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X-ray Welding Machine

Weld inspection is an important field of x-ray inspection. For example, in the production of cylinders, defects such as porosity, inclusion, crack, non-fusion, and non-penetration in the weld of cylinder do not only affect the quality of the cylinder produced, it also poses a huge security risk.

X-ray non-destructive testing equipment can be very convenient for cylinder testing and real-time imaging, detecting many defects at a glance. The online x-ray testing equipment for steel cylinders can be connected with the production line of the manufacturer. The fully automatic loading and unloading manipulator is adapted to reduce the labor cost and realize the integrated operation of production, testing, and judging, thus greatly improving the production efficiency. 

With high resolution, high definition image quality, automatic defect identification, automatic judgment function, the whole system can realize unmanned operation and 100% on-line detection of the cylinder.

All welds are for specific purposes. They need to meet the required standards and specifications. That’s why they are assessed to confirm their quality. This process is known as x ray weld inspection. There are several methods to inspect welds, but digital x-ray systems give the best and most reliable results.

Every welding job needs to be inspected for its quality and strength. Stress, fatigue, and pressure can weaken welds over time. So, it is important to check if a welding project can withstand the pressure of usage for several years without giving in. Also, welds need to be smooth and tidy for aesthetics and visual appeal. During x-ray inspection, many features of a weld will be evaluated. Some aspects of inspection focus on weld sizes, while others are for weld discontinuities/imperfections. In other words, welds are assessed against the stipulated codes and standards required by the intended application of the welds. Methods used for welding inspection are:

X-ray welding inspection
  • Destructive welding test
  • Radiographic inspection of welds
  • Ultrasonic inspection
  • Surface crack detection
  • Visual inspection


Flaws and defects of a weld are the discontinuities that do not meet the requirements of the intended application of the weld. These flaws fall into the following three categories:

·       General welding discontinuities
·       Discontinuities in TIG welds
·       Discontinuities in gas metal arc welds

the main purpose of an X-ray inspection is to detect flaws or discontinuities in welds and correct them.  Weld inspection is the quality assurance aspect of welding. Without a proper inspection, there could be welding failure and other problems in the future. The size of the weld will also be inspected.  To summarize it all, we need x-ray inspection for welds to check whether the welds meet all the required specifications, codes, and standards.

The Advantage of Digital X-ray Systems for Weld Inspection are:

  1. Using digital x-ray systems gives faster results.
  2. It exposes internal flaws that visual inspection would never detect.
  3. X ray welding tests give accurate results through their images.
  4. Digital X-ray systems are compliant to international standards.


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A Complete Guide On X-ray Welding Inspection

Are you looking out for effective equipment to inspect your welds? Why don’t you think about buying an industrial X-ray? Are you wondering why X-ray instruments?

If these are the questions that pop up in your mind, go through this article then. We’ve compiled 13 frequently asked questions and answered them to the point so that you can make the right choice.

Why do we need an X-ray welding inspection?

Due to overutilization and varying environmental conditions, welds are prone to damage over time. Hence, they should be inspected regularly to ensure their quality, tolerance, strength, safety, and reliability.

Manufacturers prefer non-destructive testing (NDT), compared to destructive testing since it saves money and time. NDT does not modify the properties of the test sample. However, among all the NDT tests, the X-ray test is more effective. Do you know why?

X-ray inspection is easy to use. It can identify the shape, location, position, as well as defect type even if it is smaller and located internally.

We require an X-ray test to inspect any object with varied volumes, thicknesses, and densities. This inspection method is used on both sides of the welded joint to detect compositional variations, surface and subsurface flaws, and internal flaws. X-ray tests can quickly examine the assembled parts as well.

What is the difference between X-ray welding and X-ray welding inspection?

X-ray welding is the latest advance in welding technology. Similar to electron beam welding and laser beam welding, a high-powered focused X-ray beam is used to produce thermal heat. It will initiate the melting of the metal to form the weld once it gets cooled. Hence, it is very fast and stable. It is also possible to increase the accuracy of the weld due to this high-powered focused X-ray beam.

Still, there is a limitation. In case the X-ray beam is not adequate to penetrate the metal, it will then form a molten metal pool on the surface.

To overcome this limitation, a keyhole is created in the metal joint for heat penetration.

This is where X-ray welding inspection is done to assess the quality of welds whether they are strong or not. It can also detect flaws during weld manufacture as well.

What is an X-ray welding inspection? How does it work?

As mentioned already, an X-ray instrument can be used to inspect the quality of welds quickly and effectively.

X-ray equipment uses highly penetrating X-rays produced from an X-ray tube to pass through the test object. Depending on the sample object’s density and thickness, you will find differences in its absorption levels.

