ATSNY© 2012 1

Basic Nondestructive

Testing

for EXPO 2012

by

Neville W. Sachs, P.E.

Applied Technical Services New York

ATSNY© 2012 2

What we plan to cover

1. Definition of nondestructive testing

2. Some philosophy on why it is helpful

and the major pitfalls

3. Basic theory

4. Explanations of common techniques

5. Demonstrations of common analysis

techniques

ATSNY© 2012 3

Nondestructive Testing

(NDT)

Also known as nondestructive examination

(NDE)

Involves inspection and analysis of

machinery or components without affecting

the operation or the properties of the subject.

(As opposed to a tensile test or other

destructive test such as sectioning.)

ATSNY© 2012 4

From the ASNT Website (American Society for Nondestructive Testing)

What Is Nondestructive Testing?

Nondestructive testing asks “Is there

something wrong with this material?”

Nondestructive testing (NDT) has been

defined as … “those test methods used to

examine an object, material or system without

impairing its future usefulness.”

ATSNY© 2012 5

The British View (BINDT)

“Non-destructive testing is the branch of engineering

concerned with all methods of detecting and

evaluating flaws in materials.”

“The essential feature of NDT is that the test process

itself produces no deleterious effects on the material

or structure under test.”

“The subject of NDT has no clearly defined

boundaries …”

ATSNY© 2012 6

A Brief History

Formal NDE dates back to early railroad days

when a mixture of oil and talc were used to detect

cracking in axles and wheels.

Since then science has developed a wide range of

tools and abilities to noninvasively detect

problems before they become disasters.

ATSNY© 2012 7

Wikipedia says

nondestructive testing is … Acoustic emission testing (AE or AT)

Blue Etch Anodize (BEA)

Dye penetrant inspection Liquid penetrant testing (PT or LPI)

Electromagnetic testing (ET)

• Alternating current field measurement (ACFM)

• Alternating current potential drop measurement (ACPD)

• Barkhausen testing

• Direct current potential drop measurement (DCPD)

• Eddy-current testing (ECT)

• Magnetic flux leakage testing (MFL) for pipelines, tank floors, and wire rope

• Magnetic-particle inspection (MT or MPI)

• Remote field testing (RFT)

Ellipsometry

Guided wave testing (GWT)

Hardness testing

Impulse excitation technique (IET)

Infrared and thermal testing (IR)

• Thermographic inspection

Laser testing

• Electronic speckle pattern interferometry

• Holographic interferometry

• Low coherence interferometry

• Profilometry

• Shearography

Leak testing (LT) or Leak detection

• Absolute pressure leak testing (pressure change)

• Bubble testing

• Halogen diode leak testing

• Hydrogen leak testing

• Mass spectrometer leak testing

• Tracer-gas leak testing method Helium, Hydrogen and refrigerant gases

Magnetic resonance imaging (MRI) and NMR

spectroscopy

Metallographic replicas [7] [8]

Near-infrared spectroscopy (NIRS)

Optical microscopy

Positive Material Identification (PMI)

Radiographic testing (RT) (see also Industrial

radiography and Radiography)

Computed radiography

Digital radiography (real-time)

Neutron radiographic testing (NR)

SCAR (Small Controlled Area Radiography)

X-ray computed tomography (CT)

Scanning electron microscopy

Surface Temper Etch (Nital Etch)

Ultrasonic testing (UT)

ART (Acoustic Resonance Technology)

Electro Magnetic Acoustic Transducer (EMAT)

(non-contact)

Laser ultrasonics (LUT)

Internal rotary inspection system (IRIS)

ultrasonics for tubes

Phased array ultrasonics

Time of flight diffraction ultrasonics (TOFD)

Time of Flight Ultrasonic Determination of 3D

Elastic Constants (TOF)

Vibration Analysis

Visual inspection (VT)

Pipeline video inspection

Corroscan/C-scan

IRIS - Internal Rotary Inspection System

3D Computed Tomography

Industrial CT Scanning

Heat Exchanger Life Assessment System

RTJ Flange Special Ultrasonic Testing

ATSNY© 2012 8

So, going back to the ASNT website,

these are the common NDT

techniques

Acoustic Emission Eddy Current

Liquid Penetrant Magnetic Particle

Ultrasonic Testing Visual Inspection

Vibration Analysis Radiography (X-ray)

Also common are:

Infrared Thermography Hardness Testing

ATSNY© 2012 9

Your Personal NDT

When you go to the market to select fruit

or veggies, what do you do? How do you

make your choice?

