How to check a weld seam

Methods for quality control of welding seams

The quality of welding work and welded joints greatly influences the strength of structures or the tightness of tanks. Failure of welds to meet the specified characteristics leads to structural failures with catastrophic consequences, the same applies to systems operating with vessels and pipelines under pressure.

Therefore, after welding work, the finished product is subjected to testing and inspection to detect defects in welded joints.

All welding quality control procedures are defined by GOST or governing documents. They also indicate acceptable error limits. After the tests, a report and protocols with the measurement results are drawn up.

Verification methods

Quality control of welding work performed in production can be destructive or non-destructive. The first methods are used selectively. One or more products from a large batch, or part of a metal product in a building structure, is checked.

It is tested on various parameters using a specific test report. But mainly they use special devices or materials to check the quality of welded joints without destroying the structure.

The main methods of non-destructive welding quality control are:

• visual;
• capillary;
• permeability test;
• radiation;
• magnetic;
• ultrasonic.

There are other methods and types of welding quality control, but due to their specificity they have not become widespread.

Checking the condition of welds is not a one-time act, it is the resulting stage that shows how the quality control system at the enterprise works.

To minimize defects in welding joints, operational control of the work is carried out. Certification is carried out regularly, at which the commission first gives permission to weld the control joint. When welders pass this test, their theoretical knowledge is tested.

Before starting work, the welder’s qualifications are checked; he must have a certificate for the right to weld certain grades of steel and a work permit.

A welding engineer and a controller from the technical control service check the quality of assembly, the condition of the edges, the performance of the welding machine, and controls the heating temperature, if this is provided for in the regulatory and technical documentation.

Quality control of welding materials is carried out from the moment they arrive at the enterprise and before use at the welding station. The electrodes are checked at each stage of storage and use, and if necessary, they are calcined.

During the actual work, check what welding mode is used: arc welding, argon arc or another type of welding. Check the order of sutures, the dimensions of the layers and the entire connection.

If special requirements are provided for in the design and technical documentation, then their implementation. Upon completion of welding, checks for the presence of the welder’s mark.

Visual inspection

Any quality check of welds begins with visual inspection. All 100% of welded joints are inspected. First, check the geometry and shape of the seam.

Visual inspection helps to identify, along with external ones, some internal defects. Thus, seam beads of variable dimensions and uneven folds indicate lack of fusion that occurs due to frequent breaks in the electric arc.

Before starting work, remove slag, scale and other contaminants from welded joints. To better see the defects, the seams are treated with nitric acid (10%). This gives the seam a matte finish, making it easier to find flaws.

After acid treatment, it is necessary to thoroughly wipe with alcohol to prevent its harmful effect on the alloy.

To improve the quality of the inspection, you can use a flashlight and an optical magnifier. To control geometric dimensions, calipers and templates are used.

Capillary method

This control method uses the property of liquid to be drawn into very small capillaries. The speed and degree of penetration into the material is related to its wettability and the diameter of the capillaries. The alloy is more wetted and the capillaries are thinner - the liquid penetrates deeper.

The capillary method of weld quality control allows you to deal not only with any metals, but also with ceramics, plastic, and glass. Its main use is associated with the manifestation of external flaws that are impossible or difficult to detect with the naked eye. Sometimes, using, for example, kerosene, you can detect through defects.

The method is very simple, it has been working since the need to check welding seams arose. A special GOST 18442-80 has even been developed for it.

In the capillary welding quality control method, penetrants are used - substances that have low surface tension and strong color contrast.

By penetrating into defective areas and highlighting them, penetrants visualize welding flaws. They are made from water, kerosene, transformer oil and other liquids.

The most sensitive penetrants can show defects as small as 0.1 microns in diameter. The capillary welding quality control method is effective for defects up to 0.5 mm wide. It does not work for large pore diameters or cracks.

The method using penetrants involves cleaning the surface, applying a control liquid and revealing flaws. A very effective way to control welded joints is using kerosene.

Despite the variety of welding quality control devices, testing by this method is still used. A chalk solution is applied on one side, time is allowed to dry, then the seam on the other side is lubricated with kerosene. Defective areas appear after a few hours in the form of dark spots.

Checking welded joints for permeability

If welding is used in the manufacture of tanks, tightness control is required. To do this, tests for tightness of connections are carried out. Quality control is carried out using gases or liquids.

The essence of the method is based on creating a large pressure difference between the outer and inner areas of the container. With through-hole flaws in the weld, liquid or gas will flow from an area of ​​high pressure to an area of ​​low pressure.

Depending on the substance used and the method of obtaining excess pressure, permeability control is carried out by pneumatics, hydraulics or vacuum.

Pneumatic method

The use of a pneumatic welding quality control method requires pumping the tank with some gas to a pressure of 150% of the nominal pressure.

Then all welds are moistened with soapy water. Bubbles form in places of leakage, which is very easy to fix. For better visualization, an ammonia additive is used, and the seam is covered with a bandage soaked in phenolphthalein. Red spots appear in areas of leakage.

If it is not possible to pump up the container, then use the blowing method. On one side the seam is blown under a pressure of at least 2.5 atmospheres, and on the other it is coated with a soap solution. If there is a defect, it will appear in the form of bubbles.

Hydraulic method

With the hydraulic method of welding quality control, the container being tested is filled with water or oil. An excess pressure is created in the vessel, which is one and a half times more than the nominal pressure.

Then, for a certain time, usually 10 minutes, the area around the seam is tapped with a hammer with a rounded head. If there is a through welding defect, a leak will appear. If the excess pressure is small, then the holding time of the tank is increased to several hours.

Magnetic flaw detection

The phenomenon of electromagnetism is used in magnetic flaw detectors. Each metal has its own degree of magnetic permeability. When passing through inhomogeneous materials, the magnetic field is distorted, which indicates the presence of foreign elements inside the structure.

This is used in the welding quality control instrument. It produces a magnetic field that penetrates the metal being tested. Inhomogeneities are recorded using magnetic particle or magnetographic methods.

In the first case, ferromagnetic powder is applied to the weld. Where the accumulation of powder occurs, there is most likely a lack of penetration, there is no continuous connection. The powder can be dry or wet, mixed with oil or kerosene.

In the second case, ferromagnetic tape is applied to the seam. It is then passed through a device where all anomalies recorded on the tape are analyzed and welding defects are determined.

The magnetic method of quality control has limitations associated with the very principle of operation of the device. It can only check the quality of welded joints of ferromagnetic materials, which do not include some steels and non-ferrous metals. Accordingly, this control method has limited application.

Ultrasonic flaw detection

Ultrasound is used to control welding quality. The operating principle of the device is based on the reflection of ultrasonic waves from the boundary between two media with different acoustic properties.

