Orbital Welding Troubleshooting Informtion

SECTION I - AUTOMATIC ORBITAL TUBE WELDING

PROBLEM 1: “BURN-THROUGH” OR “BLOWING HOLES” - After welding, there are visible holes in the weld. Holes range from pinholes in the weld up to the ends of the tubes melted away from each other.

CAUSE: The most probable cause is the tubing is inserted incorrectly into the weld head in a manner in which the tube ends are not square to each other. There must be no “end gap” greater than .002" to .003" in the fit-up of the tube ends in the weld head.
SOLUTION: To properly install tube in weld head, clamp the first side taking care to align the end of the tube with the centerline of the tungsten (and rotor gear). Then clamp the second side ensuring there is absolutely no gap in the fit-up with the opposing tube end.

CAUSE: Ends of tube are jagged causing them not to mate up. This can happen frequently when using rotary saws, portable band saws, hacksaws, and portable band saw “clamp-on” style guides.
SOLUTION: It is highly recommended that you use an end squaring machine to make sure the ends are flat and square to the run of the tube. Filing is not recommended as it could round off the edges of the tube end, effectively changing the wall thickness.

Note: There must be no ID burr on tubing because lack of fusion on protruding burr cold allow the particle to break free at a later date causing contamination.

CAUSE: Tubing with ends cut out of square.
SOLUTION: Same as for jagged tubing above. Squaring tools are the only way to ensure a true flat and square end.

CAUSE: The clamping collets in the weld head are worn to the point where fit-ups are producing gaps and inaccurate alignments.
SOLUTION: Collets should be replaced to eliminate this problem.

CAUSE: Installing weld heads on long runs of tube where lack of support is causing gaps from tube entering head at oblique angles.
SOLUTION: Use sufficient support which can hold the weight of the tubing as well as the weight of the orbital weld head and keep the tube ends aligned.

PROBLEM 2. LACK OF PENETRATION OR FUSION - Weld not penetrating to the ID surface at one or more points along the weld.

CAUSE: Travel Speed could be too fast for amperage.
SOLUTION: Mark the tube at the starting point in your weld head and mark each quadrant or level to see where lack of penetration is, then raise primary amps one or two amps to correspond with orbital weld failure. Fusion root should be uniform all the way around inside of tube. Make one or more welds and check for full fusion.

To calculate Quadrant or Level Times, use the following standard formula for time based orbital tube welding machines:

Circumference = 3.14 X Diameter
RPM = Travel speed desired ÷ Circumference
Total Weld Time = 60 ÷ RPM

Formula: Quadrant (Level Times) = Total Weld Time ÷ No. of Quadrants (Levels)

Example: Circumference = 3.14 X 1.50 = 4.71 [or 4.7]
RPM = 6 IPM ÷ 4.7 = 1.276 [or 1.3]
Total Weld Time = 60 ÷ 1.3 = 46.15 [or 47 sec.]
Level Times = 47 ÷ 4 = 11.75 [or 12 sec.]

To calculate Amperage for Tubing (using Argon gas):

Formula: 1 Amp per .001" of Wall Thickness

Example: .065" Wall Thickness = 65 Amps

Note: This will be your starting amps for level 1 (or the first quadrant on systems which use quadrants). You should always subtract 1 Amp for each of the levels or 1 amp per quarter. In this example, level 2 (or quadrant two) would be 64 amps, level 3 would be 63, and level 4 would be 62 amps. Also, final amps should always be the same as the level 4 amp setting.

Note: When developing weld parameters, you may want to lower your amperage by two amps and then by one amp per level or quarter.

To Calculate Low Pulse or Background Amps:

Formula: Always use setting 1/3 the primary amperage

Example: 65 Amps ÷ 3 = 21.66 [or 21.7] Amps

Note: When Developing your weld parameters, you may want to lower your low pulse or background amps by 2 or 3 amps.

Recommended travel speeds for tubing (IPM = In. per min.):

PROBLEM 3. BAD “TIE-IN” WELDS - Weld fades away (gets narrower) before reaching point of start of full penetration weld or there is a lack of fusion spot at the tie-in.

