Hello everyone!
If a pump/motor has just been overhauled, and is now being put in service, is a signature/readings obtained immediately after the motor start button is pushed valid? Can a sound judgment be made from this data acquired about the machine health?
Or, would you allow the machine to run a while for thermal and flow conditions to stabilize, then take readings?
Thanking all in advance.

Relying only on data immediately after startup would be a bad idea. You might miss a problme (We had a motor with rotor bar looseness that started at 0.15 ips and grew to 0.5 ips.)

Data when stabilized is better - more representative of operating conditions and more trendable.

In an ideal world. you would like to get both. A change in vibration over time after startup may give a clue to the cause of the vibration.

I second Pete.
Sometimes the vibration reading immediately after the startup is less than the stable vibration reading when the machine runs under normal operating conditions.

But I'd like to add one more important thing here. Sometimes it is the opposite. Many machines experience a "jerk" vibration during the start up. In many cases this is not an indication of a problem. Also, I've seen many cases when the motor's temperatures saturates, the vibration levels stabilize at lower values.

So do not judge motor's condition from the first minute of the start up, especially if it has come from service. Many facilities have guidelines governing the minimum running time required before concluding the vibration evaluation. Four hours is a typical test duration.

I agree as well. After we change a Roll or Gearbox or pump I will go take readings on a new instillation usually that day and then again the next day or 2 after it settles into its normal runnning conditions.The reading right after startup will tell you if theres an Obvious problem but I don't pass judgment untill I have taken several readings severalo days in a row.Also readings right after startup gives you a chance to examine the instillation while taking the data. I once went to check a Couch Roll that had been changed for initial data and the oil line had been "forgotten". I saw it , it was put on and no harm done.So I like to take "startup" data but i go back the next day as well and do it all again.

Mike

Is the data vaild? Not for analysis purposes by itself.

Is it of value? Quite possibly.

I'll add my vote for lots of data.

If the machine is safely and readily accessible and you have time, I would collect data periodically over the time to heat saturation (track temp too.) and then daily for a week, weekly for a month, then on to a regular period. That's maybe 15-20 sets of data in the first month. Probably overkill but if it only takes you a couple of hours total, it's good information to have and you can be more sure you won't have infant mortality.

Thanks guys,
Wil the same reasons apply even though the motor/pump is in a relatively cold service for example a cooling water pump?

I agree with the guys, I think that it would be good information to have, but probably not used for analysis. Unless there is something very obvious like severe turning speed vibration or severe vibration at bearing fault frequencies. IF I took the data and there was something suspect going on but not severe I would want to go back when everything settles to make sure.
Also, even if the pump is cold service, you will still get thermal issues from the motor.

Vibehigh,

Heat is heat no matter whether you are adding or subtracting it.