The sensor and emitter are tightly applied to the material being tested, after which the device produces ultrasound. It passes through the entire metal and is reflected from the back wall, returning to the receiving sensor, which in turn converts ultrasound into electrical vibrations. The device presents the received signal in the form of an image of reflected waves.

If there are any flaws inside the metal, the sensor will record a distortion of the reflected wave. It has been experimentally established that various welding defects manifest themselves differently on an ultrasonic flaw detector. This made it possible to classify them. With appropriate training, a specialist can accurately determine the type of defect in a seam.

The method of ultrasonic quality control of welded joints has become widespread due to its simplicity and ease of use, relatively inexpensive equipment, and safety of use compared to the radiation method.

The disadvantage of this method is the difficulty of deciphering the graphic image. Connection quality control can only be done by a certified specialist. It is problematic to use it for testing coarse-grained metals such as cast iron.

Radiation method

To control the quality of welding, radiation methods and devices are used. In essence, this is the same X-ray machine used in hospitals, or a device with a gamma radiation source, adapted for irradiating welded joints.

It is based on the ability of these rays to penetrate any materials. The intensity of penetration depends on the type of substances being tested. Thanks to this, an image characterizing the condition of this material remains on the photographic film behind the product under study.

All welding defects in the form of inhomogeneities are revealed on the film. The control method is very accurate, but expensive and harmful to people; it requires preparatory work to install protective screens and carry out organizational measures.

Paperwork

A special magazine is provided for welding. It is the primary document drawn up in accordance with the requirements of SNiP. The design organization draws up a list of components in the metal structure that must be handed over to the customer with the preparation of welding documents.

In addition to the magazine, welding work is accompanied by a diagram of the joints, certificates for consumables (electrodes, flux or filler wire) and quality control reports on the outside of the product are attached.

If ultrasound or other specific studies were carried out, the results and conclusions on them are also attached.

All this allows us to talk about the quality of welding and reliability of the design. Only after the welding documentation has been submitted in full are further procedures for accepting the metal structures of the facility carried out.

Source: https://svaring.com/welding/teorija/kontrol-kachestva-svarki

Everything about quality control of welded joints

Checking welding joints is a mandatory stage of any welding work. Thanks to careful monitoring, it is possible to identify obvious and hidden defects, which will subsequently affect the quality and durability of the entire metal structure. Of course, you can evaluate the quality of a weld with a naked eye, but this is only one of the methods.

Using visual inspection, you will not be able to detect internal cracks and pores. Therefore, it is important to know additional methods of quality control. In large industries, this work is performed by a welding supervisor, but in a small plant, this responsibility often falls on the shoulders of the welder. In this article we will tell you how to check seams and what types of quality control there are besides visual inspection.

Methods of weld quality control

There are various types and means of technical control, they all have their own advantages and disadvantages, features and nuances. But despite the differences, they are all designed to test the seams for strength and durability. The quality of welded joints largely depends on the welder and the components used, so the outcome of the inspection can be predicted. But we still recommend quality control to be sure that the products will last a long time.

The quality of welded joints can be determined by visual inspection (perhaps the most common method), ultrasonic, magnetic, capillary and radiation (radiographic) testing; welds are also monitored for permeability.

There are other methods for monitoring welds, but in this article we will list the most common and easy to use. We recommend performing operational quality control, i.e. first inspect the seam, then carry out penetrant testing and so on.

However, first things first.

Visual control

Let's start with visual control. This is the easiest and fastest way to find out the quality of welds. You don't need special equipment or liquids, your attentiveness is enough. Carefully inspect the welded joint: there should be no visible defects such as cracks or chips, the seam should have the same width and height in all areas.

External inspection of welding seams also allows you to check the presence or absence of lack of penetration, sagging, and uneven seam folds.

All these are defects, the detection of which can safely indicate low quality of the connection. For more effective quality control of welds, we recommend using a powerful lamp and a magnifying glass; a tape measure or ruler, or a caliper would also be useful.

With the help of such simple devices, you can measure the size of defects and understand what to do with them in the future.

Of course, using this method you will not be able to perform full inspection of welded joints of pipelines, welded joints of gas pipelines or other critical structures, but visual inspection will be the first operation, after which you can apply other inspection methods.

Penetrant control

Methods for quality control of welded joints also include weld testing. For this, the capillary method is used. Its essence is extremely simple: for control, special liquids are used that are able to penetrate the smallest pores and cracks, called capillaries.

Using capillary operational control, you can check the quality of any metal, with any composition and shape. Often this method is used when you need to find out the presence of hidden defects that are invisible to the eye, but there is no budget, since capillary testing is very easy to use and does not require expensive equipment.

Capillary assessment of the quality of welded joints is carried out using liquids called penetrants (from the English word “penetrant”, which means “penetrating liquid”). Such liquids have low surface tension, which is why they easily penetrate small capillaries and remain visible to the eye. Essentially, penetrants fill cavities and color defects, thereby making them visible.

Now you can find many recipes for preparing penetrant, each of which will have its own properties and characteristics. You can prepare a penetrant based on water or any other organic liquid (turpentine, benzene, this also includes the quite popular test of welds with kerosene. Such penetrants are very effective and sensitive to the slightest defects. They confidently occupy one of the leading positions among quality control methods.

Checking the tightness of welded seams

Weld testing does not end with liquids. They also need to be checked for leaks. The leak testing method has many names: leak testing, bubble testing, pneumatic testing, hydro testing and many others. But regardless of the name, their essence remains the same: detection of through defects that impair the sealing performance of the welded joint.


Checking welds for leaks is performed using gases (oxygen or nitrogen) and various liquids (for example, water). The method is in many ways similar to the capillary method, but here the gas or liquid is additionally supplied under high pressure, under which they are distributed into the defective cavities and come out. This method has its own classification.

There are pneumatic and hydraulic controls, and seams can also be checked using vacuum or air blowing; these are subcategories of pneumatic control. But let's talk about everything in more detail.

Let's start with the pneumatic method of quality control of seams. It involves the use of gas or air, which is directed to the connection under pressure. In this case, the seam is lubricated with a soap solution.

There is also a type of pneumatic control called vacuum control, when an artificial vacuum is created using special equipment, a part is placed in it, and the seam is also pre-wetted with a soap solution.

In areas with through cracks, bubbles will form, indicating the location of the defect.

When preparing a soap solution, use one bar of soap per liter of water. If you have to work at low temperatures (outside in winter), then it is recommended to replace more than half of the water with alcohol. We also recommend connecting a pressure gauge, with which you can monitor the pressure indicator and be able to notice how it will drop when defects are detected. It would also be a good idea to use a safety valve to maintain safety precautions.

