10 Questions For PdM

1. One method to determine the amount of impacting in a machine is to view the time waveform and the Crest Factor.

True

False

This is one good tool in working with time waveform data. Another way is to assess true peak-to-peak values.

Explanation

This is one good tool in working with time waveform data. Another way is to assess true peak-to-peak values.

2. Cross-channel phase measurements at running speed are often used to see relative motion of machine components.

True

False

. This is a nice tool to help isolate several types of vibratory issues, including couple unbalance, misalignment, soft foot, etc.

Explanation

. This is a nice tool to help isolate several types of vibratory issues, including couple unbalance, misalignment, soft foot, etc.

3. While taking data on a machine with a variable loading, the machine speed is actually shifting by 25% or more. Data presentation appears smeared in frequency. The Order Tracking technique will address this.

True

False

In fact, the sampling rate with Order Tracking is automatically adjusted to keep the 1X frequency at a nice distinct line, with speed changes from half to twice.

Explanation

In fact, the sampling rate with Order Tracking is automatically adjusted to keep the 1X frequency at a nice distinct line, with speed changes from half to twice.

4. With Demodulation, it is possible not only to see the early stages of a rolling element bearing defect, it can pinpoint the actual fault.

True

False

This is true, if and only if, the bearing is known and all characteristic frequencies are published. Then the BPFI, BPFO, FTF, and BSF fault frequencies can be overlaid on the spectra plot.

Explanation

This is true, if and only if, the bearing is known and all characteristic frequencies are published. Then the BPFI, BPFO, FTF, and BSF fault frequencies can be overlaid on the spectra plot.

5. Looking at the time waveform data can sometimes be a deciding factor as to whether a vibration problem is due to unbalance or misalignment.

True

False

Unbalance is usually shown as a nice clean 1X sine wave. Misalignment will have a distinct “W” or “M” pattern to it.

Explanation

Unbalance is usually shown as a nice clean 1X sine wave. Misalignment will have a distinct “W” or “M” pattern to it.

6. In balancing an overhung rotor, a one-plane solution with one transducer will get the job done.

True

False

This problem is a challenge for even the most experienced balancing technician. There are static and couple forces present which typically require a two-plane solution and 2 or more transducer inputs.

Explanation

This problem is a challenge for even the most experienced balancing technician. There are static and couple forces present which typically require a two-plane solution and 2 or more transducer inputs.

7. A portable data collector with an accelerometer is measuring force from rotating equipment. For a machine nominally running at 1785 RPM, a velocity only measurement should be good enough with an Fmax at about 10X.

True

False

. It all depends on machine make-up and whether there are rolling-element bearings, a gearbox, etc. It may be necessary to have a high frequency acceleration reading and a Demod as well.

Explanation

. It all depends on machine make-up and whether there are rolling-element bearings, a gearbox, etc. It may be necessary to have a high frequency acceleration reading and a Demod as well.

8. In just looking at high-frequency acceleration data alone, one can oftentimes detect early signs of rolling-element bearing problems.

True

False

A raised noise floor and “haystack” will show up in the upper end of the spectral display.

Explanation

A raised noise floor and “haystack” will show up in the upper end of the spectral display.

9. When a high 1X vibration component is present, the balancing team should be called out to get the equipment back to its normal running condition.

True

False

More data needs to be examined before making the call for correction. Trends should be examined and other potential sources of vibration, such as looseness, resonance, etc. should be ruled out first.

Explanation

More data needs to be examined before making the call for correction. Trends should be examined and other potential sources of vibration, such as looseness, resonance, etc. should be ruled out first.

10. Demodulation techniques for finding rolling element bearing defects are band passing at high frequencies and do not work for slow speed equipment.

True

False

Impacting of metal-to-metal contact on bearing defects excite high natural resonance frequencies that are picked up in the band pass. This is true for low speeds as well, and the technique has proven to work quite well.

Explanation

Impacting of metal-to-metal contact on bearing defects excite high natural resonance frequencies that are picked up in the band pass. This is true for low speeds as well, and the technique has proven to work quite well.

10 Questions For Pdm