CAUSE: Not enough rotation time of the weld head.
SOLUTION: Run the weld head with only one side of the tubing in the weld head. Mark where tungsten starts and watch the tungsten to make sure the tungsten is rotating 360º before the downslope cycle starts. If downslope cycle starts before the tungsten has rotated a full circle, add one second to one of the quadrants (or levels) and then repeat your observations. This time can be added to any of the quadrants and is done to increase the total rotational time of the weld head.

CAUSE: Problems with the motor start delay (or travel start delay).
SOLUTION: Sometimes the motor start delay may be too short and may not penetrate the weld at the beginning of the rotation. The following formula is a recommended starting point.

To calculate motor start delay:

Formula: Motor Start (Travel) Delay = Wall Thickness X 20

Example: .065 X 20 = 1.3 Seconds

Note: The motor start delay time must be added into the first level (or quadrant) to ensure a good tie-in at the end of the weld, before starting your final slope or down slope.

PROBLEM 4. WELD DISCOLORING OF ID BORE AND/OR
SUGARING (OXIDATION) OF THE ROOT PASS

CAUSE: Generally, ID purging problems cause discoloring/sugaring.
SOLUTION: You must always remember that Argon is heavier than air. With this in mind, you must always purge in the bottom of the piece on one end and vent out the gas at the top of the tube at the other end (Fig. #1). The hole size of the Argon purge inlet hose will have an ID dimension which is equal or slightly larger than the discharge hole (vent). If you have 10 CFH of incoming Argon into the ID bore of the tubing, you will be venting 10 CFH on the vent side. It ‘s important to ensure that there is no pressure build-up on the tube ID. Pressure on the inside of the weld could cause the root pass to become concave on the tubing ID, thereby reducing wall thickness at the weld line.

CAUSE: Problems with air getting into tube ID from bad end seals.
SOLUTION: Always be sure that the inlet and outlet ends of the piece being welded are sealed with dams and tape to prevent air from being sucked into the chamber (Fig. #1). This will ensure that the only gas in the tube ID is Argon.

CAUSE: Improper pressure of atmospheres on tubing ID.
SOLUTION: Before any welding is done, always make sure that the atmospheres in the ID bore of the tubing being welded is at 2% atmospheres or below (to zero). This should always be done when hand tacking any tack welds on tubing prior to automatic welding procedures. If this is not done, you will end up with oxidations between the ends of the tubes that are to be welded and this could cause oxidation at each of the tack weld points which would be a source of contamination. It is highly recommended that you always use an O2 analyzer (Fig. #1) prior to performing any tack welds by hand or doing any automatic orbital tube welds.

Note: When welding electropolished tubing, it is further recommended that you use a Differential Pressure Gauge (such as the one manufactured by MAGNAHELIC®) which checks the proper flow rate of the argon coming through the ID bore of the tube.

CAUSE: Gas leakage from jagged or unsquare ends.
SOLUTION: The only way to guarantee that the ends form a uniform gas tight fit-up is through the use of a squaring machine which will reliably prevent oxidation from gas contamination and leakage.

PROBLEM 5. SULFUR CONTENT PRODUCING LACK OF OR EXCESSIVE PENETRATION

When welding, the sulfur content of the metal can be a major factor in the proper penetration of the weld fusion (or lack thereof). Manufacturers of tubing have a sulfur content range from .001 to .030. The ideal sulfur content range for automatic orbital tube welding systems is from .005 to .017.

CAUSE: Too high or too low sulfur content. If the sulfur is from .001 to .004, the weld puddle will become much wider and the possibility of a lack of penetration exists. This is caused by the sulfur content being too low which increases the surface tension of the weld puddle. In other words, the puddle goes wide resulting in no or partial penetration. Conversely, if the sulfur content is between .017 to .030, the surface tension of the weld puddle is very weak which can cause excessive penetration on the top of the orbital weld joint and concavity on the bottom root pass of the weld.
SOLUTION: For situations where you have lack of penetration (fusion) being caused by low sulfur content, change the welding parameters to increase the weld penetration. Raise the background current amperage up by small amounts, increase the pulse rate (and/or width) of background current, raise the primary current amperage up by small amounts, or increase the pulse rate (and/or width) of the primary current.

Note: If you have been welding without any problems with your established orbital weld parameters and you start to experience lack of penetration or other problems with your welds, check your material test reports (MTR’s) which will tell you the sulfur content of the tubing being welded and check the content amount against the content of the tubing you used while developing the weld parameters. If material test reports are not readily available for the tubing you are welding, a good rule of thumb is to look at the weld joint. If it is wide and very shiny, it would indicate a low sulfur content tube. The opposite would also be true, a narrow dull weld joint indicates a high sulfur content.