In case of any defect, there will be a change in thickness. While developing the film, the flaw area will appear as dark outlines.

For example, low density inclusions like slap will appear darker, while high density inclusions will look lighter. Looking at this difference in density, the defects can be determined easily.

In a digital X-ray system, a flat panel detector is used in the place of film. Hence, the final image will be displayed on the computer in real time. 

Check out the resource below if you want to learn more:



What is the application of X-ray welding inspection?

X-ray welding inspection is employed in the following sectors listed below:

  • Manufacturing
  • Automotive
  •  Packaging
  • Transportation
  • Military
  • Waste management
  • Marine
  •  Offshore
  •  Petrochemicals
  • Power generation
  • Aerospace
  • Medical devices


What are the various types of weld defects determined by X-ray instruments?

X-ray equipment determines the size and of the presence of flaws in the given sample weld during its manufacture. The more the weld size, the more it can tolerate stress. 

Here is the list of varied weld defects:


General flaws:

  1. Cold lap/ cold shuts/ lack of fusion – Here, the weld filler metal inappropriately merges with the base metal (Figure 1).


  • Poor welding technique
  • Presence of a very wide weld joint
  • Too low welding voltage
  • Very low travel speed
  • Attempt to make a large weld in a single pass



Figure 1: Cold lap


    1. Porosity – Occurrence of dark round or irregular spots singularly, in rows, or in groups on a radiograph (Figure 2).



    • Gas entrapment in the solidifying metal
    • Failure to clean the base metal
    • Failure to shield the weld from atmospheric contamination
    • Striking with a long arc



Figure 2: Porosity


  1. Cluster porosity – It is similar to the porosity issue. But the spots will group together very closely (Figure 3).

Cause: Vaporized constituents are entrapped in the molten weld during solidification

Figure 3: Cluster porosity


  1. Slag inclusions – Occurrence of dark, jagged asymmetrical shapes on a radiograph (Figure 4).


  • Entrapment of non-metallic solid material in weld metal or between base metal and weld
  • Use of an improper welding angle with low current
  • Letting the quick cooling of the weld pool
  • Use of an extreme high weld speed
  • Improper base metal cleaning before welding begins


Figure 4: Slag inclusions

  1. Incomplete penetration/lack of penetration – It is one of the most offensive flaws where the weld does not penetrate the joint and leads to the appearance of cracks (Figure 5).


    • Use of improper welding techniques like arc misdirect
    • Failure of thick metal preheating
    • Insufficient current for weld penetration
    • Poorly designed joint



Figure 5: Incomplete penetration

  1. Incomplete fusion – Here, the weld filler inappropriately fuses with the base metal (Figure 6).


    • Use of a wrong electrode angle
    • Following wrong welding process
    • Failure of slag removal on joint surfaces
    • Failure of oxide layer break up on base metals



Figure 6: Incomplete fusion

    1. Internal concavity or suck back – Here, the weld metal contracts as it cools and draws up into the weld’s root of the weld (Figure 7).



Figure 7: Internal concavity

    1. Internal or root undercut – Here, the base metal damage occurs next to the weld’s root (Figure 8).



Figure 8: Internal undercut


    1. External or crown undercut – Here, the base metal damage occurs next to the weld’s crown (Figure 9).



Figure 9: External undercut

Causes of undercut

    • Failure to clean rust from the metal
    • Use of a damp electrode in small angle
    • Excess current use
    • Following poor welding techniques
    • Use of an incorrect filler


  1. Offset or mismatch – It occurs on the surface due to the improper alignment of two pieces while welding together (Figure 10).

Figure 10: Offset

  1. Inadequate weld reinforcement – Here, the weld metal’s thickness is less than base material’s thickness (Figure 11).

Figure 11: Inadequate weld reinforcement

  1. Excess weld reinforcement – Here, weld metal is added more in the weld area (Figure 12).

Figure 12: Excess weld reinforcement

  1. Cracks – It looks as jagged with very faint irregular lines (Figure 13).


    • Base metal contamination
    • Poor joint design
    • Use of hydrogen during ferrous metal welding
    • High welding speed and low current
    • Failure of metal preheating before welding begins
    • Shrinkage in solidification leading to a residual stress formation


Figure 13: Cracks

Flaws in TIG welds

  1. Tungsten inclusion – Here, tungsten traps in the weld if welding is done improperly. It looks lighter with a distinct outline radiographically (Figure 14).

Cause: Molten weld or filler in contact with tungsten electrode’s tip

Figure 14: Tungsten inclusion


  1. Oxide inclusion – Oxides are seen on the surface of the material being welded. It appears dark and irregular radiographically (Figure 15).

