Pipeline Welding & Methodes of Piplines Welding.ppt

Pipelines are used to transport gas, water, oils, and other liquids from one point to the other. And as all pipes are produced at a fixed length, there is a requirement of welding to join pipes and make kilometers of pipelines. So, pipeline welding is a very important activity in pipeline construction and is always a demanding profession. Pipe and Pipeline welders are required in construction industries, oil and gas fields, water industries, fabrication shops, nuclear energy industries, etc to lay new pipelines or repair an old pipe.

1. What is Pipeline Welding?
Methods of Pipeline Welding

2. INTRODUCTION
•Pipelines are used to transport gas, water, oils, and other liquids from one point to the other. And
as all pipes are produced at a fixed length, there is a requirement of welding to join pipes and
make kilometers of pipelines. So, pipeline welding is a very important activity inpipeline
constructionand is always a demanding profession.Pipe and Pipelinewelders are required in
construction industries, oil and gas fields, water industries, fabrication shops, nuclear energy
industries, etc to lay new pipelines or repair an old pipe.
•Pipeline welding is popular asgirth weldingwhich is performed along the circumference of the
pipes to be connected. As compared to pipe welding in usual plants, pipeline welding poses
various additional challenges. Pipeline welding should conform to the relevant ASME codes
likeB31.4, B31.8, ASME BPVC, etc.
•Note that there is a specific difference between pipe welding and pipeline welding. Pipe welding
normally refers to the welding of pipes inside chemical plants and oil refineries. Inside the plant a
varying range of pipe sizes and materials require welding. On the contrary, pipeline welding
concentrates on welding pipes of uniform size and material spread over hundreds of kilometers.

3. Widely used Pipeline Welding Processes
•Shielded Metal Arc Welding
•Gas Metal Arc Welding
•Flux-Cored Arc Welding
•Submerged Arc Welding
•Gas Tungsten Arc welding

4. Pipeline Welding by Shielded Metal Arc Welding
(SMAW)
•Shielded Metal Arc Welding of pipelines is also known as Stovepipe welding.
In SMAW the pipelines are welded by melting the electrodes with the heat
generated by an electric arc. The number of passes required usually varies
with the pipe thickness, electrode size, welding position, and the current used
for pipeline welding. The usual thumb rule for pipeline welding by SMAW is to
consider one pass for each 1/8 inch(3.2 mm) of pipe thickness. Electrode
diameters for SMAW pipeline welding normally vary from 1/8 inch to 3.16
inches (3.2 mm to 4.8 mm).
•The main advantage of pipeline welding by SMAW is that the welding
equipment is simple and portable. Also, no flux or shielding gases are required
during welding. However, the productivity of this method is less due to lower
travel speed.

5. Pipeline Welding by Gas Metal Arc welding
(GMAW)
•Pipeline welding by gas metal arc welding provides high productivity
as compared to the SMAW method But this method required better
control of welding variables for efficient quality work. High deposition
efficiency (90 to 97%) with low fume generation are advantages of
GMAW. This is generally performed using semi-automatic/ automatic
equipment and the welding cost is increased

6. Pipeline Welding by Flux-cored Arc Welding
•Gas Shielded Flux-cored arc welding is performed using semi-
automatic machines. Along with high productivity and excellent
welding capabilities, pipeline welding by this method provides a
broader operating range compared to GMAW. However, the wind
usually causes disturbance for the shielding gas which in turn may
cause porosity defects.
•In the case of self-shielded flux-cored arc welding, external shielding
gas is not required. However, this has lower deposition rates as
compared to the gas-shielded arc welding process.

7. Welding of Pipelines by Submerged Arc Welding
•In the semi-automatic Submerged arc welding process, the arc is not
visible and it provides the highest deposition efficiencies as compared
to all other pipeline welding methods. Such welding provides sound,
defect-free welding surfaces but tracing is very difficult due to the
invisible arc.

8. Pipeline Welding by Gas Tungsten Arc welding of
Tungsten Inert Gas welding
•TIG welding is used for welding critical joints requiring precision welds
as this method produces high-quality pipeline welding utilizing
tungsten electrodes. But, welding of pipelines by gas tungsten arc
welding has lower deposition rates and higher equipment costs.