1. Surface testing

　　Surface inspection is a commonly used nondestructive inspection method for dish end. The inspection objects mainly include joint welds, fillet welds, weld scars, and high-strength bolts. In the detection process, the penetration method can be used to detect ferromagnetic and non-ferromagnetic materials. The external and internal detections use color penetration method and fluorescent penetration method respectively; while when testing ferromagnetic materials, the magnetic powder method is preferred, and the external and internal detection methods are respectively Black magnetic particle detection method and fluorescent magnetic particle detection method.

　　2. Magnetic particle testing

　　If there is a defect on the surface or near surface of the ferromagnetic material, the continuity of the material will be affected. After the magnetization treatment, the magnetic field lines are locally distorted, and a leakage magnetic field will be formed. Under appropriate light conditions, discontinuous magnetic marks can be found on the surface magnetic powder Directly display the defect location, area, shape and nature of the pressure vessel. Overall, magnetic particle inspection has the advantages of simple process, fast inspection speed, low cost and low pollution. As long as the appropriate magnetization method is adopted, it can detect the surface defects of different types of pressure vessels. Moreover, this method can be used repeatedly and accurately The rate is higher.

　　3. Penetration testing

　　Penetration testing is mainly used in the detection of hot cracks, cold cracks, delayed cracks in the heat-affected zone of pressure vessels, and the detection of opening defects in welds. The mechanism of action is the principle of capillary action. After the surface, the penetrating fluid can penetrate from the defects (such as cracks, nicks, pits) in this part, and reflect the specific defect information under the adsorption of the display agent. This method has the advantages of simple operation, good economy, and intuitive display. It has high application value in the defect detection of large, complex and irregularly shaped workpieces, but it is only limited to surface opening defect detection.

　　4. Radiographic testing

　　The ray will gradually weaken during the penetration of the workpiece, and its strength and penetration thickness have direct practice, and the dish end has a defect, the attachment of the part will change. So the radiographic testing can realize the detection of the dish end defect. Through this detection method, the staff can obtain the X-ray effect of the detected part, which is affected by the thickness of the workpiece. Different blackness will be displayed on the picture, so that the staff can judge the location and nature of the defect. At present, this method is commonly used in the detection of welded joints in pressure vessels. It can efficiently detect defects such as cracks, slag inclusions, impermeability, fusion, and porosity. However, it must be selected for planar defects that are perpendicular to the beam. Only at the right angle can accurate results be obtained, and the relative cost is high, which can also threaten the health of the operator.

　　5. Ultrasonic testing

　　The principle of ultrasonic testing is that ultrasonic waves will be reflected in the cross section of the medium. Due to the strong penetration of ultrasonic waves and high sensitivity, defects in dish end can be detected quickly and efficiently. Due to its small size and light weight, the ultrasonic flaw detector is relatively simple to operate, coupled with extremely high defect detection sensitivity, it is currently widely used in internal defect detection and volumetric defect detection of forgings, steel plates, welded joints, This method is not accurate enough for qualitative and quantitative analysis, and it will also be affected by the location and shape of the defect, which requires careful selection.

　　6. Eddy current testing

　　Eddy current testing is mainly used to detect the corrosion state of pressure vessel heat exchange tubes. It uses an internal pass-through probe and remote eddy current detection technology to accurately detect the presence or absence of pits, perforations, and wall thinning inside or outside the ferromagnetic heat exchange tube. For other defects, if the surface of the pressure vessel is rough or there is an anti-corrosion layer, applying current to disturb the magnetic sensor can also obtain accurate test results. In addition, when the pressure vessel is out of service, eddy current testing technology can be used to detect the welded joints inside and outside the vessel, and re-inspection using magnetic particle detection method and penetration detection method to determine the crack position and area of the dish end.

　　7. Acoustic emission testing

　　Through acoustic emission detection, it can be detected whether there are active defects inside and outside the pressure vessel, and re-examination by methods such as radiation and ultrasound to determine the location and intensity of the defect. Through this method, the quality defects can be quickly identified without damaging the pressure vessel, which has a positive significance for ensuring the safe use of the pressure vessel.