Welding Technology Essay Example

Welding Technology

A. Non-destructive testing can be described as a process, in which materials, assemblies, or components are inspected for differences in their characteristics or discontinuities without the serviceability of the system or part of the system being destroyed. This implies that after the NDT have been completed the system still operates as before. In the present world, NDT are used in fabrication, in service inspection and also in manufacturing. The use of this technology ensures that the products and services delivered to consumers are reliable and of integrity, it also aids in the controlling the process of manufacturing, thus lowering production cost and maintaining uniformity level of the products (Blitz, 2012).

In welding one of the serious defects are cracks. They commonly originate from the surface, grow under stress and finally lead to failure of the entire or part of the system. In ensuring that the welds are of high quality, it is crucial to detect such cracks as early as possible. However, since the cracks are minute it becomes challenging to identify them. Applying non-destructive methods by engineers, however, has made it easier to identify such cracks and mend them.

The common NDT methods used today include:

  1. Magnetic particle testing (MT),

  2. Welding Technology

  3. Acoustic emission testing (AE)

  4. Visual testing (VT),

  5. Ground penetrating radar (GPR),

  6. Liquid penetrant testing (PT),

Welding Technology 1

  1. Guided wave testing (GW) and Ultrasonic testing (UT)

Welding Technology 2

  1. Microwave testing,

  2. Magnetic flux leakage (MFL),

Welding Technology 3

  1. Infrared testing (IR),

  2. Radiographic testing (RT),

Welding Technology 4

  1. Electromagnetic testing (ET)

Welding Technology 5

  1. Vibration analysis (VA),

  2. Leak testing (LT),

Welding Technology 6

  1. And laser testing method (LM).

Defects in welding can be majorly classified as either surface or subsurface defects. It is very important therefore to understand the defect an individual wish to identify. This will make it easier in the identification of the technique to apply in the detection of the defect. In order to test for surface cracks, the following methods are applied, eddy current, visual inspection, ultrasonic, magnetic particle testing and liquid penetrant methods. On another hand, in detecting subsurface defects, one may consider using x-ray, ultrasonic or eddy current.

B. In testing the cracks the following methods were selected;

a) Liquid penetrant testing (PT) — this method is also known as dye penetrant inspection. The method was considered since it is less expensive in relation to other methods. It is useful I the detection of breakages on the surfaces of non-porous material such as metal, ceramics, and plastics. The method was also selected since it is very useful in welding since it helps identify defects such as; surface porosity, hairline cracks, and fatigue cracks. This method operates by applying the capillary action. The test material is coated with a dyed fluid solution. The fluid is allowed to infiltrate into the material for a given time. The dye is then removed and the material subjected to the developer. The developer draws the fluid out making it easy to identify the defects (Zinck et al. 2007)

b) Visual testing- this method was applied since it is cheap. This is because the only little equipment is required. This method was preferred since it would save on extra expenditures that would be incurred by applying a sophisticated method. It is therefore recommended as a standard method to start with before applying other methods.

c) Magnetic particle testing (MT) and magnetic flux leakage (MFL)

This is a non-destructive technique helpful in the identification of cracks. This method is applied to identify cracks on the surfaces or near the surfaces of the metals. A combination of magnetic field and magnetic particles are used in order to reveal the defects. In the case of discontinuity, the magnetic flux will leak. The leakage will result since a number of magnetic fields per unit volume support by the air is far much less than one supported by the metals. In the case of leakages, an attraction of ferrous particles occurs and they will build up around the area of defects. This method was chosen since it is not very complicated. The method also indicates the defects immediately saving on time. It is also cost-friendly. The method is also applicable to a number of objects both large and small.

d) Ultrasonic inspection – it is a method in which a high-frequency sound beam is directed via the weld. Some sound will be reflected behind in case the sound beam is struck on the material under test. The sound is collected and amplified by the instruments and finally displayed on a screen. This method was applied since it is helpful in detecting both the surface and subsurface cracks on the weld. The method has an added advantage over other methods since it is too sensitive to even very small cracks that cannot be detected by other methods. The equipment is also portable and well-designed such that they can analyze the results and give the correct feedback. However, the method is relatively costly. It may also be less effective since it has been found that round gas pores have the ability to respond to the ultrasonic test.

