NDT (Non Destructve Testing)

POLY NDT Pte Ltd was established in 1975 in Singapore to provide third party and independent testing and inspection service, such as NDT (Non-Destructive Testing ) services, hazardous materials inspection services.

We are a member of CTI (Centre Testing International Co. Ltd ). which is a international testing, inspection and certification group company.

For NDT service:

  • We have ASNT Level 3 engineers to train and qualify NDT technicians to carry out radiographic, ultrasonic, magnetic particle and dye-penetrant inspection to AWS, API and ASME standards. Our technicians have also been trained by accredited institution and CSWIP (UK).
  • We are approved to carry out ultrasonic ship hull inspection such as ABS, BKI, BV, DNV, GL, IRS, Lloyds, NK, RINA and KR.
  • We have worked at all the major shipyards such as Keppel, Jurong, Sembawang and ST Marine in Singapore.
  • We are one of the few NDT companies qualified to do work for Singapore Navy and US Navy.
  • We have also worked for Shell, Exxon-Mobil, and other refineries.
  • We have carried out work in South-East Asia, China, Japan, Australia, Europe, Arica, South Pacific and the Middle East.

Non-destructive testing or (NDT) is a wide group of analysis techniques, used in science and industry, to evaluate the properties of a material, component or system without causing any damage to it or altering it in any way  Because of this, NDT  is a highly valuable technique that can save both time and money  in product evaluation, troubleshooting, and research.

Common NDT methods include ultrasonic, magnetic-particle, liquid penetrant, radiographic, remote visual inspection (RVI) and eddy-current testing.  NDT is commonly used in forensic , mechanical electrical  civil , systems  and aeronautical engineering.

Depending upon the material to be tested, NDT methods may rely upon the use of electromagnetic radiation, sound and the inherent properties of the material(s) for analysis. Whilst this testing may include microscopy to examine external surfaces in detail, there is no preparation required that may damage the material.  The more traditional methods and preparation techniques for metallography, optical microscopy and electron microscopy are generally destructive, as the surfaces must be made smooth through polishing.  Otherwise the sample must be electron transparent in thickness to allow for analysis.

With NDT, the inside of a material sample can be examined with penetrating radiation, such as X-rays and Gamma-Ray. Sound waves are also utilized in the case of ultrasonic testing. Any contrast between a defective part of the sample and the main body of the sample  may be enhanced for visual examination  by using liquids to penetrate fatigue cracks. This method (liquid penetrant testing) involves using fluorescent or non-fluorescent dyes in fluids for non-magnetic materials.. Another commonly used NDT method, used on ferrous materials, involves the application of fine iron particles (either liquid or dry dust) that are applied to a material sample whilst it is in an externally magnetized state (magnetic-particle testing). The particles will be attracted to leakage areas within the test sample, and form on the  surface of the material sample. Magnetic particle testing can reveal surface & some sub-surface defects within the sample.

Ultrasonic Flaw detection Ultrasonic Testing (UT)

Uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic inspection can used for flaw detection/evaluation, dimensional measurements, material characterization, and more. To illustrate the general inspection principle, a typical pulse/echo inspection configuration as illustrated below will be used. A typical UT inspection system consists of several functional units, such as the pulser/ receiver, transducer, and display devices. A pulser/receiver is an electronic device that can produce high voltage electrical pulses. Driven by the pulser, the transducer generates high frequency ultrasonic energy. The sound energy is introduced and propagates through the materials in the form of waves. When there is a discontinuity (such as a crack) in the wave path, part of the energy will be reflected back from the flaw surface. The reflected wave signal is transformed into an electrical signal by the transducer and is displayed on a screen. In the applet below, the reflected signal strength is displayed versus the time from signal generation to when a echo was received. Signal travel time can be directly related to the distance that the signal traveled. From the signal, information about the reflector location, orientation and other features can sometimes be gained.

X & Gamma Radiography

Radiography today is one of the most important, most versatile, of all the nondestructive test methods used by modern industry. Employing highly penetrating x-rays, gamma rays, and other forms of radiation that do not damage the part itself, radiography provides a permanent visible film record of internal conditions, containing the basic information by which soundness can be determined. In the past decade alone, the evidence from millions of film records, or radiographs, has enabled industry to assure product reliability; has provided the informational means of preventing accidents and saving lives; and has been beneficial for the user. Gamma rays are similar in their characteristics to x-rays and show the same similarities to, and differences from, visible light as do x-rays. They are distinguished from x-rays only by their source, rather than by their nature.  In industrial radiography, the artificial radioactive isotopes are used almost exclusively as sources of gamma radiation. 

Magnetic Particle Inspection

Magnetic particle inspection processes are non-destructive methods for the detection of defects in ferrous materials. They make use of an externally applied magnetic field or DC current through the material, and the principle that the magnetic susceptibility of a defect is markedly poorer (the magnetic resistance is greater) than that of the surrounding material. The presence of a surface or near surface flaw (void) in the material causes distortion in the magnetic flux through it, which in turn causes leakage of the magnetic fields at the flaw. This deformation of the magnetic field is not limited to the immediate locality of the defect but extends for a considerable distance; even through the surface and into the air if the magnetism is intense enough. Thus the size of the distortion is much larger than that of the defect and is made visible at the surface of the part by means of the tiny particles that are attracted to the leakage fields. The most common method of magnetic particle inspection uses finely divided iron or magnetic iron oxide particles, held in suspension in a suitable liquid (often kerosene). This fluid is referred to as carrier. The particles are often colored and usually coated with fluorescent dyes that are made visible with a hand-held ultraviolet (UV) light. 

Dye Penetrant Inspection

Liquid penetrant inspection is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components magnetic particle inspection is preferred for its subsurfacedetection capability. LPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.

Hardness Testing

There are three types of tests used with accuracy by the metals industry; they are the Brinell hardness test, the Rockwell hardness test, and the Vickers hardness test. Since the definitions of metallurgic ultimate strength and hardness are rather similar, it can generally be assumed that a strong metal is also a hard metal. The way the three of these hardness tests measure a metal's hardness is to determine the metal's resistance to the penetration of a non-deformable ball or cone. The tests determine the depth which such a ball or cone will sink into the metal, under a given load, within a specific period of time. The followings are the most common hardness test methods used in today`s technology: 

  • Rockwell hardness test
  • Brinell hardness
  • Vickers
  • Knoop hardness
  • Shore

 

For further enquiry, you are welcome to visit POLYNDT website.

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