The simplest form of pneumatic testing is to immerse the part in water, without lubricating the seams with soapy water or using pressure. If the seam has defects, they will make themselves known when small air bubbles begin to appear from the welded joint. This method of quality control can be called field, but it is quite effective.

There is also another type of pneumatic inspection called quality control of welds and joints using ammonia. Ammonia is supplied instead of gas or air, and the seams are pre-covered with special paper tape. Ammonia passes through the seam and if there are defects, red spots appear on the tape.

The second type of leak control is hydraulic. Here pressure is created using water or oil. This is a very interesting method, since the part is kept in liquid for 5 to 15 minutes (depending on the characteristics of the metal), while the area near the seam is tapped with a hammer, the blows should be weak. If there are defects, then upon impact, liquid will begin to flow out from the intended place with a crack or other damage.

Magnetic control

The magnetic control method uses the basics of electromagnetism. The inspector or welder, using a special device, creates a magnetic field around the seam, which emits a stream of so-called electromagnetic lines. If they are distorted, then there are defects. Distortions are recorded using magnetic particle method.

With magnetic particle welding, ferrimagnetic powder is first applied to the surface of the weld, which, when the electromagnetic line is distorted, begins to accumulate at the defect site. Because of this, magnetic inspection is only available when working with ferrimagnetic metals. Aluminum, copper, steel with a high content of chromium and nickel cannot be inspected. In general, this is a very effective, but inconvenient and expensive method, so it is used only when monitoring particularly important components.

Ultrasonic testing

The ultrasound method is very interesting. It is based on the properties of ultrasound. Ultrasonic waves are easily reflected from the edges of a crack or chip, since they have different acoustic properties. In simple words, we apply ultrasound to the seam, and if it encounters a defect along its path, it is distorted and displayed in a different direction. In this case, different types of defects distort the ultrasonic wave in different ways, so that they can be easily identified.

Weld quality control using ultrasonic devices is used everywhere, since it is a fairly effective and at the same time inexpensive method. Compared to other methods (for example, magnetic or radiation), there is no need to take into account any characteristics of the metal or purchase expensive equipment. But there are also disadvantages: ultrasonic inspection of the welded joint must be carried out by a specialist, and not by an ordinary welder.

Radiation control

Radiation weld inspection (also called “radiographic inspection” and “gammagraphic weld inspection”) is a mini version of conventional x-rays.

Gamma rays penetrate the metal and all possible hidden defects are recorded on a special film. This is the most advanced and expensive method of quality control; it requires modern equipment and qualifications from the inspector or welder.

Also, excessive work with such a device can have a negative impact on human health.

Recently, digital radiography has appeared, which is performed using a computer. Here, instead of film, special reusable plates are used, which are compatible with any radiation sources. But unlike classical radiation monitoring, with the digital method, images are saved directly to a computer, they can be scaled and cropped. In the future, the developers plan to make this process automatic so that human presence is not required.

Instead of a conclusion

The welding supervisor must be very attentive to his work, since everything depends on his attentiveness. When performing quality control of welding and welded joints, record all features and defects that you can detect. Combine different weld inspection methods to get the full picture. Do not use destructive weld inspection methods that are not suitable for certain metals.

Welding and quality control of welded joints of metal structures is not an easy task, but having learned this just once, you will be able to quickly carry out control even in the field. Also, do not forget that there are safety precautions and they must be observed not only when welding, but also when inspecting seams.

Source: https://svarkaed.ru/svarka/shvy-i-soedineniya/vsyo-o-kontrole-kachestva-svarnyh-soedinenij.html

How to check a weld in 1 hour! | Non-destructive testing magazine

Almost all characteristics of a weld can be evaluated during a weld inspection—some related to the size of the weld and others related to the presence of discontinuities in the weld.

Weld size can be extremely important as it is often directly related to the strength and performance of the weld.

For example, smaller welds may not be able to withstand the loads applied during service.

Depending on their size or location, weld discontinuities (defects within or adjacent to the weld) can adversely affect the weld's intended performance characteristics.

 Weld breaks are often referred to as weld defects, and they can sometimes cause premature weld failure due to reduced strength or additional stress concentrations within the welded component.

Weld inspection is performed for several reasons, the most common of which is to determine whether the quality of the weld is adequate for its intended application. To evaluate the quality of a weld, you must first have criteria against which you can compare the characteristics of the weld.

GOSTs, standards developed specifically for various welding applications, are used during welding inspections to determine acceptable levels of weld failure.

It is important to select a welding standard and method that is designed for use in your industry or application.

Weld inspection quality acceptance criteria can be obtained from several sources. A drawing or welding shop drawing usually provides dimensions and other dimensional information such as the length and location of welds. These dimensional requirements are usually established through design calculations. They can also be taken from proven designs that are known to meet the weld joint performance requirements.

Role of the Welding Inspector Engineer

Welding inspection requires a wide range of knowledge on the part of engineers, including understanding of welding drawings, symbols and procedures; welded joint design; code and standard requirements; and verification and testing methods.

For this reason, many welding codes and standards require that the welding engineer be formally certified. There are several welding inspection training courses and certification programs available.

Visual inspection.

When performed correctly, visual inspection can often verify the weld and is the simplest and least expensive method for many joints. However, a good-looking weld does not always ensure internal quality, and internal breaks are not always visible to the naked eye. In this case, additional methods are available, including those listed below.

Surface Crack Detection. 

Used to detect small cracks, seams, porosity and other discontinuities on a surface, surface crack detection is typically applied using one of two methods: liquid penetrant inspection or magnetic flaw detection.

X-ray and ultrasonic testing of the weld.

To test a weld and establish integrity without destroying the weld, these two non-destructive testing methods detect breaks in the internal structure of the weld.

Quality welding work requires the establishment and control of a reliable welding inspection system. Proper technique must be used.

The experience of welding engineers who carry out inspections is very important.

Source: https://nova78.ru/kak-proveryat-svarnoy-shov/

How to control the quality of welding seams and welded joints

Even a novice craftsman understands that the further functioning of the manufactured structure depends on the quality of the weld. Any defect potentially causes a decrease in strength. At the most crucial moment, the connection may fail. And even if this does not happen, the lack of tightness of the seam will make the operation of structures such as pipelines, vessels and other systems where high pressure is present impossible.

Inspection of welds is a mandatory procedure that must be performed upon completion of work. Only after this can defects be identified and corrected in time.

It is important to understand that you cannot rely solely on visual inspection. The naked eye can detect only large defects: lack of penetration, cracks, pores or undercuts. But these are not all the shortcomings that arise even among experienced welders. For example, microscopic cracks, especially if they have formed deep in the seam, will have to be determined by other methods. Often you have to resort to using special tools or devices.

