Piping Systems & Facility Welding
Piping systems are used to transport petroleum products, chemicals, utilities, process gases, fuel gases, food, and dairy products in facilities all over the globe. The integration of the following components forms a piping system:
- Pipes (Short and Long)
Importance of Welding in Piping Systems
Pipe systems welding is a tricky technique as compared to traditional welding of flat surfaces. The temperature of fluids flowing through the pipe systems can be very hot as in the case of flue gases, and it can be extremely cold in case of liquid ammonia or nitrogen. The pressure in the piping systems is also high. Suppose welding of piping system components is not properly done. In that case, there can be potential health and safety hazards of leaking fluids that can cause suffocations, fires, poisoning, and explosion hazards.
Techniques of welding of Piping Systems
Piping system welding quality requirements are more stringent than other welding techniques. Welds must reach high porosity, and arcs of the weld should not leak into the pipe. To make sure that a high-quality weld in piping systems, the following are the most applied techniques in the piping systems welding:
Root pass is the first welding pass that fills the gap between the two pipe sections. After root pass, a cap pass fills the top of the welded joint with the least amount of excessive build-up above the pipe’s surface. You may need to grind that layer to improve the weld bead and remove contamination.
Cleaning of Pipe End
There will always be a layer of oil, rust, or a coating to prevent corrosion on the pipe surface. The coating may be paint, epoxy, or varnish. Pipe cleaning is a critical step to prevent welding defects that lead to a costly repair.
Tacking of Weld
Tacking is the most critical step in piping systems welding. The standard practice is that the tack should be feathering out to ensure consistency of the final weld. If tacks are left behind, they are consumed by the weld. If there is a defect in tack, there is a risk of welding defects. In this way, cutting out of a tack can eliminate this potential risk.
Piping Systems Welding Positions
The position of the pipe determines the welding position. The pipe can be horizontal, vertical, or aligned. Based upon this, there are the following welding positions for pipes:
In 1G welding position, the pipe lays horizontally and can be rotated. The position of the welder is stationary. To weld in 1G position, the arc is started in the center of the track. The welding torch is perpendicular to the pipe with a 5 to 10-degree drag angle. The welding stick does not exceed 5/8 inch.
In this welding position, the pipe is horizontal and in a fixed position. The welder moves around the pipe in the vertical direction to perform the welding. Welder moves the electrode back and forth in a half-moon position.
Common Welding Types in Piping Systems
For piping systems welding, the following welding types are applied typically:
In shielded metal arc welding (SMAW), a stick welding electrode is used which is consumed during welding. The welding stick has a flux core that prevents the weld pool from forming the oxides.
In gas tungsten arc welding (GTAW), the tungsten electrode is used, which is non-consumable. An external filler metal wire is used for creating the weld pool. Instead of using a flux core, an inert gas usually argon is used to prevent oxidation. The welds made from GTAW are very clean and have high strength.
Preparing the material properly and choosing the correct welding process and technique is essential in achieving the best results in pipe welding. Whether the welding of the piping systems requires SMAW or GTAW, the company should be equipped with the latest technology of piping systems welding to improve the piping systems’ quality and safety.