If your car is making a new strange noise,

what do you do?

Do you ever glance at your car tires to

see if they are soft?

ATSNY© 2012 10

The goal –

A. Look at it without causing a

damaging interruption

B. Use the test information to

form a plan

ATSNY© 2012 11

NDT in everyday life

Would you rather have an MRI - or should we do exploratory surgery for that knee problem?

Would you prefer an EKG or exploratory surgery?

For both of these, consider the possible costs and the possible benefits.

ATSNY© 2012 12

The goal of NDT is to analyze a piece of

material, without damaging its performance

capabilities, and then use that information to

predict future performance.

The graph below shows leaks in the roof of a process

vessel. (Replacing the vessel will cost about $50,000,000

and take about a year.)

300

200

100

0 4

Routine inspections of a vessel with stress corrosion cracking

Roof leaks vs.Inspection date

Years from vessel installation

Nu

mb

er

of

leaks

8 12 16 20

ATSNY© 2012 13

The goal –

Look at it without causing a

damaging interruption

So, not only can we look at and inside

pieces, but we want to do that without

causing an interruption.

Then a question arises - Do humans

really commit that many errors?

ATSNY© 2012 14

Human Error Experts say the average person makes six significant errors per

week.

BUT, our surveys show the typical industry

person believes they make a significant

error about once every FIVE months

ATSNY© 2012 15

In 23 years of doing industrial training

programs and asking people to compare their

skills with others in the same job,

only 37 people have rated themselves as below

average!

For the last six years we have also asked people

to rate their safety awareness. Only TWO have

said they were below average!!!

( 23 years x 15 seminars/year x 15 people/seminar = 5100 students

37/5100 = 0.7% )

ATSNY© 2012 16

How Often Do Human Errors

Happen? (From Chemical Engineering Magazine, McGraw Hill, NY,NY)

Industrial Activities • Critical routine task - 1/1000

• Non-critical routine task - 3/1000

• General error rate for high stress rapid activities - 1/4

• Non-routine operations (startup, maintenance, etc.) - 1/100

• Checklist inspection - 1/10

General Human Error • of Observance - 1/50

• of Omission - 1/100

ATSNY© 2012 17

How Often Do Human Errors

Happen? (From Chemical Engineering Magazine, McGraw Hill, NY,NY)

Industrial Activities • Critical routine task - 1/1000

• Non-critical routine task - 3/1000

• General error rate for high stress rapid activities - 1/4

• Non-routine operations (startup, maintenance, etc.) - 1/100

• Checklist inspection - 1/10

General Human Error • of Observance - 1/50

• of Omission - 1/100

ATSNY© 2012 18

Infant MortalityF

ailu

re P

rob

ab

ilit

y

The "Reliability Bathtub"

Time (log scale)

Normal Run Period

Wear out

Infant Mortality

The period right after

the machine is started.

These failures are

usually related to errors

in assembly.

Normal Run Period

The long stable time when

successful operation can be

expected. Failure in this time

is usually from unexpected

wear or a change in operating

conditions.

Wear out -

A function of

the original design

ATSNY© 2012 19

So, what % of equipment

actually suffers from Infant

Mortality

It really depends on the training of the installation personnel and their training and care. There is data from studies of maintenance activities around the country and

have seen it range from

a low of about 5% to as high as 22%!

Several North American studies have shown

the average is about 14% substantially

defective!

ATSNY© 2012 20

The most important benefits of NDT are that

it allows us to inspect materials and

machinery:

1. Without introducing infant mortality.

2. Without damaging the material.

ATSNY© 2012 21

And .. The data shows that:

All humans make frequent errors.

We tend not to recognize those errors.

The benefit of NDT is that it can find

defective material/equipment without

damaging the pieces and without the

interruptions that increase the

probability of human error.

ATSNY© 2012 22

Common Uses for NDT

• Component/machine condition evaluation – Example – Inspection of a ski lift component or an elevator rope.

