Condition Monitoring

TechNote #CM9 OMNITREND®

Carrying out RPM-normalized measurements efficiently withthe ‘TrainSpeed’ function

Brief descriptionThe RPM is required for the normalization of shockpulse measurement (roller bearing condition) andfor the calculation of RPM-variable damagefrequencies. The RPM at any measurement locationof a machine train can be calculated using the‘TrainSpeed’ function in OMNITREND - provided that areference RPM and the corresponding translation ratiobetween the reference point and the respectivemeasurement location is known.This TechNote shows how to set up the necessarymeasurement parameters in OMNITREND and howto carry out the measurement with VIBXPERT aspart of a route.

Suitable for...Machine trains with a number of measurementlocations at which the RPM of the machine elements isdifferent due to gear translation.

AdvantagesThe RPM no longer needs to be measured at eachmeasurement location, but at a single ‘referencemeasurement location’. The RPM for all othermeasurement locations on the machine train iscalculated.

Procedure in OMNITRENDSet up the machine train with its measurementlocations and measurement tasks in the OMNITRENDdatabase. Details of how to set up database entries aredescribed in the OMNITREND online help.

A summary of the basic steps is described in thefollowing section:

ATTENTIONThe ‘LineSpeed’ function must be deactivated. Tocheck this, click on the ‘Common data’ tab in thehierarchy above the machine train (‘Location’ = Northarea).

Reference RPM n0

n1 = n0 x 1.0

n2 = n

0 x 0.6

n3 = n0 x 0.06

n4 = n0 x 0.01

Machine train with three gear translations

RPM normalization for shock pulse measurement (roller bearingcondition) and calculation of the (roller bearing) damage frequen-cies

dBn

dBn

‘Exhaust fan’ machine train = Motor + Fan Bearing

To set up the reference measurement

- Activate the ‘TrainSpeed’ function in the ‘CommonData’ tab at machine train level.

- Open the ‘Train Data’ tab.

- Enter the measurement task for the referenceRPM in the ‘Reference task’ field using ‘Drag &Drop’.

Manual input of the reference RPMTo manually enter the reference RPM in situ, anRPM transducer must first be created and adaptedaccordingly to the measurement task:

- Open the ‘Transducer Editor’ and click on ‘NewTransducer’.

- Enter a name for the new transducer (e.g. ‘RPM -manual input’).

- Enter ‘Manual Input’ as the signal type.

- Select ‘Speed’ as the measurement quantity.

- Then select the permitted min. and max. valuelimits (e.g. ‘0-100000’), and click on OK.

To change the RPM transducer for the measurementtask:

- In the tree view, click on the RPM measurementtask.

- Open the ‘Meas. Type’ tab.

- Mark the ‘VIBXPERT transducer’ entry in the‘Transducer’ field.

- Click on ‘Add’ and select the newly created ‘RPM- manual input’ transducer as the transducer forthe speed measurement with VIBXPERT.

Create the RPM transducerfor ‘Manual input’ (left)and change it for the measu-rement task (below).

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If no ‘Speed’ measurement task has yet been created,create this with the ‘Task Wizard’ and select the newlycreated RPM transducer (‘RPM - manual input’).

To enter the translation ratioEnter the respective translation ratio for the refe-rence location of each machine and each measure-ment location on the machine train:

Machine: Mark the machine and open the ‘MachineData’ tab.Measurement location: Mark the measurementlocation and open the ‘Meas. Data’ tab.

To compile the route and transferdataOpen the Route Editor and create a route with therelevant machine train.Connect VIBXPERT to the PC and load the route inthe data collector.

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Productive maintenance technology

PRÜFTECHNIKCondition MonitoringP.O. Box 12 63D-85730 Ismaning, GermanyPhone: (+49) 89 99 61 60Fax: (+49) 89 99 61 63 00www.pruftechnik.com

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Measuring with VIBXPERT

- Open the route in VIBXPERT.

- Select the measurement task for the referenceRPM.

- Measure the RPM.If the RPM needs to be entered manually, the‘Manual input’ screen appears.