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Oil and gas industries are exceedingly demanding in terms of workplace safety. These industries possess high risks because of the materials involved in processes. The best way to minimize risks is to keep the work areas free of combustibles therefore, the correct installment of gas pipes is crucial.
Due to strict safety standards, gas pipes go under harsh inspections. The materials and the installment methods need to be on par with safety regulations before usage.
Welding of Gas Pipes
Welding is the process of connecting two metal objects through heat, pressure, or both. High-pressure gas distribution networks usually use steel pipes. Licensed professionals, weld purpose-built steel pipes to build large distribution networks that power our industries and cities.
The quality of the welding is critical for the safety of the gas line since the welding joints are the weakest point of the gas line. Because of that, gas pipe welders take intensive training to obtain certificates that give them the license to perform welding on pipelines. Not every type of welding can be used on gas lines, just as not every welder is suitable for working on gas lines.
Types of Welding
Shield metal arc welding (SMAW) is a welding technique that doesn’t require flux or shielding gasses. That’s why SMAW welding machines are portable, allowing technicians to perform quick fixes in tight areas. 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.
Gas Metal Inert Gas (MIG) Welding and Metal Active Gas (MAG) Welding are two types of metal arc welding (GMAW). While these procedures are more productive than SMAW, they do necessitate superior welding variable control to produce high-quality, effective work. GMAW enables high deposition rates with minimal fume emission and is often carried out using semi- or completely automatic equipment.
Flux-Cored Arc Welding (FCAW) consists of both self-shielded and gas-shielded FCAW. Although windy conditions can disrupt the shielding gas and cause porosity defects, gas-shielded FCAW uses semi-automatic machines to provide a high-productivity welding solution for pipes. Self-shielded FCAW avoids this by not requiring a shielding gas, but deposition rates are lower.
Submerged arc welding is a semi-automatic process in which the arc is invisible, making tracing difficult. However, it has the highest deposition rates of any pipeline welding method and delivers defect-free surfaces.
Welding with Tungsten Inert Gas (TIG), also known as Gas Tungsten Arc Welding (GTAW). TIG welding has lower deposition rates and higher equipment costs than the other pipe welding methods. However, it produces extremely high-quality welds (depending on the welder’s skill), making it ideal for critical and precise welding jobs.
Joint Preparation
After the process and the equipment choice is complete, the preparation phase starts. This step is extremely important to ensure long-lasting, high-quality weldings. The joint surface needs to get cleaned off of moisture, contaminant, and coatings. Then the welding grooves get sanded down to provide the welding with a suitable surface to attach on. Some materials may require pre-treatment such as heating of the electrodes and the material to be welded.
Welding Phases
Pipe welds are performed in multiple phases. The first phase is the root. The root is the phase that fills the gap between the two sections of piping. After the root, a few hot passes connect the weld to both groove faces. After the groove, there is still a gap that needs to be filled in between the grooves, so the fill phase fully connects the grooves. The passes should complete the weld with as little build-up beyond the surface of the pipe as possible. This layer can be ground back if required to improve the weld beading and remove contamination before a final, finishing cap pass.
Inspection Of Welds
As mentioned previously, the quality of the welds needs to be checked and inspected for leaks. Even the smallest cracks can cause massive leaks. The pressure in steel gas transfer lines can be up to 19 bars. The high pressure causes cracks to get larger by ripping the surface of the steel pipe therefore, even the microscopic cracks need to get detected. Since it’s impossible to detect those cracks with the naked eye, a special set of inspection methods called non-destructive testing (NDT) is used.
The most common NDT method to inspect gas pipe welds is x-rayed inspection. A certified specialist gets x-ray photographs from the joints. Later on, these photographs are inspected for microscopic cracks. If any cracks are detected, the cracked joint can be re-welded however, the same joint can’t be repaired twice. Therefore if a crack is detected on a repaired joint, this section is discarded and new welding is required.
Summary
The oil and gas industry applies extremely tight safety procedures. A leakage of flammables can be exceedingly dangerous. Joining points of the gas lines are one of the biggest threats to leaks therefore, they need to be carefully inspected. Correct installment of pipes is crucial to ensure a safe work environment.