•Predictive method - Vibration analysis on motors, and pumps, infrared inspection of transformers.

•Product and/or material quality

assurance – Examples – Run-in test

on a new vehicle, cleanliness of steel

ATSNY© 2012 23

The PE’s Challenge

We are asking technicians to conduct an

inspection.

They are not engineers and, by definition,

must have criteria to inspect to, i.e., have

to know what is considered a defect.

ATSNY© 2012 24

So, before we ask for a

specific NDT, we have to

know what to ask for!

Q. What is the difference between a flaw and a defect?

A. Almost all materials have lots of flaws. When the flaw impacts the performance of the material, it becomes a defect.

ATSNY© 2012 25

Important Terminology -

Defects and Flaws

All parts have “flaws” of some magnitude

but the parts are not necessarily defective.

A defective component is one that will not

perform as required for the necessary

time.

A “defect” is a deviation from what is

allowable.

ATSNY© 2012 26

Dialogue of a Common Problem

Client - “We want our xyz part mag particle tested. Can you do

that?”

Us – “Sure, we do lots of mag particle testing. What is your

standard?”

Client – “Huh? The drawing says it has to be tested.”

Us – “Does the drawing have a spec on it?”

Client – “Yeah. It says MIL-TDD41.” (Unfortunately, that is a

mil spec that was retired in 1990 and the last issue described a

procedure, without specifying flaw tolerances.)

Us – “Let’s talk about what you really need.” (More than once,

we’ve have had people ask us to MagnaFlux aluminum parts!)

ATSNY© 2012 27

So, before we ask for an

NDT, we have to know what

to ask for!

… and one of the significant challenges is to define what is considered a defect.

In a precision machined part, a 0.04” flaw may be a defect, but in a large casting, it may be just a 0.4” flaw!

ATSNY© 2012 28

Defects or Flaws???

When NDE people talk about flaws

(not serious stuff) they’re called

indications.

Defects are called “relevant

indications”.

ATSNY© 2012 29

Next, the inspection should

be done by a qualified and

certified person.

ATSNY© 2012 30

Certification

A certified inspector is a person who has demonstrated their capabilities and met a legal requirement.

Please don’t risk your life or your reputation by having inexperienced and uncertified inspectors do the work. (Would you want to have a surgeon operate on you who practices once a year? Or one who has developed his skill by watching other people do the job?)

ATSNY© 2012 31

ASNT Personnel

Qualifications Level I – Can conduct a test under Level

II supervision

Level II – Knows what they are doing

within specific inspection area

Level III - Knows and can perform a wide

range of NDT methods

(Typical inspector may be certified Level II in

VT, PT, MT, and UT)

ATSNY© 2012 32

Some of the more common NDT

methods

Acoustic Emission Eddy Current

Liquid Penetrant Magnetic Particle

Ultrasonic Testing Visual Inspection

Thermography Vibration Analysis

Radiography (X-ray) Hardness Testing

ATSNY© 2012 33

Some of the more common NDT

methods

Acoustic Emission Eddy Current

Liquid Penetrant Magnetic Particle

Ultrasonic Testing Visual Inspection

Thermography Vibration Analysis

Radiography (X-ray) Hardness Testing

ATSNY© 2012 34

Visual Inspection

An assurance that the person conducting

the inspection can see and recognize the

indications.

Certification in VT is largely directed

toward weld inspection. However, to

maintain any certification, visual acuity is

tested every year.

ATSNY© 2012 35

We have actually had experience

doing these: Acoustic Emission Eddy Current

Liquid Penetrant Magnetic Particle

Ultrasonic Testing Visual Inspection

Thermography Vibration Analysis

Radiography (X-ray) Hardness Testing

ATSNY© 2012 36

Glossary

DEFECT – A flaw that can significantly impact the

performance of the material

FLAW – An irregularity in the material

TRANSDUCER – a device that converts a mechanical

force to and electrical signal and vice-versa

RELEVANT INDICATION – something to be concerned

about

ATSNY© 2012 37

Acoustic Emission (AE)

Common Applications

Pressure vessels, especially tank cars

Fiberglass and other composite tanks

Long term bridge structure monitoring

ATSNY© 2012 38

x

x x

x x

x

Computer

Inspected vessel

Acoustic Emission (AE)

Start with a selection of

transducers that are wired

into a computer.

