Software Images icon An illustration of two photographs. Images Donate icon An illustration of a heart shape Donate Ellipses icon An illustration of text ellipses. EMBED for wordpress. Want more? Advanced embedding details, examples, and help! Publication date Usage CC0 1. Org Contributor Public. The reasons for this are briefly discussed in annex A, which also defines some precise relation- ships between the above quantities when the har- monic content of the vibration waveform is known. In order to avoid confusion and to ensure correct in- terpretation, it is important at all times to identify clearly the measurement units [e.
It is common practice, based on experience, when evaluating broad-band vibration of rotating machinery to consider the r. However, other quantities such as displacement or acceleration and peak values instead of r.
In this case, alternative criteria are required which are not necessarily simply related to criteria based on r. The maximum broad-band magni- tude value measured under agreed machine support and operating conditions is defined as the vibration severity. For most machine types, one value of vibration se- verity will characterize the vibratory state of that ma- chine. However, for some machines this approach may be inadequate and the vibration severity should then be assessed independently for measurement positions at a number of locations.
Typical measurement locations are shown in figures 1 to 5. To define the vibrational behaviour at each measuring position, it is necessary to take measurements in three mutually perpendicular directions. The full com- plement of measurements represented in figures I to 5 is generally only required for acceptance testing.
The requirement for operational monitoring is usually met by performing one or both measurements in the radial direction i.
These can be supplemented by a measurement of axial vibration. The latter is normally of prime significance at thrust bearing locations where direct axial dynamic forces are transmitted. Detailed recommendations for specific machine types are provided in the additional parts of IS0 In this case it is important to ensure that all the major components of the machine and structure are installed when testing is carried out. It should be noted that valid comparisons of vibration for machines of the same type but on different foun- dations or sub-foundations can only be made if the foundations concerned have similar dynamic charac- teristics.
IS0 E 6 Figure 3 - Measuring points for small electrical machines Figure 4 - Measuring points for reciprocating engines 7. IS0 E 0 IS0 3. The support structure can significantly affect the measured vibration and every attempt should be made to ensure that the natural frequencies of the complete test arrangement do not coincide with the rotational frequencies of the machine or with any of its significant harmonics.
Additionally, the test arrangement shall not cause a substantial change in any of the major resonance frequencies. If a significant support resonance is present during acceptance testing and it cannot be eliminated, the vibration acceptance tests may have to be carried out on the fully installed machine in situ.
For some classes of machines e. In this case, all the rigid body mode frequencies of the ma- chine on its support system shall be less than one-half of the lowest significant excitation frequency of the machine. Appropriate support conditions can be achieved by mounting the machine on a resilient support baseplate or by free suspension on a soft spring. Where possible, steps should be taken to reduce the magnitude of environmental vibration if it is greater than one-third of the recommended limits.
Particular attention shall be given to ensuring that the vibration transducer is correctly mounted and that its presence does not affect the vibration response characteristics of the machine.
Two mon instrument systems itor broad-band vibrat presently in ion are acce common use to ptable, namely: a instruments which incorporate r. The scaling is based on an assumed sinusoidal relationship between r.
If the vibration evaluation is based on more than one measurement quantity i. It is desirable that the measurement system should have provision for on-line calibration of the readout instrumentation and, in addition, have suitable isolated outputs to permit further analysis as required. Additional vi- bration measurements that may be taken under other conditions are not applicable for evaluation in accord- ance with clause 5.
The evaluation criteria relate to both operational monitoring and ac- ceptance testing, and they apply only to the vibration produced by the machine itself and not to vibration transmitted from outside. For certain classes of ma- chinery, the guidelines presented in this part of IS0 are complemented by those given for shaft vibration in IS0 If the procedures of both standards are applicable, the one which is more restrictive shall generally apply.
One criterion considers the magnitude of observed broad-band. However, these values provide guidelines for ensuring that gross de- ficiencies or unrealistic requirements are avoided. In certain cases, there may be specific features associ- ated with a particular machine which would require different zone boundary values higher or lower to be used. In such cases, it is normally necessary to ex- plain the reasons for this and, in particular, to confirm that the machine will not be endangered by operating with higher vibration values.
The maximum vibration magnitude ob- served at each bearing or pedestal is assessed against four evaluation zones established from international experience. This maximum magnitude of vibration measured is defined as the vibration severity see 3. Different categorization and number of zones may apply for specific machine types, which are cov- ered by the additional parts of IS0 Interim values for the zone boundaries are presented in annex B.
Zone A: The vibration of newly commissioned ma- chines would normally fall within this zone. Zone B: Machines with vibration within this zone are normally considered acceptable for unrestricted long- term operation. Zone C: Machines with vibration within this zone are normally considered unsatisfactory for long-term con- tinuous operation.
