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INSTRUMENTATIONS & DATA ACQUISITION

Presenter: Abid Khan

VIBRATION MEASURING INSTRUMENTS

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o What do you want to achieve?

o What is your present and future budget for equipment &training?

o Person power? Knowledge level?

o Number of machines to be monitored?

o Type of machines to be monitored?

o Environment?

CHOOSING YOUR INSTRUMENTATION

o Overall Level Meters

o Quick Check Analyzers

o FFT Data Collector/ Analyzers

o Full Feature Analyzers

o Real Time Spectrum Analyzers

o Instrument Quality Tape Recorders

o Dedicated Balancing instruments

INSTRUMENT TYPES

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DATA ACQUISITION SYSTEM

o Sensor/transducer for measurement of physical variables

o Signal-Conditioner/transmission circuitry, that enablesconversion of signal outputs from transducers to a readableform for Data Acquisition/interface modules

o The Data Acquisition Hardware comprising Amplifier, A/DConverter, Buffer Memory, etc. to digitize the analog signals forCPU

o Computer/CPU to process the digital data for data processing,display, outputs (control), storage, transmission, etc.

DATA ACQUISITION SYSTEM

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o A transducer is a device which transforms a non-electricalphysical quantity (i.e. temperature, sound or light) into anelectrical signal (i.e. voltage, current, capacity…)

o In other word it is a device that is capable of converting thephysical quantity into a proportional electrical quantity such asvoltage or current.

WHAT IS TRANSDUCER?

o Sensitivity• The transducer must be sensitive enough to produce detectable output

o Operating Range• The transducer should maintain the range requirement and have a good resolution over the entire

range

o Accuracy• It is defined as how close the output of the transducer is to the expected value. High accuracy is

required

o Size• Depending on the application of the transducer, the size may be of primary importance

o Environmental Compatibility• The transducer is selected based on the various environmental conditions it can work

o Insensitivity to unwanted signals• The transducer should be minimally sensitive to unwanted signals and highly sensitive to desired

signals

o Cost• The cost of a transducer is an important consideration, especially when many sensors are needed

for one machine

SELECTION OF TRANSDUCER

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VIBRATION TRANSDUCERS

Sensors…Transducers…Probes…What is it?

It basically converts mechanical vibration to an

electrical signal

AccelerometerCharge Type &

Line Drive

Constant Voltage &

Constant Current

Velocity Probe DisplacementShaft Riders

Proximity Probes

(Eddy Current Probes)

EDDY CURRENT DISPLACEMENT PROBES

Advantages:

• Measures displacement

• Non contacting

• No moving parts

• No wear

• Permanent installation

Disadvantages:

• Value of displacement is small at high

frequencies

• Variation in geometric irregularities &

magnetic properties of shaft give

incorrect results

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VELOCITY PICKUP

Advantages:

• Measure Velocity

• Self Generating

• Low Impedance

Disadvantages:

• Moving parts prone to wear

• Large size

• Sensitive to orientation

• High lower limiting frequency (> app. 10 Hz)

PIEZOELECTRIC ACCELEROMETER

Advantages:

• Rugged

• Very large dynamic range

• Wide frequency range

• Compact, often low weight

• High stability

• Can be mounted with any orientation

Disadvantages:

• High impedance output

• No true DC response

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FREQUENCY RESPONSE & MOUNTING TECHNIQUE

FREQUENCY RESPONSE & MOUNTING TECHNIQUE

Sen

siti

vity

Freq.

StudMount

HandProbe

Dual RailMagnet

FlatMagnet

MountingPad

1.5KHz 10KHz 32KHz

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FREQUENCY RESPONSE & MOUNTING TECHNIQUE

What is the frequency range of your…Instrument…Cables

…Sensor …Sensor Coupling

What is the fault frequency you are looking for ?

FREQUENCY RANGE, SENSITIVITY & APPLICATION

Sensor freq. = 12 KHzInstrument freq. = 80 KHz

Cable length ?

Sensor coupling ?

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o A drop on hard floor or hit against machine part may result inchange in sensitivity or even severe damage to theaccelerometer

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HANDLING OF VIBRATION SENSORS

o Whether it is your job to collect the data and/or analyse the datait is important to understand that the technologies will not giveyou the answer to a machines problem unless you havecollected meaningful, quality data

o There are certain considerations that must be taken prior to anydata being collected, these are

• A good understanding of the internal make up of the machine, in order tounderstand the best transmission path for data collection - bearing locations,load zones etc

• Ensure data is collected in a repeatable manner so we can compare two ormore readings to each other - trending purposes

• Variable speed machines - it is very important to collect data with the correctrunning speed enter into the analyser

DATA QUALITY

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o Damaged caused to a machine component will cause a certainamount of vibration/sound or heat to propagate away from theinitial impact

• It is the effect of the impact/force that we are trying to detect

o In many cases the further you are away from the initial eventthe weaker the signal will become, resulting in the dataappearing to be lower in value

• In more extreme cases the impact can be lost amongst other machine noise bythe time it has reached your transducer, resulting in no detection of a machineproblem

o Usually the best place to acquire data from a machine, is at thebearings

• This is because the bearings are the only part of the machine that connect theinternal rotating components to the stationary components (Casing)

TRANSMISSION PATH

o Collect data in the same manner each time.

• This consistency will allow you to trend the machinery condition and properlyjudge the progression of faults

o In order to aid with repeatable data the analyser requests fordata to be collected in certain locations on the machine.

• These are called ‘Measurement Points’

• A measurement point is determined by three characters and a description.

• Each character refers to a particular place on the machine being monitored

• E.g. M1H is a typical measurement point

REPEATABLE DATA

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o A measurement point is defined as three alpha numeric digitsalong with their respective definition

• Orientation and location on each component

o The image on the right is taken from the screen of the 2130analyser during a collection ‘route’

o The measurement ‘point identifier’ can be seen in the top rightwhile the ‘point description’ is shown just below

MEASUREMENT POINTS

o The first letter of the ‘Point Identifier’ refers to the type of machinebeing monitored• M = Motor

• P = Pump

• F = Fan

o The second character represented by a number indicates the locationon the machine• Inboard (Drive End)

• Outboard (Non Drive End)

o The third letter refers to the orientation of the sensor or the type ofprocessing being done by the analyser• H = Horizontal

• V = Vertical

• P = PeakVue

• A = Axial

MEASUREMENT POINTS

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o The following example shows how the numbering systemchanges as you cross from one component to the next

• M1H – Motor Outboard Horizontal

• M1P – Motor Outboard Horizontal Peakvue

• P1H – Pump Inboard Horizontal

• P1P – Pump Inboard Horizontal Peakvue

o Notice how the ‘1’ is not always the ‘Outboard’

• This changes when the next component is required for data collection

The numbering system starts from 1 again

MEASUREMENT POINTS

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CREATION OF ROUTE

⚫ The machines due to be monitored are defined within the software.

– As much information as possible about the machines being monitored is preferred when building the database.

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CREATION OF ROUTE

o Each technology is stored and analyzed from a single softwareplatform, allowing the analyst to

• Store all data and information in one database

• Easily cross reference data for conformation of analysis

• Collaborate all data into one single report

CREATION OF ROUTE

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