我给客户培训时经常提到，成为一个优秀的振动分析工程师通常需要3个方面的综合能力：1，对设备的了解；2，对振动知识的了解；3，对分析仪器的了解。

       但我这里要讨论的不是能力，而是优秀的振动分析工程师必需的品质。

      《The simplified handbook of vibration analysis》一书中提到了这样一个故事，原文如下

A one hundred horsepower belt-driven center-hung centrifugal fan at a nuclear power plant exhibited excessive vibration on the outboard fan bearing at motor frequency. The fan was classed as CAT 1(Category 1), meaning that it was critical for plant operations and could not be shut down.

The analyst assumed that the fan bearing pedestal was resonant at the frequency of the motor and was being excited by imbalance in the motor. He requested permission to remove the belts and balance the motor in place. Since this was a CAT1 fan, he wasn’t allowed to remove the belts. Therefore he elected to balance the motor with the belts on. Vibration data taken on the motor was unstable, making the balance operation almost impossible.

After completion of the in-place balance operation, data was again taken on the fan bearings. The high vibration at motor frequency on the belt side fan bearing was the same as the original data.

The analyst then assumed that the bearing pedestal resonance was a high Q (lightly damped) system. He recommended that the pedestal be redesigned in order to remove the resonance well above motor frequency.

An engineering order was written and the necessary steps were taken to remove the unit from service and modify the fan bearing pedestal. In a nuclear facility, this is not a simple procedure.

After the modification were complete and the unit was returned to service, the vibration level on the outboard fan bearing at motor frequency was still above that permitted for a CAT 1 fan.

The authors were then retained to examine the unit and make recommendations to reduce the vibration on the fan bearings.

Vibration data was taken in-line and at 90 degrees to the belt direction, and these rectangular coordinate vectors summed in order to determine the direction of maximum amplitude. The phase of the maximum amplitude at the fan bearing was in-line with the dynamic belt tension, indicating pitch line runout on motor sheave.

Once again an engineering order was written to check the motor pulley. When this work was done, the pitch line runout on the motor pulley was measured as 0.011 inches. The pulley was replaced and the fan bearing vibration was reduced well below the acceptable level.

Incomplete data collection and fault analysis can result in very expensive yet unnecessary modifications to the system.

        我在现场也遇到了很多类似的情况，分析人员提出了不准确的分析建议后，维修人员要花大量的精力与时间去拆检或更换这台设备，但拆出来后却不能发现什么问题。

        我的建议是，如果你对你的分析没有6成以上的把握，请慎重发表你的意见。不准确的分析建议同样造成了大量的浪费，且还会造成大家对你的不信任。

       所以优秀的振动分析工程师必需的品质是……

       太晚了，大家回复一下帮我补上吧。