Handout Liquid Penetrant Test Level II August 2009
description
Transcript of Handout Liquid Penetrant Test Level II August 2009
-
TRAINING HAND OUT
LIQUID PENETRANT TESTING
General
PT. INSPEKTINDO PRATAMA Jakarta : Gedung Wisma Raharja lt. 4, Jl. TB Simatupang Kav-1, Jakarta Selatan 12560,
phone (021)-78841462,Fax (021)-78841461, workshop : Jl. Ciputat Raya No. 20 E
Pondok Pinang, Jakrta Selatan 12310, Phone (021)-7509518, Fax (021)-7509517,
web : www.inspektindo.co.id, Email :[email protected]
Balikpapan : Jl. Jend. Sudirman Ruko Bandar Balikpapan Blok B-22 Balikpapan 76122 Phone
(0542)-739310, Fax (0542)-739311
Rev. 0, december 2011
Page 0
PT. INSPEKTINDO PRATAMA INSPEKTION, CERTIFICATION & TECHNICAL SERVICES
-
CONTENTS
page
CHAPTER ONE
Introduction
Basic Principles
The Nature of Discontinuity
Surface Conditioning
History
Commercially Available Liquid Penetrant Materials
Chapter One Review
CHAPTER TWO
Introduction
Surface Preparation
Detergent Cleaning
Vapor Degreasing
Steam Cleaning
Solvent Cleaning
Rust and Scale Remover
Paint Removal
Etching
Ultrasonic Cleaning
Mechanical Cleaning
Stationary Penetrant Test Equipment
Portable Penetrant Test Equipment
Black Light Equipment
5
5
7
8
9
10 11 15 16 16 16 17 17 17 17 18 18 18 18 18 20 21 22
Page 1
-
Penetrant Material Combinations
Penetrant Testing Materials
Safety Precaution
Chapter Two Review
CHAPTER THREE
Introduction
Cleaning
Penetrant Application
Penetration (Dwell) Time
Penetrant Testing Processes
Leak-through Technique
Filtered Particle Technique
Fixing and Recording Indications
Chapter Three Review
CHAPTER FOUR
Introduction
Post-emulsifiable Penetrant (PE Penetrant)
Lipophilic Method
Hydrophilic Method
Developers Application
Dry Developers
Wet Developers
Guidelines to Choose Developer
Chapter Four Review
23 24 26 29 28 28 28 29 31 33 37 37 38 39 40 40 40 43 44 45 45 46 48 49
Page 2
-
CHAPTER FIVE
Introduction
Inspection
Interpretation and Evaluation of Indications
Typical Indications in Penetrant Inspection
False Indications
Nonrelevant Indications
True Indications
Depth Determination of Penetrant Discontinuities
Post Cleaning
Quality Control of Penetrant Process Variables
Aluminum Test Block
Sensitivity Test
Meniscus Test
Ceramic Block Test
Water Content Test
Viscosity Test
Fluorescent Penetrant Fade Test
Water Washability Test
Developer Test
Portable Equipment
Lighting
Chapter Five Review
50 50 50 50 51 51 52 52 56 56 56 56 57 57 58 58 58 59 59 59 59 60 61
Page 3
-
CHAPTER SIX
Introduction
Categories of Discontinuities
The Origins of Discontinuities
Casting Discontinuities
Processing Discontinuities
Working the Billet
Forging Discontinuities
Service Discontinuities
Chapter Six Review
CHAPTER SEVEN
Introduction
Identification and Comparison of Discontinuities
Training and Certification
Chapter Seven Review
CHAPTER EIGHT
Introduction
Controlling Liquid Penetrant Tests
Standards
Specifications
Written Practice
Sample Specification Penetrant Testing Process
Chapter Eight Review
REFERENCES
62 62 62 63 64 66 66 68 73 75 76 76 76 77 79 80 80 80 80 80 82 83 90 93
Page 4
-
CHAPTER ONE
INTRODUCTION
Liquid penetrant testing is a nondestructive
means of locating surface discontinuities
based on capillarity or capillary action. Capillary
action is responsible for both penetrant entry
and exit from discontinuities.
In the liquid penetrant method, the liquid is
applied to the surface of the specimen and
sufficient time is allowed for penetration of
surface discontinuities. If the discontinuity is
small or narrow as in a crack or pinhole,
capillary assist the penetration.
After sufficient time has passed for the
penetrant to enter the discontinuity, the surface
of the part is cleaned. Capillary action is again
employed to act as blotter to draw penetrant
from the discontinuity.
PENDAHULUAN
Pengujian cairan penetrant merupakan pengujian
tanpa merusak untuk menemukan diskontinuitas
permukaan berdasarkan prinsip kapilaritas.
Kapilaritas bertanggung jawab terhadap masuk
dan keluarnya cairan penetrant dari dan ke dalam
diskontinuitas.
Pada metoda cairan penetrant, cairan diaplikasikan
di atas permukaan spesimen dan diberikan waktu
yang cukup untuk menyusup ke dalam
diskontinuitas. Jika diskontinuitasnya kecil dan
sempit seperti pada retak atau lubang jarum,
kapilaritas membantu penetrasi.
Setelah waktu mencukupi bagi penetrant untuk
memasuki diskontinuitas, permukaan spesimen
kemudian dibersihkan. Gaya kapiler sekali lagi
bekerja sebagai penghisap yang menarik
penetrant keluar dari dalam diskontinuitas.
Page 5
-
Liquid penetrant inspection is a physical-
chemical process. Application and reaction of
the penetrant (chemical) is dependent upon the
nature of the test article and the discontinuity it
contains (physical).
The ability of penetrant to spread over a solid
surface is referred to as the wetting ability. The
wetting ability and contact angle between solid-
liquid are inversely proportional. The higher the
wetting ability, the smaller the contact angle.
The contact angle determines the wetting
ability.
Pemeriksaan penetrant merupakan proses fisika-
kimia. Aplikasi dan reaksi cairan penetrant (kimia)
tergantung pada sifat artikel yang diuji dan
diskontinuitas yang terdapat padanya (fisika).
Kemampuan penetrant untuk menyebar di atas
pemukaan benda padat disebut kemampu-
basahan (wetting ability). Wetting ability dan sudut
kontak (contact angle) antara benda cair dan
padat adalah berbanding terbalik secara
proporsional. Sudut kontak menentukan wetting
ability.
Penetrating capability of a liquid penetrant is
controlled by:
Surface tension.
Contact angle.
Kemampuan penyusupan
dikendalikan oleh:
Tegangan permukaan.
Sudut kontak.
cairan penetran
Page 6
-
BASIC PRINCIPLES
To insure visibility, the liquid penetrant contains
either a colored dye easily seen in white light,
or a fluorescent dye visible under black
(ultraviolet) light.
A penetrant examination consists of the
following basic steps, regardless of the material
tested:
Step 1: The test object or spot is
thoroughly cleaned and
dried.
Step 2: The penetrant is applied.
Dwell time is allowed to
penetrate discontinuities.
Step 3: The excess surface
penetrant is removed.
Step 4: Developer is applied
Step 5: Indications are evaluated
and accepted or rejected.
Step 6: After the penetrant test, the
test object or spot is
postcleaned.
PRINSIP-PRINSIP DASAR
Agar dapat terlihat, cairan penetrant diberi pewarna
merah yang dapat dilihat dengan cahaya biasa
atau pewarna fluorescent yang dapat dilihat
dengan cahaya ultraviolet.
Pengujian penetrant terdiri dari tahapan-tahapan
berikut tanpa mempertimbangkan material yang
diuji:
Langkah 1: Pembersihan dan pengeringan
benda atau lokasi yang
diperiksa.
Langkah 2: Aplikasi penetrant. Dibiarkan
beberapa lama agar menyusup
ke dalam diskontinuitas.
Langkah 3: Pembersihan penetrant sisa
di permukaan.
Langkah 4: Aplikasi developer
Langkah 5: Evaluasi indikasi, diterima
atau ditolak.
Langkah 6: Pembersihan benda atau lokasi
setelah selesai diuji.
Page 7
-
THE NATURE OF DISCONTINUITY
Discontinuities that are subsurface in one stage
of production could be open to the surface at
another stage, such as after grinding or
machining.
Nonmetallic inclusions and porosity in the ingot
may cause stringers, seams, forging laps, cold
shuts, and the like as the billet or slabs is
processed in the manner shown below.
SIFAT DISCONTINUITAS
Diskontinuitas yang terletak dibawah permukaan
pada satu tahapan produksi dapat terbuka ke
permukaan pada tahapan lainnya seperti akibat
penggerindaan dan permesinan.
Inklusi nonlogam dan porositas dalam ingot dapat
menyebabkan stringers, seams, lipatan tempa,
cold shuts, dan sejenisnya saat billet atau slab
diproses dengan cara seperti di bawah ini.
Page 8
-
SURFACE CONDITIONING
Anything that could block the penetrant from
entering the discontinuity must be removed.
A list of contaminants that must be removed
would include DIRT, GREASE, RUST,
SCALE, ACIDS, and even WATER. The
cleaning solvent used must be volatile
(readily vaporized) so that it easily
evaporates out of the discontinuity and does
not dilute the penetrant.
Surface preparation by mechanical cleaning
such as wire brushing, abrasive blasting, emery
cloths, and metal scraping are not generally
recommended, but there are times when they
must be used.
When they are used, discontinuities that are
open to the surface may be closed as ilustrated
below.
PENGKONDISIAN PERMUKAAN
Semua kotoran yang menghalangi penetrant untuk
memasuki diskontinuitas harus dibersihkan.
