How to identify the quality of seamless steel pipe

How to identify the quality of seamless steel pipe?

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)

visual testing

Internal and external surface, uniformity of wall thickness, gloss, smoothness, no cracking, no bubbles, hollow section roundness, straightness, etc.


2. Ultrasonic Testing (UT)

NDT ultrasonic testing

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.

NDT eddy current testing

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. Radiographic 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.

magnetic flux leakage testing

Where the object has no flaws, the magnetic flux will remain undisturbed.

magnetic flux leakage testing

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.

Most widely used thermal insulation steel pipe---polyurethane/PU foam thermal insulation steel pipe for oil,steam and gas pipeline

Most widely used thermal insulation steel pipe—polyurethane/PU foam thermal insulation steel pipe for oil,steam and gas pipeline

PU foam thermal insulation coating of steel pipe is made of polyether polyol composition and methyl polyphenyl polyisocyanate through chemical reaction and foaming.Polyurethane thermal insulation pipe is used in various indoor and outdoor pipelines, central heating pipelines, central air conditioning pipelines, chemical, pharmaceutical and other industrial pipeline insulation, cooling engineering.Overview of polyurethane foam insulation tube polyurethane synthetic materials, it has been as a kind of excellent heat insulation material and got rapid development, its application scope also more and more widely, more because its construction is simple and remarkable energy-saving anti-corrosion effect and is widely used in all kinds of steel line pipes such as heating, refrigeration, oil, steam, etc.

Most widely used thermal insulation steel pipe---polyurethane/PU foam thermal insulation steel pipe for oil,steam and gas pipeline

Main components of polyurethane thermal insulation steel pipe:
I.Protective case: high density polyethylene(HDPE) or glass fiber reinforced plastics.
II.Insulation layer: rigid polyurethane foam
III.Working steel tubes: welded steel tubes, seamless steel tubes and double-sided submerged arc spiral welded steel tubes shall be used according to the technical requirements of the conveying medium.
IV.leakage alarm line: manufacturing high temperature, the prefabricated directly buried insulating pipe are close to the steel pipe insulation, embedding a warning line, once the pipeline leakage somewhere, conduction through the warning line, can be on the special detecting instrument alarm and show the leaking of accurate location and the size of the degree of leakage, in order to inform the maintenance staff quickly deal with a leaky pipe section, to ensure the safe operation of the heat supply network.
There are three kinds of laying methods: directly buried, overhead and trench.
We have accumulated a lot of rich experience in the long-term polyurethane insulation and thermal insulation construction of pipe fittings, whose quality has reached the national and international standards, and won the trust and praise of the majority of customers.
Most widely used thermal insulation steel pipe---polyurethane/PU foam thermal insulation steel pipe for oil,steam and gas pipeline

Most widely used thermal insulation steel pipe---polyurethane/PU foam thermal insulation steel pipe for oil,steam and gas pipeline
Polyurethane thermal insulation steel pipe, with the advantages of light bulk, high strength, thermal insulation, sound insulation, flame retardant, cold resistance, corrosion resistance, non-water absorption, simple and fast construction as well as other excellent characteristics, has become the construction, transportation, petroleum, chemical industry, electric power, refrigeration and other industrial sectors thermal insulation, waterproof plugging, sealing and other indispensable materials.
Small thermal conductivity:
The thermal conductivity of polyurethane foam is the lowest in the thermal insulation materials, so it can reduce the heat loss of materials to the minimum.
Waterproof, anticorrosive, aging resistant:
Due to the closed pore ratio of polyurethane foam is more than 92%, the use of polyurethane foam as the insulation layer of directly buried pipelines can not only play a role in heat preservation and insulation, but also effectively prevent the infiltration of water, moisture and other corrosive liquids and gases, and prevent the growth and development of microorganisms.
Polyurethane insulation pipe is popular because of its excellent performance, convenient construction and long service life.