Securely anchor the

transducers to a vessel or

structure in precisely

determined positions.

The computer records the

high frequency signals from

the transducers.

ATSNY© 2012 39

Acoustic Emission (AE) Start with a selection of transducers that are

wired into a computer.

Securely anchor the transducers to a vessel wall

in precisely determined positions.

One time test

• Increase the pressure (stress) in the vessel above the

normally experienced pressures (stresses).

Long term test

• Compare the recorded data over the time period

Analyze the noises detected by the transducers.

If the noises are relevant, triangulate the signal

and specify additional testing in that area.

ATSNY© 2012 40

A

D E

B C

F

Computer

Inspected vessel

*

Acoustic Emission (AE)

Start with a selection of

transducers that are wired

into a computer.

When the noise signals

exceed a limit, triangulate

the indication.

Then do further inspection

in that area with other

methods.

*

ATSNY© 2012 41

Eddy Current (EC)

Common Applications

Heat exchanger tubes

Aircraft fuselage and wing surfaces

Easily contacted surfaces

Tube and wire production

Ferrous and nonferrous bar production

ATSNY© 2012 42

Eddy Current (EC)Testing

A probe with an AC field is moved across

a metallic surface at a relatively controlled

speed and the response from the field is

monitored.

When the field is interrupted by a change

in the structure, the response changes.

ATSNY© 2012 43

Radiography (X-rays)

Common Applications

Critical fabrication welds

Any material inspection where a record

has to be available for future reference

Searching for unwanted contaminating

materials

ATSNY© 2012 44

Penetrant Testing

“PT”

ATSNY© 2012 45

Penetrant Testing

“PT”

We’re going to do a penetrant test, but it is a

relatively time consuming procedure (and it is also

more prone to human error than other NDT). So

within the “PT time”, we’re going to do a magnetic

particle test.

ATSNY© 2012 46

The Types

There are three types of penetrant tests but the common ones are those using either visible or fluorescent dyes. The photo to the right shows the results of a visible penetrant test on a vessel weld.

ATSNY© 2012 47

The Types

Also, there are solvent cleanable and water washable tests.

We’ll do a solvent-based test.

ATSNY© 2012 48

Visible PT - How it works

1. We suspect our piece has a defect that is open to the

surface. So we thoroughly clean the surface. Then

allow the part to dry. (5-10 minutes)

2. Next, we spray a coating of a thin red liquid, the

penetrant, onto the surface and allow the liquid to be

absorbed into the defect. (5 to 25 minutes)

ATSNY© 2012 49

Visible PT - How it works

3. Then we thoroughly clean the surface again, but

carefully, so we don’t clean the penetrant out of the

defect. Then we allow the part to dry. ( 5 to 10 min.)

4. Next, we spray a very thin layer of a white paint-like

material onto the surface, allow the “paint” to absorb

the penetrant out of the defect, (5 to 15 minutes) and

visually inspect the piece.

ATSNY© 2012 50

The Procedure

1. Clean

2. Spray penetrant

3. Dwell

4. Carefully clean off

excess penetrant

5. Spray developer

6. Wait and watch

ATSNY© 2012 51

The

Procedure

This shows a weld inspection. One of our

people is waiting for the penetrant dwell

period inside a large process vessel.

ATSNY© 2012 52

Visible

Penetrant

After the penetrant is

cleaned off, the

developer is sprayed.

Note that there is

no dye remaining!!

ATSNY© 2012 53

Applications

Parts with cracks open to the

atmosphere that can be cleaned well

For mechanical components -

structural components or aluminum,

stainless, or steel, etc.

Relatively inexpensive initial cost for

materials

ATSNY© 2012 54

What can it find

Really depends on the surface

cleanliness and roughness.

On polished stainless parts we have

found cracks that were 0.00004” wide

and 0.003” deep!

ATSNY© 2012 55

PT Problem Areas

Is probably the most frequently misused NDT

technique. Frequently done by inexperienced

personnel leading to gross procedure errors,

misinterpretation, and wasted $$$.

Requires careful and thorough precleaning before penetrant application.

Grinding and other mechanical power cleaning can hide indications.

Time consuming, manpower intensive and greatest opportunity for human error.