Jenis kotoran yang harus dibersihkan meliputi
DEBU, GEMUK, KARAT, KERAK, ASAM,
bahkan AIR. Solvent yang digunakan untuk
pembersih harus mudah menguap sehingga
cepat keluar dari dalam dikontinuitas dan tidak
mengencerkan penetrant.
Pembersihan permukaan secara mekanis seperti
memakai sikat baja, abrasive blasting, kertas
gosok, dan alat sekrap umumnya tidak
direkomendasikan, namun ada kalanya cara-cara
tersebut harus digunakan.
Apabila digunakan cara-cara di atas, diskontinuitas
yang membuka ke permukaan dapat tertutupi
seperti gambar di bawah ini.
Page 9
-
HISTORY
Historically, penetrant inspection was called oil
and whiting method. The oil and whiting
method used in the railroad industry, i.e.
locomotive parts, etc. (axles, crank pins and
couplers), in the early 1900s was the first
recognized use of the principles of penetrants
to detect cracks.
The oil and whiting method used dirty or dark-
colored lubricating oil that was thinned with
kerosene followed by the application of a
whiting or chalk coating, which absorbed oil
from the cracks revealing their locations.
By the 1940s, fluorescent or visible dye was
added to the oil used to penetrate test objects.
Following is stages of oil and whiting method.
Experience showed that temperature and soak
time were important.
This started the practice of written instructions
to provide standard, uniform results. The use of
written procedures has evolved, giving the
ability for design engineers and manufacturers
to get the same high standard results from any
properly trained and certified liquid penetrant
testing technician.
SEJARAH PENGUJIAN PENETRANT
Menurut sejarahnya, pemeriksaan penetrant
dulunya disebut metoda minyak dan kapur. Pada
awal tahun 1900an, metoda ini digunakan dalam
industri perkeretaapian untuk memeriksa kompo-
nen lokomotip (batang torsi, batang penggerak,
dan coupler, dll.), yang merupakan awal mula dike-
nalnya prinsip penetrant untuk mendeteksi retak.
Metoda minyak dan kapur memakai minyak lumas
hitam yang diencerkan dengan minyak tanah,
diikuti dengan aplikasi bubuk kapur di atasnya
yang akan menyerap minyak dari dalam retak
sehingga dapat diketahui lokasinya.
Pada tahun 1940an, zat pewarna merah dan
fluorescent dicampurkan ke dalam oli yang
digunakan untuk pemeriksaan.
Berikut adalah tahapan metoda pengujian minyak
dan kapur.
Pengalaman mengajarkan pentingnya mempertim-
bangkan suhu dan waktu celup.
Hal tersebut memicu diterapkannya penggunaan
instruksi tertulis agar hasil pengujian menjadi
standard dan seragam. Pemakaian prosedur
tertulis diharapkan menjadikan pemeriksaan
penetrant akan memberikan hasil dengan standard
tinggi jika dikerjakan oleh teknisi yang terlatih.
Page 10
-
COMMERCIALLY AVAILABLE LIQUID
PENETRANT MATERIALS
The liquid penetrants used in nondestructive
testing can be categorized by the type of dye
they contain.
1. Visible dye penetrants contain a colored
(usually red) dye.
MATERIAL CAIRAN PENETRANT YANG
TERSEDIA DI PASARAN
Cairan penetrant yang dipakai di dalam NDT dapat
dikagorikan berdasarkan jenis zat pewarna yang
ditambahkan.
1. Visible dye penetrants mengandung zat
pewarna merah.
2. Fluorescent penetrants
fluorescent dye
contain a 2. Fluorescent penetrants mengandung zat
pewarna fluorescent (hijau-kuning).
3. Dual sensitivity penetrants contain a
combination of visible and fluorescent
dyes.
Penetrants can be further categorized by the
processes used to remove the excess
penetrant from the specimen.
1. Water-washable penetrants, are either
self-emulsifying or removable with plain
water.
2. Post-emulsifiable penetrants require a
separate emulsifier to make the penetrant
water washable.
3. Solvent-removable penetrants must be
removed with a solvent which is typical
when using visible dye in pressurized
spray cans.
The basic liquid penetrant classification system
is shown in Table 1.1.
3. Dual sensitivity penetrants, mengandung
kombinasi kedua zat pewarna, visible dan
fluorescent.
Penetrant dikelompokkan lebih lanjut berdasarkan
proses pembersihan sisa penetrant dari permu-
kaan spesimen.
1. Water-washable penetrants, mengandung zat
pengemulsi atau dapat dibilas dengan air.
2. Post-emulsifiable penetrants, memerlukan
pengemulsi terpisah untuk menjadikan
penetrant dapat dibilas dengan air.
3. Solvent removable penerants, harus
dibersihkan dengan solvent khusus jika
menggunakan penetrant visible dalam
kaleng bertekanan.
Sistem klasifikasi cairan penetrant dapat dilihat
dalam Tabel 1.1.
Table 1.1. Basic liquid penetrant classification system.
Page 11
-
The flowchart below illustrates the processing
Diagram alir berikut memperlihatkan urutan proses
sequence with visible and fluorescent dengan penetran visible dan fluorescent.
penetrants.
Page 12
-
Dual sensitivity penetrants would follow a
processing sequence similar to that shown
below.
The selection of the best process depends
upon:
1. Sensitivity required.
2. Number of articles to be tested.
3. Surface condition of part being
inspected.
4. Configuration of test specimen.
5. Availability of water, electricity,
compressed air, suitable testing area,
etc.
Dual sensitivity penetrants mengikuti urutan proses
yang diperlihatkan diagram alir di bawah ini. Pemilihan proses terbaik ditentukan oleh:
1. Sensitivitas yang disyaratkan.
2. Jumlah artikel yang diuji.
3. Kondisi permukaan komponen yang
diperiksa.
4. Konfigurasi benda uji.
5. Ketersediaan air, listrik, udara bertekanan,
lokasi pengujian yang sesuai, dll.
Page 13
-
Penetrant testing is succesfully used on most
any materials, including metallic and
nonmetallic objects.
Metallic materials include aluminum, magne-
sium, titanium, cast iron, stainless steel,
powdered metal products, copper, brass, and
bronze, as well as most other common alloys.
Nonmetallic materials include ceramics, plastic,
molded rubber, composites, and glass.
Penetrant testing is limited by its inability to test
materials with discontinuities that are NOT
OPEN to the surface or having extremely
porous surface.
List below indicates the penetrant systems,
ranging from the most sensitive and expensive
to the least one.
1. Post-emulsified fluorescent.
2. Solvent-removable fluorescent.
3. Water-washable fluorescent.
4. Post-emulsified visible.
5. Solvent-removable visible.
6. Water-washable visible.
Pengujian penetrant secara memuaskan dapat
diplikasikan pada kebanyakan material, termasuk
material logam dan nonlogam.
Material logam termasuk aluminium, magnesium,
titanium, besi cor, stainless steel, produk serbuk
logam, paduan tembaga, kuningan, perunggu,
juga paduan-paduan lainnya.
Material nonlogam termasuk keramik, plastik,
karet, komposit, dan kaca.
Pengujian penetrant tidak dapat diaplikasikan
untuk menemukan diskontinuitas yang TIDAK
MEMBUKA ke permukaan dan permukaan material
yang berpori.
Daftar berikut menunjukkan tingkat sensitivitas
sistem penetrant, dari mulai yang paling senfitif
dan paling mahal.
1. Post-emulsified fluorescent.
2. Solvent-removable fluorescent.
3. Water-washable fluorescent.
4. Post-emulsified visible.
5. Solvent-removable visible.
6. Water-washable visible.
Page 14
-
CHAPTER ONE REVIEW
_______ 1.
_______ 2.
_______ 3.
_______ 4.
_______ 5.
_______ 6.
_______ 7.
_______ 8.
_______ 9.
Nonmetallic inclusions and porosity in the steel ingot are commonly found using liquid penetrant inspection techniques. Type II penetrants, according to our test, are those containing a fluorescent dye. Because of the capillary action of penetrants, this process of inspection works well on parts with very porous surfaces. When doing a liquid penetrant test, the configuration of the specimen has little effect on the effectiveness of the test. Liquid penetrant inspection can be used only on metals such as aluminum and steel. The penetrant inspection method is used only on the finished product. Oil and whiting are the names of the two men who invented the penetrant test method. The first important step in penetrant testing is surface preparation. One of the most common contaminants in the penetrant method is water.
_______ 10. The most common method of surface preparation for penetrant testing is
sandblasting.
_______ 11. Chemical etching Is sometimes used to remove smeared metal from a surface to open discontinuilies.
_______ 12. Some subsurface defects can be tested with the highly sensitive Type II
penetrants.
_______ 13. Blow holes and gas porosity may be detected with the penetrant method.
_______ 14. Solvent cleaning is a common method of surface cleaning parts before penetrant testing.
_______ 15. The one major limitation to penetrant testing is that the part must be
metallic.
_______ 16. Grease and rust would usually be considered a contaminant on the surface of a test piece.
_______ 17. To locate a defect with penetrant testing, the defect must be open to the
surface.
_______ 18. It is considered advantageous for a liquid penetrant material to have low tension and high capillarity.
Page 15
-
CHAPTER TWO
INTRODUCTION
This chapter discusses the equipment and
material required to perform the various
penetrant test and the required PRE and POST
test cleaning.
SURFACE PREPARATION
As discussed in Chapter 1, there are SIX basic
steps required for a penetrant test. Surface
preparation is entered on the flow diagram
below as step one.
Surface preparation, including proper cleaning
is essential to liquid penetrant testing for TWO
reasons:
1. If the specimen is not physically and
chemically clean and dry, penetrant
testing may be ineffective.
