Can a 100% RT test be used as a substitute for a helium leak test?

Thank you! Why isn’t it possible? I don’t know much about helium testing; I hope you can give me some guidance.

Use nitrogen-hydrogen leak detection to improve airtightness http://www.cjkj88.com/

I don’t think so. Ammonia testing is a leakiness test; methods such as flaw detection can ensure strength, but they may not necessarily ensure leaklessness. I’m not in the construction business; I’m just trying to stimulate discussion among everyone.

Could the original poster explain in detail the purposes and methods of various leak detection and inspection procedures?

(1) Visual inspection: 1. Use a low-power magnifying glass or the naked eye to check whether there are surface defects such as undercutting, slag inclusions, pores, cracks, etc. on the weld surface. 2. Use a welding inspection gauge to measure weld bead height, weld bumps, depressions, misalignment, etc. 3. Check whether the welded part is deformed. For example, regarding the visual inspection requirements for welding on large vertical cylindrical storage tanks, the root gap depth of butt welds must not exceed 0.5 mm ； The continuous length of undercutting shall not exceed 100 mm; the total length of undercutting on both sides of a weld shall not exceed 10% of the length of that weld. To check the depth of undercutting, it is necessary to press the weld inspection gauge tightly against the base metal on one side of the weld bead. (II) Tightness test 1. Liquid filling leak test: For containers, equipment, and pipelines that are not under pressure, the method of directly filling them with the liquid used for testing can be employed; the tightness of the welds is assessed by checking whether there are any leaks on the outside of those welds. 2. Airtightness test: Compressed gas is introduced into the container or pipeline to the specified test pressure; a foaming agent (such as soapy water) is applied outside the welds to check for any bubble leaks at those areas. 3. Ammonia test: Ammonia gas is introduced on one side of the weld, while a test strip soaked in a phenolphthalein-alcohol-water solution is placed on the other side of the weld; if there is a leak, the test strip will turn red. 4. Kerosene leak testing: Apply a solution of chalk powder to one side of the weld; once it dries, a layer of chalk powder will remain on the weld. Dip the other side of the weld in kerosene. If there is a leak, oil stains will appear on the chalk powder at the leakage point. 5. Helium test: Helium is introduced on one side of the weld, while the other side is inspected using a helium leak detector. If there is a leak, the helium detector will emit an alarm. This is used to determine the density of the weld. 6. Vacuum chamber test: Apply a foaming agent (such as soapy water) to the weld, cover the weld to be inspected with this foaming agent using a vacuum chamber, and then evacuate the air. If there is a leak, bubbles will be visible through the observation window of the vacuum chamber. The vacuum leak testing chamber method is suitable for areas where the other side of the weld is sealed, such as the welds at the bottom of storage tanks. (III) Strength test: 1. The hydraulic strength test is usually carried out using water, with the test pressure being 1.25 to 1.5 times the design pressure. 2. The strength test is conducted using gas as the medium, with the test pressure being 1.15 to 1.20 times the design pressure. (IV) Non-destructive testing: Common non-destructive testing methods for welds include: 1. Radiographic testing (RT). The most widely used radiographic testing method makes use of penetrating radiation emitted by (X, Y) radiation sources; this radiation passes through the weld, causing the film to become sensitive to light. Images of defects within the weld are then displayed on the processed radiographic film, allowing the detection of defects such as pores, inclusions, cracks, and lack of penetration within the weld. 2. Ultrasonic testing (UT) utilizes piezoelectric transducers to generate pulsed vibrations through instantaneous electrical excitation; these vibrations are transmitted into the metal via an acoustic coupling medium to form ultrasonic waves. When these ultrasonic waves encounter defects on their path, they are reflected back to the transducer, where the sound pulses are converted into electrical pulses. By measuring the amplitude and propagation time of these signals, it is possible to determine the location and severity of defects in the workpiece. Ultrasonic testing is more sensitive than radiographic testing; it is flexible and convenient, requires a short cycle time, has low costs, high efficiency, and is harmless to the human body. However, it does not provide an intuitive display of defects, leading to inaccurate assessment of these defects, and its results are greatly influenced by the experience and skill level of the inspector. 3. Penetrant Testing (PT): When a penetrant containing pigments or fluorescent agents is sprayed or applied to the surface of the weld to be inspected, the capillary action of the liquid causes it to penetrate into defects that are open on the surface. Excess penetrant on the surface is then removed by cleaning, and after drying, a developer is applied to draw the penetrant from within the defects onto the surface of the weld, thereby allowing the presence of these defects to be detected. Liquid penetrant testing is primarily used to detect surface openings such as those on the groove surfaces after groove preparation, on the surfaces cleaned by carbon arc gas gouging or after weld defects have been removed, on the surfaces cleared by fixtures, and in areas where magnetic particle testing is not feasible. 4. Magnetic particle testing (MT) is a method that utilizes the fact that defects on the surface and near the surface of ferromagnetic materials cause changes in magnetic susceptibility; when magnetized, a leakage magnetic field is generated on the surface, and magnetic particles, magnetic tapes, or other methods for measuring magnetic fields are used to detect and display these defects. Magnetic flaw detection is mainly used to detect surface and near-surface defects. Compared with the penetrant testing method, this approach not only offers higher sensitivity and faster speed but also enables the detection of defects at a certain depth beneath the surface. 5. Eddy current testing (ET) utilizes the high-frequency current flowing within the probe coil to generate eddy currents on the surface of the weld; defects alter the magnetic field of these eddy currents, resulting in changes in the coil’s output (such as voltage or phase), which serve as indications of the presence of defects. Its inspection parameters are relatively difficult to control, and it can detect surface or near-surface defects in the conductive material surface or welds, as well as in the surfacing layer surface. 6 The Time-of-Flight Diffraction (TOFD) method relies on the diffraction energy obtained from the \"corners\" and \"ends\" of the internal structure of the component under inspection – primarily defects – to detect such defects, as well as to quantify and locate them. The diffraction time-of-flight ultrasonic (referred to as TOFD) detection technique has been used in the welding inspection of ultra-high pressure pipelines.