Figure 15: Oxide inclusion

Flaws in GMA (Gas Metal Arc) welds

    1. Burn-Through – It occurs when surplus heat causes weld metal to enter the weld zone. These lumps of metal sag create a thick glob (icicles) on the backside of the weld (Figure 16). 



Figure 16: Burn-Through

  1. Whiskers – These are short weld electrode wires found within the weld or on its top or bottom surface (Figure 17).

Figure 17: Whiskers


What is the difference between X-ray welding inspection and Ultrasonic testing?

Although both ultrasonic testing (UT) and X-ray welding inspection highlight the weld’s defects without destroying its internal integrity, there are several variations between them. Let us go through in detail:


Characteristics X-ray welding inspection Ultrasonic testing
Speed and cost Comparatively slower and expensive Comparatively faster and cheaper
Source X-rays emitted by an X-ray tube Sound waves emitted by laser at high frequency
Sample assessment All material types Only metals, plastics, ferrous as well as nonferrous substances
Principle When X-rays are penetrated through the test weld sample, its internal structure is displayed in the film. There will be differences in energy absorption depending on both thickness and density. Hence, the region of the sample where the energy is not absorbed due to defects will be found darker in the film (Figure 18). When ultrasonic energy is passed on the test sample, it diffuses with insignificant loss of energy. If there is any defect, these waves may reflect back to the point of origin that gets displayed on the monitor. By measuring the amplitude of the reflected pulse, UT can locate and examine the defects (Figure 19).
Geometry Suitable to assess complex welds Require special probes in varied geometries for weld assessment
Types of flaws detected Surface and subsurface flaws, but not fine defects Surface, subsurface, thicker section, deep finer planer or linear defects, lamination-like flaws, submerged-arc weld, control spot welding, and friction stir weld
Assessment Can automatically assess the position and type of flaws from both sides Can assess the accurate position, location, length, and type of the flaw as well as the thickness of the test sample from one side only
Result storage Permanent Temporary

Poor resolution and wrong flaw size

Easier to interpret a 2-D image of the discontinuity compared to a 3-D image.

The film is so delicate to tolerate temperature, humidity, and pressure.

Need access to both sections of the test sample.


The surface must be available for the transmission of ultrasound waves.

You need a coupling medium to boost the diffusion of sound energy into the sample.

You need reference standards for equipment calibration and flaw characterization.

Tougher to evaluate cast iron and other coarse-grained metals because of an increase in noise signals with less sound transmission.

It is also difficult to assess thin, rough, non-homogenous, and irregularly designed tiny samples.

Need access to both ends or sections of the test sample.



Figure 18: X-ray Inspection – Principle



Figure 19: Ultrasonic Inspection – Principle

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What are the skills and responsibilities of an X-ray technician?

A skilled X-ray technician should have professional certification, like an AWS welding certificate, proper expertise, and sufficient expertise regarding the system operation. This person should be an expert to use the system and interpret final X-ray images.


The X-ray technician should know to install the system and make sure that the right radiation at the right intensity is used to get the final image. He should be able to perform regular quality checks and annual maintenance services.


The technician should stay tuned with the technological and developmental updates. He should prove his skill by capturing the X-ray image of an unusual part that was ignored by others. He should also be involved in the quality control and research department.


The technician should perform preventative maintenance of welding tools. Furthermore, he should have great attention to detail. The technicians should follow safety standards and remember to use protective clothing like face shields and gloves while working on the X-ray system. Furthermore, he should have experience in using various welding equipment and procedures.


The X-ray technician should know to operate angle grinders to prepare sample welds and align components using rulers, clamps, and calipers (Figure 20). 


Figure 20: An X-ray Technician


What is the salary of an X-ray technician?

Usually, the pay scale for a full-time X-ray technician will be between $15.00 – $20.00 per hour. However, this pay scale can be changed as per the professional certification and experience.

For more details about salary of x-ray technican, kindly go through as below



How does an X-ray technician stay protected from radiation?

The more the dose, the more the risk of getting acute health hazards like skin burns, radiation sickness, as well as cancer. Hence, the Environmental Protection Agency has set the safety limit as below 100 millisieverts (10 rem).


There are three major factors to protect from excess radiation exposure (Figure 21):


Figure 21: Factors to protection from radiation

  • Limit the exposure time
  • Increase the distance from the source to reduce radiation dose
  • Shield the X-ray devices in lead or concrete lined rooms to limit the radiation dose.

During emergencies, stay safe till the arrival of the emergency officials to manage the disaster.


Radiation Signals (Figure 22)

  • A trefoil sign on a yellow background shows high level radiation.
  • The red ionizing radiation warning symbol denotes the IAEA Category 1, 2, and 3 depending on the danger level.


