Ultrasonic Testing (UT)

Ultrasonic inspection is a nondestructive method in which beams of high-frequency sound waves are introduced into materials for the detection of subsurface flaws in the material. The sound waves travel through the material with some attendant loss of energy (attenuation) and are reflected at interfaces (cracks or flaws). The reflected beam is displayed and then analyzed to define the presence and location of flaws or discontinuities.

Visual / Optical Testing (VT)

Visual inspection is one NDT method used extensively to evaluate the condition or the quality of a weld or component. It is easily carried out, inexpensive and usually doesn't require special equipment. It requires good vision, good lighting and the knowledge of what to look for. Visual inspection can be enhanced by various methods ranging from low power magnifying glasses through to boroscopes.

Penetrant Testing - (PT)

Apart from visual inspection this is probably the oldest and most widely used of all the NDT methods. It can be used on any non-porous material. Its use is confined to the detection of surface breaking defects.

Liquid penetration inspection is used to reveal surface breaking flaws by bleedout of a colored or fluorescent dye from the flaw. Test objects are coated with visible or fluorescent dye solution. Excess dye is then removed from the surface, and a developer is applied. The developer acts as blotter, drawing trapped penetrant out of imperfections open to the surface. With visible dyes, vivid color contrasts between the penetrant and developer make "bleedout" easy to see. With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen.

Penetrant inspection can be used on any material and is most often used on materials clad in stainless steel, and stainless welded items which cannot be inspected by other methods.

Magnetic Particle Testing - (MT)

Magnetic particle inspection (MPI) is used for the detection of surface and near-surface flaws in ferromagnetic materials. A magnetic field is applied to the specimen, either locally or overall, using a permanent magnet, electromagnet, flexible cables or hand-held prods. If the material is sound, most of the magnetic flux is concentrated below the material's surface. However, if a flaw is present, such that it interacts with the magnetic field, the flux is distorted locally and 'leaks' from the surface of the specimen in the region of the flaw. Fine magnetic particles, applied to the surface of the specimen, are attracted to the area of flux leakage, creating a visible indication of the flaw.
The materials commonly used for this purpose are black iron particles and red or yellow iron oxides. In some cases, the iron particles are coated with a fluorescent material enabling them to be viewed under a UV lamp in darkened conditions.

Hidro test

Hidro test dilakukan untuk pemeriksaan kebocoran dengan prinsip air bertekanan. Air dipompa ke dalam sistem perpipaan dengan menggunakan hydro pump sampai batas tekanan standarnya. Standar tekanan air yang digunakan untuk tangki adalah sebesar 0,18 MPa atau setara dengan 1,8 bar. Namun pada kenyataannya nilai ini selalu dilebihkan menjadi 0,2 MPa atau 2 bar. Sedangkan untuk pressure test sistem perpipaan, nilai besarnya tekanan adalah 1,5 kali dari tekanan kerja. Sehingga ada faktor keamanan sebesar 50% dari tekanan kerja pipa. Dengan indikasi adanya kebocoran adalah terdapat rembesan air, terutama pada daerah sambungan las. Untuk sistem perpipaan adalah daerah flange sambungan pipa.

Electromagnetic Testing - (ET)

Eddy current, penetrating radar and other electromagnetic techniques are used to detect or measure flaws, bond or weld integrity, thickness, electrical conductivity, detect the presence of rebar or metals. Eddy current is the most widely applied electromagnetic NDT technique. The eddy current method is also useful in sorting alloys and verifying heat treatment. Eddy current testing uses an electromagnet to induce an eddy current in a conductive sample. The response of the material to the induced current is sensed. Since the probe does not have to contact the work surface, eddy current testing is useful on rough surfaces or surfaces with wet films or coatings.

Acoustic Emission (AE)

Acoustic emission is the technical term for the noise emitted by materials and structures when they are subjected to stress. Types of stresses can be mechanical, thermal or chemical. This emission is caused by the rapid release of energy within a material due to events such as crack initiation and growth, crack opening and closure, dislocation movement, twinning, and phase transformation in monolithic materials and fiber breakage and fiber-matrix debonding in composites.
The subsequent extension occurring under an applied stress generates transient elastic waves which propagate through the solid to the surface where they can be detected by one or more sensors. The sensor is a transducer that converts the mechanical wave into an electrical signal. In this way information about the existence and location of possible sources is obtained. Acoustic emission may be described as the "sound" emanating from regions of localized deformation within a material.
Until about 1973, acoustic emission technology was primarily employed in the non-destructive testing of such structures as pipelines, heat exchangers, storage tanks, pressure vessels, and coolant circuits of nuclear reactor plants. However, this technique was soon applied to the detection of defects in rotating equipment bearings.

Radiography Test (RT)

This technique involves the use of penetrating gamma or X-radiation to examine parts and products for imperfections. An X-ray machine or radioactive isotope is used as a source of radiation. Radiation is directed through a part and onto film or other media. The resulting shadowgraph shows the internal soundness of the part. Possible imperfections are indicated as density changes in the film in the same manner as an X-ray shows broken bones.
Radiographic applications fall into two distinct categories evaluation of material properties and evaluation of manufacturing and assembly properties. Material property evaluation includes the determination of composition, density, uniformity, and cell or particle size. Manufacturing and assembly property evaluation is normally concerned with dimensions, flaws (voids, inclusions, and cracks), bond integrity (welds, brazes, etc.), and verification of proper assembly of component pieces.