2. If all tracess of penetrant materials are
not removed after the test, they may have
a harmful effect on the specimen after the
test object is placed in service (chlorine
and sulfur may affect some alloys).
Selection of the cleaning process breaks down
to the following basic factors.
Type of contaminant.
Composition of the base material.
Degree of cleanliness required.
Availability of cleaning equipment.
Cost and time factors.
Unless the cleaning methods and chemicals
are known to be compatible with the penetrant,
a final cleaning should be done with the solvent
recommended by the manufacturer.
PENDAHULUAN
Bab ini mendiskusikan peralatan dan bahan yang
diperlukan untuk melakukan pengujian penetrant
serta pembersihan material SEBELUM dan
SESUDAH pengujian.
PENYIAPAN PERMUKAAN
Telah disampaikan dalam Bab 1 bahwa ada ENAM
langkah dasar pengujian penetrant. Penyiapan
permukaan dimasukkan sebagai langkah pertama
dalam diagram alir berikut.
Pembersihan permukaan sangat penting dalam
pengujian cairan penetrant karena DUA alasan:
1. Jika spesimen tidak bersih secara fisika dan
kimia, pengujian penetrant menjadi tidak
efektip.
2. Jika semua bekas material penetrant tidak
dibersihkan setelah pengujian, maka akan
merusak spesimen setelah benda tersebut
terpasang (klorin dan sulfur dapat merusak
beberapa jenis paduan).
Pemilihan proses pembersihan ditentukan oleh
faktor berikut.
Jenis kotoran yang dibersihkan.
Komposisi logam induk.
Tingkat kebersihan yang disyaratkan.
Ketersediaan peralatan pembersih.
Faktor-faktor biaya dan waktu.
Jika kompatibilitas antara metoda pembersihan,
cairan pembersih dan penetrant tidak diketahui,
pembersihan akhir sebaiknya dilakukan dengan
solvent yang direkomendasikan oleh pabrik
penetrant.
Page 16
-
DETERGENT CLEANING
Immersion tanks and detergent solution may
be used as an effective method for removing
surface soils, particularly when employed as a
hot tank process.
However, since the solutions used may be
either acidic or alkaline in nature, precautions
must be taken to ensure that the selected
detergent is noncorrosive to the article being
cleaned.
When thoroughly rinsed and dried, detergent
cleaning leaves a test surface that is physically
and chemically clean.
VAPOR DEGREASING
Vapor degreasing is effective in the removal of
oil, grease, and similar organic contaminants.
This method does not remove solid contami-
nants such as varnish, paint, scale, or oxide.
However, this method is considered as the
most effective means of precleaning a test
item prior to a penetrant test
Safety and environmental concerns have
virtually eliminated vapor degreasing. The chlo-
rinated solvents employed (methyl chloroform),
if acidic, can be harmful to certain materials
such as nickel, stainless steel, and titanium.
STEAM CLEANING
Steam cleaning is an excellent method of
cleaning large articles, or portions of large
articles that cannot be washed with detergents.
It removes inorganic soils as well as many
organic contaminants, but it may not reach to
the bottom of deep discontinuities. A follow-up
solvent soak is often recommended.
SOLVENT CLEANING
Solvent cleaning may use immersion tank, or
the solvent may be sprayed, brushed, or wiped
on and wiped off. Solvent cleaning is the
process most commonly used for spot
inspections.
Solvent cleaners should only be used to
remove organic contaminants, and are not
recommended for removing rust and scale,
welding flux or spatter. Typical solvents are
kerosene, paint thinner, alcohol, benzol, and
trichloroethylene.
PEMBERSIHAN DENGAN DETERJEN
Tangki perendam dan larutan deterjen dapat
dipakai sebagai metoda yang efektip untuk
membersihkan kotoran permukaan, utamanya jika
memakai proses tangki panas.
Namun demikian mengingat larutan yang dipakai
dapat bersifat asam atau basa, harus diperhatikan
agar deterjen yang dipilih tidak mengakibatkan
korosi terhadap benda yang dibersihkan.
Bila dibilas dengan bersih dan dikeringkan,
pembersih deterjen menghasilkan permukaan
yang bersih secara fisika dan kimia.
PEMBERSIHAN DENGAN UAP SOLVENT
Uap solvent efektif untuk membersihkan minyak,
gemuk, dan kontaminan organik sejenisnya.
Metoda ini tidak menghilangkan kontaminan padat
seperti pernis, cat, kerak, dan oksida.
Namun demikian, metoda ini dianggap sebagai
cara yang paling efektip untuk membersihkan
benda sebelum diuji penetrant.
Masalah keselamatan dan lingkungan telah
melarang penggunaan metoda ini. Chlorinated
solvent yang dipakai (methyl chloroform), jika
bersifat asam dapat merusak material seperti
nickel, stainless steel, dan titanium.
PEMBERSIHAN DENGAN UAP AIR
Pembersihan dengan uap air merupakan cara
yang unggul untuk membersihkan benda beruku-
ran besar yang tidak dapat dicuci dengan deterjen.
Cara ini menghilangkan kotoran organik dan
inorganik, namun tidak dapat mencapai dasar
diskontinuitas yang dalam. Pencelupan ke dalam
solvent setelahnya seringkali direkomendasikan.
PEMBERSIHAN DENGAN SOLVENT
Cara ini dilakukan dengan pencelupan,
penyemprotan, penyikatan, atau pengusapan.
Pembersihan dengan solvent merupakan proses
yang umum digunakan untuk pemeriksaan
setempat.
Solvent pembersih hanya untuk menghilangkan
kotoran organik dan tidak diremomendasikan
untuk menghilangkan karat dan kerak, flux
pengelasan, atau percikan las. Cairan solvent
contohnya minyak tanah, thinner cat, alkohol,
benzol, dan trichloroethylene.
Page 17
-
RUST AND SURFACE SCALE REMOVER
Rust removers (descaling solutions, either
alkaline or acid), pickling solutions (acid), and
sometimes wire brushing are used to remove
rust and surface scale. Wire brushing is
accomplished with a minimum of pressure to
avoid closing surface discontinuities or filing
them with smeared metal.
PAINT REMOVAL
Dissolving type hot tank paint strippers and
bond release or solvent paint strippers may be
used to remove paint in precleaning.
ETCHING
Etching is normally required on soft metallic
materials (such as aluminum and magnesium),
materials that tend to smear (such as titanium),
and materials which have been mechanically
process-ed by machining, grinding, or similar
procedure. Etching is accomplished with either
an acid or an alkaline solution to open up
grinding burrs and remove metal from surface
discontinuities.
ULTRASONIC CLEANING
Ultrasonic cleaning equipment is useful in the
cleaning of large quantities of small test
objects. Ultrasonic cleaning is often combined
with a solvent or detergent bath to improve
cleaning efficiency and reduce cleaning time.
The method works best with water and deter-
gent cleaning when contaminants to be
removed are inorganic, and with solvents when
contaminants are organic.
MECHANICAL CLEANING
Cleaning processes that are not generally
recommended include abrasive blasting (shot,
sand, grit, or pressure), liquid honing, emery
cloth, wire brushes, and metal scrapers, but
there are times when they must be used.
These processes tend to close discontinuities
by peening or cold working the surface of the
specimen.
PENGHILANG KARAT DAN KERAK PERMUKAAN
Penghilang karat dan kerak (larutan penghilang
kerak, basa atau asam), larutan pickling (asam),
dan kadang kala sikat baja digunakan untuk
menghilangkan karat dan kerak permukaan.
Penyikatan dilakukan dengan tekanan rendah
untuk mencegah penutupan atau pengisian
diskontinuitas permukaan oleh gram.
PENGHILANG CAT
Pengelupas cat dan pelepas ikatan memakai
tangki pelarut panas atau solvent pengelupas cat
dapat dipakai untuk menghilangkan cat saat
pembersihan awal.
ETSA
Etsa biasanya disyaratkan pada material logam
lunak (seperti aluminium dan magnesium), material
yang cenderung teroksidasi (seperti titanium), dan
material yang telah diproses secara mekanis
melalui permesinan, penggerindaan atau sejenis-
nya. Etsa dilakukan dengan larutan asam atau
basa untuk membuka bekas gerinda dan
menghilangkan gram dari permukaan diskonti-
nuitas.
PEMBERSIHAN ULTRASONIK
Peralatan ultrasonik dipakai untuk membersihkan
benda berukuran kecil yang jumlahnya banyak.
Pembersihan ultrasonik seringkali memakai bak
berisi cairan solvent atau deterjen untuk mening-
katkan efisiensi pembersihan dan menghemat
waktu.
Campuran air dan deterjen merupakan yang
terbaik untuk membersihkan kontaminan inorganik,
sementara cairan solvent untuk membersihkan
kontaminan organik.
PEMBERSIHAN SECARA MEKANIS
Proses pembersihan yang umumnya tidak direko-
mendasikan adalah abrasive blasting (pelor, pasir,
atau tekanan), cairan pengasah, ampelas, sikat
baja dan penyekrapan. Namun ada kalanya cara-
cara tersebut harus dilakukan.
Proses ini cenderung menutup diskontinuitas
dengan cara pemukulan atau pengerjaan dingin
pada permukaan spesimen.
Page 18
-
When mechanical cleaning must be used,
closed discontinuities can be reopened with a
chemical etch that removes a very slight
amount of material from the surface.
Saat pembersihan mekanis harus dilakukan,
diskontinuitas yang menutup dapat dibuka kembali
dengan pengetsaan yang akan menghilangkan
lapisan tipis material dari permukaan.
Table 2.1. Mechanical cleaning processes.
Table 2.2. Chemical cleaning processes.
