KHOR AL ZUBAIR PORT in Destructive Testing ( NDT )
KHOR AL ZUBAIR PORT in Ultrasonic Testing (UT)
Traditional Ultrasonic inspection uses high frequency sound energy to conduct examinations and perform measurements. Considerable information may be gathered during ultrasonic testing such as the presence of discontinuities, material or coating thickness. The detection and location of discontinuities is enabled by the interpretation of ultrasonic wave reflections generated by a transducer. These waves are introduced into a material and travel in a straight line and at a constant speed until they encounter a surface. The surface interface causes some of the wave energy to be reflected and the rest of it to be transmitted. The amount of reflected vs. transmitted energy is detected and provides information on the size of the reflector, therefore the discontinuity encountered. Three basic ultrasonic techniques are commonly used:
1. Pulse-echo and through transmission
In pulse-echo testing a transducer sends out a pulse of energy and the same or a second transducer listens for reflected energy, also known as an echo. Pulse echo is especially effective when only one side of a material is accessible.
Through transmission is performed using two transducers on opposing sides of the specimen. One acts as a transmitter and the other as a receiver. Through transmission is useful detecting discontinuities that are not good reflectors when signal strength is weak.
2. Normal/Angle Beam
Normal beam testing uses a sound beam that is introduced at 90 degrees to the surface, while angle beam utilizes a beam that is introduced into the specimen at some angle other than 90 degrees. The choice between the two is made based on:
The orientation of the feature of interest so that the sound may produce the largest reflection from the feature.
Obstructions on the surface of the specimen that must be avoided.
3. Contact and Immersion
To get useful levels of sound energy into the material, the air between the transducer and the specimen must be removed. This is referred to as coupling. Two types of coupling are utlizied:
In contact testing, a couplant such as water, oil or a gel is applied between the transducer and the specimen.
In immersion testing, the specimen and the transducer are placed in a water bath. This allows better movement of the transducer while maintaining consistent coupling.
Some of the most common Ultrasonic applications are:
Flaw detection (cracks, inclusions, porosity, delaminations etc.)
Erosion/Corrosion thickness gauging
Assessment of bond integrity
Estimation of grain size in metals
Estimation of void content in composites and plastics
Info from ultrasonic inspection can be presented in a number of formats:
A-Scan displays the amount of received ultrasonic energy as a function of time.
B-Scan displays a profile view (cross-sectional) of a specimen.
C-Scan displays a plan type view of the specimen and discontinuities.
Hybrid/Stitched displays a C-Scan plan view with A and/or B Scan views along with C-Scan views that have been woven together to illustrate a clearer picture of the damaged areas of a specimen. The stitched views are used for larger specimens and surface areas.
Some of the major advantages of ultrasonic testing are:
Detects surface and subsurface defects.
Depth of penetration vs. other test methods is superior.
Only single sided access is required with a pulse-echo technique.
High accuracy regarding estimating discontinuity size and shape.
Minimal specimen preparation is required.
Instantaneous results produced by using electronic equipment.
Detailed images can be produced with automated systems.
Major limitations of ultrasonic testing are:
Surface must be accessible.
Skill training is more extensive that with some other methods.
Normally requires couplant to promote sound transfer.
Surface roughness, complex geometries, small parts or exceptionally thin materials are difficult to inspect.
Coarse grained materials i.e. cast iron are difficult to inspect due to low sound transmission and high signal noise.
Linear defects oriented parallel to the sound beam go undetected
Reference standards are required for equipment calibration
KHOR AL ZUBAIR PORT in Magnetic Particle Testing (MT)
Used for finding surface/near surface defects in ferromagnetic material, Magnetic Particle testing is a versatile inspection method used for field and shop applications. Magnetic particle testing works by magnetizing a ferromagnetic specimen using a magnet or special magnetizing equipment. If the specimen has discontinuity, the magnetic field flowing through the specimen is interrupted and leakage field occurs. Finely milled iron particles coated with a dye pigment are applied to the specimen. These are attracted to leakage fields and cluster to form an indication directly over the discontinuity. The indication is visually detected under proper lighting conditions.