PROBLEM 6. TUNGSTEN GEOMETRY AFFECTING WELD

CAUSE: The tungsten in use may be improperly ground, causing inconsistencies in welding results and deviance from test results.
SOLUTION: It is highly recommended that you observe any specifications stated by the orbital equipment manufacturer’s operator’s manual for tungsten grinding geometry. When developing orbital welding programs, you should always document the geometry of the tungsten being used so that when production welds are performed, they will match the results of your test welds.

CAUSE: When tubing is X-Rayed, white specks are seen as a result of Tungsten inclusion. (This is not permissible by codes.)
SOLUTION: For automatic orbital tube welding, the tungsten should always be ground from 22º to 30º angle with a .015" to .020" blunt point on the end. Never have the tip of the tungsten come to a needle point which, when the arc starts, can be burnt off and go into the weld puddle (tungsten inclusion). The blunt point will prevent this from happening while still producing a good arc.

SUMMARY: As you can see, achieving a perfect weld is really creating a consistent set of parameters from a chaos of variables. Many of the problems, besides sulfur content, are ones which result from how you set-up and prepare for welding. Most problems can be dealt with by observing a few simple rules and formulas. Probably the most significant thing to producing high quality welds is to generate perfectly flat, square, and burr free ends which will eliminate the majority (up to 90%) of the problems which arise from improper fit-up and lack of proper weld end preparation. Tube squaring equipment will provide the consistent ends for repeatable results and all orbital welding equipment manufacturers endorse the use of tube squaring machines prior to tube welding.

SECTION II - AUTOMATIC ORBITAL PIPE WELDING

PROBLEM 1. WELDING PROBLEMS AS A RESULT OF POOR WELD PREPARATION

CAUSE: Inconsistent pipe welds due to improper weld preparation.
SOLUTION: Many of the problems associated with automatic orbital tube welding apply to pipe as well. With pipe, differences in wall thickness can indicate that a special prep be applied which is uniquely applicable to orbital welding. This prep is the J Prep which derives it’s name from the fact that the weld profile includes a straight upper angle and then a radiused bottom, forming an extension and land. The Prep may include specifications for a counterbore which would be generated on the ID surface of the pipe.

For automatic orbital pipe welding, it is very critical that the land thickness, the extension of the land past the J radius, and the bevel always be as consistent as possible. A good standard for welding a carbon steel J Prep is that the land thickness be .045" ±.005". Some system manufacturers may recommend .050" ±.005" for carbon steel. For the land extension past the radius

Most machinery manufacturers recommend a .035" to .050" extension for most automatic orbital pipe welding . This dimension is usually set forth by the customer’s joint design specifications for the job. The only way to accurately produce this weld joint profile is with portable ID mount weld preparation equipment. The J Prep joint design is a must to ensure repeatability in automatic orbital pipe welding. The most important thing when machining any J Prep configuration is to make sure that the ID bore of the pipe and/or fittings are consistent and the land thickness dimension is within a ±.005" tolerance of the specifications. Inconsistent ID bore or out of tolerance land thickness will result in burnthrough or lack of penetration. The land extension beyond the radius should always be at the same dimension as set forth in the weld configuration specification. By having the same repeatable precision joint profiles, this will ensure that the welds will produce repeatable results.

When a J Prep configuration is used on stainless steel, most manufacturers of automatic orbital equipment recommend a land thickness of .060" to .065" ±.005". As was mentioned in the section on orbital tube welding, many of the same problems occur when the pipes to be welded are not properly prepared for welding. Many of these problems are eliminated with an accurate and consistent weld prep each and every time.

PROBLEM 2. PIPE WELDING INCONSISTENCIES AS A RESULT OF FILLER WIRE PROBLEMS

CAUSE: Filler wire enters puddle at wrong angle.
SOLUTION:If the filler wire entering the weld is too high or above the top of the puddle, the wire will melt off in droplets resulting in a lack of fusion on the sidewalls. If the wire enters too low into the puddle, the filler wire could bottom-out into the bottom of the puddle. When this occurs, you will notice the weld head and filler wire guide tube start jumping or moving erratically. When Filler wire is used with automatic orbital pipe welding, it is very important that the wire entry angle going into the puddle is always theoretically entering into the front edge of the puddle at about 22º for carbon and stainless steel welds (Fig.#3). Every effort should be made to ensure that the wire flows and melts evenly into the weld puddle for consistent results.

