{"id":232,"date":"2022-05-28T05:53:00","date_gmt":"2022-05-28T05:53:00","guid":{"rendered":"https:\/\/mewelding.com\/?p=232"},"modified":"2024-03-18T10:52:56","modified_gmt":"2024-03-18T10:52:56","slug":"pipe-welding","status":"publish","type":"post","link":"https:\/\/mewelding.com\/pipe-welding\/","title":{"rendered":"Pipe Welding"},"content":{"rendered":"\n
Welding of pipes is commonplace. Pipes are used for transporting oil, water, gas, etc. The pressure inside the pipe may range from a vacuum pressure to gage pressure running into several hundreds of pounds per square inch. For such joints, mechanical joints such as rivets, threaded joints, etc. are not adequate for the purpose, hence welding becomes necessary. In this article, we shall touch upon a few aspects of pipe welding such as steps involved in making a pipe weld, welding positions in pipes, multi-pass welding in pipes, and various processes used for pipe welding.<\/p>\n\n\n\n
Welding allows us to achieve a joint of leak proof and high strength. Also, a welded joint has lesser weight, and lowers the cost of installations. The welding of pipes is commonly done by various electric arc welding processes such as SMAW, FCAW, GTAW, GMAW, SMAW, etc. depending upon the pipe diameter and thickness.<\/p>\n\n\n\n
When a pipe needs to be welded, it first needs to be beveled to obtain the right edge preparation. Before that, we may also need to do cutting of the pipe depending upon the situation. After that, the pipe must be cleaned, a correct fit-up with backing rings and tack welds. Before all these, the welding position and welding process should be established for making the joint.<\/p>\n\n\n\n
We shall discuss below a few of the steps involved in making welds in pipes:<\/p>\n\n\n\n
The right edge preparation between the two parts is important to obtain the necessary strength in the joint.<\/p>\n\n\n\n
Usually, in base metal thicknesses up to \u00be inch (19 mm), a 32.5\u00b0 angle on both sides with a root face of 1\/16 inch (1.6 mm), such that a V-groove is formed, is sufficient. For heavier pipes, a U groove is preferable.<\/p>\n\n\n\n
Before welding, cutting of the pipe is sometimes necessary to meet a specific length requirement. If cutting is done in a work shop, saw cutting is possible. However, if cutting is done in a field setting, oxy-acetylene is one of the few feasible options.<\/p>\n\n\n\n
The cutting should be done in a true circle, perpendicular to the centerline of the pipe. This can be done by marking on the surface of the pipe using a soapstone pencil. For this purpose, a heavy paper, or leather belting, or sheet gasket material with edge longer than the circumference of the pipe can be used.<\/p>\n\n\n\n
The material is wrapped around the pipe, and overlapped. And marking is done along the edge of the material. After cutting the beveling of the pipes can be done using a oxy-acetylene cutting torch, or any other suitable means. The angle of cutting may be 30\u00b0-35\u00b0, with a small amount of root face.<\/p>\n\n\n\n
For obtaining good quality weld, proper cleaning of the surfaces to be welded is very important. Before welding, the beveled surfaces must be made free from all rust, oxides, dirt, scale, and any other foreign matter. If beveling has been done using oxy-acetylene cutting, the residual oxides on the cut surface must be compulsorily removed before welding can be commenced.<\/p>\n\n\n\n
Cleaning can be done using any suitable means such as a file, wire brush, grinding, buffing wheel, etc. Cleaning on the inner diameter side is equally important as the outer side and the beveled surfaces. Care should be taken to clean the beveled surface, as well as some length on both the inner surface as well as outer surface.<\/p>\n\n\n\n
A proper fit-up of the joint contributes substantially to the final acceptability of the joint for the application. A correct alignment, and tack welding such that the alignment does not get disturbed due to tack welding is therefore important.<\/p>\n\n\n\n
For alignment, one of the ways is to use a line-up clamp. The ends of the two pipes can be securely held in this clamp. After insertion in the clamp, a root spacing should be ensured. For oxyacetylene welding, a root spacing should be approximately 1\/8 inch (3.2 mm). For arc welding, the root spacing depends on the diameter of the filler rod to be used.<\/p>\n\n\n\n
The root spacing should be at least equal to the diameter of the filler rod.<\/p>\n\n\n\n
In order to align the pipes straight, if a pipe line-up clamp is not available, a jig may be developed. The function of the jig is to ensure that the centerlines of the two pipes coincide, and the root spacing in the joint is uniform throughout the circumference of the joint. For small pipe diameters, an iron angle as shown in the figure below can serve as a simple jig. For higher diameters, one may need to use section of channel or I-beams to obtain a satisfactory fit-up.<\/p>\n\n\n\n