memb453 ndt lp intro

7/25/2019 Memb453 Ndt Lp Intro

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Liquid Penetrant Testing

MEMB453

NONDESTRUCTIVE TESTING (NDT)

LIQUID PENETRANT TESTING

INTRODUCTION

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Definition

HistoryBasic Process

Advantages

Disadvantages




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• Definition

–

Liquid penetrant testing is a non-destructivemethod mean of locating and determining theseverity of surface discontinuities that areopen to the surface of solid and essentiallynon - porous material, is based uponcapillarity action.




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• Definition(cont.)

– Liquid penetrant testing(PT) is a non -destructive testing method of detectingdiscontinuities which are open to the surfaceof solid and essentially non - porous

material.




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• Brief Historical background of LiquidPenetrant Testing

19th century - Oil non colour penetrant

– Railroad industries - Rods, axles, crank pins

1938 - Colour dye penetrant 1941 - Flourescent penetrant

1957 - Post Emulsification penetrant




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SMLP2/6

• Basic process of liquid penetrant– i. Pre-cleaning

– ii. Penetration : Applying the penetrant

– iii. Wash : Removing the excesspenetrant

– iv. Development : Applying the developer

–

v. Inspection, Interpretation,Evaluation and Record

– vi. Post-cleaning

– vii. Report




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SMLP2/7

• Medium Liquid medium containing dye or fluoresent

substance

• Nature of signal

Capillarity bleedout of liquid trapped in flaws

• Detection Localized staining of applied developer

powder




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SMLP2/8

• Indication/recording method Direct visual observation for dye penetrant

Black light for fluoresent• Interpretation basis

Direct indication(dependent on propermethods for application of penetrant anddeveloper)

• Discontinuities/separations Surface cracks, laminations, laps, seams,

pinholes, laps, cold shuts and leaks

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SMLP2/9

• Application

• Applicable material

All non-porous, nonabsorbing materials• Applicable features and forms

Surfaces, entire objects and complex shapes

•

Component Weldments, joints, tubings, castings andbillets, gas turbine disks and blades, enginemounts and gears.

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SMLP2/10

• Advantages and limitation

• Advantages

The geometry and size of the part is not alimitation.

The indication appears directly on the testsurface.

Simple and economic method.

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• Limitations Access required for surface decontaminationand cleaning.

Discontinuity must be surface connected andopen.

Not applicable on rough and porous surface.

Discontinuity depth is not indicated.

Not applicable for high temperature (above120F and very cold less than 40F)

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SMLP2/12

• Sensitivity/resolution Microcracks to 1 micrometer width

• Interpretation limits False indications from shallow scratches andsmearing

• Others

Porosity of surface may mask importantindications.

Discontinuity depth is not indicated.

Vapor hazard.

Not applicable for high temperature(above120F and very cold less than 40F)

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• CRITERIA FOR SUCCESFULLINSPECTION

i. Equipment or penetrant system aresuitable for specific application.

ii.Clear defination of test problems.

iii.Realistic acceptance criteria.


memb453 ndt lp intro

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