ATSNY© 2012 56

PT Demonstration

ATSNY© 2012 57

Magnetic Particle Testing

“MT”

ATSNY© 2012 58

MT Procedure 1. Generally inspect the part and review the testing

criteria.

2. Clean the part well.

3. Set up a magnetic field in one direction.

4. Cover the field area with a contrasting magnetic

medium. (Can be a dry powder or an oil with

fluorescent particles.)

5. Set up a magnetic field in another direction.

6. Again, cover the field area with a contrasting

magnetic medium.

7. Inspect the areas where the particles accumulate.

ATSNY© 2012 59

Set up the Magnetic Field

SouthNorth

Steel or Nickel Plate

Particles onEdges of Flaw Flaw

SouthNorth

Then find the irregularities

ATSNY© 2012 60

MT Procedure

1. Clean the part well.

2. Set up a magnetic field.

3. Cover the field area with a

contrasting magnetic

medium. (Can be a dry

powder or an oil with

fluorescent particles.)

4. Inspect the areas where

the particles accumulate.

ATSNY© 2012 61

Two

views of

a weld

crack

This is WFMP testing –

wet fluorescent mag

particle.

It is viewed with a

black light.

Results of MT inspection with black light

Showing attracted particles after exam

ATSNY© 2012 62

MP Tests Dry powder particles

Both of these exams

used wet fluorescent

particles

ATSNY© 2012 63

Typical Applications of MT

Steel parts and martensitic stainless

with cracks open to the atmosphere.

(not many nickel parts)

Moderate initial cost for materials.

Lowest applied cost.

ATSNY© 2012 64

MT Problem Areas

Training is not extensive or expensive and

leads to good results.

Requires an understanding of the magnetic fields.

Can’t be used on nonmagnetic materials.

Poor cleaning and grinding can hide defects.

Generally WFMP is far superior to dry particle

testing.

ATSNY© 2012 65

Dry Magnetic Particle Demo

ATSNY© 2012 66

Infrared Inspection

Infrared inspections allows us to see

thermal images (radiation) much as our

eyes see visual images.

ATSNY© 2012 67

A Belt Drive on a Air Handler

We can see that the belt

temperatures are suspect.

(c) 2012 by Applied Technical Services, Inc.

ATSNY© 2012 68

We can see that these belts are

much too hot and are slipping.

(c) 2012 by Applied Technical Services, Inc.

ATSNY© 2012 69

Infrared Inspection

Applications Transformers, switchgear, and other

electrical equipment where there may be

poor connections, etc.

Insulation system effectiveness (air

leaks, wet insulation)

Process equipment liquid levels, etc.

Steam trap operation

ATSNY© 2012 70

Infrared Inspection Cautions Two common errors with scanners:

• Reflections – In much the same manner as

light reflects, infrared radiation can also

reflect and give erroneous readings

• Emissivity – Black body objects have

significantly different emissivity that polished

and shiny objects and the images will differ.

With hand-held infrared thermometers – They will average the temperature over a given

target area, and that may be much larger than

your area of interest!

ATSNY© 2012 71

Infrared Thermography

Demonstration Rather than me give a demo of how an infrared

scanner works, I’ll pass one of ours around so you

can look through it.

COMMENTS:

• It is focused for the range from about 5 feet to

infinity.

• I know this is a bunch of engineers that want to

play with controls, so I’ve taped the controls

closed so the next person doesn’t get a useless

demo! (If you want to play with it, please see me

afterward.)

ATSNY© 2012 72

Ultrasonic Flaw and

Thickness Testing

- “UT”

ATSNY© 2012 73

UT

Common Applications Thickness testing of tanks, vessels,

piping, etc.

Quality inspection of components such

as forgings, castings, welds, etc., looking

for internal voids

Flaw testing of materials looking for

process induced cracking (bolts, shafts,

etc.)

ATSNY© 2012 74

Ultrasonic

Audible Sound - 20 to 20,000 cps (Hz)

Normal UT Range

• 100,000 to 25,000,000 Hz

• 0.1 to 25 MHz

Wavelength = Velocity/Frequency

10 100 1000 10000 100000 1000000 10,000,000

Subsonic

Cycles per second (Hertz)

UltrasonicAudible to Humans

ATSNY© 2012 75

UT Application

A field check on a weld

of a large process vessel

ATSNY© 2012 76

Wave Types

Longitudinal

Shear

Surface

Plate

Others

Selection depends on application.

