Pipe Welding Procedures
Pipe welding is often more challenging than other types of welding and requires a higher level of welder skill. This can be due to the working conditions as well as factors such as the travel angle of the weld, the pipe position and the diameter of the pipe. The difficulty increases as the position changes from 1G to 6G.
Pipe Welding Procedures
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Pipe welding can be dangerous if the correct precautions are not taken. Welding can expose welders to fumes, dust and other airborne particles, as well as heat and dangerous levels of light that can be harmful without the correct safety equipment. The hazards are increased due to the conditions that pipe welders may be required to operate in, making pipe welding potentially dangerous.
5G pipe welding relates to the position in which the pipe is welded. In 5G welding, the pipes are placed horizontally in a fixed position and the welder moves around the pipes, welding in a vertical direction.
6G pipe welding relates to the position in which the pipe is welded. In this position, the pipe is placed at an angle so that it slopes at around 45 from the horizontal (X) axis or vertical (Y) axis. The pipe is fixed and the welder moves around the pipe to perform the weld. This is the most advanced pipe welding position.
Pipe and pipeline welders undertake welding jobs in the construction industry, at oil and gas fields, in the water industries, fabrication shops and nuclear power stations, among others. Working to connect new pipes or repair old ones, pipe welding is generally performed to conform with relevant codes and standards.
Also known as stovepipe welding, using SMAW for pipe welding means that no flux or shielding gas are needed during welding, making the welding equipment simple and portable. The metal is welded by melting the electrodes through the heat generated by an electric arc. Although SMAW has some advantages, the slow travel speed means that it is not as productive as other techniques.
Offering greater productivity than with SMAW, these techniques do require better control of the welding variables to deliver high quality, efficient work. Usually performed with semi or fully automatic equipment, GMAW offers high deposition rates with low fume generation.
Gas-shielded FCAW uses semi-automatic machines to provide a high productivity welding solution for pipes, although windy conditions can disturb the shielding gas and lead to porosity defects. Self-shielded FCAW avoids this by not requiring a shielding gas, but has lower deposition rates.
Submerged arc welding is a semi-automatic process where the arc is not visible, which can make tracing difficult. However, it offers the highest deposition rates of all the different pipeline welding methods as well as delivering defect-free surfaces.
TIG welding has low deposition rates and higher equipment costs than the other methods for pipe welding. However, it produces very high quality welds (according to welder skill), making it perfect for critical and high-precision welding jobs.
There are four types of pipe welding position; 1G, 2G, 5G and 6G. Each position details whether the pipe is stationary or rotating and whether the pipe is placed horizontally, vertically, or inclined at an angle.
Welders will learn each type of position in turn, with 1G being the easiest to master and 6G the most difficult. A welder will need to gain certification in each position in turn, so someone qualified in 1G positions cannot weld 2G, 5G or 6G, but if you are qualified in 6G you can weld in any of the other positions. These standardspreserve the safety of the work environment when performing pipe welds.
Welding eliminates the need for fittings to join straight sections of pipe. A screwed pipe requires a fitting between every joint while welding can quickly join pipes following end preparation of the parts to be joined.
Welded pipe can use thinner wall pipe than with screwed connections, leading to significant cost savings for long runs and larger jobs. Screwing pipes together can also require higher labour costs along with the higher costs of the threaded fittings themselves.
Welded systems are generally easier to repair than screwed systems. Where a welded pipe can often be repaired in place, a screwed system requires disassembly and reassembly for repair. This obviously increases labour costs and downtimes for the pipe system.
While the labour required to weld or screw smaller pipes is about the same, as the pipe size is increased, so the labour costs and time required to install the welded pipe decreases as the screwed pipe increases. A screwed pipe also requires different tooling for different pipe sizes, while a skilled welder can use the same welding machine for a range of pipe sizes.
Firstly, the pipes to be joined need to be prepared correctly, making sure the edges to be joined a clean and straight. If this is not done correctly there can be problems including a lack of fusion in the weld, slag trapments and hydrogen inclusion.
Aside from the preparation, there are a number of challenges associated with welder working conditions. The process itself can produce a risk of injury unless the correct precautions are taken. The risks include the heat created by the welding tools, the bright light created by the arc, and the release of particles or gases.
Pipe welding can add additional hazards due to the working conditions associated with pipes. This includes having to work in uncomfortable or even dangerous positions and locations, including underground or underwater. Other factors may include working in very hot or cold conditions, depending on the location of the pipe as well as hazards associated with the contents of the pipe, whether sewage or oil.
Since pipe welding refers to the connecting of metal pipes, there are a wide range of applications for this skill. The number of applications is increased further as welding is one of the most cost-effective methods for connecting several sections of pipe.
Consequently, pipe welding is used across a range of industries including transporting natural resources to oil refineries, through cross-country or international pipelines, and to mineral processing plants.
Pipe welding can be a difficult skill and can also involve working in uncomfortable or potentially hazardous places, however with the correct expertise, safety measures and standards, welding is often preferable to other pipe joining methods.
When welding two pipes, pipe welding is the most appropriate technique. In this case, welders can use several processes such as TIG, arc welding, and MIG welding to get the desired weld. While all these methods are applicable in pipe welding, TIG welding is the most common process. When undertaking projects such as fusing cylindrical metal tubes and curved metals, pipe welding is a great option.
These are the first passes and are often used when welders fill gaps between piping sections. Manual passes are also a perfect alternative to root passes as they have continuity throughout the tack welds. Gas metallic arc welding is another alternative to root passes. The only difference is that it is an open root weld without any backing rings.
Hot passes are single welds used to join the root weld through groove faces. When using the 2G welding position, welders can split the hot passes to achieve the desired weld. In the event of an abnormally large root opening, welders may break the hot passes.
Fill passes are a great way to fill up grooves during welding. In some instances, welds develop cavities that alter the overall quality of the welds. To mitigate these cavities, welders are frequently required to perform a beading sequence to achieve a strong joint. A fill pass is the portion of the weld bead needed to fill the specific welding joint. Usually, the fill pass is produced after the root passes.
Of all the welding positions, the 6G welding position is the most tasking since it requires you to fix the workpieces at a 45-degree angle. The method requires a high level of accuracy and swiftness as welding is performed from a fixed position.
The fillet break test is most effective for testing root penetration and examining possible defective sections on the assembly. Most welders perform the test at the beginning and the end of a welding process. If a weld bends without breaking into pieces, it means that the welds are strong and pass the test. The only exemptions to this test are fractures and cracks not exceeding 10 mm.
The macro etch testing method involves cutting out a sample of a welding joint and testing it. The test is performed by applying an acidic solution onto the sample and observing the reaction. The reaction will cause clear visibility of the macro-structural defects. Some of the common defects tested with this method are mold slag, grain size hydrogen flakes, porosity, and mold slag.
Regardless of how experienced and careful a welder may be, mistakes are inevitable in pipe welding. Both beginners and experienced welding professionals are susceptible to making welding errors. Here are common mistakes and suitable ways to minimize them. 041b061a72