There are several ways to implement quality control of welds, differing in the methodology, technical equipment, and efficiency. All these methods are conventionally divided into destructive and non-destructive.

Destructive methods of quality assessment involve exposure to loads of critical importance. Naturally, this negatively affects the structural properties of the parts, which is why non-destructive methods are considered the most popular. These include the following activities:

• visual inspection;
• radiation flaw detection;
• ultrasonic flaw detection;
• magnetic flaw detection;
• penetrant flaw detection;
• pneumatic and hydraulic method of checking seams for permeability

Visual inspection

Any connection is initially assessed visually. Often, ordinary observation is enough to identify external and some internal defects. For example, changes in the dimensions of the seam in height and width indicate that the arc broke during the welding process. As a rule, it becomes the cause of lack of penetration.

Before inspection, the seam must be cleaned of any slag or splashes that have formed. If a detailed examination is necessary, the welding zone is treated with alcohol and a 10% nitric acid solution. As a result of this treatment, the surface becomes matte, and cracks or pores are clearly visible on it. After completing the inspection, the remaining acid should be removed with alcohol, otherwise it will corrode the metal.

Visual inspection is provided to identify incorrect geometry of seams, cracks, pores, sagging and lack of fusion. Additional equipment includes lighting lamps and a magnifying glass. Using these tools, burns and undercuts are recognized.

In addition, it is possible to monitor the behavior of the crack during operation. A precision measuring device that allows you to record small elements - a caliper. But an ordinary ruler can also be useful.

Some defects are detected using special templates.

Penetrant flaw detection

This principle is based on the phenomenon of drawing liquid into thin tubes due to the action of surface tension forces. The intensity of capillary filling depends on its diameter and the wettability of the material. The greater the wettability and thinner the capillary tube, the faster and deeper the liquid is drawn.

Note that this method is suitable for assessing the quality of connections made of metal, plastic or ceramics.

After the liquid penetrates the capillary, all flaws reveal themselves. Special substances for performing penetrant flaw detection are called penetrants. They are characterized by their color contrast, as well as the low surface tension forces that arise. Defect cavities are filled with penetrants and become easily visible.

Currently, several dozen penetrant formulations have been developed, and they all have different properties. Some of them are made on a water basis, as well as on the basis of kerosene, benzene or turpentine.

Organic liquids are most acceptable, as they increase the sensitivity of the product to the smallest defects. A special case of capillary examination is luminescence flaw detection. With this research method, luminescent substances are included in the penetrant formulation.

The surface under study is irradiated with ultraviolet rays, after which the substance that has penetrated into the crack or pore begins to glow.

All substances for penetrant flaw detection are divided according to sensitivity. The highest degree is considered the first class of sensitivity. Substances of class 1 penetrate into capillaries whose diameter is 0.1 microns. There is also an upper limit value at which liquid is still drawn into the capillary. It is approximately equal to 0.5 mm. Another requirement for a capillary is that its length must be tens of times greater than its diameter.

Penetrants are usually released in the form of an aerosol. With this release form it is convenient to apply it to the surface. But the set of tools for flaw detection also includes a cleaner (for pre-treatment), as well as a developer (for forming the final pattern). The use of penetrants has its advantages and disadvantages.

• The positive aspects include the low cost of the process, the elementary nature of the technology, productivity, and a wide range of designs being studied.
• The disadvantages boil down to the need to thoroughly clean the seam, the ability to check only surface defects, and the impossibility of using the method for capillaries with a diameter of more than 0.5 mm.

Quality control of welding seams using kerosene should be classified as a permeability test, but this method is still based on capillary phenomena. It is considered the simplest and most accessible in material terms.

Kerosene has high fluidity and is able to penetrate into the smallest cracks. Looking ahead, it can be noted that the capillary method using kerosene is as effective as the hydraulic method under a pressure of 3-4 kgf/mm2.

It is not for nothing that some penetrants contain kerosene.

The algorithm for checking a weld seam comes down to a few simple steps. The seam is cleaned from both sides of dirt, scale and slag. One of the sides is selected for observation and covered with an aqueous solution of chalk (400 g of powder is taken per 1 liter of water). To increase the drying speed of the suspension, you can dry the seam with a stream of hot air. The reverse side of the surface is generously moistened with kerosene. It is necessary to repeat the wetting procedure 2-3 times with an interval of 15-30 minutes.

The number of repetitions and interval depend on the thickness of the metal. Wetting is carried out in any available way (rags, brush, spray gun). Kerosene leakage will become noticeable on the side covered with the chalk slurry. Over time, dark spots or streaks will appear. It is necessary to record the location of the defects immediately after their appearance, otherwise the kerosene stains will blur and it will be difficult to determine the location of the crack, fistula or pore.

The test may take several hours. The higher the ambient temperature, the lower the viscosity of kerosene. Consequently, at elevated temperatures, the process of assessing the quality of the weld will be faster. Kerosene is primarily used when testing butt joints. Overlapping seams are much more problematic to check in this way.

During the manufacture or repair of various containers, pipeline systems, pneumatic systems, not only strength, but also tightness requirements are imposed on the weld. Permeability testing can be carried out in different ways, including hydraulic and pneumatic. The main purpose of such a check is to determine the presence of through pores through which liquid or gas will subsequently exit the tank.

The test substance used is air, nitrogen, water or oil. Usually normal pressure is not enough, so excess pressure is created to make the picture of defects more clear.

When using the pneumatic method, the test container is filled with gas (air, inert gas, nitrogen). The gas is brought to a pressure one and a half times higher than the working pressure. To visually observe the leak, the outer surface of the seam is moistened with a soap solution.

If there is a defect, bubbles will form. If tests are carried out at negative temperatures, the soap solution is applied to alcohol.

During the test, it is necessary to monitor the pressure and not exceed a certain norm. Typically, a pressure gauge and a bypass safety valve are installed in the tank. Small tanks are filled with air and immersed in water without lubricating with soapy water. The released air will form bubbles in the water.

The pneumatic method of testing for permeability includes testing with ammonia. The seam is covered with gauze or a bandage soaked in phenolphthalein. A mixture of ammonia and air is supplied from the back side of the seam. If ammonia passes through the seam, the bandage turns red. This method is considered reliable.

The most primitive method of pneumatic control involves blowing air over the seam. The reverse side of the connection must first be lubricated with a soap solution.

To implement hydraulic control, the cavity is filled with a liquid, usually oil or water. This also means testing under pressure exceeding the operating value by 50-100%. To detect leaks, it is enough to keep the container in this state for about 10 minutes. In parallel with this, the seam and the heat-affected zone are tapped evenly with a hammer. If it is not possible to create excess pressure, then the container with liquid should be kept for at least two hours.

