Does any one has experience with vibration analysis for Earthmoving equipments and Heavy duty Engines ranging from 180 KVA to 2000 KVA.
Pls share....

Thanks for your time.

Bala.

Are you talking about draglines, shovels, and MG sets??

Dave

Bala,

One of the essentials in both vibration diagnostics and condition monitoring using vibration analysis is getting data when the equipment is both loaded, and in a "steady-state" condition (load and/or speed not changing). This is probably the most challenging aspect of capturing data on earthmoving equipment. Many problems do not show up unless under load and for these machines many times the load is not maintained long enough to get repeatable data from one condition monitoring survey to the next (if you try to capture data in a conventional way).

For machines that remain loaded and at steady state for only a couple moments you will probably have to deviate from the normal routine of 4 averages for your data collection and set the gain on your data collector manually so that when you time the pushing of the "collect data" button on your data collector, it actually grabs some data instead of trying to go through its auto-gain routine and then capture 4 sets of data to average. You may also have to settle for less resolution in your FFT because even one data block from the time domain may be too long if you have the resolution set to 3200 FFT lines! You may have to settle for only 400 lines in order to get a shorter time block. You may also do more of your analysis in the time domain and set up a time block of data that is actually long enough to capture the whole cycle of an event, so you can "see" the complete motion in the time domain to make sure you are not missing something.

Vendor Warning! - MAARS makes an on-line system designed for use in mobile equipment like earthmoving equipment and cranes. It was designed for these types of applications by having the entire electronics enclosure isolated on rubber mounts and also by having the internal electaronics isolated on soft mounts. This helps the electronics survive the harsh conditions. The system is equipped with a variety of means to trigger automatic data capture on multiple channels of data when relays and speed sensors indicate conditions are correct to capture repeatable data. This makes the trends valid for comparison over a long period of time.

If you can get a handle on the above issues relative to acquiring data with the machine loaded in a repeatable fashion, the analysis method is comparable to other rotating and reciprocating machinery. You also have to take into consideration that, compared to fixed machinery on concrete foundations, the mobile equipment is likely to have higher levels and more resonance issues due to variable speeds, impacts from the work, harmonics from reciprocating engines, and support structures that are both lower mass and less stiff.

Skip Hartman

We have a customer who is taking very successful measurements on draglines and shovels at a coal mine. Skip makes good points, except I would go even further.

Consider that the load on a dragline is always changing. The weight of the cable reeled in is significant, so the speed increases as the bucket is lifted. The result is smeared data. Rather than a peak in the vibration signature, there's a "mound" of data. Clearly, less resolution is better, even down to 50 or 100 lines. This of course also shortens acquistion time, which is an advantage too.

Less resolution. Less averages. Lots of effort to make sense of smeared data. It works, but it's not easy.

Jon
Spintelligent Labs