Selecting the Right Vibration Monitoring Strategies for Your Machinery

Hybrid Approaches: The Key to Effective Vibration Monitoring

When it comes to monitoring the vibration of machinery throughout your plant, there are several factors to consider in order to determine the best strategy for you. Each piece of equipment should be handled individually, rather than taking a one-size-fits-all approach with purely wireless sensors, wired systems, or route-based collection.

This type of strategy could compromise the benefits of monitoring the condition of your machinery. The most successful programs will typically utilize a hybrid approach of portable collection, wireless, and wired systems. The differentiators that shape a strategy include:

Machine Types – How Does It Run?

It is difficult to define a strategy for vibration monitoring based on machine type, because of the differentiators mentioned above and what the actual machine is (e.g. fan, pump, compressor) don’t matter as much as the frequencies each component of a machine train generates. Below are some important things to consider about your machine(s):

• Bearings: What types of bearings? Rolling element or journal/sleeve?
• Speed: How fast does it run?
  • Are there belts, chain drives, or gearboxes that change speed from driver to driven?
  • Is it variable speed? If so, how does it vary during operation?
• Orientation: Is the orientation vertical or horizontal? Overhung or Centerhung?
• Mounting: Is the mounting rigid or flexible?
• Frequency: What are the expected frequencies of interest?
  • How close are these frequencies to each other?
  • What are the highest and lowest frequencies we need to see in our data?

Operation

How a machine operates can also direct your hardware selection. Different operating modes can have an effect on vibration. Varying levels of speed, pressure, load, viscosity, impacting, etc. could be relevant to your pursuit. Additionally, does the machine run intermittently like a batch process or 24/7 or somewhere in between? This could influence how you collect data – moving from a scheduled ‘X’ times per day to only collecting when defined operating conditions are met.

Criticality

The criticality of a machine can be defined a number of ways. The most common include:

The strategy for your least critical machines is likely not the best solution for your most critical and vice versa. Knowing the criticality of your machines will point you towards which machines to outfit with hardware first. You may have a problem piece of equipment that is top-of-mind for monitoring hardware, but it is low criticality and should be lower on your list.

Environment/Accessibility

Environmental impact is covered as a part of the criticality section. This section is meant for the environment the equipment lives in day after day.

• How harsh is it?
• Is it intrinsically safe or radiologically hot?
• Are there other chemicals present?
• Is it too hot or too cold for a person to comfortably work regularly?
• Is it in a hard-to-reach area or confined space?
• Is it in a remote location?

Some of these obstacles can be overcome with permanently mounted sensors routed to a junction box so that portable route data can still be collected. Others would require automatic collection with either a wired or wireless system.

Failure Mode

How a machine fails, and most importantly, how quickly a problem can develop and cause failure is important to identify. It is also important to estimate the likelihood of these potential failures. For example, a fan can be thrown out of balance relatively easily, but with proper monitoring, it is something you can watch develop over days, weeks, months, or years. Conversely, the cage on a bearing can crack and fail in seconds or hours. So, how often you measure is the difference between catching and missing these different failure modes.

Personnel

The plant personnel supporting this reliability effort are, of course, paramount to the success of the program. It is important to consider their:

• Time: If they are stretched thin, time is better spent analyzing/correcting issues than collecting data and not having the time to analyze?
• Experience: Analyzing FFT and time waveform data is where the true value of vibration monitoring resides. Relying only on overall data does not give enough information to determine the component causing an increase in amplitude.
• Coordination: Some plants have collection duties split between departments like electrical and mechanical which could make coordinating schedules difficult. Additionally, some machines don’t run all the time, and scheduling your route for when it is running could be difficult.
• Safety: Speaks for itself.

Visualization

As we know, collecting the right data at the right time is critical to success. However, the visualization tools you use for viewing that data are also key. Different departments may want access, and they may want different levels of data. Operators will want to know when their machines are in alarm, and maybe overall trends. Maintenance will want to know what machines are in critical condition. Management will want a plant wide overview.

The analyst will want to see everything from the overview to the spectra and time waveforms. The information needs to be easy to access and ideally, all in one place. Finding a hardware + software solution that can communicate the right levels of information to the right people will boost plant-wide communication and promote success.

Both Acoem’s NEST Vision and NEST i4.0 predictive maintenance software can provide your plant with an overview of machine health:

Vibration Monitoring Strategies

In summary, the strategy you deploy at your plant is dependent upon not only your machines but also the circumstances around that machine. Acoem has found that the best approach starts with knowing the criticality and failure modes of your equipment. Then consider how it runs and operates.  Finally, consider the environment and personnel. From there, you can define what you need to properly monitor. Of course, there will be scenarios where more than one piece of hardware can do the job, so consider what is most important and factor your ROI into the decision:

• Portable

• Hybrid: Portable + Online (Wireless and Wired)

• Online: (Wireless or Wired)

The following chart provides a comparison chart into the essential features of different monitoring methods. The following specifications are based on Acoem’s technology but should still provide insight into the advantages of each method: