Hello guys,
I have a centrifugal pump with high vibration amplitudes at 1XTS.

I made cross-phase measurement and got the result listed in file .PPT.

The pump has just returned from balancing.

can I hit the hammer to cut the pipe?

Has anyone ever been in this situation?

Thank you!

Andersovv

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Original Post

Your data does not show pump discharge nozzle dynamic pipe strain, since at flange it is 0-degrees and vertically it is 0-degrees, all in-phase,  with pivot about the pump's primary (NDE) foot. When flange is moving from left to right the pump case is moving down. I am not sure why you included the flange 180-degree measurement that is redundant with the 0-degree from opposite side. Perhaps you have a lot of other data on pipe and pump? 

Walt

Walt Strong posted:

Your data does not show pump discharge nozzle dynamic pipe strain, since at flange it is 0-degrees and vertically it is 0-degrees, all in-phase,  with pivot about the pump's primary (NDE) foot. When flange is moving from left to right the pump case is moving down. I am not sure why you included the flange 180-degree measurement that is redundant with the 0-degree from opposite side. Perhaps you have a lot of other data on pipe and pump? 

Walt

Thanks for your time Walt.

Maybe the sketch is not so clear.

When putting the sensor (ch1) on the pump discharge nozzle and the sensor (ch2) on the pipe nozzle the phase between is 180°.

ANDER,

Your sketch shows two measurements on the pump discharge nozzle. You have to declare consistent phase directions. When you move the accelerometer from the left side of the nozzle to the right side, then the accelerometer phase orientation changes by 180-degrees. My experience indicates that the correct phase is on the left side (0-degrees), and the phase on the right side was not corrected (unless you did) for mounting orientation. Applying the orientation correction to the right side would make the actual phase 0-degrees (180 - 180), and then both sides of the nozzle would be moving in-phase. The entire motion of the pump would then be clockwise rotation about the pump's primary base. For ODS tests, I define positive X-Y-Z directions for the structure using the right-hand rule. This can be important, for example when making axial measurements on motor and pump on opposite sides on the shaft coupling. In that case, one of the measurement points has to have 180-degrees subtracted from the measured phase. You cannot define pipe strain, as shown, in the vertical direction without at least 4 measurements (90-degrees apart) on the nozzle in the vertical direction. Nozzle loads are typically defined as tension/compression, bending, and shear (lateral/twist). You might draw conclusion from your data that there is a resonant structure (pump-pipe), but you cannot conclude there is excessive pipe/nozzle strain.

Walt

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