Processing PT T

Surface Method Training Course 1

PT - PROCESSING

Asosiasi Uji Tak Rusak Indonesia


CONTENT

Surface Preparation

Penetrant Application

Removal of Excess Penetrant

Developer Application

Inspection

Post Cleaning


1. SURFACE PREPARATION

PURPOSE

To have a clean and dry test surface

Clean no rust, no scale, no paint, nocorrosion product

Dry no oil, no grease, no water

Because if contaminants are present, it willprevent the penetrant from entering thediscontinuities.

Example of contaminants:Oil, grease, scale, rust, welding flux, acids,waterPaint?Plating?


METHODS OF CLEANING

Mechanical CleaningChemical Cleaning

MECHANICAL CLEANING

To remove rust, scale, paint, dust and etc.

Methods of cleaningWire brushingGrindingPolishingSand blastingUltrasonic cleaning

If we use sand blasting, be careful sandblasting of low hardness material may closediscontinuity


SAND BLASTING

BEFORE AFTER

Soft part

It deforms and close the discontinuity


CHEMICAL CLEANING

To remove grease, oil, etc.

Methods of cleaning:

Detergent cleaningRemove surface soilDetergent may be alkaline or acid and shall be non-corrosiveThorough rinsing and drying required

Vapour degreasingRemove organic contaminants such as oil, greaseUse of solvent vapourChlorinated solvent can be harmful to Ni, Stainless Steel, Ti

Steam cleaningSuitable for large articleRemoves inorganic or organic contaminants


CHEMICAL CLEANING

Solvent cleaningRemove grease and oilTypical solvent: alcohol, acetoneCleaner /remover normally supplied bypenetrant manufacturer

De-scaling solutionRemove oxide film

After the cleaning the part should be dried sothat no water or solvent remains in or over thediscontinuities, as this will hinder entrance ofthe penetrant

Drying can be done by using:Infra-red lampsDrying ovenForce air circulationNormal evaporation


2. PENETRANT APPLICATION

TYPES OF PENETRANT

Non-fluorescent/visible dye penetrant

Fluorescent penetrant

PENETRANT SYSTEMS

Water washable

Post-emulsified

Solvent removed


PENETRANT SYSTEMS

Sometimes referred to water washable andnon water washable penetrants

The only different is emulsifier agents

Water washable

Non-water washable

SolventDye

Emulsifier agents

Solvent

Dye


HOW THEY ARE APPLIED

MethodsDipping (or immersing)SprayingBrushingPouring (flowing)Compressed air spray gun

The way we applied is not very important

The temperature of the test part should be between 160C 520C (600F 1250F) for most of the standards

If out of this range, then the standards say your procedure should be proved well apply


PENETRATION TIME

Definition the period of time during whichthe penetrant is permitted to remain on thespecimen. This is known as penetration timeor dwell time

Application Technique

Soak Time

Dwell Time

Penetration Time

ImmersionPeriod of article is in bath

drainingSoak time

+ dwell time

Others - Time

penetrant remains on article

Dwell time


FACTORS THAT AFFACTING PENETRATION TIME

Types of penetrant used (related to surfacetension () and wetting ability (cos) lesstime for non-water washable)

Specimen wetting ability

Material processes (forged parts required moretime than for casting parts)

Types of discontinuity that we are looking for

Temperature of the part


TEMPERATURES OF THE PART

Normally in standard the penetration timesgiven are minimum recommended times

Example ASME the penetration times arevalid for temperature range 160C 520C

Parts with low or high temperature then thepenetration time indicated in manual(manufactures recommendation) is not validany more

Lower temperature of the part - higher thepenetration time and vise versa


THE GENERAL RECOMMENDED FOR PENETRATION TIME*

*NOTE - use recommended values given bymanufacturer

If we use immersion method, then we do notneed 15 minutes to dip the part inside thetank.

1000C


3. REMOVAL OF EXCESS PENETRANT

It depends on the type of penetrant, namely;

Water washable

Non water washable

Solvent removed

Post emulsifiable process (hydrophilic remover,lipophilic emulsifier)


WATER WASHABLE PENETRANT

How to remove it from the surface of the testpart?

Two ways:

a) Simply apply water with certain pressure.

Normal standard the maximum pressureof water jet is less or equal to 50psi.

Excellent result if P ~ 20psi and apply waterat an angle of 450 max.

Good for rough surface, water temperature160C 430C.

900 450

wrong OK much better


WATER WASHABLE PENETRANT

b) For field application where we do not havepressurised water/large amount of water then wecan use wet towel to remove excess penetrant, andthen use water applicator (no pressure) to removethe residual penetrant

WaterWet towel

Discontinuity


NON WATER WASHABLE PENETRANT

a) POST EMULSIFIED PROCESS

The penetrants employed in the post-emulsified process do not contain an emulsifying agent

The penetrant is not soluble in water

Use emulsifier to render non water washable penetrant to become water washable

Two types of emulsifier:

Lipophilic

hydrophilic



LIPOPHILIC (OIL BASE)is applied by dipping, spraying and NEVER bybrushHow it works?

