1. Evaluation of Facility Importance

• High value machinery（Private power generator, High pressure compressor etc.）

  Mechanical failure is directly linked to stop of operation

• Important machinery（Boiler, Pump,Compressor etc.）

  Mechanical failure may cause a decrease of production

• Ordinary machinery（Intake or exhaust fan etc.）

  Mechanical failure may cause inconvenient for operation

• Low value machinery(Small general purpose motor etc.）

  Mechanical failure is not linked to operation and repair/replacement is much cheaper

Permanent Monitoring System

• Contact Sensor Type Vibration Monitoring System（VM-9301）

  Click here for the product page.

• Vibration Switch（VM-90A）

  Click here for the product page.

Offline Monitoring System

• CardVibro Air2（VM-2012/VM-2012C）

  Click here for the product page.

• SmartVibro（VM-4424H/VM-3024H/ VM-7024H）

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2. What is Simple Diagnosis?

The aim is to diagnose facilities and clearly show the degree of deterioration by measuring vibration. Judgment value will be needed for precise evaluation. There are three main judgment methods in simple diagnosis. Using these three methods will ensure more accurate measurement.

1.Absolute Value Judgment

Facilities are classified into several types (small type, medium type, large type). It is a method that if measured vibration exceed a certain level , it is diagnosed as abnormality.

Advantage

Judgment is easy because diagnosis standard is already established.

Disadvantage

Judgment may change depending on types or parts of facilities and makers.

Judgement Example

ISO vibration evaluation standard
This standard is widely used for synthetic judgment of rotational machinery.
The current ISO standard 10816-3：2009 describes the absolute value judgment by velocity rms

• Objective machinery is classified into 2 major groups

  • Machinery Group1Large Machinery

    Output: 300kW～50MW, Shaft height：> 315mm

  • Machinery Group2Medium Machinery

    Output: 15kW～300kW, Shaft height: 160mm～315mm

• 

  Figure: requirements for vibration severity measuring instruments 10816:2009.

2. Relative Value Judgment

The method of setting up the standard velocity RMS value and comparing the normal value with some absolute values for judgment. Normal value of velocity RMS which is originally set up by someone is multiplied by x times to be regarded as “alert value” or “dangerous value”. For example, when the velocity RMS value of motor shows 5.00 most of times after more than ten times measurement, “5.00” can be set up to be the normal value. 10.00 （two times as high as normal value） is set up to be alert value, 25.00 （five times as high as normal value） is “dangerous value.” The normal value should be decided after more than ten times measurement.

Advantage

More precise than absolute value judgment

Disadvantage

Because the normal value is decided according to each personal experiences, so ambiguity remains in the validity of the judgment values.

Judgement Example

This is a case which alert value is set to be two times as high as normal value. Dangerous value is set to be five times as high as normal value.

V(RMS) Trend Analysis Graph

3. Intercomparison Value Judgment

A method of judgement by comparing vibration amount at the same measuring point of the same machine. If numerical value is more than twice as big as equivarent facilities, there is a possibility of abnormality.

Advantage

More precise than relative value judgment

Disadvantage

Applicable machinery is limited

Judgement Example

When there is over two times difference between the two same machinery, there may be an abnormality.

3. What is Precise Diagnosis?

The aim is to analyze waveform with FFT and identify machine part that have deteriorated with frequency distribution, producing more reliable results than simple diagnosis.
When a normal machinery and an abnormal machinery are compared with FFT, it may show a big change at a feature frequency value. The following chart is about the feature frequency and the kinds of abnormal state.

Bearing Abnormalities and Feature Frequency

	Kinds of abnormal state		Mode to be checked	Feature frequency
1	Imbalance		Velocity	1 × N/60 and its frequency (little)
2	Misalignment		Velocity	M × N/60
3	Ball bearing scratch	Outer ring damage	Acceleration	0.4 × (number of ball) × N/60 and its harmonics
		Inner ring damage	Acceleration	0.6 × (number of ball) × N/60 and its harmonics
		Rolling element damage	Acceleration	2.5 × N/60 and its harmonics
		Cage damage	Acceleration	0.4 × N/60 and its harmonics
		Grease or oil lacking	Acceleration	N/60 and its harmonics
		Progress of deterioration,worn-out	Acceleration	0.4 × (number of ball) × N/60 and its harmonics or、 0.6 × (number of ball) × N/60 and its harmonics or、 0.4 × N/60 and its harmonics or、 2.5 × N/60 and its harmonics
4	Gear	Grease or oil lacking	Velocity/Envelope	PHz (pitching frequency)
		Pitching (defect of tooth surface)	Velocity/Envelope	P
		Chipped tooth (partial wear)	Velocity/Envelope	P±MN
		Chipped tooth	Velocity/Envelope	MN
		Eccentricity	Velocity/Envelope	MN or P±MN P＝Z × N/60
5	Bending shaft		Velocity	1 × N/60 and its harmonics
6	Cracking shaft		Velocity	1 × N/60 and its harmonics
7	Resonance		Velocity/Acceration/Envelope	Vibration of natural frequency
8	Electrical signal		Velocity	50 or 60Hz
9	Rubbing		Envelope	High frequency vibration (>1 kHz)
10	External vibration		Velocity/Acceration/Envelope	Depending on other facilities

N＝Number of circulation (rpm), M＝Multiple (1, 2, 3…), P＝Pitching frequency *Abnormality described above can be recognized correctly by che cking the specified mode.