Magnetic

Magnetic flaw detection technology uses the effect of a magnetic field on ferromagnets. A special device is a source of magnetic field. Magnetic induction lines become bent when passing through a metal with a defect. All that remains is to detect these changes.

The indicator is ferromagnetic powder, which is applied to the surface in dry or dissolved in water form. In places where cracks form, this powder accumulates. More visualization of defects is possible when using a special ferromagnetic tape. It is applied to the surface and then viewed through the device.

The disadvantage of this technology is the selectivity of the method to the surface material. For example, parts made of nickel, chromium, aluminum or copper cannot be tested.

Ultrasonic

An ultrasonic wave has penetrating power and can be reflected from the interface between media in which sound propagates differently. This property is the basis of this method. The device consists of a source and receiver of an ultrasonic wave.

If there are no defects inside the metal, then the speed of sound passing through the part in the forward and reverse directions is calculated. If there are cracks or pores, the wave reflected from the bottom face will come with distortion.

There is a special classification of the resulting paintings that allows one to distinguish between different types of defects.

Ultrasonic flaw detection is superior to magnetic and radiation in its popularity and applicability. The disadvantage is the complex signal decoding system. To conduct the research, a special qualification of the master is required. The limitation on the use of the described method is associated with the coarse-grained structure of metals. Austenitic steels and cast iron are not subject to examination.

Radiation

Radiation flaw detection is similar in principle to X-ray examination. Gamma rays released during a nuclear reaction have a high penetrating ability. Passing through the material, the radiation hits the photographic plate. After its development under a microscope, you can examine the distribution of the defect in the metal.

The interesting question about the harmfulness of gamma radiation remains relevant. Despite the protective measures provided, the human body receives an increased amount of radiation. If we add the high cost of equipment, it becomes clear that this method is not a priority.

Source: https://svarkoy.ru/teoriya/kontrol-svarnyx-shvov.html

Quality control of welded joints and seam inspection: equipment inspection log

The quality of the welding work performed affects the reliability and durability of the entire structure.

The presence of various defects can significantly reduce the performance characteristics of products and their strength properties. In this regard, quality control of welded joints is a necessary procedure that must be carried out after work is completed.

Main stages of welding quality control

Welding quality control is necessary to confirm the suitability of the product for use. It is this procedure that establishes the compliance of the work performed with the customer’s requirements.

Factors affecting the quality of welds.

Since this process is a crucial moment, we should dwell in more detail on the features of its implementation.

The following stages of control are distinguished:

• checking the welder's qualifications;
• assessment of the quality of connected parts;
• checking the sequence of welding technology;
• seam quality control;
• mechanical tests.

The first stage involves testing the workers' skills. During this process, each welder shows a special passport with a welding permit and makes a test connection.

Test connections are made with the same equipment and the same materials as in the main work. The resulting products are assessed through visual inspection and subjected to mechanical tests. If a quality part is received, the welder is allowed to work.

When checking compliance with the sequence of actions performed, the following is monitored:

• compliance of connection assembly;
• welding parameters: current, voltage;
• method of making joints;
• cleaning of slag and scale before applying subsequent layers of welding.

Checking the seams is carried out either through visual inspection or using specialized equipment.

Types of control

The quality of welded joints must correspond to the subsequent conditions of use of the products. In this regard, there are different requirements for the work carried out.

In any case, the following indicators are required to be checked:

• appearance of seams;
• connection density;
• physical and chemical properties of seams.

Design features of the flaw detector.

There are also two types of verification: preliminary and final. In the first case, preliminary control of preparation for work is carried out. The materials used, equipment, fixtures, and, naturally, the readiness of the welder are checked.

During the work itself, they monitor compliance with welding technology, the correct choice of parameters and modes for the devices, the order of applying the edges of products and their processing.

The final type of inspection is carried out after completion of welding. It includes an external inspection to detect external defects. This procedure is performed by an appropriate specialist using a magnifying glass.

The technologist inspects the product for lack of penetration, sagging, and cracks. He also checks that the parts are positioned correctly. It is necessary to make sure that during welding there is no displacement of the elements relative to each other.

If containers, pipes and other products operating under high pressure are inspected, permeability tests are carried out. The method for checking seams is selected based on the pressure source.

If the container is supposed to be used for water, then it is completely or partially filled with liquid. She stays in this state for anywhere from two hours to a day. The connection is considered to be of high quality if during this time it remains dry on the outside.

When checking pipes, these products are filled with water under high pressure, the value of which is twice as high as the working one. Then the pressure is reduced to the standard value and the pipe is tapped with a hammer.

The presence of wet areas indicates the presence of defects. They are marked with chalk and after draining the liquid, re-welding is performed.

To check resistance to pressure from the gas side, the container or pipe is filled with air in accordance with the product specifications. After this, the joints are lubricated with a soap solution. If they are of poor quality, then soap bubbles will appear.

After all checks have been completed, their results are entered into the inspection log.

Radiation monitoring methods

Detection of weld defects.

Quality control of welding joints using gamma radiation or x-rays is the most reliable and sensitive. Such methods make it possible to detect defects located inside the part at a depth of up to hundreds of millimeters, depending on the material of the product.

Gammagraphy is the process of penetration of gamma radiation into the depth of the material under study. In this case we are talking about metals. The radiation intensity may vary depending on the presence of defects in the product. This is the principle of operation of this method.

The advantages of radiation monitoring are: high sensitivity, the ability to determine the type of defect, its size and location.

At the same time, the method is not without drawbacks, including: the high cost of such devices and their large dimensions, as well as the complexity of the technology.

The use of radiation technology makes it possible to ensure that the connection is perfect not only in accordance with external signs, but also due to the absence of defects in the thickness of the seam.

Bottom line

Inspection methods are necessary to inspect seams produced using welding equipment. Depending on the requirements for products, testing options may vary.

For parts that do not require great resistance to mechanical and plastic loads, only a visual inspection may be sufficient. While large enterprises often require additional checks using mechanical tests and radiation methods.

Source: https://tutsvarka.ru/tb/kontrol-kachestva-svarnyh-soedinenij

Methods for quality control of welds and joints

Quality control of welds is a very important procedure that is carried out after completion of welding work.

This is required so that the obtained result meets the stated requirements, and the products can function safely without a high risk of breakdown, which will lead to an accident.

The quality of welds according to GOST is checked using strictly defined methods. They are installed in advance, depending on the material, product, assigned responsibility and other features.

Determination of the inspection zone of welded joints

Organization of weld inspection

Checking welds is one of the prerequisites for production. Several methods are used to organize it. The first is control of welding work. The most responsible method to reduce the likelihood of seam defects. This control of welded joints is especially effective in automatic welding.

