ISO MECHANICAL VIBRATION – EVALUATION OF MACHINE VIBRATION BY MEASUREMENTS ON ROTATING SHAFTS – PART 3: COUPLED . Mechanical vibration – Evaluation of machine vibration by measurements on rotating shafts – Part 3: Coupled industrial machines (ISO. Full text of “IS/ISO Mechanical vibration – evaluation of machine vibration by measurements on rotating shafts, Part 3: Coupled Industrial Machines”.
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Isk main task of technical committees is to prepare International Standards. Draft 77919-3 Standards adopted by the technical committees are circulated to the member bodies for voting. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. This second edition cancels and replaces the first edition ISO ISO consists of the following parts, under the general title Mechanical vibration — Evaluation of machine vibration by measurements on rotating shafts: Machine sets in hydraulic power generating and pumping plants?????
Evaluation criteria, based on previous experience, are given for use as guidelines for assessing the vibratory conditions of such machines. A general description of the principles that are generally applicable for the measurement and evaluation 79119-3 shaft vibration of izo machines is outlined in ISO Coupled industrial machines 1 Scope This part of Isl gives guidelines for applying evaluation criteria of shaft vibration under normal operating conditions, measured at or close to the bearings of coupled industrial machines.
These guidelines are presented in terms of both steady running vibration and any amplitude changes which can occur in these steady values. The numerical values specified are not intended to serve as the only basis for vibration evaluation since, in general, the vibratory condition of a machine is assessed by consideration of both the shaft vibration and 79193- associated structural vibration. In particular, the conditions for in-situ operation, performing acceptance tests and the influence of bearing clearance given in ISO shall be taken into account when evaluating the shaft vibration of pumps This part of ISO is neither applicable to land-based steam turbine-generator sets for power stations with outputs greater than 50 MW see ISOnor machine sets in hydraulic power generating and pumping plants with outputs of 1 MW or greater see ISO 79199-3 For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document including any amendments applies. ISOMechanical vibration of non-reciprocating machines — Measurements on rotating shafts and evaluation criteria — Part 1: In industrial machines, shaft vibration relative to the bearing is normally measured. Therefore, unless stated otherwise, this part of ISO always refers to relative vibration displacement.
For monitoring purposes the measuring system shall be capable of covering overall vibration isi to a frequency equivalent to 2,5 times the maximum service speed. Iao, it should be noted that for diagnostic purposes it might be desirable to cover a wider frequency range.
The vibration magnitude is the higher value of 77919-3 peak-to-peak displacement measured in two selected orthogonal measurement directions. The values presented are the result of experience with machinery of this type and, if due regard is paid to them, acceptable operation can be expected.
If only one measuring direction is used, care should be taken to ensure that it provides adequate information see ISO The 79193- are presented for the specified steady-state operating conditions at the rated speed and load ranges.
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They apply for normal slow changes in load but do not apply when different conditions exist or during transient changes, for example during start-up and shut-down jso when passing through resonance ranges. In these cases alternative criteria are necessary. It should be noted that overall judgement of the vibratory state of a machine is often made on the basis of both shaft relative vibration as defined above and of measurements made on non-rotating parts see ISO . One criterion considers the magnitude of the observed broad-band relative shaft vibration; the second considers changes in magnitude, irrespective of whether they are increases or decreases.
Caution should be exercised when ios the criteria presented in Annex A to ensure that no contact occurs between the rotating shaft and stationary parts. Therefore, in certain cases the shaft displacement limits isp in this part of ISO may exceed the available clearance. In such cases the evaluation zone limits should be adjusted accordingly.
Vibration magnitude at rated speed under steady operating conditions This criterion is concerned with defining iwo for ios vibration magnitude consistent with acceptable dynamic loads on the bearings, adequate margins on the radial clearance envelope of the machine, and acceptable vibration transmission into the support structure and foundation.
The maximum shaft vibration magnitude observed at each bearing is assessed against four evaluation zones established from international experience. The vibration of newly commissioned machines normally falls within this zone. Machines with vibration within this zone are normally considered acceptable for unrestricted long- term operation. 79119-3 with vibration within this zone are normally considered unsatisfactory for long-term continuous operation.
