Specifies the node number increment used to step from Start Node to Stop Node. Each node incremented between the start and stop nodes is displaced with the value of Displacement. This value is optional.
Example 1
A large ethylene compressor shakes the node exiting the compressor flange a field-measured 8 mils in the Y direction, and 3 mils in the Z direction. The dynamic displacements are assumed to be simultaneous with no phase shift. This is because the load causing the displacements is believed to be from the compressor plunger moving in the X, or axial, direction. The displacements are skewed because the piping configuration entering the compressor is itself skewed.
Harmonic Displacements at Compressor Flange
|
0.008 |
Y |
0.0 |
330 |
|
0.003 |
Z |
0.0 |
330 |
Example 2
Applying estimated eccentric forces to the pump described in the harmonic force example did not produce the displacements witnessed in the field. Field personnel have measured the dynamic displacements in the vertical (Y) and transverse (Z) directions at the pump piping connections. The centerline of the pump, at the intersection of the horizontal suction and vertical discharge is node 15. The magnitude of the Z displacement is measured at 12 mil. The magnitude of the Y displacement is measured at 3 mils. It is assumed that the vibration is due to the rotation of the pump shaft, and so the Z and Y loads will be taken to be 90 degrees out of phase.
Harmonic displacements modeling pump vibration on the inline pump DOH-V33203001:
Z magnitude of the load - zero deg. phase shift
0.012 Z 0 15
Y magnitude of the load - 90 deg. phase shift
0.003 Y 90 15