Pipeline welding is similar to traditional welding in a lot of ways, but it can get tricky. There are some different techniques that are necessary when you’re welding pipes instead of flat surfaces, and it can require much more finagling. When it comes to pipeline welding, TIG welding is usually the preferred method.
This guide will let you in on some tips and tricks for pipe welding and let you know what you need to do to adjust your welding technique. BY the end, you should be well prepared to start preparing as a pipe welder and having joints that pass stress tests!
Techniques, Positions, and Procedures
There are several passes to know about when it comes to welding. Root passes are your first weld passes. This fills gaps between two sections of piping. Manual passes are continuous all the way around and through the tack welds. GMAW passes usually use an open root weld with no backing ring.
Hot passes are next. This is a single weld that joins the root weld with both groove faces. Splitting your hot pass is acceptable for 2G welding or when you have an abnormally large root opening.
Fill passes should do exactly what they’re named for… that is, they should fill every grove almost completely.
It may be necessary to do a beading sequence, and if so then use an alternating pattern from face to face on your joint.
Each bead’s location should have a uniform lap that is adequate for each subsequent weld bead.
If your weld develops a narrow cavity between beads or between the face of the joint and the bead, you may end p with slag contamination or an unfused joint. If this happens, grind the area to eliminate the cavity and improve the lap weld before you continue.
The cap pass should completely fill the top of your joint with the least amount of excessive build up as possible past the surface of your pipe. You may need to grind this layer to improve your weld beading and remove contamination before making your final cap pass.
Pipe Welding Basics
One of the important things to do is to establish good techniques early. Learn all the safety techniques. Make sure you’re wearing proper equipment – auto-dark helmet, apron, flame resistant clothing, safety goggles, work boots, ad possibly earmuffs.
Prepare your materials ahead of the weld. Make sure they’re sanitized. Grind anything that needs grinding. Bevel thicker edges.
Pipe Welding Positions
Your welding position can be determined by the position of your pipe. There are fixed and rotating pipes that are fixed or inclined, horizontal or vertical.
To weld in the 1G rolled position, start your arc in the center of your tack. Your gun should be perpendicular to your pipe with a 5 to 10 degree drag angle. Your stick out should not exceed 5/8 inch.
Your weld position should be in the center of the puddle as your pipe rolls away from you. Drag your welder. You don’t want to weave for this position unless your gap is larger than 3/16 inch and requires a sidewall bridge.
For this position, you’re going to start welding the arc in he center of a tack weld with a 5 to 10 degree drag angle and the same stick out length. This time, you want to move your electrode back and forth across the gap with a half moon position, where the moon faces down.
Gravity will begin pushing the puddle down the joint. Once this happens, stop weaving and direct the electrode back to the center of your weld puddle. Use a slight side-to-side position at the bottom. End your bead on the feathered tack weld. Otherwise, you will end up with a pinhole at the end of your weld.
Make sure that you grind out the end of your weld before you resume. Once you complete the root pass, you will also need to grind out your starts and stops before making fill passes.
Testing Your Pipe Welding
There are several ways to test your pipe welds. Some of them can be pretty destructive, so if your weld passes muster you’re doing great!
Macro etch exams involve coating some etching specimens in acid. This will allow you to examine your macro structural integrity. They will take pictures of cracks, center voices, unsoundness, pinholes, inclusions, porosity, grain size, hydrogen flakes, mold slag, and other defects.
A fillet break test will examine root penetration instead of penetration depth. This test includes all of the possible points of failure in a weld at the stop and restart.
Passing the test means the weld will bend flat on itself without splitting, fracturing, or breaking. If a fracture occurs, the break shouldn’t show any cracks or incomplete fusions and the cracks can’t be more than 10 mm.
A bend test will bend the weld to a defined shape with a jig. This determines whether the face and root of a joint are sound. It gets bent roughly 180 degrees, with either the face or root in tension depending on what is being tested.
If you’re newer to welding and don’t want to destroy the joint, try an electromagnetic test. This induces electric and magnetic currents. The test will show any defects in the weld because it will create a measurable response to the electromagnetic resonance.
Common Issues in Pipe Welding and How to Resolve Them
Spatter is the most common issue with welding, especially for new welders. This happens when molten material scatters droplets near your welding arc. If this happens, try reducing your currents and making sure you’re using the right polarity. Reducing your arc length and increasing the work angle can also reduce it. Dragging and pushing also have a huge effect on splatter so make sure you’re moving the right direction for your welding job.