Control is also carried out using sample samples. To do this, samples are pre-produced from identical materials with the same size parameters. All the necessary experiments are carried out on the sample taken to understand whether it meets the requirements for welds in this case. It is used to evaluate all other products that must have the same characteristics.

The following method uses generalizing parameters that have a direct relationship with welding quality. One example is the dilatometric effect that occurs during resistance welding. This method is complex, since it is not always possible to find a generalizing parameter for a specific type of connection.

Control of welding parameters. Inspection of welded joints shows better results if the operating mode of welding machines is initially controlled for certain types of joints.

Important! Correctly defined characteristics provide more accurate and effective results.

Checking welds for defects

Defects in welded joints and the reasons for their occurrence

Quality control of welded joints and seams is aimed at identifying defects. To check their reliability, you need to know what to look for. All of them lead to a decrease in the strength of the connection and its faster destruction. Modern methods of inspection of welded joints make it possible to identify the following defects:

• Swells. They appear when molten metal flows onto an already cooled one or one that has not melted. The length of the influx may vary depending on the nature of the work. The main reasons for the appearance of sagging are too high an electric arc and excessive current parameters during welding.
• Undercuts. Tests on welds show that when they are present, the strength becomes less strong. An undercut occurs when an oblong depression is formed next to the seam. It is located along the edge of the connection, creating the weakest point in the entire structure. The reason for the appearance of such a defect is the displacement of the electrode during operation, due to which the metal melts not only at the place where the seam is formed, but also nearby.
• Burnout. Even visual control of the quality of welded joints and seams allows you to determine burn-through, since it is very clearly visible even without special equipment. It appears when a hole is formed in the base metal due to the influence of an electric arc. This happens when the current is too high, the weld pool is held in one place for a long time and when it comes off. Most often, burns also appear when joining thin sheets.
• Lack of penetration. Technological methods for monitoring welds are more relevant for lack of penetration, since they are more difficult to notice with the eye, especially without removing slag. This defect consists in the absence of a welding connection in some places. The edges remain unwelded to each other, which reduces the strength of the joint and makes it leaky. Requirements for the quality of welded joints do not allow such problem areas that appear due to low current strength and too high speed of weld creation.
• Cracks. Standards for assessing the quality of welded joints do not allow the presence of cracks, since this is one of the most dangerous defects. They form in the heat-affected area and in the joint itself. They can have any direction of location and size. The most difficult to notice are microcracks, which pose a high level of danger. They appear due to the high content of phosphorus, sulfur or carbon in the weld pool.
• Slag inclusions. Inspection of welds according to GOST 23118 99 allows one to determine the presence of slag inclusions inside the weld. This defect appears when the edges are poorly cleaned. The presence of oxides in the base metal and consumable material creates problematic situations during welding, which lead to the appearance of slag inside the weld. It also appears due to poor cleaning during multilayer welding.
• Gas pores. Only a complex method for quality control of welded joints in metal structures will determine the presence of gas pores inside the weld. During metal crystallization, some gases may not escape from it, leaving pores inside. This is due to the high level of carbon in the metal. Incorrectly selected shielding gases and rapid weld creation can also affect their formation.

Types of non-destructive testing of welded joints

Methods of non-destructive testing of welds

The requirements for welded seams of metal structures in modern conditions of use cannot be fully verified without appropriate types of inspection of welded joints. If it is possible to carry out everything without destroying the seam, then this method becomes a priority. There are the following methods for monitoring welded joints according to GOST:

1. Kerosene control. It is based on the physical effect of capillarity. If there are cracks or other through defects, kerosene will pass through them and appear on the other side. Its permeability in this case is much higher than that of other liquids. This physical method of testing welded joints allows you to check quality at a relatively low cost.
2. Ammonia control. Assessment of the quality of welded joints is thus based on the change in color of certain indicators when exposed to an alkaline environment. The reagent is ammonia, which can penetrate into thin crevices and cracks. On one side there is paper with an indicator, and on the other - ammonia. If the seam has defects, they will appear when ammonia passes through them.
3. Air pressure control. Such testing is carried out on those products that will work under pressure. This type is necessarily included in the technological map for quality control of welded joints of metal structures. The pressure is supplied 10-20% higher than the main operating pressure. If the pipe holds up, then it can work normally in the future.

Destructive quality control of welded joints

Methods of testing with destruction of welded joints

When carrying out operational quality control of welded joints, it is not always possible to check the quality without destroying the latter. This technique is used when testing large batches, when only one sample is tested.

Here it is worth considering what the controlled zone of a control welded joint is, since the check can be carried out for the entire metal of the product, specific sections of the weld, or only the heat-affected zone.

Destructive testing methods involve the following types of tests:

• for static tension - carried out until the connection breaks, in order to find out at what force this is possible, and how much the metal stretches to the maximum;
• statistical bending - it is determined at what bending forces will not allow the product to function normally;
• impact bending - determines the critical force of a mechanical impact that damages the seam;
• hardness measurement - determines the strength of the seam;
• resistance to aging – negative conditions are artificially created under which all stages of seam aging appear much faster

Source: https://svarkaipayka.ru/oborudovanie/raznoe/metodyi-kontrolya-kachestva-svarnyih-shvov-i-soedineniy.html

How to check a weld for leaks

06.07.2019

Objects intended for transportation or storage of liquid and gaseous substances must be subject to control of the tightness of welded joints. The tightness test is carried out by the company's quality control department. Periodic monitoring during operation is carried out by the owner within the time limits determined by regulatory documents.

The essence of monitoring the tightness of welded joints

Leak testing is a non-destructive testing method based on the ability of gases or liquids to leak through tiny holes. After it is carried out, the mass of the working fluid leaking through the flaws in the welded joint is visually assessed or measured. The obtained result is compared with the permissible values ​​specified in regulatory documents. When determining the frequency of tightness testing and the method of implementation, take into account:

• physical and chemical properties of the working environment;
• pressure value;
• ambient temperature;
• terms of Use.

Methods for checking welds for leaks

Before testing for tightness, the weld seam must be prepared. The surface is cleaned of slag and scale is etched if necessary. If the inspection does not reveal major defects, choose an acceptable method of checking the tightness.

Hydraulic test

Depending on the purpose and size of the object, to check welds for leaks, choose one of 3 options:

1. Pipelines and vessels operating under pressure are sealed, water is pumped through the fitting, creating a pressure higher than the working pressure by 25 - 50%. The test is carried out for 10 - 15 minutes at positive temperatures. The result is judged by leaks, fogging, and the amount of pressure drop.
2. Reservoirs and tanks for storing liquids are filled with water at a temperature of at least 5⁰ for a day. The degree of tightness is determined by the decrease in level. After eliminating the defects, the test is repeated.
3. For large objects, joints are checked for leaks with a stream of water directed along the seams under a pressure of 1 atm. The fire hose is kept at a distance of no more than 2 meters from the surface. Defects appear on the reverse side in the form of leaks, water droplets, and sweating of seams.