The basic procedure that is followed to perform magnetic particle testing consist of the following:
1. Pre-cleaning of component
2. Introduction of Magnetic field
3. Application of magnetic media
4. Interpretation of magnetic particle indications
It is essential for the particles to have an unimpeded path for migration to both strong and weak leakage fields. Therefore, the component in question should be clean and dry before beginning the inspection process. The presence of oil, grease or scale may compromise the inspection. The introduction of the magnetic field can be introduced a number of ways including use of a permanent magnet, flowing of electrical current through the specimen or flowing an electrical current through a coil of wire around the part or through a central conductor running near the part. Two types of magnetic fields can be established within the specimen. These are a longitudinal magnetic field that runs parallel to the long axis of the part or a circular magnetic field that runs circumferentially around the perimeter. Longitudinal magnetic fields are produced using a magnetic coil or a permanent magnet called a magnetic particle yoke. Circular magnetic fields are produced by passing current through the part or by placing the part in a strong circular magnetic field.
Magnetic particle inspection can use either wet or dry magnetic media. The dry method is more
portable, while the wet method is generally more sensitive since the liquid carrier gives the magnetic particles additional mobility.
Indications that are formed after applying the magnetic field must be interpreted by a skilled inspector. This requires the individual to distinguish between relevant and irrelevant indications.
The following are the advantages of magnetic particle inspection:
Can detect both surface and near subsurface indications
Can inspect parts with irregular shapes easily
Pre-cleaning is not as critical as for some other inspection methods
Fast method of inspection and indications are visible directly on the specimen surface
Considered low cost compared to many other NDT techniques
Very portable inspection especially when used with battery powered equipment
KHOR AL ZUBAIR PORT in Liquid Penetrant Testing (PT)
Penetrant testing based on the properties of capillary action, or the phenomenon of a liquid rising or climbing when confined to a small opening due to surface wetting properties of the liquid. Penetrant testing is used for finding surface breaking discontinuities on relatively smooth, nonporous surfaces.
The types of defects that can be found with penetrant inspection are:
Rolled Products: penetrant identifies anomalies (cracks, seams or laminations)
Castings: cold shuts, hot tears, porosity, blow holes or shrinkage
Forgings: illuminating cracks, laps or external bursts
Welds: to identify cracks, porosity, undercut, overlap, lack of fusion or lack of penetration
There are two main types of penetrant; fluorescent or visible. Within each method there are several methods including water washable, postemulsifiable-lipophilic, solvent removal and postemulsifiable-hyperdrophilic. The type and penetrant method are chosen based on sensitivity levels 1-4 and are based on job site conditions and other variables.
There are six main steps involved with penetrant testing:
1. Pre-Clean: Parts must be free of dirt, grease, rust, scale, oil or grease.
2. Application of Penetrant Material: The penetrant material may be applied by brushing, spraying, dipping/immersing or flow on the material.
3. Dwell Time/Penetrant Removal: The solution must be allowed to "dwell" on the surface to allow the penetrant to fill any defects that are present. Dwell times vary according to penetrant type, temperature and material types and finishes. Removal technique depends upon the type of penetrant used i.e. Solvent Removable, Water Washable or Post-Emulsifiable.
4. Developer Application
5. Inspection/Evaluation: In almost all cases the inspector evaluates the penetrant indications a specified accept/reject criteria and attempts to determine the origin of the indication.
