Remote monitoring
January 1st 2005

David Dutton, operations manager of VCI looks at the advantages offered by a remote monitoring system

Predictive maintenance is in principle very simple; it works by monitoring the condition of a machine in service giving the opportunity to plan for maintenance when it is required and more importantly before failure occurs. It is reliant on the collection of measurement data at regular intervals. Although there are a variety of parameters that can be measured on a machine, vibration is probably the most important and informative of them all. This parameter is the only one that can provide information on the severity of the problem and also help to determine the cause(s) of the problem(s). The readings are monitored for change, and it is the rate of the change that predictive maintenance systems are observing since this is far more informative than absolute “snapshot” levels. It is not uncommon to initially find high readings and then discover over the course of time that these are the normal operating levels, which do not affect the mechanical condition of the machine and are thus acceptable.

Although the idea of predictive maintenance is simple there are many different ways it can actually be implemented. The most common is through the use of a hand held data collector which requires an individual to collect the required data from the machines at predetermined measurement positions and then to transfer the data to a base computer.

This method however has a number of significant drawbacks: • It can be time consuming to collect the necessary data.

• It is necessary for the individual collecting the data to be trained (this is an area that has recently been addressed by BINDT by the introduction of ISO certified training courses) • It leaves the system open to the possibility of user error or misuse.

• Data collection can be missed due to absenteeism, or poor system management.

• Machinery may be located in dangerous and/or remote locations.

Increasingly it has been recognised that these problems can be overcome by the use of fixed monitoring systems. Until recently these systems were quite rudimentary and had limited functionality generally giving only overall data without the facility to determine the fault. However, there have been significant developments as manufacturers recognise the need for their systems to be able to provide more detailed, informative and useful data by the use of software packages and communications enhancements. This is particularly driven by the modern business environment that requires reduced maintenance costs with increased reliability from their products and facilities.

The VCI/Dtect has been developed for use in locations that are generally unmanned such as wind-farms, which are often in very inhospitable and isolated locations. The system comprises of a small processor unit, that can store a substantial amount of data onboard, with the appropriate amount of sensors mounted on the generator and gearbox and constantly monitors and stores the maintenance parameters setup in the associated software package. This type of system has major advantages over handheld systems, as it provides continuous data collection and storage without operator involvement thus reducing the possibility of erroneous data caused by operator error.

A remote monitoring system needs to be versatile in the way it communicates with its host computer, the data collected by the VCI/Dtect remote monitor, for example can be transmitted via several different methods. This transfer of data can be by email, Ethernet, GSM, public telephone networks, satellite phone, radio, fibre optic cable, the Internet and download to a laptop using a simple serial cable.

Many machines operate at various running speeds during normal operations and can have varying acceptable vibration levels. Applications where the VCI/Dtect has successfully been applied for variable speed machines include large turbochargers (with speeds typically ranging from 5000 to 15000 rpm) which couldn’t be monitored in a meaningful way by the older generation of condition monitoring systems. The VCI/Dtect can not only measure both vibration and speed but is able to relate the two variables and this allows meaningful alarm trending to be introduced. It is also possible to monitor other parameters such as temperature, pressure or displacement with the VCI/Dtect providing the correct sensors are used. The data collected by systems like the VCI/Dtect is very detailed; and can be used to diagnose and determine the cause of developing faults and poor refits or overhaul work. The system can retain the machines life history which can then be evaluated anywhere in the world thanks to modern communication technology. This data can not only be used to pre-plan maintenance but could also potentially aid in the development of new machines if a specific node of failure is identified.

Additionally the VCI/Dtect system also has the capability to provide an output signal, which can be linked to a shutdown system to reduce the potential damage should a sudden change in condition occur e.g.

blade failure of a turbine.

Remote monitoring systems are designed to run continuously without maintenance and therefore are particularly suited to applications where monitoring can directly increase profitability such as; remote pumping stations, inaccessible or dangerous locations of power stations or chemical plants, remote rigs at sea and as already widely proven wind farms.

The VCI/Dtect has a low capital cost when compared both to the cost of the assets being monitored and the costs incurred by downtime, production delays or missed targets. Further the use of remote monitoring has additional financial benefits; it negates the need for in-house vibration expertise, costs associated with training and loss of qualified staff.

If specialist help is needed to interpret the data produced by the remote monitoring system it can be outsourced when required to specialists in the predicative maintenance field. Insurance companies and classification societies are recognising the benefits of such systems and it may be possible to gain further financial benefits from reduced premiums or restrictions.