Page 19
-
STATIONARY PENETRANT TEST
EQUIPMENT
Stationary equipment is that equipment which
is normally located in one place. The equip-
ment varies in size and is largely dependent
upon the size and type of the test specimen.
Depending on the type and process used, a
stationary system could include the following:
1. Precleaning Station (usually remote from
penetrant test station)
2. Penetrant Station (tank)
3. Drain Station (used with penetrant tank)
4. Emulsifier Station (tank)
5. Rinse Station (tank)
6. Developer Station (tank, dust chamber,
or spray equipment)
7. Dryer Station (usually an oven type)
8. Inspection Station (enclosed booth or
table with lighting facilities)
9. Postcleaning Station (usually remote from penetrant test station)
PERALATAN PENGUJIAN PENETRANT
STASIONER
Peralatan stasioner maksudnya adalah peralatan
yang letaknya menetap di satu lokasi. Peralatan
tersebut ukurannya bervariasi yang bergantung
pada ukuran dan jenis spesimen uji.
Tergantung pada jenis dan proses yang diguna-
kan, sistem stasioner terdiri dari bagian-bagian:
1. Tempat pembersihan awal (jauh dari lokasi
pengujian)
2. Tangki berisi cairan penetrant
3. Tempat pengering (digunakan bareng
dengan tangki penetrant)
4. Tangki berisi cairan pengemulsi
5. Tangki pembilasan
6. Lokasi developer (tangki, dust chamber, atau
peralatan penyemprot)
7. Tempat pengeringan (berupa oven)
8. Tempat pemeriksaan (bilik tertutup atau meja
dengan lampu penerangan)
9. Tempat pembersihan akhir (jauh dari lokasi
pengujian)
Page 20
-
PORTABLE PENETRANT TEST
EQUIPMENT
Both visible and fluorescent dye penetrants are
available in kits which can be used at a remote
location, or when testing a small portion of a
large article. The liquids are usually supplied in
pressurized (aerosol) spray cans.
A visible dye kit usually consists of:
Solvent cleaner or penetrant remover.
Visible dye penetrant.
Nonaqueous wet developer.
Wiping cloths and brush.
A fluorescent dye kit usually contains the
following:
Solvent cleaner or penetrant remover.
Fluorescent dye penetrant.
Nonaqueous wet developer.
Wiping cloths and brush.
Portable black light and transformer.
Hood to provide darkened area for
viewing indications.
PERALATAN PENGUJIAN PENETRANT
PORTABEL
Baik penetrant visible maupun fluorescent tersedia
dalam bentuk paket yang dapat dipakai memeriksa
di lokasi terbuka, atau saat menguji bagian dari
benda berukuran besar. Keduanya dikemas dalam
bentuk kaleng semprot bertekanan.
Paket penetrant visible terdiri dari:
Kaleng berisi solvent pembersih.
Kaleng berisi penetrant.
Kaleng berisi nonaqueous wet developer.
Kain lap dan kuas.
Paket penetrant fluorescent biasanya terdiri dari:
Kaleng berisi solvent pembersih.
Kaleng berisi penetrant fluorescent.
Kaleng berisi nonaqueous wet developer
Kain lap dan kuas.
Lampu ultraviolet dan trafonya.
Tudung kain hitam untuk melakukan
pemeriksaan.
Page 21
-
BLACK LIGHT EQUIPMENT
Black light equipment is required in fluorescent
penetrant testing since it supplies light of the
correct wavelengths that fall between visible
and ultraviolet, i.e. 365 nm (3650 angstroms)
to cause fluorescent materials to fluoresce.
For correct test results, the lamp should
produce an intensity of at least 1000 W/cm2
(microwatts per square centi-meter) at the test
surface.
Fluorescent penetrant dyes are usually in the
range of 475 nm to 575 nm, which is in the
visible spectrum of green to yellow.
The deep red-purple filter is designed to pass
only those wavelengths of light that will activate
the fluorescent material. Provided that the filter
is not broken or cracked, there is no danger of
injury to the human eye. It is suggested that the
filter be checked prior to each use.
At least 5 minutes of warm up is required to
reach the required arc temperature when using
mercury arc lamp. Once turned on, the lamp is
usually left on during the entire test or work
period, since switching the lamp on and off
shortens bulb life. If the black light is switched
off, it may take up to 10 minutes for the bulb to
cool sufficiently to reestablish an arc.
LAMPU ULTRAVIOLET
Lampu ultraviolet diperlukan pada pengujian
penetrant fluorescent karena menghasilkan cahaya
dengan panjang gelombang 365 nm (3650
angstroms) yang mengakibatkan material fluores-
cent berpendar.
Agar hasil pengujiannya akurat, lampu tersebut
harus menghasilkan intensitas cahaya minimum
1000 W/cm2 pada permukaan benda yang
diperiksa.
Zat pewarna fluorescent memiliki panjang gelom-
bang antara 475 nm sampai 575 nm, dapat terlihat
dengan spektrum warna hijau sampai kuning.
Filter berwarna merah-keunguan dirancang hanya
untuk dilalui cahaya dengan panjang gelombang
tertentu yang akan mengaktifkan material fluores-
cent. Asalkan filternya tidak pecah atau retak,
lampu ultraviolet tidak membahayakan mata. Disa-
rankan agar filter diperiksa tiap kali akan dipakai.
Minimum 5 menit disyaratkan untuk pemanasan
jika memakai lampu mercury. Setelah dinyalakan,
lampu tersebut sebaiknya dibiarkan menyala
selama pemeriksaan berlangsung karena sering
mematinyalakan lampu akan memperpendek usia
pakai. Jika dimatikan, lampu ultraviolet perlu waktu
10 menit untuk pendinginan yang cukup sebelum
bisa menyala lagi.
Page 22
-
PENETRANT MATERIAL COMBINATIONS
Penetrant testing materials can be used in a
variety of combinations. Most materials are
available in either pressurized spray cans or in
bulk quantities.
The flow chart below illustrates the different
material combinations. However, care should
always be taken to assure that manufacturers
specifications or company procedures are
closely followed.
Among the combinations, DRY DEVELOPER
KOMBINASI MATERIAL PENETRANT
Material untuk pengujian penetrant dapat dipakai
dalam berbagai kombinasi. Kebanyakan material
tersedia dalam kaleng bertekanan atau cairan
berkuantitas besar.
Diagram alir di bawah ini memperlihatkan kombi-
nasi material penetrant yang berbeda. Namun
demikian perlu diperhatikan agar selalu mengikuti
spesifikasi pabrik pembuat atau prosedur
perusahaan.
Diantara kombinasi tersebut, DEVELOPER KERING
should not be used with VISIBLE DYE sebaiknya tidak dipakai dengan VISIBLE DYE
PENETRANT because of the poor contrast
provided by the thin coating of very fine
powder.
PENETRANT karena kontras yang jelek antara
lapisan tipis serbuk developer dengan cairan
penetrant yang berwarna merah.
The most sensitive developer-penetrant Kombinasi developer-penetrant yang paling
combination: nonaqueous-fluorescent.
The least sensitive developer-penetrant combi-
nation: water suspended-visible.
sensitip: nonaqueous-fluorescent.
Kombinasi developer-penetrant yang paling tidak
sensitip: water suspended-visible.
Page 23
-
PENETRANT TESTING MATERIALS
Penetrant materials are often restricted to
specific groups. The established groups of
penetrant materials will use the following in a
variety of combinations to obtain the best
results.
1. Water-washable penetrants contain an
emulsifying agent which makes them
easily removable by a water rinse or
wash. This penetrant material can be
obtained with either a visible or
fluorescent dye.
2. Post-emulsifiable penetrants are highly
penetrating, oily visible or fluorescent
penetrants which are not soluble in water.
These penetrants must be treated with an
emulsifier before they can be removed by
a water rinse or wash.
3. Solvent-removable penetrants are oily
penetrants that do not contain an
emulsifying agent and are removable
only by solvents specifically designed for
that purpose.
4. Emulsifier when applied to a penetrant-
coated specimen make the resultant
mixture removable by water rinse or
wash. Emulsifiers have low penetrant
characteristics and do not remove
indications from the specimen surface.
5. Removers (solvent) are designed to be
used in conjunction with specific
penetrants. Typical removers are
available in bulk or pressurizes spray
containers.
6. Dry developers are a fluffy, absorbent
white powder that is used in both
fluorescent and visible dye penetrant
tests. It functions to draw the penetrant
inside discontinuities to the surface thus
making them visible.
7. Wet developers function similarly to dry
developers except that they are a mixture
of a developing powder and water.
8. Nonaqueous wet developers differ from
wet developers in that the developer
powder is mixed with a rapid-drying liquid
solvent.
MATERIAL UNTUK PENGUJIAN PENETRANT
Material penetrant seringkali dibatasi dalam
kelompok-kelompok khusus. Kelompok material
tersebut menggunakan kombinasi di bawah ini
untuk memperoleh hasil terbaik.
1. Water-washable penetrant mengandung
zat pengemulsi yang membuatnya mudah
dibersihkan dengan bilasan air. Material
penetrant ini dapat dibeli dalam bentuk
visible atau fluorescent.
2. Post-emulsifiable penetrant memiliki
kemampuan penetrasi yang bagus, berupa
minyak fluorescent atau visible yang tidak
larut dalam air. Emulsifier harus diaplikasikan
pada permukaan penetrant agar dapat
dibilas dengan air.
3. Solvent-removable penetrant berupa
minyak penetrant yang tidak mengandung
zat pengemulsi, dan hanya bisa dibersihkan
dengan solvent yang khusus digunakan
untuk tujuan tersebut.