Generally, the machine may be operated for a limited period in this condition until a suitable opportunity arises for remedial action. Zone D: Vibration values within this zone are normally considered to be of sufficient severity to cause dam- age to the machine.
The vibration of a particular machine depends on its size, the characteristics of the vibrating body and mounting system, and the purpose for which it is de- signed. It is therefore necessary to take account of the various purposes and circumstances concerned when specifying ranges of vibration measurement for different machine types. For nearly all machines, re- gardless of the type of bearings used, measurements of the broad-band r.
In most cases, it has been found that vibration vel- ocity is sufficient to characterize the severity of vi- bration over a wide range of machine operating speeds. However, it is recognised that the use of a single value of velocity, regardless of frequency, can lead to unacceptably large vibration displacements. This is particularly so for machines with low operating speeds when the once-per-revolution vibration com- ponent is dominant.
Similarly, constant velocity cri- teria for machines with high operating speeds, or with vibration at high frequencies generated by machine component parts can lead to unacceptable acceler- ations. Consequently, acceptance criteria based on velocity will take the general form of figure6. This in- dicates the upper and lower frequency limits fu and 3 and shows that below a defined frequency fX and above a defined frequency fy the allowable vibration velocity is a function of the vibration frequency see also annex C.
The r. IS0 E 0 IS0 For many machines, the broad-band vibration consists primarily of a single frequency component, often shaft rotational frequency. In this case, the allowable vi- bration is obtained from figure6 as the vibration vel- ocity corresponding to that frequency. Examples are the following. The allowable vibration displacement and acceleration should be consistent with the velocity corresponding to the sloped portions of figure6.
The equivalent broad-band velocity can be obtained using equation A. It should be noted that, except for the case when the broad-band vibration consists primarily of a single frequency component, a di- rect comparision of the frequency spectrum com- ponents with the curves of figure6 would yield misleading results. This value should then be evaluated relative to the constant velocity between fX and fv- The evaluation criteria for specific machine types will be given in the additional parts of IS0 as they become available.
Annex C provides additional guid- ance. For certain machine types, it may be necessary to define further criteria beyond those described by figure6 see for example, 5. Zone0 Frequency, f Figure 6 - General form of vibration velocity acceptance criteria 8 A significant increase or decrease in broad-band vibration magnitude may occur which re- quires some action even though zone C of Criterion I has not been reached.
Such changes can be instan- taneous or progressive with time and may indicate that damage has occurred or be a warning of an im- pending failure or some other irregularity. Criterion II is specified on the basis of the change in broad-band vibration magnitude occurring under steady-state op- erating conditions.
When Criterion II is applied, the vibration measure- ments being compared shall be taken at the same transducer location and orientation, and under ap- proximately the same machine operating conditions. Significant changes from the normal vibration magni- tudes should be investigated so that a dangerous situation may be avoided.
Criteria for assessing changes of broad-band vibration for monitoring purposes are given in the additional parts of IS0 However, it should be noted that some changes may not be detected unless the dis- crete frequency components are monitored see 5. ALARMS: To provide a warning that a defined value of vibration has been reached or a significant change has occurred, at which remedial action may be nec- essary. In general, if an ALARM situation occurs, op- eration can continue for a period whilst investigations are carried out to identify the reason for the change in vibration and define any remedial action.
General guidelines 3 Measurement procedures The measurement procedures and instrumentation shall comply with the general requirements of ISO and are as follows. Pages with related products. A significant increase or decrease in broad-band vibration magnitude may occur which requires some action even though zone C of Criterion I has not been reached. This includes gas turbines directly coupled to other prime movers such as steam turbines, but the evaluation of the steam turbine vibration is not dealt with in this part of ISO see the following exclusion list.
If the TRIP value is exceeded, immediate action should be taken to reduce the vibration or the machine should be shut down. Such conditions allow for small changes in variables such as generator power output at the normal operating speed. The characteristics of the measuring system should be known with regard to the effects of the environment including: Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
It should be noted, however, that the vibration of a gas turbine can be influenced by its mounting system and coupling arrangement to driven machines. When Criterion II is applied, the vibration measurements being compared shall be taken at the same transducer location and orientation, and under approximately the same steady-state operating conditions of speed, load, and thermal condition.
However, experience with a specific machine may prescribe a different value. For gas turbines, the measurement system used shall be capable measuring broad-band vibration over a frequency range from 10 Hz to at least six times the highest shaft rotational frequency. Annexes B and C are for information only. It must be recognized, however, that these criteria do not form the only basis for judging the severity of vibration.
Write a customer review. Please first verify your email before subscribing to alerts. Isi Inspire Digital Educational Resources. Generally, the machine may be operated for a limited in this condition until a suitable opportunity isso for remedial action. All standards are subject to revision, and parties to agreements based on this part of ISO are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below.
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