CAUSE: Filler wire not entering puddle directly under tungsten.
SOLUTION: If the filler wire entering the puddle is left or right of the centerline of the tungsten electrode (and weld joint line), the weld puddle will favor one side of the weld or the other. Remember that as the filler wire is coming off of the spool, the helix angle or curvature of the wire radius gets smaller. For these reasons, you should always maintain visual contact to ensure that the wire is always in line with the centerline of the electrode (Fig.#3). Wire feed into the puddle is critical to prevent the weld favoring one bevel side over the other which could result in lack of fusion with the other bevel.

CAUSE: Filler wire guide too far from the tungsten electrode.
SOLUTION: One important consideration for all automatic orbital pipe welding systems is the distance of the filler wire guide from the tungsten electrode. The distance from the end of the filler wire guide should never be more than .5" from the electrode tip (Fig.#3). If the wire guide is more than .5" away, the wire going into the puddle could wander left or right of the centerline of the tungsten, causing the same side preference problems discussed above.

CAUSE: Filler wire guide condition causing feed problems.
SOLUTION: Always check from time to time the condition of the filler wire guide and wire guide tube. Make sure the guide is clean and permits the wire to feed smoothly. Replace the feed tube if it becomes worn by the filler wire passing through. A little maintenance on the filler wire guide can save you considerable trouble and result in better wire flow into the puddle.

PROBLEM 3. WELDING PROBLEMS ORIGINATING WITH BAD CONTROL SETTINGS

CAUSE: Weld problems caused by oscillation not meeting profile.
SOLUTION: All manufacturers of automatic orbital pipe welding systems have controls called “oscillation width” which controls the distance the electrode moves from each side of the centerline to meet the weld prep profile. This is a critical reason why it is so important to have the best possible weld prep in order to achieve repeatable orbital welding success. By starting with a precision weld preparation, the operator can control how far the electrode moves from the centerline of the joint to the left or right towards the sides of the bevels.

CAUSE: Lack of fusion on sidewalls due to insufficient dwell times.
SOLUTION: The dwell control for orbital welding systems controls the amount of current which is applied to the side walls of the weld bevels.As the oscillation control moves the tungsten to meet the bevel, the dwell holds the tungsten at the edge of the side wall, at which point the current stays on high current for a given amount of time. This dwell time is generally measured in milliseconds (one thousand milliseconds = 1 second). For most applications, the tungsten dwell will be around 3 ms or a little above. The operator can adjust the dwell time to influence the amount of time current is applied to ensure he has good side wall fusion.

CAUSE: Inconsistent welds due to improper transverse speed/excursion time.
SOLUTION: The control called transverse speed or excursion time on some units can cause improper welds if not set correctly. The control determines how fast the oscillating weld head travels from one side of the weld to the other. If the transverse speed is too fast, the weld puddle will not be able to travel across the joint to make good, uniform filler passes or it could leave holes in the center of the weld. If the transverse speed is set too slow, the weld puddle will sag in the center of the weld which could cause a lack of fusion with the side walls of the weld. Always make sure that the weld puddle is uniform from one side wall to the other without the puddle sagging on the sides or middle. The transverse speed can be determined as a part of the weld procedural development to achieve perfectly uniform welds.

In Conclusion...
As you can see, the variables involved with orbital welding, regardless of whether on tube or pipe, show the critical need for consistency with each and every weld preparation and fit-up. The more consistently you can operate, the more you can adjust and fine tune the welding parameters to produce repeatably successful welding results, each and every time. The importance of weld preparation equipment cannot be overstated. Poor weld preparation accounts for 90% of the problems you will encounter. Precision weld preparation, either through perfectly flat and square ends for tube welding or with an accurate J Prep for pipe welding, is the foundation on which reliable control settings can be determined and adhered to. By maintaining the good practice of proper weld preparation, combined with observation of key indicators and troubleshooting know-how, you can significantly improve your automatic orbital welding results in your specific applications which will save you time and money because of less rework.

Tubing Tips and Techniques for Orbital Welding