4. Zat Pengemulsi jika diaplikasikan pada
lapisan penetrant di permukaan spesimen
menghasilkan campuran yang dapat dibilas
dengan air. Emulsifier memiliki sifat penetrasi
yang buruk sehingga tidak menghilangkan
indikasi dari permukaan benda uji.
5. Remover (solvent) didisain untuk
digunakan bersama dengan jenis penetrant
khusus. Remover tertentu dijual dalam
jumlah besar atau dalam kaleng semprot
bertekanan.
6. Developer kering serbuk penyerap, halus,
berwarna putih yang dipakai bersama
dengan pengujian penetrant visible dan
fluorescent. Fungsinya adalah untuk menarik
penetrant dari dalam diskontinuitas sehingga
tampak di permukaan.
7. Developer basah fungsinya mirip dengan
developer kering, hanya saja merupakan
campuran serbuk developer dengan air.
8. Nonaqueous wet developer berbeda
dengan developer basah, dimana serbuk
developer dicampur dengan cairan solvent
yang mudah menguap.
1.
Liquid oxygen (LOX) compatible materials must be used when articles inspected are subjected to contact with either liquid or gaseous oxygen.
Page 24
-
9.
Liquid oxygen (LOX) compatible
materials must be used when articles
inspected are subjected to contact with
either liquid or gaseous oxygen. These
materials are specifically designed to be
inert when in the presence of LOX.
During manufacture and testing of the
article, special care is taken not to
contaminate the article with combustible
materials.
By itself, liquid oxygen is nonexplosive,
but whenever it comes in contact with a
combustible material, a spontaneous
explosive situation occur where the
slightest spark could set off a violent
9.
Material yang kompatibel dengan oksigen
cair (LOX) harus digunakan saat benda
yang diperiksa bersinggungan dengan
oksigen cair atau gas oksigen. Material jenis
ini khusus didisain menjadi mulia saat
terkena oksigen cair.
Selama pembuatan dan pengujian artikel,
perhatian khusus harus diberikan untuk tidak
mengotori artikel tersebut dengan material
yang mudah terbakar.
Berdasar sifatnya, oksigen cair tidak mudah
meledak, namun saat terkena kontak dengan
material yang mudah terbakar, ledakan
spontan dapat terjadi akibat adanya percikan
api yang kecil saja.
reaction.
10. Low sulfur and low chlorine When small
quantities of sulfur and chlorine are
ionized and come into contact with
austenitic stainless steels, high nickel
alloys, cobalt alloys and titanium alloys,
corrosion may result.
This corrosiveness is accelerated when
the alloys are used at elevated tempe-
ratures and/or under residual stress
resulting in intergranular corrosion,
hydrogen embrittlement and stress
corrosion.
Sulfur and chlorine are not essential to
penetrant systems but they do exist in
trace amounts in the raw materials.
Nuclear and boiler codes specify from
0.5% to 1% by weight as the maximums.
10. Kadar sulfur dan klorin yang rendah Korosi
akan terjadi apabila sejumlah kecil sulfur dan
klorine terionisasi dan bereaksi dengan
austenitic stainless steel, paduan nickel
kadar tinggi, paduan cobalt, dan paduan
titanium.
Laju korosi akan dipercepat saat paduan
tersebut digunakan pada suhu tinggi
dan/atau terkena tegangan sisa hingga
terjadi korosi batas butir, penggetasan
hidrogen, dan korosi tegangan.
Sulfur dan klorin bukan merupakan unsur
penting dalam sistem penetrant, namun
mereka dalam jumlah kecil terdapat dalam
bahan baku penetrant.
Codes untuk nuklir dan boiler menyebutkan
batas maksimum sebesar 0.5% hingga 1%
berat.
Page 25
-
SAFETY PRECAUTION
In general, the materials used in penetrant
inspection can be flammable and can cause
skin irritations.
ULTRAVIOLET RADIATION The ultraviolet
spectrum of light rays generated from the
mercury arc lamp can cause sunburn and
may be injurious to the eyes. However, if the
proper filter for fluorescent dye inspection is
used, the harmful rays will be filtered out.
Personnel who use ultraviolet lights to
perform penetrant tests with fluorescent
penetrant that glows in the green-yellow
range should consider wearing yellow
glasses to block ultraviolet light from their
eyes.
FIRE many penetrant materials are
flammable. Occupational Safety and Health
Administration (OSHA) regulations requires
that penetrant materials used in open tanks
have a flashpoint of greater than 93C. The
higher the flashpoint of a material, the less
fire hazard it presents.
SKIN IRRITATION skin irritation can be
avoided by preventing unnecessary contact
and by the use of gloves, aprons, and
protective hand creams.
AIR POLLUTION the developing powders
are considered nontoxic but excessive
inhalation must be avoided. Exhaust fans
should be installed in any confined area
where dry developers or vapors from
penetrants are present.
MASALAH KESELAMATAN KERJA
Pada umumnya material yang dipakai dalam
pemeriksaan penetrant mudah terbakar dan dapat
menyebabkan iritasi kulit.
RADIASI SINAR ULTRAVIOLET spektrum sinar
ultraviolet yang dihasilkan oleh lampu mercury
dapat mengakibatkan kulit terbakar dan melukai
mata. Namun demikian jika filter lampu
digunakan dengan benar, sinar yang merugikan
dapat disaring.
Personil yang menggunakan lampu ultraviolet
untuk melakukan pengujian dengan penetrant
berwarna hijau-kuning sebaiknya memakai kaca
mata pelindung warna kuning untuk
menghalangi masuknya cahaya ultraviolet ke
dalam mata.
KEBAKARAN kebanyakan material penetrant
mudah terbakar. Peraturan OSHA mensyaratkan
bahwa material penetrant yang digunakan
dalam tangki terbuka memiliki titik nyala lebih
dari 93C. Makin tinggi titik nyala suatu material,
makin rendah bahaya kebakaran yang
ditimbulkannya.
IRITASI KULIT iritasi kulit dapat dihindari
dengan mencegah kontak yang tidak perlu dan
dengan pemakaian sarung tangan, baju
pelindung, dan krim pelindung tangan.
POLUSI UDARA serbuk developer tidak
beracun, namun menghirupnya secara
berlebihan harus dihindari. Kipas penghisap
udara sebaiknya dipasang pada daerah tertutup
dimana terdapat serbuk developer atau uap
penetrant.
PENETRANT MATERIAL DISPOSAL - PEMBUANGAN MATERIAL PENETRANT
Penetrant waste should be collected and
treated. This can be very expensive; the best
way to reduce this cost is to control the
amount of penetrant materials used.
Buangan penetrant harus dikumpulkan dan
diolah. Hal ini bisa sangat mahal; cara terbaik
untuk menghemat biaya yaitu dengan mengen-
dalikan jumlah material penetrant yang dipakai.
Page 26
-
Page 27
-
Page 28
-
CHAPTER TWO REVIEW
_______ 1.
_______ 2.
_______ 3.
_______ 4.
_______ 5.
_______ 6.
_______ 7.
_______ 8.
_______ 9.
Wire brushing Is a common and acceptable method of surface cleaning a test part that is to be penetrant inspected. A good exhaust system is recommended when working with cleaning solvents. Vapor degreasing is often used to remove oxidation, rust, and scale before a part is penetrant inspected. Parts that have been painted usually cannot be inspected with penetrants because suitable paint removing techniques have not been developed. Detergent cleaning is acceptable for postcleaning but should never be used for precleaning because it may affect the emulsifier during the penetrant test. Etching is often effective in precleaning a part that has been machined to a specific tolerance by surface grinding. Only visible dye penetrants are available in portable kits because fluorescent dyes will not function in pressurized spray cans. Dry developers are usually only used with visible dye penetrants. Emulsifiers and solvents are both commonly used in penetrant testing as postcleaners.
_______ 10. Wet developers should never be used when they will come into contact with
gaseous or liquid oxygen because of the results caused by oxygen and water mixing.
_______ 11. Emulsifiers must have high penetrating characteristics to emulsify
penetrants that lie in fillets and corners.
_______ 12. The black light used in fluorescent penetrant inspection is not hazardous to the human eyes if the correct filter is in place and not broken or cracked.
_______ 13. Penetrant materials are often placed in groupings that will assure a valid test
with materials that are compatible with each other.
_______ 14. Nonaqueous developer refers to a powder that is applied dry.
_______ 15. Post-emulsifiable penetrants are usually soluble in water after the application of an emulsifier.
_______ 16. Water-washable penetrants are cornmonly used with either a visible or
fluorescent dye.
_______ 17. Flashpoint refers to the lowest temperature at which vapors will ignite when exposed to flame.
Page 29
-
CHAPTER THREE
INTRODUCTION
This chapter discusses penetrant application.
As discussed in Chapter 2, surface cleaning is
the first step prior to the penetrant application.
CLEANING
The effectiveness of liquid penetrant testing is
based upon the ability of the penetrant to enter
surface discontinuities. All paint, carbon, oil,
varnish, oxide, plating, water, dirt, and similr
coating must be removed before application of
penetrant.
Liquid penetrant placed on the surface of a
specimen does not merely seep into
discontinuities. It is pulled into them by capillary
action. This is the reason one can cover the
under surface of an item with a penetrant and
still have a valid test.
The following are typical cleaning methods
discussed earlier.
1. Detergent cleaning
2. Vapor degreasing
3. Steam cleaning
4. Solvent cleaning
5. Rust and surface scale remover
6. Paint removal
7. Etching
8. Ultrasonic cleaning
9. Mechanical cleaning
PENDAHULUAN
Bab ini mendiskusikan aplikasi penetrant. Seperti
dibahas dalam Bab 2, pembersihan permukaan
adalah tahap pertama sebelum aplikasi penetrant.
