low carbon steel

Understanding pipe welding

Welding joint

Pipe welding is the best technique for joining pipes used in the field. Another way of connection is to use a flange and treaded. The pipe material itself already contains welded joints. There is a longitudinal weld and spiral weld. Only a few pipes are seamless, for example ASTM A106 grade B or ASME SA106 grade B pipes which are often used in the field.

Because pipe materials consist of various types, pipe welding also consists of various types. In general, the pipe material is Carbon steel, Carbon Moly,  Ferro Nickel, Stainless Steel, PVC and Chrom-Moly. There are some pipes that use HDPE material. Setting pipe welding refers to the Welding procedure Specification ( WPS ).

Pipe material

In addition to considering the type of material, pipe welding pays attention to the diameter of a pipe and the thickness of the pipe. thick pipes usually use the SMAW method, while thin pipes use the GTAW method. But sometimes, we use a mixed method, namely GTAW in the root section, then proceed with the SMAW method. The joint welding is usually used on pipes with a diameter of at least 10 mm, for example in welding oil refinery pipes, top and bottom boiler drums and others. In the welding process must pay attention to the process of heat treatment (preheat) and post-weld heat treatment (PWHT). Specific heat treatment process to reduce the residual stress that occurs due to the welding process.

incomplete penetration welding defect
incomplete penetration

Each welding process on pipes has advantages and disadvantages. a welding engineer will make a WPS according to the needs of the project, then a welding inspector will supervise the welding process so that there is no deviation and the welding quality is good. After welding, we do a visual check or NDT. Welding supervisor is responsible for productivity and rejection rate.

related articles:
1. advantages of SMAW
2. Advantages of GTAW

Here are the steps you need to do before starting welding.

1. CLEANLINESS
Clean the surface of the pipe to be welded first. because a dirty surface will affect the adhesion between the weld crust and the iron. In addition, a dirty surface will create a lot of spatter that comes out of the welding results.

Spatter that is too much and large will harm your weld results and can also damage the surface of the weld object. For that, it’s a good idea to clean the surface of the object you are going to weld and in this case the pipe.

2. PREPARATION

The second point that you need to do before starting welding is to prepare your welding needs according to WPS. For example, if you use MIG welding, you have to set the gas pressure that comes out. Then also set the wire speed that you will apply.

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