CID Fan Newkirk Effect

Problem Detection:

Due to the vibration problem experienced in the CID fan motor in a power plant, support was requested from the Resonance Institute technical team.
A constantly changing vibration character is observed in both bearings of the engine.
While this symptom is not seen in the measurements taken with the accelerometer on the bed, the shaft sensors transferred to the DCS system show the variable vibration character very clearly.
To diagnose the problem, 5-day continuous measurements were taken with multi-channel analyzers over DCS.

When long-term measurements are evaluated, it has been determined that the amplitude and phase of 1X (rotation frequency) are constantly changing.
In some cases, it was observed that the vibration levels approached the B/C limits according to the ISO 7919-2 standard.
It has been determined that the 1X amplitude and phase makes one full revolution with a period of approximately 4-5 hours.
A literature study was conducted and it was thought that the situation was caused by the "Soft friction" (Newkirk Effect) phenomenon seen in the sealing elements.
It is recommended to check the sealing elements.

Under the leadership of Siemens Adana motor maintenance workshop technical service manager Veli Can Yeşil, an inspection was made on the CID fan motor.
As predicted, it was observed that the oil in the sealing elements became carbonized.
In order to prevent this situation from happening again, it was decided to place V-rings in front of the sealing elements and to increase the gaps of the sealing elements.