PEMBERSIHAN
Efektifitas pengujian cairan penetrant bergantung
pada kemampuan penetrant untuk menyusup ke
dalam cacat permukaan. Semua cat, karbon, oli,
pernis, oksida, lapisan, air, kotoran dan cat
sejenisnya harus dihilangkan sebelum aplikasi
penetrant.
Cairan penetrant di atas permukaan benda uji tidak
semata-mata meresap ke dalam diskontinuitas.
Penetrant tertarik ke dalamnya oleh gaya kapiler.
Inilah mengapa permukaan bagian bawah dari
suatu benda masih dapat diperiksa dengan
penetrant dan memperoleh hasil yang valid. Berikut adalah metoda pembersihan permukaan
seperti didiskusikan sebelumnya:
1. Pembersihan dengan deterjen
2. Pembersihan dengan uap solvent
3. Pembersihan dengan uap air
4. Pembersihan dengan solvent
5. Penghilang karat dan kerak permukaan
6. Penghilang cat
7. Etsa
8. Pembersihan ultrasonik
9. Pembersihan secara mekanis
Page 30
-
PENETRANT APPLICATION
Since penetrant application is step two in the
process, lets add it to the flow diagram.
Almost any liquid could be considered a
penetrant, but modern penetrants must have:
1. The ability to hold a dye material in
suspension.
2. The ability to spread the dye evenly over
the surface.
3. The ability to carry the dye into any
discontinuity open to the surface.
4. The ability to bring up the dye as it is
coaxed back to the surface.
5. The ability, when desired, to be easily
removed.
There are two types of dye used in modern
penetrants:
1. Visible or color contrast a brightly
colored dye that is highly visible under
normal lighting conditions.
2. Fluorescent or brightness contrast an
almost colorless dye which emits visible
ligh rays when viewed under black light.
A dye with dual sensitivity, or dual-mode, or
dual-response contains a combination of
visible and fluorescent dyes.
The visible color is generally a bright red and
the fluorescent color a bronze-orange or
blue-green.
The combination permits penetrant tests to
be made under visible light and question-
able indications to be resolved under black
light; hence the term dual response.
APLIKASI PENETRANT
Aplikasi penetrant merupakan tahapan kedua
dalam proses pemeriksaan.
Hampir semua cairan dapat dianggap sebagai
penetrant, namun penetrant moderen harus
memiliki:
1. Kemampuan menahan zat pewarna dalam
suspensi.
2. Kemampuan menyebarkan pewarna secara
merata di atas permukaan benda.
3. Kemampuan membawa pewarna ke dalam
diskontinuitas yang terbuka ke permukaan
4. Kemampuan membawa kembali pewarna ke
permukaan.
5. Kemampuan, jika diinginkan, untuk dibersih-
kan dengan mudah.
Ada dua jenis zat pewarna yang digunakan dalam
penetrant moderen:
1. Visible atau color contrast pewarna merah
yang tampak jelas di bawah kondisi
pencahayaan normal.
2. Fluorescent or brightness contrast pewarna
yang akan memancarkan cahaya tampak
apabila dilihat dengan lampu ultraviolet.
Pewarna dengan sensitivitas ganda atau mode
ganda atau respon ganda mengandung kombinasi
pewarna visible dan fluorescent.
Pewarna visible umumnya merah menyala dan
pewarna fluorescent berwarna kuning-perunggu
atau biru-hijau.
Kombinasi ini memungkinkan pengujian
penetrant dilakukan di bawah cahaya biasa dan
indikasi yang meragukan diperiksa di bawah
cahaya ultraviolet.
Page 31
-
Penetrants, either fluorescent or visible can be
applied by any one of the following means:
1. Spraying usually using a conventional
low pressure spray guns or from
pressurized spray cans.
2. Brushing or swabbing usually applied
with rags, cotton waste, or brushes, when
testing a small, specific area of the
specimen.
3. Dipping or immersion the article is
generally lowered into a tank of
penetrant, then raised and allowed to
drain. This method is impractical when
dealing with large articles, and is wasteful
when only small areas of a large
specimen are to be tested.
4. Flowing or drain-dwell the penetrant is
simply poured over the surface and
allowing it to drain.
The terminology used in penetrant application
is listed in Table 3.1.
Penetrant, baik fluorescent maupun visible dapat
diaplikasikan dengan salah satu dari cara berikut:
1. Penyemprotan biasanya menggunakan alat
penyemprot bertekanan rendah atau dari
kaleng semprot bertekanan.
2. Kuas atau kain bisasanya diaplikasikan
dengan kain lap, kapas, atau kuas, apabila
menguji sebagian kecil/lokasi dari suatu
benda.
3. Pencelupan benda uji dibenamkan ke
dalam tangki penetrant, lalu diangkat dan
ditiriskan. Metoda ini tidak cocok untuk
benda berukuran besar dan merupakan
pemborosan apabila hanya daerah kecil saja
yang diuji.
4. Penuangan penetrant dituangkan di atas
permukaan benda dan setelah itu ditiriskan. Istilah yang digunakan dalam aplikasi penetrant
dapat dilihat dalam Table 3.1.
Table 3.1. Liquid penetrant application terminology.
Page 32
-
PENETRATION (DWELL) TIME
The period of time during which the penetrant
is permitted to remain on the specimen is a
vital part of the test. This time, known as dwell
time, is directly related to the size and shape of
the discontinuities anticipated since the
dimensions of the discontinuities determine the
rapidity with which penetration occurs.
Tight, crack-like discontinuities may require in
excess of 30 minutes for penetration to an
extent that an adequate indication can be
expected. Gross discontinuities may be
suitably penetrated in 3 to 5 minutes.
The temperature of the specimen and
temperature of the penetrant can affect the
required dwell time.
Warming the specimen accelerates
penetration and shortens dwell time.
However, care should be taken not to
overheat the specimen since too much heat
may cause evaporation of the penetrant
from the discontinuity, and thereby reduce
sensitivity.
Dwell times are based on the assumption
that the penetrant will remain wet on the part
surface. Additional penetrant may be
applied during dwell time.
In each instance, dwell time is determined by
the anticipated discontinuities and the
penetrant manufacturers recommendations.
Typical minimum penetration times are shown
in Table 3.2.
WAKTU PENETRASI (WAKTU DIAM)
Jangka waktu dimana penetrant berada di atas
permukaan benda uji merupakan bagian
terpenting dari pengujian. Jangka waktu ini dikenal
sebagai waktu diam, yang berhubungan langsung
dengan ukuran dan bentuk diskontinuitas yang
dicari mengingat ukuran diskontinuitas menentu-
kan kecepatan terjadinya penetrasi.
Diskontinuitas yang rapat, seperti retakan
memerlukan waktu penetrasi lebih dari 30 menit
untuk terbentuknya indikasi. Diskontinuitas
berukuran besar memerlukan waktu penetrasi
antara 3 sampai 5 menit.
Suhu benda uji dan suhu cairan penetrant dapat
mempengaruhi waktu diam yang disyaratkan.
Menghangatkan benda uji mempercepat
penetrasi dan mempersingkat waktu diam.
Namun demikian perlu diperhatikan agar tidak
berlebihan memanaskan spesimen karena suhu
yang terlalu tinggi menyebabkan penguapan
penetrant dari dalam diskontinuitas, yang
akhirnya akan mengurangi sensitivitas.
Waktu diam didasarkan pada asumsi bahwa
penetrant tetap dalam kondisi basah pada
permukaan benda. Penambahan penetrant
selama waktu diam diperbolehkan.
Pada tiap kasus, waktu diam ditentukan oleh jenis
diskontinuitas yang hendak dicari dan
rekomendasi dari pabrik pembuat penetrant.
Waktu penetrasi minimum untuk kasus tertentu
diperlihatkan dalam Tabel 3.2.
Page 33
-
Table 3.2. Typical minimum penetration time.
Page 34
-
PENETRANT TESTING PROCESSES
We previously mentioned the two types of
penetrants: visible and fluorescent. For both
categories, there is a further breakdown.
1. Water-washable (visible or fluorescent).
2. Post-emulsifiable (visible or fluorescent).
3. Solvent-removable (visible or fluorescent).
Water-washable Penetrants (WW Penetrants)
WW penetrants have a built-in emulsifier, or
what-so-called self-emulsifying penetrants.
The penetrant is soluble in water and is easily
removed by a water rinse.
Care must be taken to insure that the spray
volume and force does not wash penetrant out
of the discontinuity. A solid stream of water is
not desirable. A coarse droplet size provides
optimal removal. Water pressure should not
exceed 40 psi.
The recommended temperature range for water
rinse is 10oC - 38oC. Water temperatures above
38oC are not recommended because this may
speed up the evaporation of the penetrant.
At angles of 80-90 degree, the spray droplets
will rebound into oncoming spray, which diverts
the droplets and reduce velocity. Generally, an
angle of 45-75 degree is most effective.
The sketch below represents the steps in a
water-washable penetrant test.
PROSES PENGUJIAN PENETRANT
Telah disebutkan sebelumnya ada dua jenis
penetrant: visible dan fluorescent. Kedua jenis
penetrant tersebut dapat dirinci menjadi:
1. Water-washable (visible atau fluorescent).
2. Post-emulsifiable (visible atau fluorescent).
3. Solvent-removable (visible atau fluorescent).
Water-washable Penetrants (WW Penetrants)
WW penetrant mengandung zat pengemulsi, atau
dinamakan penetrant self-emulsifying. Penetrant
ini larut dalam air dan mudah dibersihkan dengan
bilasan air.
