Pipe Welding: First Steps From Plate to Pipe

Pipe welders join the lines that carry water, steam, oil, gas and chemicals. Their welds often hold pressure and get checked by X-ray, so the work demands more precision and control than most plate jobs. Most people come to pipe after learning to weld on plate. If that is you, expect to feel like a beginner again for a while, and expect a job site that has its own set of dangers.

What You Will Be Able to Do

• Describe what pipe welders do and where they work.
• Explain why pipe is harder than plate.
• Name the hazards that can hurt you on day one.
• Read the common position names.
• Start your first practice on pipe.

What the Work Looks Like

Pipe welders work with fitters, who cut and line up the pipe, and with inspectors and X-ray crews, who check the welds. A helper may grind, carry leads and set up your work area. Many people start as helpers and learn on the job, or come through a union or trade school program.

Most code work requires you to pass a test for each process and position you weld.

Why Pipe Is Harder Than Plate

On plate, you can hold one position along a straight joint. Pipe curves away from you, and if the pipe cannot turn, you have to move around it. On a fixed horizontal pipe, a single joint takes you from flat at the top, through vertical at the sides, to overhead at the bottom.

The root, or first pass, also has to go all the way through the wall and look clean on the inside, where you cannot see it. A joint can look perfect from the outside and still fail an X-ray.

Position Names

Most welders start on 1G, and a 6G test is the common goal.

What Will Hurt You on Day One

Argon and Other Gases

Stainless and alloy pipe is filled with argon while it is welded. Argon pushes out oxygen and has no smell. Putting your head into a purged pipe or vessel, or working in a low spot where gas has collected, can make you pass out with no warning.

Confined Spaces and Tight Spots

Pipe often runs through tanks, vaults, trenches and pipe racks. Never enter a permit space without the permit, air testing and an attendant. In a trench, make sure it has the protection the site requires.

What Was in the Pipe

Before you cut or weld an existing line, make sure it has been isolated, drained and cleared. Pipe that has carried fuel, chemicals or steam can hold pressure or vapors. Do not assume. Ask to see the permit and the lockout.

Heat and Fire

Hot work on a refinery or plant site needs a permit, and sparks can find their way a long way from you. Stay hydrated. Plant areas and preheated pipe can be very hot, so learn the signs of heat illness.

Fume

Welding inside a pipe rack or a tight area keeps fume close to you. Stainless and alloy pipe give off fume containing hexavalent chromium and nickel. Use the extraction and respirator the job requires.

Falls and Pinch Points

Pipe is heavy, it rolls, and it can pinch you when it shifts in a clamp. Chock it, and keep your hands out from between pipe and stands. Pipe racks and scaffolds need fall protection.

Grinders

You will use a grinder more than you may expect. Use the guard, the right disc and a face shield over safety glasses. Keep the sparks away from coworkers and from gas hoses.

X-Ray Crews

Radiographers use real radiation sources. When they rope off an area, stay out until they clear it.

Tools You Will Use

• Stick and TIG equipment
• Angle grinder, with flap discs and cutoff wheels
• Bevel gauge and hi-lo gauge
• Filler rod or wire for setting the gap
• Mirror and flashlight
• Soapstone and a wrap-around for marking pipe
• Chipping hammer and wire brushes

Your First Week

Expect to spend time grinding, fitting and watching. Pay attention to how experienced welders plan their body position before they strike an arc. Ask to see a bad X-ray, and ask what caused the flaw.

Your First Exercise

Set a short section of 6 inch pipe on a stand, in a flat position. Roll it by hand, or on a rotator, and run a bead across the top using the process you know best. Stop, roll the pipe, and tie in your next bead. Your goal is clean starts and stops, and an even bead width. Then fix the pipe so that it cannot roll, and run a bead from the side to the bottom. Notice what changes as you go. That change is what pipe welders spend their careers mastering.

Common Mistakes

• Skipping fit-up checks. A bad gap makes a bad root.
• Rushing the first pass. The root decides whether the weld passes.
• Putting your head in a purged pipe. It can kill you.
• Trusting that a line is empty. Check the permit and the lockout.

Check Your Understanding

You need to check the inside of a stainless pipe that has been purged. A coworker tells you to stick your head in. What do you do?

Do not do it. Argon can knock you out without warning. Use a mirror or a borescope, and ask how the purge is being vented.

You are told to cut a section out of an existing line. What do you want to see first?

The permit and proof that the line is isolated, drained and locked out. Old lines can hold pressure and vapors.

A joint looks great from the outside but fails an X-ray. How is that possible?

X-rays show the inside. The root may have a flaw, such as poor penetration, that cannot be seen from outside.

A pipe on a stand starts to roll while you are welding. What should have been done?

It should have been chocked or clamped. Pipe is heavy and can pinch or crush you.

Key Takeaways

• Pipe welders work in shops, plants, pipelines and buildings, often on code work.
• A single fixed joint takes you through flat, vertical and overhead.
• The root has to be sound on the inside, where you cannot see it.
• Argon, confined spaces and unknown line contents can kill you.
• Most welders move up from 1G to a 6G test.