7.8 LIMITS OF BEARING HOUSING VIBRATION
The following limits of vibration are for machines running at no load, uncoupled, and resiliently mounted
according to paragraph 7.6.1. For machines tested with rigid mounting, these values shall be reduced by
multiplying them by 0.8.
Vibration levels shown in the following paragraphs represent internally excited vibration only. Machines as
installed (in situ) may exhibit higher levels. This is generally caused by misalignment or the influence of the driven or driving equipment, including coupling, or a mechanical resonance of the mass of the machine with the resilience of the machine or base on which it is mounted. Figure 7-6 establishes the limits for bearing housing vibration levels of machines resiliently mounted for both unfiltered and filtered measurements. For unfiltered vibration the measured velocity level shall not exceed the limit for the appropriate curve on Figure 7-6 corresponding to the rotational frequency. For filtered vibration the velocity level at each component frequency of the spectrum analysis shall not exceed the value for the appropriate curve in Figure 7-6 at that frequency. Unfiltered measurements of velocity, displacement, and acceleration may be used in place of a spectrum analysis to determine that the filtered vibration levels over the frequency range do not exceed the limits of the appropriate curve in Figure 7-6. For example, for the top curve in Figure 7-6 the unfiltered velocity should not exceed 0.15 in/s peak (3.8 mm/s), the displacement should not exceed 0.0025 inch (p-p) (63.5 microns), and the acceleration should not exceed 1g (peak).
NOTE"”International Standards specify vibration velocity as rms in mm/s. To obtain an approximate metric rms
equivalent, multiply the peak vibration in in/s by 18.
Note that they use the unfiltered vibration in lieu of filtered vibration as long as the unfiltered vibration meets the limit. The logical basis for this is that the unfiltered vibration refers to the overall and the filtered vibration refers to individual spectral peaks. Both are given here in units of "peak". There is no limit imposed on "true peak" by these specifications. (whether or not there should be is a different question).
Also note they suggest the factor of 18 (=25.4/sqrt2) for converting between peak ips and rms mm/sec.
The assumptions inherent in this terminology:
"peak overall" is NOT the same as "true peak". (twf peak)
peak overall is defined as sqrt(2) times rms overall.
If you intend to compare your vibration to the NEMA MG-1 specifications, the easiest way is to express your overalls in "peak". If you use Entek equipment, your meter and software will facilitate this comparison by displaying the spectrum and the overall in units of peak / 0. I am very sure there are many other standards and instruments that use the same conventions. I am also pretty sure that at least 75% of people in the US state their housing velocity overalls in units of ips pk/0 (as I have defined, not as true peak).
The fact that Entek Emonitor does it the wrong way is not a justification.
I have already agreed with you that rms overall is a more logical way to express an overall. BUT what is the most logical to us is not the ONLY way to do it. The fact that you happen to prefer a different terminology does not make this terminology wrong.