Dear sea friends, the DCS shows a shaft displacement of -0.12 and -0.14 for the main fan. How should these values be interpreted?
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The main fan shaft system on the DCS shows shaft displacements of -0.12 and -0.14. I asked the instrument technician: the zero point of the shaft displacement probe is set in the middle of the thrust clearance – do -0.12 and -0.14 indicate the direction in which it is offset? There is another question: the manual for this main fan specifies a thrust clearance of 0.60 to 0.70, with an alarm value of ±0.40 and an interlock value of ±0.80. Are there any standards or criteria behind the setting of these alarm and interlock values?
I’m asking whether, in your instrument settings, a negative value corresponds to being close to the probe or far from it? ? ? ?
Hello, generally, an axial displacement in the forward direction is negative, while a displacement in the backward direction is positive. Axial displacements of -0.12 and -0.14 indicate that the rotor has moved forward by 0.12 mm and 0.14 mm relative to the midpoint of the thrust clearance. According to the manual for this main fan, the thrust clearance is specified as 0.60 to 0.70, with an alarm threshold of ±0.40. This means that the rotor can move forward or backward by 0.4 mm; thus, the total range of movement is 0.8 mm. Since this exceeds the allowable thrust clearance of 0.70, it indicates that there is some compression on the main or auxiliary thrust bearings. At this point, an alarm should be triggered. The interlock threshold is set at ±0.80, and at this value the shaft displacement has already exceeded the alarm limit by 0.4 mm. Under normal circumstances, this suggests that the thrust bearings may be worn out, so the system should be shut down via interlock! Fully typed by hand, please give a like~:victory:
I checked the gauge; it shows a positive value near the probe