Good vibrations

From wireless technology to mathematical modelling, there are monitoring systems to guard against expensive equipment failure in many industries. Colin Carter reports.

Monitoring the condition of equipment is big business. Think of the consequences of unnecessary downtime in the oil industry where prices are so high it would not take many lost barrels to lose a significant amount of money.

There has been innovation in this field in recent years. One example that has received attention over the past year is the first energy-independent condition monitoring system with wireless data transmission.

Developed by Pruftechnik Condition Monitoring, together with its partners Perpetuum and Nanotron Technologies, the system harnesses vibration energy to use as a power source for the vibration monitoring of fixed speed rotating machinery. The benefit is that power and cabling costs are minimised — leading to claimed savings of up to 50 per cent of costs in these areas.

Another innovative approach to machine condition monitoring has been developed from NASA technology by Artesis in Ankara, Turkey. The Artesis MCM system uses a mathematical modelling technique to detect and diagnose faults in electric motors and connected equipment from the electrical behaviour of the motor itself.

The system operates by defining the electromechanical properties of the motor and associated equipment during a ‘self-training’ process whereby the three input voltages and three output currents are continuously measured and processed to determine the model parameters under a full range of operating states. As part of this process a ‘normal’ operating state is defined mathematically.

When a fault begins to develop anywhere in the system this has an effect on the output current waveform. By matching changes against the equivalent physical characteristic of the motor or driven system and assessing the severity of the change, the software can determine whether performance is ‘normal’ or not and what action needs to be taken.

Most of the common mechanical faults associated with electric motor-driven equipment, from unbalance and misalignment to bearing problems can be identified by the diagnostic system.

The system can only be used where electric motors are employed, but with everything from the largest oil plant to everyday consumer items being packed with motors these days there is plenty of scope for use.

In the water industry MCM’s systems monitor equipment providing city water services. MCM cites one example where a water company had little diagnostic expertise and wanted a system that would do most of the routine analysis for them. As much of its equipment was located in remote sites spread over a wide area, access problems meant it needed a permanently-installed system.

In the first year of operation it is claimed maintenance costs were reduced by some 10 per cent and that after three years no unpredicted breakdowns occurred on equipment covered by the system. This has led to an extensive retrofit programme and the inclusion of Artesis MCM units as standard in all new build specifications.

Condition monitoring is also ‘an essential factor in ensuring continous supply from wind turbines’ according to Andreas Kuel, condition monitoring specialist at FAG Industrial Services in Germany. The company has installed 49 WiPro (Wind Turbine Protection) systems across two sites in Victoria, Australia. At Codrington Wind Farm there are 14 turbines, each with an output of 1.3MW, and at Challicum Hills Wind Farm 35 turbines have an output of 1.5MW each.

The online condition monitoring system, developed jointly with National Instruments, can handle up to 16 channels of sensor information with additional analogue and digital input and output to enable it to apply to single machines or to monitor complete systems such as the wind farms.

Individual turbines at the two wind farms are linked by GSM (satellite) at the Challicum Farm site and by Code Division Multiple Access (CDMA) modems at Codrington, as the network coverage doesn’t allow a sufficiently strong signal. The CDMA modems have the advantage that information can be shared over the internet, but with lower data security levels.

The wind farms are connected to a service station run by Condition Monitoring Services Australia (CMSA) for the remote monitoring of the turbine data, where the data is analysed and any maintenance activity initiated to prevent turbine component failures.

Another energy-related application is in the condition monitoring of more than 1,500 components used on the 1,776km Baku-Tbilisi-Ceyhan crude oil pipeline, which carries oil from Azerbaijan through Georgia and across to Turkey’s Mediterranean coast for distribution.

The pipeline is mostly underground and transports around one million barrels of crude oil per day. AV Technology is responsible for the condition monitoring of components such as pumps, fire pumps, emergency generators and other equipment making up the 1,500 or so pieces.

In addition to always having a pair of eyes on-site for visual inspection, the regime is largely based on vibration monitoring of the components, although monitoring of lubricating oils and pressure and temperature is also undertaken. The result for pipeline operating company Botas is that production problems have been averted as machinery problems were identified before failure occurred.

This illustrates that the cost of implementing condition monitoring of plant can far outweigh the expense of installation.