ATSNY© 2012 77

UT Transducer

HousingDamping Material

Piezoelectric Crystal

Power Cable

Inspected Material

SoundPattern

Transducer sends

out a sound wave

and then reads the

reflected wave

To get an accurate

measurement, the signal

has to be essentially

perpendicular to the flaw

FLAW

ATSNY© 2012 78

Ultrasonic Testing

Ultrasonic Device

Transducer

1.500"

Sound Wave

The “black box” generates a signal and sends it to the transducer, then reads the signals returning from changes in “Acoustic Impedance”.

ATSNY© 2012 79

Thickness Testing

Ultrasonic Thickness Tester

Transducer

Used to measure thethickness of materials1.500"

Sound Wave

ATSNY© 2012 80

Straight beam transducer

HousingDamping Material

Piezoelectric Crystal

Power Cable

Inspected Material

SoundPattern

ATSNY© 2012 81

Angle beam transducer

Housing

Piezoelectric Crystal

Power Cable

Inspected Material

Plastic Wedge

45 deg60 deg

70 deg

Changing Wedges results in different signal paths

But what do you do

when the flaw lies

at an odd angle?

(such as a weld)

ATSNY© 2012 82

Ultrasonic Flaw Tester

Transducer

Used to search for internal variations in materials

Ultrasonic Flaw Tester

Transducer

Sound echoes back fromchanges in acoustic impedence

UT Flaw Testing

ATSNY© 2012 83

dB

Calibrated Distance

Rel

ativ

e p

ow

er (

dB

)

6 dB

Calibrated Distance

Rel

ativ

e p

ow

er (

dB

)

How does the technician

know the true size of the

flaw?

Compare the size of the

echoes and we know that

6dB represents a doubling

in size.

Flaw Testing

ATSNY© 2012 84

UT Flaw Testing

Demonstration

ATSNY© 2012 85

UT Testing Comments

What sort of accuracy is there when a digital Thickness Testeris used and the backwall isn't flat?

Transducer

1.500"

Where does that sound wave reflection go?

ATSNY© 2012 86

Common UT Application

53 1/4"22 1/4"

228 13/16"

70 1/2"

31.3"18 3/4"

64 1/16"

20"

29.4

9"

25.4

9"

27"

30.0

0"

30"

Bearing Fit Bearing Fit

Drum Fit

Find the depth of the crack in this headshaft

crack

ATSNY© 2012 87

Unusual UT Inspection

Application

Transducer

Flaw Tester Screen

Axle

Axle and Hub Assembly

Ideal Sound Path

Testing the shrink fit tightness

ATSNY© 2012 88

Transducer

Flaw Tester Screen

Axle

Axle and Hub Assembly

Loose FitSound Path

Unusual UT Inspection

Application (cont’d)

Finding it is loose!!

ATSNY© 2012 89

Phased Array UT

Courtesy of Olympus NDT

Newer UT Method

This is essentially the same as the

ultrasound tests used on humans

and animals. There are multiple

crystals in the transducer and the

computer software analyzes them.

ATSNY© 2012 90

Common Applications

Complex and Internal Welds

Shafts

Bolts

Internal areas that are hard to

inspect with other methods but

have a known crack geometry

ATSNY© 2012 91

UT Problems Areas

Very operator intensive

Requires good knowledge of the part

geometry

Insensitive to flaws that are basically

parallel to the sound path

Have to have certified, qualified inspector

ATSNY© 2012 92

Vibration Analysis

A. Purpose of Vibration Analysis

B. Basic Principles of Vibration

Analysis

C. Basic Terminology

ATSNY© 2012 93

Vibration Analysis

As mechanical machinery became larger and more

complex, science began to realize the problems that

resulted from excessive vibration. By the end of WWII the

first methods to analyze and control vibration had been

developed.

Vibration analysis is used to measure

machinery movement to understand

why it is happening.

ATSNY© 2012 94

Comments • Frequently used as an acceptance gage on new

machinery.

• Is an excellent comparative method for monitoring machine condition.