Harus diperhatikan agar volume dan kekuatan
semprot tidak sampai membasuh penetrant dari
dalam diskontinuitas. Aliran air yang pejal tidak
diinginkan. Air dalam bentuk percikan kasar
menghasilkan pembersihan yang optimal. Tekanan
air tidak boleh melebihi 40 psi.
Suhu air pembilas yang direkomendasikan sebesar
10oC - 38oC. Suhu air melebihi 38oC tidak direko-
mendasikan karena dapat mempercepat pengua-
pan penetrant.
Pada sudut 80-90 derajat, titik-titik air akan
memantul kembali dan menabrak titik air yang
datang sehingga mengurangi kecepatan. Sudut
semprot yang paling efektif adalah 45-75 derajat.
Gambar di bawah memperlihatkan langkah-
langkah pengujian water-washable penetrant.
Page 35
-
Water-washable penetrants are usually
preferred for use on articles with a rough
surface or if they contain threads or keyways.
The built-in emulsifier provides the best
penetrant removal from blind holes and other
hard-to-reach locations, but has the
disadvantage of poor reliability in detecting
wide or shallow discontinuities.
Post-emulsifiable Penetrants (PE Penetrants)
The penetrants employed in the PE process
DO NOT contain an emulsifying agent. The
penetrant is NOT soluble in water.
PE penetrants require a two-step removal
process. Excess penetrant is removed by
applying a separate emulsifier to make the
penetrant water-washable. The emulsifier is
usually applied by dipping/immersion,
spraying, or flowing. The amount of dwell time
in the emulsifier is in the range of one to four
minutes in accordance with manufacturer
recommendations and the type of defects
expected.
The resultant penetrant-emulsifier mixture is
removed by water rinse.
Solvent-removable Penetrants (SR Penetrants)
The solvent removable method employs post-
emulsification-type penetrant. But instead of
using an emulsifier and water wash, excess
penetrant is removed by a solvent.
SR penetrants have the advantage of portability
and can be used outdoors without using heavy
complex equipment.
They are excellent for many maintenance
inspection and for checking portions of larger
structure.
Water-washable penetrant biasanya digunakan
untuk memeriksa benda yang permukaannya kasar
atau benda yang ada ulir atau alurnya.
Emulsifier yang ada di dalamnya mengakibatkan
penetrant mudah dihilangkan dari lubang buntu
dan lokasi yang sulit dijangkau, namun memiliki
kelemahan dalam mendeteksi diskontinuitas yang
lebar dan dangkal. Post-emulsifiable Penetrants (PE Penetrants)
Penetrant yang dipakai pada proses PE tidak
mengandung zat pengemulsi. Penetrant ini tidak
larut dalam air.
PE penetrant memerlukan dua langkah proses
pembersihan. Sisa penetrant dibersihkan dengan
aplikasi emulsifier secara terpisah sehingga
penetrant dapat dibilas dengan air. Emulsifier
biasanya diaplikasikan dengan pencelupan,
penyemprotan, atau penuangan. Lamanya waktu
diam untuk emulsifier adalah satu sampai empat
menit mengacu pada rekomendasi pabrik
pembuat dan jenis cacat yang dicari.
Hasil campuran antara penetrant dan emulsifier
selanjutnya dapat dibilas dengan air.
Solvent-removable Penetrants (SR Penetrants)
Metoda solvent removable menggunakan
penetrant jenis post-emulsification. Solvent
digunakan untuk menghilangkan pentrant sisa
yang ada di permukaan benda.
SR penetrant menguntungkan dari segi portabilitas
dan dapat digunakan di luar tanpa menggunakan
peralatan yang berat dan rumit.
Cara ini sangat memuaskan untuk pemeriksaan
pemeliharaan dan untuk memeriksa bagian dari
suatu struktur yang besar.
Page 36
-
Penetrant is often applied from a pressurized
spray can which makes the system very
portable.
After the specified dwell time, the excess
penetrant is first removed by wiping with
absorbent towels and then cleaned with towels
dampened with solvent.
Solvent is NEVER applied directly to the
specimen as it might wash out or dilute the
penetrant in the discontinuity.
Table 3.3 lists the preferred processes for
various penetrant test problems.
Penetrant seringkali diaplikasikan dari kaleng
semprot bertekanan yang membuat sistem ini
sangat portabel.
Setelah waktu diam terpenuhi, penetrant sisa pada
mulanya diseka dengan lap penyerap dan
kemudian dibersihkan dengan lap yang dibasahi
dengan solvent.
JANGAN PERNAH menyemprotkan solvent secara
langsung ke permukaan benda karena akan
melenyapkan penetrant dari dalam diskontinuitas.
Tabel 3.3 memperlihatkan macam-macam proses
pengujian penetrant dan kegunaannya.
Table 3.3. Process selection guide.
Page 37
-
1. Water-washable
2. Post-emulsifiable
3. Solvent-removable
Page 38
-
LEAK-THROUGH TECHNIQUE
The leak-through technique is well suited for
finding leaks in such articles as tanks, piping,
tubing and hollow castings. There is no
knowledge concerning other quality characte-
ristics of the specimen is obtained.
The sketch below illustrates the liquid penetrant
leak-through test as used on a large plate
section.
FILTERED PARTICLE TECHNIQUE
Filtered particle testing uses small particles
suspended in the penetrant liquid. In most
instances these particles are fluorescent.
The size of the suspended particles varies and
depends upon the porous nature of the
inspection surface.
When testing a porous surface with filtered
particles, all of the liquid penetrant will be
absorbed. There will be no excess requiring
removal. Where a discontinuity (such as a
crack) is present, the increased area created
by a crack (its walls, etc.) will cause more of the
penetrant to be absorbed there than elsewhere.
The crack will filter the penetrant, leaving the
fluorescent particles on the surface. Since more
penetrant will be absorbed there, a greater
buildup of particles will be found at the site of
the crack. This particel buildup provides an
indication of discontinuities open to the
surface.
TEKNIK PEREMBESAN BOCORAN
Teknik perembesan bocoran sangat sesuai untuk
mendeteksi kebocoran pada tangki, pipa, tube,
dan cor-coran berongga. Tidak ada informasi lain
yang diperoleh mengenai karakteristik kualitas
benda.
Gambar di bawah memperlihatkan pengujian
kebocoran dengan penetrant untuk memeriksa
bagian dari suatu pelat.
TEKNIK PARTIKEL TERSARING
Teknik ini menggunakan partikel berukuran kecil
yang tersuspensi dalam cairan penetrant. Partikel
yang dipakai biasanya fluorescent.
Ukuran partikel yang tersuspensi bervariasi,
tergantung pada kondisi pori-pori permukaan
benda yang diperiksa.
Saat menguji permukaan berpori dengan cara ini,
semua cairan penetrant akan diserap. Tidak ada
langkah pembersihan penetrant sisa pada teknik
ini. Pada tempat dimana terdapat diskontinuitas
(seperti retak), penambahan luasan akibat retak
(dinding retak, dll.) akan mengakibatkan penetrant
lebih banyak terserap di daerah tersebut.
Retak akan menyaring penetrant, meninggalkan
jejak partikel fluorescent pada permukaan. Karena
lebih banyak penetrant terserap di sana,
pengumpulan partikel lebih banyak terjadi di
daerah retak. Pengumpulan partikel ini menun-
jukkan adanya diskontinuitas yang membuka ke
permukaan.
Page 39
-
FIXING AND RECORDING INDICATIONS
Fixing and recording indications can be carried
out by:
1. Photographs digital photography
provide excellent permanent records. In
addition to photographs, video cassette
recorders (VCRs) and closed-circuit
television cameras (CCTVs) are used to
record indications.
2. Special wax and plastic film developers
have been developed to absorb and fix
the penetrant indication to form a
permanent record.
a. Strippable lacquers are sprayed in
several coats over the indication and
when dry can be lifted to provide a
permanent record.
b. Special fixers are sprayed over the
indication and when dry are lifted with
transparent tape.
PEMELIHARAAN DAN PEREKAMAN INDIKASI
Pemeliharaan dan perekaman indikasi dapat
dilakukan dengan:
1. Fotografi foto digital merupakan cara
terbaik untuk merekam indikasi. Disamping
itu video kaset dan kamera CCTV juga dapat
digunakan untuk merekam indikasi.
2. Lilin khusus dan lapisan plastik developers
dikembangkan untuk menyerap dan
mengawetkan indikasi penetrant dan
membentuk rekaman permanen.
a. Lapisan lak disemprotkan beberapa lapis
di atas indikasi, dan setelah kering dapat
dikelupas untuk menghasilkan rekaman
permanen.
b. Fixer khusus disemprotkan di atas indikasi
dan setelah kering diangkat dengan pita
transparan (isolasi).
Page 40
-
CHAPTER THREE REVIEW
_______ 1.
_______ 2.
_______ 3.
_______ 4.
_______ 5.
_______ 6.
_______ 7.
_______ 8.
_______ 9.
A dual sensitivity penetrant contains a special dye that is visible in white light and will fluoresce without the use of a black light. A part being penetrant inspected must stay immersed in the penetrant tank for the entire specified dwell time. The liquid penetrant leak-through test refers to the ability of a penetrant to spread through the dry developer evenly. Visible dye penetrants are usually considered to be less sensitive than fluorescent penetrants. Water-washable penetrants have a built-in emulsifier that permits good results in penetrant removal from parts suspected of having wide or shallow discontinjuities. Solvent-removable penetrants are available in both visible and fluorescent dye. Excess post-emulsifiable penetrant is commonly removed by spraying the surface of the part with cleaner (solvent) and then wiping with a lint-free towel. Water washable penetrant systems are usually very portable because the materials are commonly used in pressurized spray cans. Warming the specimen to temperatures up to about 20o C tends to accelerate penetration and shortens dwell time.
