1. Overview about tubes vortex detection
Tubes can be classified into seamless tube, welded tube from types, and also divided into ferromagnetic pipe and non ferromagnetic pipe from material. According to conditions of different products, tubes can be online detected (shown in figure 1), or off-line detected (shown in figure 2):
Figure 1. online vortex testing
Figure 2. off-line vortex testing
For welded pipe vortex testing, according to the needs of different customers, we can make on-line detection or off-line detection. Distinguishing from methods, the detections can be divided into traverse type full inspection and partial type welds testing.
For vortex testing of seamless pipe, in view of the different production processes, seamless pipe are generally off-line vortex. Distinguishing from methods, it can be divided into traverse type full inspection and rotary type full inspection. In particular encounter ferromagnetic material seamless pipe, in addition to using rotary detection method, the magnetization and demagnetization devices are recommended.
2. Pipe vortex testing process
1）Welded pipe traverse type testing
The reference images in site for welded pipe traverse type testing are shown in figure 3 below:
Traverse type testing refers to the detection method that pipe passes through from inside probe and the probe fully covers outer surface of the pipe. Steel pipe passes through from the traverse type probe, the probe and tube should be adjusted to concentric, the state of surface and near surface of the pipe can be detected real-time. In general, in order to ensure stability in the process of steel pipe detection, the clamping rollers are configured on probe both sides to avoid pipe local bounce, at the same time play a role to drive.
And whether using the magnetizing device, depend on whether the materials is ferromagnetic material. The ferromagnetic material needs to increase the magnetizing device, but non-ferromagnetic material does not require.
Magnetizing device actual images as shown in figure 4, traverse type probe actual images as shown in figure 5.
When using magnetic device, probe is installed in magnetization device, the steel pipe is in and out from left and right side inner holes of magnetizing device, as shown in figure 4
2）Welded pipe local detect only welds
Site reference diagram for welded pipe local test only welds are shown in figure 6 below
The method of local testing only welds is probes to cover over the weld, as the red circle marked in left side of figure 6, the probe only covers certain circular arc of steel tube surface (weld must be within the scope of the cover). The local test method is generally online test, in test process only the parts of steel tube within range of probe covering will be detected. The physical map of local detection probe is shown in figure 7.
Fig 7. The physical map of local detection probe
3）Seamless tube traverse type testing
Site reference diagram of seamless tube traverse type testing is shown in figure 8 below.
For seamless tube traverse type vortex testing, the conveying and clamping mechanism of pipes production line usually cannot be used, loading and unloading, conveying parts and testing will be proceeded by separately designed machinery transmission system.
The part traverses in probe (as shown in figure 8), the clamping and driving mechanism on both sides of probe drive steel pipe forward, and ensure the stability of steel pipe in process of detection. And whether using the magnetizing device, depend on whether the materials is ferromagnetic material. The ferromagnetic material needs to increase the magnetizing device, but non-ferromagnetic material does not require.
The actual diagram of magnetizing device is shown in figure 9, the actual diagram of traverse type probe is shown in figure 10. When using magnetic devices, the probe is installed in magnetizing device, the steel pipe passes in and out from the inner hole of magnetizing device left side, as shown in figure 9.
4）Seamless tube rotation detection
When meeting larger diameter pipe and needing to test longitudinal crack, the rotation detect way is needed. Welded steel pipe (especially straight welds pipes) is not used for rotating detection. When rotating detection, relative spiral movement is created between steel tube and detection probe, the relative spiral movement is generally divided into the following three ways: probe spins in place, pipe progress straight line; probe fixes in place, pipe spiral progress; Probe level progress, pipe spins in place.
Take the manner of probe level progress, pipe spin in place in fig 9 for an example: The steel pipe passes firstly level driving roller, then is sent to testing station, it again is drive by rotating roller and spins in place. By this time the probe lands and close to the pipe, the trolley begins to move. Probe level movement speed depends on pipe rotating velocity and probe diameter, you must ensure that the probe’s progress step distance is not greater than pitch, otherwise there will be a leak detection.
The point probe used for rotating detection is commonly the combination of multiple probes, coil diameter for each probe is not too big. The outline of ordinary single point probe is shown in figure 12.
Fig12. point probe
3. Pipes vortex testing technology characteristics
· High detection efficiency: vortex testing with top speed of near km/min, ensure product to be completely nondestructively tested.
· Long service life: using non-contact detection, the probe do not contact directly with parts and not easy to wear.
· High degree of automation, can communicate with PLC programmable control, realize automation works such as feeding, alarming, marking, picking up the waste, unloading, etc.
· High temperature resistant, with specially designing and processing of sensor, can test under harsh environment of high temperature of near kilo-degrees.
· With powerful detection functions: in addition to defect detection, also can measure wall thickness, coating and clad layer thickness, prevent different type steel from mixing, etc.
· With good economy and relatively low costs.
· Security: the detection technology will not produce any radiation to human body.
4. Recommend detection instrument for pipes vortex test
Eddysun company’s instruments are designed with the most advanced digital electronic technology and microcomputer technology, and suitable for online or offline detection. The instruments can output different real-time signal and delayed signal according to the types and features of detected parts, the instruments can form a complete set flexibly with mechanical and electrical automation equipments to achieve all automatic detections such as: automatic feeding, detecting, unloading and sorting (separate qualified products and wastes). The instruments can also be installed directly on production line for real-time on-line detection, and separate qualified products and wastes by connecting with PLC programmable controller.
The instruments can connect externally with code disc, realize high precision marking and automatic sorting function nothing to do with the unit speed. At the same time, the instruments can also be connected to A – scan switch to realize A - scan mode detecting, and automatically cut head and tail vortex signal of each steel pipe, conveniently and intuitively show the number of each tube defects, location, and cumulatively detect the quantity of tested products and wastes.
5. Pipe inspection application cases
Baoji titanium industry co., LTD
Yangzhou Cheng-De steel tube co., LTD
Xuzhou Guang-Huan steel tube (Group) co., LTD
Jiangsu Suntory Group
Zhejiang Hua-Di stainless steel group co., LTD
Wuxi Shida precision Welded Tube Manufacturing co., LTD
ShengDa Copper co., LTD. TaiXing
ZheJiang HongTian Copper
Jiaxing yongxin precision welded pipe
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