Generally, the machine may be operated for a limited period in this condition until a suitable opportunity arises for remedial action. Vibration values within this zone are normally considered to be of sufficient severity to cause damage to the machine.
The recommended values illustrated in Figure A. These values are not intended to serve as acceptance specifications, which shall be subject to agreement between the machine manufacturer and the customer.
However, they provide guidelines for ensuring that gross deficiencies or unrealistic requirements are avoided. In certain cases, there can be specific features associated with a particular machine, which would require different zone boundary values lower or higher to be used.
For example, with 799-3 tilting pad bearing it might be necessary to specify alternative vibration values, whilst in the case of an elliptical bearing different vibration criteria can apply for the directions of maximum and minimum bearing clearance.
In particular, it should be recognized that the allowable vibration can be related to the journal diameter since, generally, running clearances will be greater for larger diameter bearings.
Consequently different values can apply for measurements taken at different bearings on the same 791-93 line. In such cases, it is normally necessary to explain the reasons for this and, in particular, to confirm that the machine will not be endangered by operating with higher vibration values. Higher values of vibration can be permitted at other measuring positions and under transient conditions, such as start-up and run-down including passage through critical speed ranges.
Change in vibration magnitude This criterion provides an assessment of a change in vibration magnitude from a previously established reference or baseline value for particular steady-state isl. A significant increase or decrease in shaft vibration magnitude can occur which would require some action even though zone C of Criterion I has not been reached. Such changes can be instantaneous or progressive with time and can indicate that damage has occurred or be a warning of an impending failure or some other irregularity.
Criterion II is specified on the basis of the change in shaft vibration magnitude occurring under steady-state operating conditions. The reference value for this criterion is the typical, ixo normal vibration, known from previous 719-3 for 7199-3 specific operating conditions.
A decision on what action can be taken, if any, should then be made after consideration of the maximum value of vibration and whether the machine has stabilized at a new condition.
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 machine operating conditions. For example, the propagation of a crack in a rotor can introduce a progressive change in vibration components at multiples of rotational frequency, but their magnitude might be small relative to the amplitude of the once-per- revolution rotational frequency component.
Consequently, it can be difficult to identify the effects of the crack propagation by looking at the change in the broad-band vibration only. Therefore, although monitoring the change in broad-band vibration will give some ios of potential problems, it might be necessary in certain applications to use measuring and analysis equipment which is capable of determining the iao of the vector changes that occur in individual frequency components of the vibration signal.
This equipment can be more sophisticated than that used for normal supervisory monitoring and its use and application requires specialist knowledge. Hence, the specification of detailed criteria 791-3 measurements of this type is beyond the scope of ixo part of ISO However, for those machines for which continuous monitoring of vibration is employed, it is common practice to establish operational vibration limits.
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 719-3.
Io general, if an ALARM situation occurs, operation can continue for a period whilst investigations are carried out to identify the reason for the change in vibration and define any remedial action. To specify the magnitude of vibration beyond which further operation of the machine may cause damage. If the TRIP limit is exceeded, immediate action should be taken to reduce the vibration or the machine should be shut down. Different operational limits, reflecting differences in dynamic loading and support stiffness, may be specified for different measurement positions and directions.
The values chosen will normally be set relative to a baseline value determined from experience for the measurement position or direction for that particular machine. Where there is no established baseline for example, with a new machine the initial ALARM setting should be based either on experience with other similar machines or relative to agreed acceptance values.
After a period of time, the steady-state baseline value will be established and the ALARM setting should be adjusted accordingly. If the steady-state baseline changes 7919- example, after a machine overhaulthe ALARM setting should be revised accordingly. Different operational ALARM settings may then exist for different bearings on the machine, reflecting differences in dynamic loading and bearing support stiffnesses.
The values used will, therefore, generally be the same for all machines of similar design and would not normally 79119-3 related to the steady-state baseline value used for setting ALARMS.
General guidelines  ISOMechanical vibration — Evaluation of machine vibration by measurements on non-rotating parts — Part 3: Rotodynamic pumps for industrial applications, including measurements on rotating shafts?????
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