Figure 22: Radiation Signals


Here is the list of few more safety instructions to be followed by an X-ray technician while using the X-ray systems:

  • Wear the proper personal protective equipment (PPE) kits including lead aprons, lead glasses, lead gloves, lead shields, and lead masks before starting the X-ray inspection work.
  • Never dispose of the radioactive wastes in general garbage.
  • Only one person should stay in the X-ray room during the X-ray inspection.
  • Maintain a written record of the radiation dose rates emitted in the X-ray room.
  • Pay attention to the position and direction of the X-ray system during installation.

Check out the resource below if you want to learn more:



How much does it cost to buy an X-ray machine for welding inspection?

You get the customized cost according to your requirements. You get what you pay for.

Factors such as power, voltage, spot size, degree of automation, generator specifications, choice of a flat panel detector or an image intensifier, detector resolution, and the vicinity of the X-ray source to the sample object can have an impact on the price. 


Open or closed tube?


Figure 23: Open and closed tube

Looking for a minimum resolution of 1μm with high magnification and quick replacement time? You can get the open tube which is expensive and can be broken easily. The initial capital cost is high. You will have to replace every 200-300 hours or so of use.

However, closed tube types can last for years. Its lifespan is about 10000 hours. It is comparatively less expensive and more stable. But it has high replacement cost, low magnification, and low resolution for low density components (Figure 23).


Online or offline inspection?

Online or offline? It depends on the quantity and level of inspection.

If the level of inspection is simple with more quantity of samples to be evaluated, opt for offline type. It is quick to run and cost-effective.

If the level of inspection is complex with lesser samples, opt for an online type. It is comparatively expensive. However, if you have more sample quantities, opt for an online type.


2D or 3D?

Figure 24: 2D and 3D


Selecting 2D or 3D with online or offline options can determine the time taken for inspection, quality of inspection, and quantity of test objects.


Do you just want to rotate and tilt the sample mechanically? Would you like just one side? 2-D is enough then. It is quick and takes less time for inspection.


What if you need to inspect dual sides of the given sample? Not only from top-down angles but you can also rotate and tilt the sample at oblique angles to check parts from multiple orientations. In that case, you require a 3-D type. Due to the extensive and high throughput inspection, it can take more time. And of course, 3D will be pretty expensive.

For more info about x-ray machine price, please refer as following



How to buy a suitable X-ray welding machine?

Usually, Germans are considered as the best in offering high quality X-ray equipment across the world. But nowadays, the Chinese have started developing quality products at an affordable budget. So, it would be great to consider X-ray welding machines from other credible suppliers as well instead of just going by the brand name alone.


Note down your requirements and set your priorities. After shortlisting the manufacturers, go through their products list and try to finalize the product you want. Or else, convey your requirements to the shortlisted manufacturers and try to find out whether they can offer the customized product.


Furthermore, consider safety, application support, service maintenance, automation facility and certification for import or installation before making the final choice. 


How to source a good supplier of X-ray welding machines?

Choose the renowned X-ray manufacturer in the market based on the online and offline reviews.


Check the value of their products, customization offers, online/offline customer service, maintenance services, quality check, training, R&D, and experience.


The power supplies, connectors, and cables should be replaced in time to prevent any radiation leakage or failure modes.


Make sure you consider all the above points before rounding off the appropriate supplier.


Useful resources for X-ray welding inspections

ASNT (The American Society for Nondestructive Testing) aims to create a safer world by developing scientific, engineering, and technical knowledge in the field of nondestructive testing. It offers three sections:

  • ASNT Learn – ASNT offers online courses, webinars, glossaries, and more to accelerate your career and education.
  • ASNT Pulse – ASNT offers a blog section and a go-to resource section for the latest industry updates, career tips, and more.
  • ASNT Store – ASNT offers educational resources and NDT publications in their official store. You can join ASNT and become its member to get exclusive discounts during the purchase.


The Upshot

As described already, X-ray weld inspection is recommended for weld manufacturers as it is the best-quality guarantor.


Have you decided to buy the X-ray system? Are you looking out for a customized system with high-resolution image quality at an affordable cost? Don’t forget to contact UNI X-ray company who is renowned for manufacturing hi-tech X-ray equipment to assess the welds accurately!


Established in the year 2002, Uni X-ray Technology Ltd. is headquartered in Shenzhen, China. This company is renowned for not only supplying hi-tech industrial X-ray machines as per their customer’s requirements. But they are also involved in its design, research, and development. Uni X-ray Technology innovates the integration of the internet of things and cloud computing technology in operations so that they can successfully meet the production beat of most enterprises. Furthermore, they are renowned for quality, services, and affordability when compared to other manufacturers. 

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