Porosity happens when nitrogen, oxygen, and hydrogen get absorbed into your weld pool. Most often, this happens because a welder fails to properly grind and clean a piece of material before beginning to weld with it.
If you’ve cleaned properly and still get porosity, try rebaking, using fresh welding consumables, and checking your torch for leaks.
Undercutting happens when your arc voltage is too high and when your arc is too long. It also happens when your angle is wrong or your electrode is not the right type for the plate thickness. If these don’t fix the issue, then make sure that you weld at a steady pace, not moving too quickly.
Cracks are much harder to fix. You can’t jut fill it again with new material. To fix a crack, you need to grind the joint out and start a new weld. Prevent cracks by grinding properly before welding and cleaning your plate edges to make an easy fit. You also want the right heat level.
Preparing a Joint for MIG Processes is Different than with Stick Welding
MIG welding is usually reserved for smaller weld joints and finer welding processes. Stick welding is more for structural welding, pipelines, and reactors that have to withstand the test of time.
MIG welding requires a lot of preparation. Your MIG welders have a harder time cutting through the scaling on the surface of your piece. It becomes more difficult to get good penetration and fusion. Here’s how to fix that.
Grind and brush your weld surface area. Cleaning your metal can make it a much smoother process. This will let you achieve a dependable weld. Clean surfaces are critical in MIG welding. Grind some bevels as well. This will provide proper penetration so you achieve a structurally sound weld that will withstand the stress tests.
Your wire must match your weld size. The fusion at the joint’s root is entirely dependent upon the size of your wire. Find a wire size that lets you see your fusion and penetration degree as it happens. Smaller wires will give you m ore time to weld deeply.
Make sure your gas flow and wire feed rates are properly adjusted. Use your manufacturer recommendations for settings and fine tune from there. Grind your piece properly so your wire will strike the right arc. Keep your wire at the leading edge of your puddle.
For stick welding, you still need to clean the surface, but not as rigorously. Just make sure all rust and possible corrosions are gone. Beveling is required if your plate thickness is 1/8 inch or more. Stick welding usually takes smaller beads to complete joints, too, so you won’t need to bevel every edge if your metal isn’t that thick. Learn more about stick welding in this article.
Buy a Machine that Can Handle the Work… And Then Some
Different machines are able to do different jobs because there are several different ways to weld. Whether you’re looking for MIG, TIG, or stick welding equipment, the important thing to know is what you’re working with regularly.
Knowing what material you will use and how thick it will be can quickly determine the right style of welding is right for you and the equipment you will need to get the job done. Once you’ve narrowed that done, you can find the best MIG welders here and the best TIG welders in this review.
Pipe Welding Certifications
You have gotten pretty good at welding pipe and really enjoy it. Is it possible to become a professional pipeline welder? Absolutely! Can you live off a typical pipeline welder salary? Definitely! So what are the best pipe welding schools? The good news is that professional welding doesn’t require a degree. They offer certifications instead!
All you need to do is pass a hands on welder qualification test to see if you and your machine can produce a quality weld that meets standards. These certifications are issued based on whether you’re trying to work with plates, for structural welding, or with pipes, as a pipe welder.
The positions you will need to master for pipe welding certification are I, 2, 5, 6, and R positions. I is for a rolled pipe in a horizontal position. 2 is for pipes that are in the fixed vertical positions. 5 handles horizontally fixed pipe positions.
A 6 certification is when your pipes are in 45-degree angles for their fixed position. R is restricted positions. Each certification position comes in F or G types. F is for fillet joint welds. G is for groove welds.
What Else Do You Need to Know?
By now, you should know pretty much everything you will need to know about pipe welding. You’ve learned about the different passes, some basic safety tips, how to correct and avoid imperfections, and even how to become a professional!
As a last word, I will remind you to know your material and your project. Pipes come in all different shapes, sizes, and materials and knowing what you’re working with will make the difference between a great job and a lack of proper fusion.
The rest of the information will come with time. Remember that welding is a skill that a lot of people do professionally. You can’t expect to be perfect if you’re just starting out so give it time. Practice your technique on simple joints so you’ll be ready and prepared to work on the actually joint that needs to be adequately reinforced.