Source: https://svarkaprosto.ru/tehnologii/germetichnost-svarnykh-shvov

How to check the quality and tightness of a pipe weld?

During the construction of long pipelines, a large number of welded joints are formed, the quality of which largely determines the performance of the system. Weld defects arise due to poor quality of pipes, violations of welding technology, and insufficient qualifications of the worker.

They lead to a deterioration in appearance, a decrease in the strength characteristics of the pipeline, and its durability. They can be superficial and internal, which require special methods and equipment to identify.

To check the pipe for cracks and other defects without compromising the integrity of the seam, non-destructive testing methods are used.

Types of weld defects

Surges

They appear as a result of the flow of molten metal onto cold sections of the pipe located in the heat-affected area. They may take the form of individual drops or extended formations.

https://www.youtube.com/watch?v=nv3EecJ2ADY

Reasons for appearance:

• welding current is too high;
• incorrect movement of the electrode;
• incorrect angle of inclination of pipes when connecting them.

Accompanying phenomena: uneven weld penetration, external and internal cracks.

Undercuts

They are grooves that appear in heat-affected areas. Negative consequences are a reduction in the cross-section of the weld, excessive stresses that provoke the formation of cracks with possible complete destruction of the welded joint.

Burns

Holes through which the melt from the weld pool flows.

Reasons for education:

• insufficient speed of the welding process;
• too large a gap between the ends of the connected pipes;
• excess current.

Cracks

Attention! Cracks are the most dangerous type of defect. They can form at any point in a seam or near-weld area. They are located longitudinally or transversely.

They are divided into microcracks and cracks. Causes of appearance: incorrect welding technology or increased content of harmful impurities.

Foreign inclusions

Particularly dangerous are slag residues on the surface of the welds, which accelerate the corrosion of steel.

Gas pores

Internal defects. They can be located individually, in chains, or in groups. This type of defect reduces strength. Chains of pores provoke depressurization of the system.

Magnetic method

It consists of magnetizing the area under study and studying magnetic dispersion when structural inhomogeneities occur. There are the following subtypes of the method:

• Powder. To implement it, iron filings are used, which are scattered on the surface of the weld. When a magnetic field is created, iron particles form a picture of the magnetic spectrum and signal the presence of deep cracks and pores.
• Induction. In this case, finders are used that produce an audible or visual signal when the magnetic flux dissipates.
• Magnetographic. Flux dissipation is recorded on a magnetic tape located on the suture surface. The search for defects is carried out by comparing the results obtained with the standard.

How to check a weld for leaks?

There are several ways to check the tightness of an assembled pipeline.

Capillary

The tightness of the weld is checked using kerosene, which has the property of penetrating through internal pores and cracks. An aqueous chalk solution is applied to the weld and then dried. Kerosene (in large quantities) is applied to the side opposite the surface treated with chalk. If the weld is damaged, the kerosene will bleed through the chalk surface.

Bubble

Check with air supplied under pressure. The seams are lubricated with soapy water. When compressed air is supplied, soap bubbles appear on a leaking seam.

Using a gas-electric finder

This method is used to test critical piping systems. To implement it, highly permeable helium gas is used. The appearance of gas is detected by a special probe, and its quantity is determined using an electronic unit.

How to check the pipes of a “warm floor” system?

Before laying the finished floor, be sure to check the heat pipes for leaks. The method is determined by the pipeline material.

Metal-plastic pipes are checked during the day with cold water supplied under a pressure of 6 bar. If the pressure does not change, then the system is considered to have passed the test.

The pipeline made of cross-linked polyethylene is checked with cold water at a pressure 2 times higher than the working pressure, but not less than 6 bar. The pressure will drop. After half an hour, it is necessary to restore the test pressure. This procedure is repeated 3 times. After the third time, bring the pressure to the test pressure and leave for a day. If after this no leaks appear and the pressure drops by no more than 1.5 bar, then the system is considered operational.

After pressure testing of the cold water pipeline, an additional check of the “warm floor” system is carried out at the maximum operating temperature. The system is warmed up for 30 minutes. After this, all collet connections are checked for leaks. If necessary, they are tightened.

Attention! The screed can be poured after the system has cooled. Pipes must be under pressure.

Source: https://www.navigator-beton.ru/articles/germetichnost-svarnogo-shva.html

Methods for quality control of welds and connections

[Weld quality control] is a necessary procedure for determining the quality of a metal structure.

If the seam is not tight enough, with broken tightness and other deformations, all this will inevitably affect the service life of the metal structure.

This will happen especially quickly if the metal structure is under constant pressure.

To control quality and check the compliance of seams with GOST, there are special procedures, the types of which (ultrasonic, visual, etc.) will be covered in detail in the article.

Purpose of the procedure and method of visual inspection

Before checking a metal structure for compliance with GOST requirements, it is first necessary to check how well the seams are made - at this stage, all external and internal defects of the seams are identified and corrected, if possible.

Each finished product is subject to careful control before it is allowed to be used.

The first and simplest level of quality control: visual inspection.

A visual inspection of the metal structure allows you to identify external and most obvious deformations of the seams, such as cracks, lack of penetration and other defects.

Most of these deformations can be determined by a normal visual inspection of the metal structure without the use of additional equipment, however, in some cases the use of special devices is practiced.

Types of inspection of welds are divided into destructive and non-destructive.

The first type of control involves only a visual inspection; all other, more complex inspection techniques belong to the second type.

The second type of control can be capillary, ultrasonic, radiation, magnetic and permeability testing.

With any non-destructive testing method, the appearance of the metal structure is not deformed, which makes it more convenient and in demand than the destructive method.

The destructive - visual - method of control is used only if the welded part is welded using a constant type of welding without changing the conditions.

Methods for monitoring welds are also different. When carrying out inspection in accordance with GOST, different types of procedures are carried out in turn to identify the quality of the weld.

Procedures are divided into chemical, mechanical, physical, as well as visual and ultrasound examination.

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The most budget-friendly is a visual inspection, since it does not require any financial costs.

However, it is not used for reasons of economy, but out of necessity, since it allows one to identify the most significant violations of the seams.

Visual inspection is necessary for absolutely all types of metal connections, regardless of what control methods follow it.

Often, a visual inspection according to GOST is carried out without the use of any auxiliary devices, but in some cases, in order to make the inspection more accurate, a magnifying glass is used, which can increase the inspected seam space by 10 times.

In this case, you can notice even the smallest lack of penetration, undercuts, sagging and other defects.

