2. Objectives
• Discuss three general categories of pipe welds, including
how they are used and what type of weld root
penetration and strength they require
• Compare pipe to tubing
• Discuss the advantages of welded pipe
• Discuss the preparation needed before welding pipe
• Explain the importance of not having arc strikes outside
of the weld groove on pipe welds
3. Objectives
• Describe the purpose of the root, filler, and cover passes
for a pipe weld
• Name advantages of the horizontal rolled pipe position
• Describe the vertical fixed position and give advantages
and disadvantages
• Discuss how to make a weld in the horizontal fixed
position
• Describe the 45º fixed inclined position
4. Pipe and Tubing Different specifications and
uses
• Pipe sizes given by inside diameter
• Tubing sizes given by outside diameter
• Wall thickness of tubing measured in inches
• Wall thickness of pipe determined by its pressure
range
5. • Both available as welded or extruded
• Most pipe that will be welded into a system carries liquids or
gases
• Small diameter flexible tubing
• Carries pressurized liquids or gases
• Rigid tubing
• Used for structural appliances
• This chapter
• Term pipe will refer to pipe only
6. Advantages of Welded Pipe
• Thickness and strength of the pipe and fitting is the same
when welded
• Resistant to leaks
• Resist corrosion caused by electrochemical reactions
• Less turbulence as material flows through the pipe
• Threaded fittings are larger and weigh more than welded
fittings
7. Other Advantages
• Ability to make specially angled fittings
• Odd-shaped parts can be fabricated
• Highly specialized equipment is not required
• Easier alignment of parts
• Removing, replacing, or changing parts is easy
8. Preparation and Fitup Important considerations
• Ends of the pipe must be beveled
• Bevel must be at the correct angle
• Sharp inner edge should be ground flat
• Forms a chafer
• Final shaping done with a grinder
• Root gap will be uniform
• Root face
• Controls penetration and root suck back
9. Preparation and Fitup (cont'd.)
• Root suck back
• Caused by surface tension of molten metal
• Molten metal tries to pull itself into a ball
• Forms a concave root surface
• Fitting pipe and holding it in place
• More difficult with larger diameter
• Hold pipes in place with a vice for tack welding
10. Practice Welds Major challenge Electrodes
• Learning how to transition from one position to
another
• Start with a large diameter pipe
• Skills develop: use a smaller diameter pipe
• ElectrodesE6010 or 6011 electrodes: complete the
weld
• E7018 electrodes: complete the joint or entire weld
11. Practice Welds (cont'd.)
• Practice pipes used in a school shop
• Shorter than those used in the industry
• Avoid positioning yourself where longer pipe would
eventually be located
• Do not stand at the end of a short practice pipe
12. Weld Standards Weld quality is very important
to the industry
• Major parts of the weld come under a higher level of
inspection
• No arc strikes should be made on the surface of both
sides of a weld
• Arc strikes outside the weld area are defects
• Try to avoid from the beginning
13. Root Weld First weld in a joint
• Part of a series of welds that make up a multiple pass
weld
• Internal root face is the most important part
• Inside of each welded joint must be smooth
• Excessive penetration is known as icicles
14. Hot Pass Burns out slag trapped on edge of the
root pass
• Can also reshape the root pass
• Slag is mostly composed of silicon dioxide
• Floated to surface by melting surrounding metal
• Fast travel speed
• Prevents burn-through
• Forms a concave weld bead
15. • It is ready to be filled
• Filler pass
• May be a series of stringer beads or a weave bead
• Stringer beads require less skill
• Done correctly, stringer beads are as strong as weave
beads
16. Filler Pass (cont'd.) Weld bead
• Must be cleaned before next electrode is started
• Failure to clean the crater will result in slag inclusions
• High-strength pipe: crater should be slightly ground
• Bead goes around the pipe
• Should continue past the starting point
• Stagger starting and stopping spots for each pipe
17. Cover Pass Final covering on a weld
• It may be a weave or a stringer bead
• Should not be too wide
• Should not have too much reinforcement
• Excessively large cover passes reduces strength
• Should be as uniform as possible
18. 1G Horizontal Rolled Position
• Characteristics
• Penetration and buildup are more easily controlled
• Weld visibility and welder comfort are improved
• Welder fatigue is less of a problem
• Pipe can be rolled continuously
• Weld can be made in one continuous bead
19. 2G Vertical Fixed Position
• Characteristics
• Pipe is vertical and weld is horizontal
• Welder does not need to change welding positions
constantly
• Area to be welded is often located in corners
• Reaching back side of weld can be difficult
• Welds must be done in the correct sequence
20. 5G Horizontal Fixed Position
• Characteristics
• Root pass can be performed by welding uphill or downhill
• Close parallel root opening can be welded uphill or
downhill
• Root opening that is wide or uneven must be welded
uphill
• Electrode angle should always be upward
• Arc must always be struck inside the joint preparation
groove
21. 6G 45 Degree Inclined Position
• Characteristics
• Most difficult pipe position
• Qualifying in this position will certify welder in other
positions using same-size electrodes and pipe sizes
• Must continuously change weld pattern, electrode angle,
and weld speed
• Small multipass stringer beads work best
• Weave beads are possible
22. Summary Pipe welding Experienced welders
Good pipe welded joint
• Looked upon by many as the pinnacle of the welding trade
• Presents its own challenges because of the constantly
changing weld position
• Experienced welders
• Spend a significant amount of time in preparation
• Control weld size
• Good pipe welded joint
• May have many small weld passes