Apply P.E penetrant (non-water washablepenetrant)

Apply emulsifier before removing the penetrant

Apply emulsification dwell time

Non-water washable penetrant

Non-water washable penetrantEmulsifier

Non-water washable penetrant

Water washable


NON WATER WASHABLE PENETRANT(LIPOPHILIC)

The emulsifier will completely mix with thepenetrant on the surface become water washable

Inside discontinuity it still non-water washable

For fluorescent penetrant washing should bechecked with black light

The amount of time that the emulsifier is permittedto remain prior to the removal process is usually inthe range of 1 to 3 minutes, seldom exceeds 5minutes

The exact emulsification dwell time must bedetermined by experiment



HYDROPHILIC (WATER BASE)REMOVER/EMULSIFIER

Before dipping the part (after penetrantapplication) into detergent tank rinse the partwith water sprayed is preferred

Immerse the part into detergent

Emulsification time or contact time may varyfrom 30 sec. 15 min. depending on sample ordiscontinuity to be inspected

Wash with water


NON WATER WASHABLE PENETRANT( Post Emulsified Process)

THE EMULSIFICATION TIMEIs the most important parameter in P.E processTo short emulsification time;

Emulsifier not completely mix with penetrantDuring washing difficult to remove the penetrant fromthe surface

To long emulsification time;Emulsifier will mix with penetrant inside thediscontinuitiesDuring washing it is possible that the penetrant insidethe discontinuities will also be removed as well reducesensitivity

The best emulsification time can only be determinedon the part itself. The best time is the minimum timethat leaves no excess penetrant on the surface

emulsifier

Non water washable penetrant

Water washable penetrant



b) REMOVED BY SOLVENTUse cloth/paper tissueUse solvent or penetrant removal from thesame penetrant manufacturerMethod

Remove as much excess penetrant as possiblewith dry lint-free clothRemove the remaining excess with removerdampened lint free cloth (clean) until no trace ofpenetrant on clothWhen using visible dye penetrants, checked forcomplete removal by nothing that the lastremover dampened wipe is `colour freeWhen removing fluorescent penetrants, checkprogress with black light and stop when testsurface no longer fluoresces

Never apply (or spray) solvent directly tospecimen, because we also can clean some ofthe penetrant inside the discontinuities

The less solvent we use the better is the result

solvent Less sensitivity


4. DEVELOPER APPLICATION

Sequence

1. Dry developer or non aqueous developer

The part should be dried first before applythe developer

2. Water soluble or water suspendable

The parts have to be dried after applying thedeveloper


WET AQUEOUS DEVELOPER (WATER SOLUBLE)

How it applies?

By dipping the part into tank container (contain developer)

Difficult to get uniform layer of developer

After developer application, the part has to be dried in oven (80oC 100oC)

By pouring or flowing

By using compressed air spray gun


DRY DEVELOPER

By dipping the part into the tank

By using powder applicator or rubber squeeze bulb or low pressure spray gun

NON AQUEOUS DEVELOPER

Spray can or spray gun or electrostatic sprayer

Note never blow air to accelerate solvent evaporation


DEVELOPING TIME

Is the time from developer application to the time part is inspected

Rule of thumb to use a developing time of around half of the penetration time

Example: penetration time : 20 minutesdeveloping time : 10 minutes

10 minutes is 99.9% good because if the indication is not seen after 10 minutes then the part contain no discontinuities


5. INSPECTION

LIGHTING REQUIREMENTS

Good illumination should according to standard

White Light : visible penetrant

350 Lux or 32.5 ft/candles

Black light : fluorescent penetrant

ASME Code 1000watts/cm2 at 38cm from the surface;

MIL-I-25135D - 1200watts/cm2


GENERAL RECOMMENDATION (BLACK LIGHT)

Allow a minimum of 5 minutes to warm thelamps before starting inspection

Stay a minimum of 5 minutes in the darkenedarea before starting inspection

DONT switch ON and OFF the lamp often itwill shortened the life of lamp

Keep the filter inside the lamp clean all thetime


INSPECTION(two Steps)

INITIAL INSPECTIONIs done as soon as possible after applying the developer

Remember we have to write a report

Mainly good for porosityTo know better the type, nature and extend of discontinuities

Need initial inspection

Big porosity

In-line porosity

Four porosity

Immediately after applying

developer

PorosityAfter 1 minute

After 3 minutes

After 10 minutes


INSPECTION(two Steps)

FINAL INSPECTION

Is done when the developing time has elapsed

Wrong interpretation it looks like a big defect

Therefore, initial inspection is required becausenormally porosity has small opening but withbig volume inside

Final inspection

Big porosity

In-line porosity (looks like linear discontinuity)

Four porosity

(looks like big porosity)


6. POST CLEANING

After complete the inspection we have toclean the part (as soon as possible especiallyfor standard sample)

Method (for standard sample)

Best vapour degreasing or ultrasonic cleaning

Apply developer if indication reappear thenthe cleaning procedure should be repeated.

PT - PROCESSINGCONTENT1. SURFACE PREPARATIONMETHODS OF CLEANINGSAND BLASTINGCHEMICAL CLEANINGCHEMICAL CLEANING2. PENETRANT APPLICATIONPENETRANT SYSTEMSHOW THEY ARE APPLIEDPENETRATION TIMEFACTORS THAT AFFACTING PENETRATION TIMETEMPERATURES OF THE PARTTHE GENERAL RECOMMENDED FOR PENETRATION TIME*3. REMOVAL OF EXCESS PENETRANTWATER WASHABLE PENETRANTWATER WASHABLE PENETRANTNON WATER WASHABLE PENETRANTNON WATER WASHABLE PENETRANTNON WATER WASHABLE PENETRANT(LIPOPHILIC)NON WATER WASHABLE PENETRANTNON WATER WASHABLE PENETRANT( Post Emulsified Process)NON WATER WASHABLE PENETRANT4. DEVELOPER APPLICATIONWET AQUEOUS DEVELOPER (WATER SOLUBLE)DRY DEVELOPERDEVELOPING TIME5. INSPECTIONGENERAL RECOMMENDATION (BLACK LIGHT)INSPECTION(two Steps)INSPECTION(two Steps)6. POST CLEANING

Documents

Processing PT T