e) Eddy current testing; this method was used since it can test both the surface and subsurface defects. The method applies electromagnetic induction. A copper wire is coiled. It is then excited with electrical current and magnetic fields are produced around the wire. Taking the coil next to a conductive material, an opposite current to one in the coil will be induced. In case the material has some defects, the eddy current has to be disturbed. Due to this disturbance, a local magnetic field is created which destabilizes the system.

C. Conclusion

a) It is economical to apply the NDTs. This is because maintenance cost of the welded products is reduced. This ensures that system failures in which the welded components are used in assembling are reduced b) Reliability; the NDT techniques is reliable in testing the defects of the system. Welded materials can be tested for any form of the defect without interfering with the entire system. The welded component can, therefore, contribute to effective products since these techniques complement each other.

c) Accuracy- in welding, accuracy is highly demanded. NDT can be used to ensure that any breakage or cracks either on the surface or the subsurface. Detecting the defects in the welded components using NDT is accurate.

d) Safety; it is safe to detect cracks and other forms of the defect by using NDT techniques. In testing the defects, skilled personnel is employed and this reduces the risk that may occur as a result of exposure to the harmful rays. It is, therefore, safe to detect the defects using these techniques.

e) Quality assurance; appropriate use of NDT ensures that the results are impressive. This ensures that in welding, the number of replacement and repairs are reduced. High-quality deliverables are assured in case the techniques are well applied.

f) The durability of the material; detecting minute cracks either on the surface or subsurface ensures that the life span of a material or that of a machine is increased. It will be cheaper and efficient to repair minor cracks than replacing parts or the entire system. NDT will ensure that there is the efficient maintenance of the welded material. Any leakage will be detected early and repaired. This will increase the operating time of the companies.

g) The other advantage of using the NDT in welding is that the test object is not altered in any way. The method of testing defects would be more expensive in case the test object is destroyed. During welding, it is very difficult to come up with objects that are free from defects. It is therefore important to keep testing the objects at each stage of construction.

h) Saving of cost; initially, the NDT were majorly applied to ensure the safety of the individuals. However, its use has greatly increased as a result of saving on cost during the process of quality assurance.

On the other hand, the method is also associated with a number of limitations such as;

In order to have the right results, it is important to apply a number of methods. This is because a particular method would not be in a position to detect certain defects while other would detect them. For this reason, therefore, it becomes expensive to use many techniques.

The tests are rarely quantitative but qualitative. The results, therefore, do not indicate the intensity of the defect.

Countries should, therefore, endorse non-destructive tests since they are cost friendly and reduced replacement of the defective products. This will ensure that there is less dumping of scraps on the surrounding. It will also ensure that the citizens are safe. The firms will also be motivated to produce more products with the risks minimized. This will have a positive impact on the country’s economy (Martin et al. 2007)

Since NDT acts as a tool of quality management, in the production sector, it will ensure that the products and services offered are of high quality. This will ensure competitive advantage of the products in the product market.

Finally, modern NDT are increasingly becoming non-intrusive and quantitative. In construction, welding is a crucial process. It is therefore important that individuals have full information on the properties of the materials and the conditions of operation. It is also important to consider the criteria of accepting the defects of the welds basing on the integrity required.

References

Blitz, J., 2012. Electrical and magnetic methods of non-destructive testing (Vol. 3). Springer Science & Business Media.

Martin, N.D., Smith, W.R., Cole, T.J. and Preece, M.A., 2007. New height, weight and head circumference charts for British children with Williams syndrome. Archives of Disease in Childhood92(7), pp.598-601.

Zinck, N.D.T., Rafuse, V.F. and Downie, J.W., 2007. Sprouting of CGRP primary afferents in lumbosacral spinal cord precedes emergence of bladder activity after spinal injury. Experimental neurology204(2), pp.777-790.