External inspection of seams includes not only direct visual inspection, but also measurements of welds, edge measurements and other procedures.

If products for metal structures that are subject to control are produced in mass quantities, then in this case a special template is used to create them, which allows for accurate and identical measurements of all weld parameters.

If the visual inspection is successful, it is followed by a physical inspection, which reveals the quality of the seam joint and other characteristics.

The purpose of such control is to ensure that the characteristics of the welds fully comply with GOST.

Testing by physical and chemical methods is carried out with the connection of special equipment, for example, an electromagnetic core, as well as other devices.

the purpose of any type of control check is to identify not only the immediate condition of the seams, but also to check how high quality the metal part itself is, and whether there were any violations during welding work.

Depending on the type of metal, the characteristics of the seams will differ slightly from each other, however, all of them must comply with GOST-6996-66, which specifies all types of inspection work that must be performed.

Other control methods

Quality control of welded joints of pipelines and other metal structures is carried out using different methods, but all of them are necessary to establish how well the manufactured products comply with GOST.

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After the visual inspection is completed, it is scanned. This procedure requires the use of X-rays or gamma rays.

When checking with x-ray, the device is installed on the inside of the metal structure.

Using an x-ray, you can see places where the welding equipment has had insufficient impact - on the film they will be marked with spots of darker shades than the main color of the joints.

Using this method, cracks in metal structures, lack of penetration, slag inclusions and other deformations that are invisible during external inspection are identified.

Using X-raying, you can evaluate metal joints with a thickness of no more than 6 cm; when defects are detected, twice as many joints are X-rayed.

Magnetographic quality testing is necessary to detect the stray field that forms where defects exist.

The method involves magnetizing the surface of the part, after which a field area appears on top of the magnetic tape, which is pressed onto the surface of the seams.

The entire process of checking a metal structure is recorded using a flaw detector, and then the information is read and, thus, it is established whether there are defects in the seams.

This method makes it possible to detect the presence of cracks, pores, lack of penetration, slag inclusions and other defects that arise during the welding process.

Also, using the magnetographic method, it is possible to determine the presence of transverse cracks, wide lack of fusion or rounded pores on the surface of the seams, however, this method copes somewhat worse with the search for defects of this kind.

It can only be used for metal workpieces whose thickness does not exceed 1.2 cm.

Ultrasonic quality testing is often used to assess steel and non-ferrous metal products for compliance with GOST.

The ultrasonic method involves sending sound vibrations to the surface of the metal and subsequent reflection to identify possible defects.

To produce an ultrasonic wave, several piezoelectric quartz plates are used, which are fixed in the probe.

After oscillations, the ultrasonic waves, which are reflected from the metal, are captured by a special device - a finder, which converts the ultrasonic beam into an electrically charged pulse, which is transmitted to an amplifier and then reproduced using an indicator.

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In order for the ultrasonic method to be effective, before the ultrasonic beam is directed at the metal, its surface is first coated with auto scrap or compressor oil.

Opening the seams is a more radical method of checking when the probability of defects is quite high, but neither ultrasound nor other methods can detect it.

The seams are opened with a special device only in the area where there is a high probability of a defect.

Opening occurs by drilling a recess, the diameter of which should be slightly larger than the size of the seam, and then the surface is ground and treated with diluted nitric acid.

This method noticeably deforms the metal workpiece, and after it the boundary of the seams appears very clearly, therefore this method of control is not used unless necessary.

The chemical method of monitoring compliance with GOST consists of treating the surface of the seams with a phenolphthalein solution; before this, the surface must be thoroughly cleaned, removing all slag and dirt.

After applying the solution, the treatment area is covered with a cloth, which is soaked in silver nitrate (5% solution).

This method allows you to identify the presence of local leaks: in these places, silver will take on a silver-black appearance, and phenolphthalein will appear red.

In order to determine how much the density of the weld corresponds to GOST, the kerosene test method is used.

Thanks to it, you can find the smallest defects, the size of which can be about 0.1 mm.

To identify quality defects, the seams are covered with kaolin or chalk on one side and moistened with kerosene on the other.

If there is a hole in the seam, greasy yellow spots will appear on the surface of the kaolin or chalk.

They do not appear immediately, so checking for GOST using this method takes at least 4 hours.

Source: https://rezhemmetall.ru/kontrol-kachestva-svarnyx-soedinenij.html

Checking welds for tightness, strength, rupture

Checking welds for tightness, strength, rupture

Checking welds is a mandatory procedure if there are special requirements for welding, regarding tightness, tensile strength, etc. A weld will be airtight only when gaseous and liquid substances do not pass through it.

Checking the weld for leaks is a prerequisite when welding pipelines and containers intended for storing fuels and lubricants. For these purposes, various methods are used, using kerosene, pneumatic, and other devices.

At home, when there is no special equipment at hand, you can check the weld for leaks using kerosene or acetone. How exactly a weld is checked before use will be discussed in this article on the site about manual arc welding mmasvarka.ru.

Pneumatic control of welds

This method of checking welds is carried out using compressed gas or steam. Most often, inert gas, air or nitrogen is supplied to the welded product. Depending on the size of the product being tested for leaks, it can be immersed in water, where absolutely all flaws and welding imperfections will be visible.

It is especially effective to check welds using a foam indicator, which is a soap solution of water and detergent. Compressed air pumped into the pipeline exits through defects in the welds, which are pre-coated with a soap solution.

Hydraulic testing of welded joints

With this method of checking the quality of welds, a liquid is used, most often it is water. To pump water into a pipeline or some other welded product, a special hydraulic press or pump is used. Water is pumped into the pipeline with a fairly high pressure, approximately several times higher than the operating pressure in the vessel.

An important nuance in this case is the pressure holding time; it should be at least 5 minutes. In this case, the welds must withstand water pressure and liquid must not leak through them. Otherwise, this indicates low quality of the welded joint.

Checking welds with kerosene

Checking the quality of welded joints using kerosene deserves special attention. This method of verification is notable in that it can be carried out without special equipment and at home. Testing welds using kerosene is based on the properties of liquids, in this case, their good fluidity.

To check a weld with kerosene, you need to do the following:

• Apply a diluted chalk solution (chalk diluted in water) liberally to one side of the weld;
• After the chalk solution has dried, the weld will turn completely white;
• Then, on the other side of the welded joint, kerosene is applied with a brush, after which you need to wait a while.

How long to wait until the kerosene comes through the seam depends entirely on its thickness, as well as on the ambient temperature. As a rule, various welding defects are determined quickly enough by this method, so you won’t have to wait long, but you will be able to identify a poor-quality welded joint in time.

Source: https://mmasvarka.ru/proverka-svarnyh-shvov.html