Production standard

Related standards for polyurethane insulation pipes is CJ/T114 <High Density Polyethylene Outer Protective Pipes Polyurethane Foam Prefabricated Directly Buried Insulation Pipes Standard> or EN253 <Integrated Precast Insulation System for Underground Water Heat Pipe Network Consisting of Working Steel Tubes, Polyurethane Insulation Layer and Polyethylene Outer Casing Insulation Pipes>.

PQF mill, the world’s most advanced continuous steel pipe rolling equipment

PQF mill, the world’s most advanced continuous steel pipe rolling equipment

PQF mill, the world’s most advanced continuous steel pipe rolling equipment

PQF mill is the latest and advanced steel pipe rolling mill to improve product quality, reduce cost and improve economic benefits.

From the perspective of technology, PQF mill has the following advantages compared with MPM mill.

(1) Closed-type pass design makes rolling more stable

The roll frame of the PQF continuous pipe rolling machine adopts the three-roll closed-type pass design, as shown in FIG. 1.

PQF mill, the world’s most advanced continuous steel pipe rolling equipment











                                                                               Fig. 1



In the rolling process, the metal deformation is stressed in three directions at the same time, so that the metal deformation is more uniform in the same section. The three rollers are arranged in 120 degree angles, and the front and rear stand rollers are arranged in 60 degree angles each other, to ensure the mandrel in the groove better alignment, so as to make the rolling process more smooth and stable.


(2) Unique mandrel circulation system and fewer holes in the spare mandrel

After the end of rolling, the mandrel stops. After the tube is extracted from the mandrel by the tube stripper, the mandrel is not sent back, but runs forward. After the tube stripper is put through, the mandrel is pulled out and then sent back, cooled and lubricated.

It retain the original advantage of MPM process, that is high precision characteristics of wall thickness. On the premise of better wall thickness precision than MPM, It reduces the mandrel line to be rolled (non-rolling) time, thus effectively shortens the rolling cycle, speeds up the rolling rhythm, and the fastest speed can reach 24s per piece.

The three-roll geometry can be adjusted to a larger range under the same mandrel without large tolerance effect.

As a result, the range of the wall thickness that can be rolled on the mandrel of one specification is increased, which greatly reduces the number of mandrel specifications (by 50%) and the frequency of tool replacement, and the production organization is also more flexible.


(3) It can improve the quality of steel tube and wall thickness precision, rolling thinner wall thickness steel tube.

Because of the small difference of linear velocity between the bottom and the edge of the roll pass of PQF continuous rolling pipe mil, the pass with smaller opening can be adopted, therefore, the metal deformation of the rolled piece is more uniform when the pipe is rolled by PQF continuous rolling pipe mill, and the transverse flow of the metal is less, which is better than that of the steel tube rolled by the two-roll MPM continuous rolling pipe mill in the following four aspects:

  • wall thickness tolerance significantly improved;
  • the surface of the pipe is much smoother;
  • the D/S value of finished pipe can be increased without affecting the quality;
  • mandrel continuous rolling pipe technology enters the field of small diameter steel pipe production;

Using the three-roll closed-type pass design, metal deformation on the same cross section is uniform, three roll can be simultaneously or separately adjusted under single drive and separate servo hydraulic pressure, realizing the roll gap adjustment model, so as to improve the wall thickness accuracy and reduce the wall thickness difference between end and the central part of the waste pipe.

The 120 degree angle arrangement of the three rollers ensures a better alignment of the mandrel in the pass, which results in a significant improvement in the tolerance of the wall thickness of the wasted tube after rolling.

Three roll sealing groove design, reducing the rolling roll bending moment, can achieve uniformity and stability of metal deformation, and rolling pressure, especially peak pressure decreases. Cracks and concave defects caused by uneven deformation in the process of rolling, has been basically eliminated, that means it can make rolling thin wall pipe and high grade varieties, such as rolling of 159 mm x4.0 mm, 463.0 mm x4mm thin wall steel tube, etc.