteasy to set uprobust and reliable. In additionthe system’s modular construction means it can readily cater for various condition monitoring and maintenance strategies employed across different industry sectors. For examplethe system is Atex-certified and can therefore be used in hazardous or potentially explosive environmentsand it has a range of communications interfaces so that it can be integrated with a company’s existing plant management or production control and maintenance systems. As well as vibrationfurther parameters such as temperaturepressureloadspeedtorqueoil status and oil quality can be recorded and correlated with the vibration data. Procheck systems can be expanded and customised by means of expansion slots and digital filter algorithms.

Once set upthe system operates automaticallywithout further intervention from the userto measurerecordanalyse and issue alerts on vibration data from rotating plant. Data is subjected to an initial assessment by the Procheck system andif defined alarm limits are exceededalert warnings are generated and sent to defined interfaces – where they undergo further assessment. The system can be configured and adapted either by the machine builderend user customer or by Schaeffler’s maintenance and asset management service divisionFAG Industrial Services (FIS). Communication with Procheck systems can be via network (TCP/IP)serial or modem links.

So far we have discussed mainly vibration monitoringbut temperature can also be an important indicator of condition. Optris offers a broad range of infrared thermometersthe latest of which is the Optris CT laser high-performance series for applications from
-40 to 975¢ªC. One of the main advantages of this sensor is the small spot size that enables accurate non-contact temperature measurements to be made.

It allows low- and high-temperature measurements to be made with a spot size as small as 0.9mm at a range of 70mm without the need for mechanical choppers; maximum measurement range is 1260mm. The CT laser operates in ambient temperatures of up to 85¢ªC without coolinggiving a selectable analogue output of 0/4–20mA0–5/10V or thermocouple type K or J. Alternativelythe CT series infrared thermometers are available with an integrated digital Profibus DPUSBRS232RS485 or Can interface.

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