There are many reasons to consider an online vibration monitoring system.
Criticality. This is the most common reason why online monitoring systems are installed. Air compressors, main mill drives, chillers, or any potential production bottlenecks are the primary candidates.
Safety. Rotating equipment can be dangerous to be around. Excessive noise, heat or moving product can be a treacherous environment in which to work. Often guards, interlocks, safety devices, and other safety-related obstructions prevent us from getting good data. This is especially true in containment areas, hazardous locations and in confined spaces.
Accessibility. Just because the machine is visible does not mean that it is accessible. The area may be restricted, moving equipment may block access to it, or the critical asset itself may move (such as a locomotive or mining equipment that is not readily accessible.) Complicating considerations are commonly related to cost, logistics or manpower.
Remote locations. Distant pumping stations, offshore platforms, or a shipboard machinery at sea may make onsite data collection and analysis very difficult and expensive to justify. An online monitoring system can be the ideal solution for these situations.
Time & Cost. Often an asset runs intermittently or is only used in certain cycles. Sometimes the cost of assigning a person to collect the data and the time it takes to travel to and from an asset is greater than the value of the data it offsets. If this cost and time, including waiting time for the machine to run a cycle, exceeds the perceived value of the manually collected data, on online system might be considered.
New Equipment. An online system may be useful for new rotating assets, especially if they embody a new design for which little or no historical data exists, or involve high criticality or just need to be monitored to ensure they function correctly through the new equipment break-in period or warranty period.
Older equipment. If an asset needs to be nursed through late life cycle stages and monitored for continued proper operation even though it is entering the wear-out zone of its components, an online system will give the information needed to make those judgment calls or to buy enough time to get through a production run.
Unique Machinery. For machines that are one-of-a-kind, unusual, or might contain a great deal of foreign content whose replacement parts have a long delivery lead time, an online system will give the advance warning one needs to avoid service disruptions.
High Accuracy. Primarily in machining processes, or for highly precise machinery that has no tolerance for deviation, online systems can provide advance early warning of developing problems and other critical information as to operating conditions, correlate conditions that can lead to problems in production quality and provide the clues required to avoid recurrence of future problems.
Quality Control. Cost has historically been a limiting factor in this area. Most QC relies on a trained eye, or post production inspection and measurement. An online system may provide real-time QC information as product is being made, as problems are being caught, or before a batch or a production run has to scrapped, re-worked or treated as "seconds".
Repeatability. With data collected from an online system, one always gets consistent data from the same sensor mounted at the same angle, with the same pressure, time after time. The only real change from one reading to the other, once adjusted for changes in operating parameters, is the condition of the machinery itself. An online system will capture very small deviations long before they turn into problems. This is especially valuable on very sensitive equipment.
Always on. An online condition monitoring system delivers data with never a break and is always available. A complete set of data is obtained instead of mere chunks of data sporadically collected by hand.
Protection. Online systems can be configured to enable an output relay upon alert and/or absolute fault. This is something that is best done after some time has been spent looking at the historical data and trends. Establishing "alert" and "alarm" levels can protect the equipment being monitored. You can also use an output relay to a flashing light or audible alarm.
Intermittent duty. Much time is wasted waiting for a machine to reach a steady state or run at a certain speed or run at all when collecting route-based vibration data. An online system will run the route unattended, and can be set to collect data only when certain parameters are met such as a certain speed or temperature, or at particular times.
Remote diagnostics. Online systems permit remote or off-site analysis of data, reducing dependence on local expertise. It is therefore easier to trend, correlate and diagnose.
True Machinery Condition. Vibration is conditional and subject to many variables such as speed, load, temperature, pressure, power supply, valve condition etc. An online system can record and store these additional inputs and can trend and cross reference this data.