• On existing operating machinery, monitoring and analyzing vibration data allows for very early warnings (2-3 months) of impending failures.

• The data is relatively easy to gather and, with computers and software programs, relatively easy to handle.

• Requires skilled, well-trained and certified inspectors.

ATSNY© 2012 95

Vibration Analysis Example

Readings on the motor

and the pump tell us the

condition of the bearings and

the coupling, the alignment,

and whether the base, grout,

and foundation are in good

condition.

High frequency monitoring of the

bearings can tell us the lubricant

film thickness.

Trending of this data can alert us to worsening problems.

Motor

Coupling

Pump

Base Plate

Foundation Block

Grout

ATSNY© 2012 96

Typical Machine

Monitoring

How often do you have to check? That depends on

the operating conditions and the criticality of the

machine. It could vary from once per month to once

every six months.

Motor

Coupling

Pump

Base Plate

Foundation Block

Grout

ATSNY© 2012 97

Vibration Terminology

Measurement Units

Amplitude - Describes the amount of

vibration and is expressed in three ways.

• Displacement (miles)

• Velocity ** (miles/hour)

• Acceleration (0 to 60 mph time)

Frequency - Describes the periodical nature of the vibration

and is expressed in one of three ways;

• CPM or Cycles Per Minute

• Hz or CPS or Cycles Per Second

• Orders or multiple of a frequency of interest

ATSNY© 2012 98

Looking at a Vibration Spectrum

Misalignment, imbalance,

structural problems, etc.

Bearing, gear, and

lubrication problems

Overall reading gives a general

guide to the machine condition. A

M

P

L

I

T

U

D

E

FREQUENCY – CPM or Hertz

ATSNY© 2012 99

Data Trending A doctor doesn’t need a lot of your medical history to diagnose a

broken arm, but it does help your long-term health to understand how

blood pressure, cholesterol, etc., are changing. In a similar manner, the

vibration analyst can immediately spot imminent serious problems, but

trending of data can alert the site to longer term situations.

ATSNY© 2012 100 100

One Last Nondestructive

Inspection Method –

Hardness Testing

There is a relationship between hardness and

tensile strength. The relationship is much

better for some (steel) than for others (cast

iron, rock).

The harder a material is, the stronger it is.

ATSNY© 2012 101

Commonly used as a QC tool to readily

verify the tensile strength or other

property of a metal or plastic.

Metals – Rockwell and Brinell are the

common types of test

Plastics – Barcol

Elastomers - Durometer

Hardness Testing

ATSNY© 2012 102 102

Hardness vs.

Tensile

Strength

for Steel

200 300 400 500

Te

ns

ile

str

en

gth

(k

si)

80

0

Brinell Hardness Number

40

120

160

200

240

Typical Hardness -Tensile Strength Range for Steel

data from SAE handbook

100

HBN x 500 ≈ Tensile Strength

HRC x 10 ≈ HBN

Easy Conversions

ATSNY© 2012 103 103

Brinell Hardness

Circa 1900

Two common scales, 500

kg and 3000 kg

Very good for castings

where there may be

inhomogenities

Problems with thin

materials

Applied Load

10 mm ball

Measure impressiondiameter, interpretfrom ASTM chart

d

ATSNY© 2012 104 104

Rockwell Hardness

13 ranges - with the

most common as HRC, HRB, HRA

Operation - Apply a minor load to reduce surface effects, then apply the major load. After movement stops measure the change in depth.

Versatile - with a wide range of applications

Minor load depth

Major load depth

Indenter with loaddepending on scale

Rockwell test indenters include

diamonds and balls. The loads

vary from 15 to 150 kg.

ATSNY© 2012 105

There are lots of other NDT tools

available from coating thickness

gauges to magnetic flux leakage

devices (checking for loss of material in tubes and tank

floors) to X-ray diffraction (checking for residual

stress in metallic components).

ATSNY© 2012 106

How do we suggest YOU

should approach NDT?

Sit down with your knowledgeable folks and ask

yourselves what your real materials, mechanical,

and electrical challenges or unknowns are.

Then ask, “Can they be anticipated?”

If the answer is either “Yes” or “I don’t know.”,

call somebody in the NDT business, describe

your problem, and ask them for their ideas.