How to identify the quality of seamless steel pipe?
When purchasing steel pipe, no matter for final user or trader, the quality, determining project safety and its service life, must rank first. Then how to evaluate and get top quality is the key points in the process of purchase. And quality control and assurance is guaranteed by quality testing methods. Here are some common testing methods as followings for your reference.
Nondestructive Testing (NDT)
NDT, shorted for nondestructive testing, is a widely-used method in pipeline inspection. The common inspection methods of NDT are visual testing (VT), ultrasonic testing (UT), radio-graphic testing(RT), eddy current testing (ET), magnetic flux leakage (MFL) testing, and hydrostatic testing (HT) to inspect its line pipes.
1. Visual Testing (VT)
Internal and external surface, uniformity of wall thickness, gloss, smoothness, no cracking, no bubbles, hollow section roundness, straightness, etc.
2. Ultrasonic Testing (UT)
Ultrasonic testing (UT) is a non-destructive test method that utilizes electronic transducers that transmit high-frequency sound waves to a material. These sound waves bounce back images, which reveal key characteristics of a material’s properties. The images created by ultrasonic testing can indicate cracks, weld grooves and fractures, as well as indicate material thickness and moving components.
3. Eddy Current Testing(ET)
Eddy-current testing (also commonly seen as eddy current testing and ET) is one of many electromagnetic testing methods used in nondestructive testing (NDT) making use of electromagnetic induction to detect and characterize surface and sub-surface flaws in conductive materials.
In its most basic form — the single-element ET probe — a coil of conductive wire is excited with an alternating electrical current. This wire coil produces an alternating magnetic field around itself. The magnetic field oscillates at the same frequency as the current running through the coil. When the coil approaches a conductive material, currents opposite to the ones in the coil are induced in the material — eddy currents.
Variations in the electrical conductivity and magnetic permeability of the test object, and the presence of defects causes a change in eddy current and a corresponding change in phase and amplitude that can be detected by measuring the impedance changes in the coil, which is a telltale sign of the presence of defects. This is the basis of standard (pancake coil) ET. NDT kits can be used in the eddy current testing process.
4. Radio–graphic Testing (RT)
Radio-graphic Testing (RT) is a nondestructive testing (NDT) technique that involves the use of either x-rays or gamma rays to view the internal structure of a component. In the petrochemical industry, RT is often used to inspect machinery, such as pressure vessels and valves, to detect for flaws. RT is also used to inspect weld repairs.
Compared to other NDT techniques, radiography has several advantages. It is highly reproducible, can be used on a variety of materials, and the data gathered can be stored for later analysis. Radiography is an effective tool that requires very little surface preparation. Moreover, many radio-graphic systems are portable, which allows for use in the field and at elevated positions.
5. Magnetic Flux Leakage Testing
The basic principle behind MFL involves magnetizing a ferrous metal object to saturation level with a powerful magnetic field.
Where the object has no flaws, the magnetic flux will remain undisturbed.
Where there is internal or external metal loss, the magnetic flux leaks from the object.
The magnetic flux leakage testing is a non-destructive testing technology based on ferromagnetic material magnetic changes. When the ferromagnetic material is magnetized, and generates a leakage magnetic field due to the presence of defects on the workpiece surface, and therefore, through the detection of the magnetic flux leakage can be found in defects in the large caliber seamless thermal expansion material. Steel pipe magnetic flux leakage testing technology is divided into two kinds of magnetic particle inspection method and magnetic field measurement method. The former is simple. but requires the naked eye to observe the magnetic marks, it is difficult to automate. The latter despite the device complexity, high cost and the ope ration is difficult, but it is picked up by sensors leakage magnetic field information, and therefore easy to automate testing.
6. Hydrostatic Testing
Hydrostatic testing pipes or pipelines are performed to expose defective materials that have missed previous detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system. It is a way in which pressure vessels such as pipelines, gas cylinders tube, boilers tube can be tested for strength and leaks.
Hydrostatic testing is a type of pressure test that works by completely filling the component with water, removing the air contained within the unit, and pressurizing the system up to 1.5 times the design pressure limit the of the unit. The pressure is then held for a specific amount of time to visually inspect the system for leaks. Visual inspection can be enhanced by applying either tracer or fluorescent dyes to the liquid to determine where cracks and leaks are originating.
IMRISTEEL has the most advanced testing equipment, and each pipe individually will get non-destructive tested. We also provide OEM testing according to customer’s request. If you have any need or further question, welcome to contact us [email protected], we will give you professional scheme and best quality steel pipe.