_______ 10. For the dwell time to be accurate, the surface of the specimen must stay
wet with penetrant for the entire time specified.
_______ 11. The typipal dwell time for most penetrant Inspections is about 20-30 minutes.
_________________________ 12. _________________________
_________________________ 13. _________________________ _________________________
List two (2) of the commonly used methods of applying penetrants to a specimen that is to be inspected. List four (4) of the commonly used methods of precleaning the specimen before penetrant inspection.
_________________________
_______ 14. If you were asked to examine 200 steel bolts, each 3/8 x 3 inches with rolled threads, which penetrant method would you choose?
(a) Post-emulsification (b) Water-washable
_______ 15. The filtered particle method of penetrant inspection used extra fine
fluorescent particles that will not pass through a #120 sieve.
Page 41
-
CHAPTER FOUR
INTRODUCTION
This chapter discusses emulsification,
penetrant removal, and developer application.
POST EMULSIFIABLE PENETRANT (PE
PENETRANT)
This type of penetrant emulsification is
accomplished by dipping, spraying, or flowing,
but NEVER by brushing. Brushing makes
emulsification more difficult to control, besides
the bristle of the brush may enter the
discontinuity.
PENDAHULUAN
Bab ini mendiskusikan proses emulsifikasi,
pembersihan penetrant, dan aplikasi developer. POST EMULSIFIABLE PENETRANT (PE
PENETRANT)
Emulsifikasi penetrant jenis ini dilakukan dengan
pencelupan, penyemprotan atau penuangan,
namun TIDAK BOLEH diaplikasikan dengan kuas.
Aplikasi dengan kuas menyulitkan pengontrolan
emulsifikasi, disamping bulu-bulu kuas bisa masuk
ke dalam diskontinuitas.
Page 42
-
The skecth below represents the steps in a
post-emulsifiable penetrant test.
Gambar berikut menunjukkan langkah-langkah
pengujian post-emulsifiable penetrant.
Page 43
-
The length of time the emulsifier is left to dwell
before commencing the penetrant removal
cycle is determined by the emulsifier used and
the type of discontinuities suspected.
If too short an emulsification time is used, not
all penetrant will be removed, which will cloud
over discontinuities.
If too long a time is used, penetrant within the
discontinuities will also become water soluble
and be washed away with excess penetrant.
The PE penetrant makes the water wash less
critical.
The sketches below compare the effects of
water-washable and post emulsification
penetrants.
Jangka waktu emulsifier dibiarkan di atas
permukaan benda sebelum dilakukan pembersi-
han penetrant ditentukan oleh jenis emulsifier dan
diskontinuitas yang dicari.
Jika waktu emulsifikasi terlalu singkat, tidak semua
penetrant akan tersapu, yang nantinya akan
menghalangi munculnya diskontinuitas.
Jika waktu emulsifikasi terlalu panjang, penetrant di
dalam diskontinuitas akan bereaksi dengan
emulsifier dan akan tersapu oleh air.
PE penetrant membuat pembilasan dengan air
menjadi tidak terlalu kritis.
Gambar di bawah ini membandingkan antara
pemakaian WW dan PE penetrants.
Page 44
-
There are two types of emulsifiers used in the
removal process LIPOPHILIC (Method B)
and HYDROPHILIC (Method D).
Lipophilic and hydrophilic processes have
completely different mechanisms in converting
the oil based penetrant into a mixture that can
be washed.
LIPOPHILIC METHOD
Lipophilic emulsifier is applied by immersion to
prevent mechanically mixing emulsifier into the
penetrant. In some automatic installations, the
emulsifier is applied as a fog or mist.
The mechanism of lipophilic emulsification is by
DIFFUSION. Molecules of emulsifier enter into
the penetrant layer while at the same time
molecules of penetrant enter the emulsifier
layer. The rate of diffusion increases with
increased concentration and higher
temperatures.
The three properties of lipophilic emulsifiers
that control the washing characteristics are
activity, viscosity and water tolerance.
If a penetrant is highly resistant to water, an
emulsifier with a high activity is needed. High
viscosity emulsifiers diffuse more slowly than
low viscosity emulsifiers. Lipophilic emulsifier
should tolerate 5% water by weight without
gelling, separating or coagulating and still be
capable of passing the penetrant removability
test.
Method B emulsifiers are supplied in the ready-
to-use form and do not require further mixing.
Terdapat dua jenis emulsifier yang digunakan
dalam proses pembersihan LIPOPHILIC (Metoda
B) dan HYDROPHILIC (Metoda D).
Proses lipophylic dan hydrophilic memiliki
mekanisme yang sangat berbeda dalam merubah
penetrant berbahan dasar menjadi campuran yang
bisa dibilas dengan air.
METODA LIPOPHILIC
Emulsifier lipophilic diaplikasikan dengan cara
pencelupan untuk mencegah bercampurnya emul-
sifier dengan penetrant. Pada instalasi otomatis,
emulsifier diaplikasikan secara pengkabutan.
Mekanisme emulsifikasi lipophilic adalah dengan
cara DIFUSI. Molekul emulsifier memasuki lapisan
penetrant, sementara pada saat yang bersamaan
molekul penetrant memasuki lapisan emulsifier.
Laju difusi akan bertambah dengan peningkatan
konsentrasi dan penambahan suhu. Tiga sifat emulsifier lipophilic yang mengontrol
karakteristik pembilasan adalah aktivitas,
kekentalan, dan toleransi terhadap air.
Jika suatu penetrant memiliki ketahanan tinggi
terhadap air, maka diperlukan emulsifier dengan
aktivitas yang tinggi. Emulsifier dengan kekentalan
tinggi berdifusi lebih lambat ketimbang emulsifier
yang encer. Lipophilic emulsifier harus mampu
mentolerir 5% air tanpa mengalami penggumpalan
atau pembekuan dan mampu lulus uji pember-
sihan penetrant.
Emulsifier metoda B dijual dalam bentuk siap pakai
dan tidak memerlukan pencampuran lagi.
Page 45
-
HYDROPHILIC METHOD
Hydrophilic emulsifier is a water based solution
and is a mixture of chemicals called
surfactants. They are supplied as a concentrate
and are mixed with water either before or
during the removal process. The concentrate is
required to contain a maximum of 5% water.
Hydrophilic emulsifier works based on the
principle to peel the penetrant away or by
dissolving droplets so they do not redeposit on
the surface.
Because post-emulsifiable penetrant is
incompatible with water, prerinsing before
application of emulsifier is recommended.
Prerinsing removes 60-80% of the surface layer
of penetrant, which greatly reduces
contamination of the emulsifier. It also provides
an even layer of surface penetrant.
Hydrophilic emulsifier is applied either by
immersion or spraying.
Immediately following the emulsification, a
fresh water rinse of the entire part is required.
This stops the action of any emulsifier
remaining on the part.
METODA HYDROPHILIC
Emulsifier hydrophilic adalah larutan antara air dan
zat kimia yang disebut surfactant. Dijual di pasaran
dalam bentuk konsentrat dan harus dicampur dulu
dengan air sebelum atau selama proses
pembersihan. Konsentrat disyaratkan mengan-
dung air maksimum sebesar 5%.
Emulsifier hydrophilic bekerja berdasar pada
prinsip pengelupasan lapisan penetrant, atau
dengan melarutkan penetrant sehingga tidak
terdeposit kembali ke permukaan.
Karena post-emulsifiable penetrant tidak
kompatibel dengan air, direkomendasikan untuk
melakukan pembilasan awal sebelum aplikasi
emulsifier. Pembilasan awal menghilangkan 60-
80% lapisan penetrant di permukaan, sehingga
banyak mengurangi terjadinya kontaminasi pada
emulsifier. Pembilasan awal juga menghasilkan
lapisan penetrant permukaan yang rata.
Emulsifier hydrophilic diaplikasikan dengan cara
pencelupan atau penyemprotan.
Segera setelah proses emulsifikasi, disyaratkan
untuk membilas seluruh bagian benda uji dengan
air bersih. Langkah ini akan menghentikan aksi
emulsifikasi yang masih tersisa di permukaan
benda.
Page 46
-
DEVELOPERS APPLICATION
Some indications may be visible prior to the
application of a developer, but this step will
ensure that ALL discontinuities are visible to the
naked eye.
Developing is accomplished when a highly
absorbent powder is applied to the item being
tested after excess penetrant is removed.
The penetrant is actually drawn out of the
discontinuity by the strong capillary action of
the developer.
As shown above, the image of the discontinuity
in the developer will actually be larger than the
actual size of the discontinuity.
There are two common types of developers in
use today dry and wet. Both use a white
powder and the primary difference is in the
method of application.
DRY DEVELOPERS
Dry developer is supplied as a fine-grained
fluffy white powder.
Methods of application include the use of low
air pressure, such as that from a rubber
squeeze bulb or a spray gun. A soft brush may
sometimes be used; or, since the developer is
a very fine powder, articles may be simply
dipped in the developer, raised, and the
excess powder removed by gently blowing,
shaking, or tapping the article.
APLIKASI DEVELOPER
Beberapa indikasi bisa saja nampak sebelum
developer diaplikasikan, namun langkah ini akan
memastikan bahwa SEMUA diskontinuitas akan
tampak oleh mata telanjang.
Proses developing dilakukan dengan mengapli-
kasikan serbuk berdaya serap tinggi ke permukaan
benda uji setelah sisa penetrant dibersihkan.
Penetrant akan tertarik keluar dari diskontinuitas
akibat gaya kapiler yang kuat dari serbuk
developer. Seperti diperlihatkan dalam gambar di atas, cit