6. Post Clean: The final step is to remove all penetrant processing materials from the component.
The main advantages of Penetrant testing are:
Relatively easy to use
Used on a wide range of material types
Large areas or large volumes of parts/material can be inspected rapidly and at low cost
Parts with complex geometries can be inspected easily
Indications are produced directly on the surface of the part providing a visual image of the anomaly
Aerosol spray cans can make equipment very portable
KHOR AL ZUBAIR PORT in Radiographic Testing (RT)
Industrial radiography is used for a variety of applications but is commonly performed using two different sources of radiation, X-Ray and Gamma ray sources. The choice of radiation sources and their strength depends on a variety of factors including size of the component and the material thickness. Within the broad group of X-Ray and Gamma ray sources are a variety of camera choices with varying radiation strengths. International ship supply X-Ray capabilities run the gamut from 4 MEV units utilized to radiograph extremely large and thick castings and forgings, to portable X-Ray cameras used for field weld applications and thin wall material inspection. Gamma sources vary from very low level fluoroscopic units to perform real time corrosion under insulation surveys, to Iridium (Ir192) and Selenium (Se 75) sources used for a variety of weld inspections, to Cobalt (Co 60) inspections for thick component testing.
There are many advantages to radiography including:
Inspection of a wide variety of material types with varying density
Ability to inspect assembled components
Minimum surface preparation required
Sensitivity to changes in thickness corrosion, voids, cracks and material density changes
The ability to detect both surface and subsurface defects
The ability to provide a permanent record of the inspection.
The disadvantages of radiography are:
Safety precautions are required for the safe use of radiation,
Access to both sides of the specimen are required
Orientation of the sample is critical
Determining flaw depth is impossible without additional angled exposures
international ship supply a complete line of radiographic services for both shop and field applications. Our staff of qualified, certified, professional radiographers operate within strict safety parameters and produce high quality radiographs that allow us to utilize our interpretation skills honed through many years of experience to determine if an anomaly is actually a defect or can be accepted per code requirements.
KHOR AL ZUBAIR PORT in Visual Testing (VT)
A visual inspection or visual examination of objects, parts or components is the oldest and reliable non-destructive testing method. The test method is applied to almost every product as a quality assurance tool. The most detrimental unacceptable discontinuities in the objects or items are the surface opening discontinuities. Visual scanning, inspection or testing can successfully detect these unacceptable surface discontinuities without applying expensive test methods.International Ship Supply perform visual examination of welded joints or fabricated components, castings, forgings, rolled products and several other wrought products in accordance with AS 3978, ASME V Article 9, ASE IX QW 194, EN 970, ISO 10042, ASTM other similar standards.
KHOR AL ZUBAIR PORT in Ultrasonic Thickness Measurement (UTM)
One of the most widespread NDT methods in mechanical equipment of industrial installations for the characterization of erosion and deterioration is the thickness measurements with the ultrasonic method. International Ship Supply offers high level thickness measurement services on pipes, pressure vessels, boilers, tanks etc, by its experienced and certified inspectors. Thickness measurement is achieved by placing the UT probe on the object surface. Local or general reductions of thickness can be located and measured with high precision. The instruments that are used for the measurement are portable and light with possibilities of saving the measurements data in a data logger. The use of different probes offers the capability to perform thickness measurements in inaccessible surfaces, on very thin plates, on high temperature environments, above paint as well as on surfaces with intense local corrosion without any surface smoothing required.
Advantages of the method:
Quick measurements with direct results
High precision measurements
The inspected object can be in-service.
No particular surface preparation required.
Measurements can be made without removal of the paint.
Measurements can be made in inaccessible regions using suitable probes.
In many cases there is the possibility of measuring corroded surfaces without the need of cleaning the surface (using special probes).
Corrosion rate calculations can be made with thickness reduction observations with repeated measurements in the same points.
Measurements on high temperature surfaces possible.
Display of corrosion profile on B-Scan form.
KHOR AL ZUBAIR PORT in Ferrite Measurement
Austenitic, Duplex, Super-duplex stainless steels require adequate proportion of ferrite in the product to obtain acceptable corrosion resistance and strength and especially resistance to Stress Corrosion Cracking (SCC). The laboratory based destructive method such as microstructural analysis on the test specimen or sample obtained from the batch of the product or components provides statistical quality assurance.