TIG Welding Pipe – Weld Techniques and How to Walk the Cup

8/10/2019 TIG Welding Pipe Weld Techniques and How to Walk the Cup

1/4

TIG Welding Pipe!

Learning Center

WeldingIntroduction to WeldingHistory of Welding

Art of Welding

Welding Processes

Stick WeldingMIG Welding

Flux Cored ArcWeldingTIG Welding

Welder Certifications

Welding Certification3G SMAW4G SMAW6G Pipe SMAW3G MIG Welding3G FCAW

Welder Resources

Why Learn Fitter MathWelding JobsWelder StaffingWelding SchoolsResources

TIG Welding Pipe and How to Walk the Cup

Walking the cup is a welding technique that is almost exclusive to TIG welding pipe! This technique is the industrystandard for TIG welding pipe. Many companies that hire TIG welders wont even consider someone if they do not weldpipe by using the walking the cup technique. My personal experience is that every interview I had for TIG welding pipewas about do I know how to walk the cup.

There are three ways to walk the cup:

Ratcheting the Cup

Wobbling the Cup

Sliding the Cup

The Welding Business Owners Handbook Review - The Fabricator!The Welding Business Owners Handbook Featured on Hobart's "World of Welding Magazine

Ratcheting the Cup

The first is the ratchet technique; it is just like turning a ratchet on a bolt.Ratcheting the cup is typically used anywhere there is a flat area to lean the TIGtorch cup on. This is done by placing the cup on the pipe and turning the handle

just like a ratchet on a bolt. The forward motion is created by having a slighttwitch of the wrist at the end of each ratchet reversal. This is the hardesttechnique for walking the cup but also the best when it comes to weld quality.The reason behind this is the arc length is kept extremely close to the puddlewhile maintaining a consistent height at all times.

AMV4000 Welding Monitorwww.weldmon.com/

Fast data ac uisition flexible monitorin data anal sis etc.

$0.01 Web Hosting

www.hostgator.com/1Penny

Scalable Secure Web Hostin . Tr Our Award-Winnin Service Now!

Welding Pipe Weld Techniques and How to Walk the Cup http://www.gowelding.org/TIG_Pipe_We

2/3/2014


2/4

Wobbling the Cup

The second way to walk the cup is to wobble the cup side to side like moving a heavy barrelthat is standing. This is typically used with a larger cup sizes and is best used on a flat surfaceor directly over another weld. This method is a lot easier the ratcheting the cup but also not asprecise! This is because the arc length is always changing from the wobble of the cup. It stillbeats free hand welding and I use still use it in tight spots where I need to weld left handed witha mirror. Wobbling the cup is a good start to learning to walk the cup. Once wobbling the cup ismastered its time to take it to the next level by mastering ratcheting the cup. This is where youwill learn to perfect TIG welding pipe.

Sliding t he Cup

Sliding the cup is just that! The cup slides and you literally push itto guide the tungsten to where it needs to be. Sliding the cup isdone anywhere that is too odd of a surface to walk the cup. Morecommonly sliding the cup is used in the grove of a heavy wallpipe. You have a large bevel with a cup size that fits between the

joint. Simply set your tungsten to the right height and start slidingthe cup from side to side and forward to spread your filler wire.Sliding the cup is also used for putting in the root and hot pass ona heavy wall pipe. This technique is never mentioned in weldingbooks but is typically learned in the field. Sliding the cup is alsoused when a pipe is almost filled and ready for the cap. In thiscase, the surface the cup is leaning on is not flat enough to walkthe cup and not deep enough in the grove to slide the cup.Compromise is what is needed! You do whatever it takes to fill the

joint. Most of the time half the motion of the cup is sliding and theother half is walking it. Its a little tricky but just takes some time to

get used to.

TIG Welding Pipe with an Open Root

When it comes to TIG welding pipe with an open root the joint preparation is more than half the battle! The bevel must beClean and Even all the way around the pipe. The mill scale should be ground back at least 1 inch on the inside and outsideof the pipe. The bevel should have a feathered edge and the gap should range between 1/16 to 1/8 of an inch dependingon the size of the filler wire being used. For most students practicing in school the gap can be set by using a TIG wire bentinto a V. Simple place the TIG wire on the bevel and then place the other coupon on top of it. Make sure the pipes arealigned properly. The main thing is you want the gap to be even all the way around the pipe and just small enough to putyour filler wire into the grove without it being able to slip inside the pipe.

Tacking the Pipe

Tacking the pipe is done by placing the filler wire into the grove and going over it with the TIG torch. If you will be using a1/8 filler wire you will set the gap with a 1/8 filler wire. To tack the pipe you want to find a spot that the filler wire cant slipthrough the grove. Then simply tack the pipe. Once the first tack is in you need to puller the spacer out a little very quickly.What will happen is the tack will shrink and then you put in another tack on the opposite side of the pipe. Once the firsttwo tacks are in you will need to pull the spacer out. Now check the gap all the way around the pipe and make sure it iseven. If not make some adjustments. Ideally you want the tacks to be about of an inch long.

The technique used to tack the pipe is almost a shake of the TIG torch. You place the filler wire into the grove and runover it while making sure you fuse both sides of the bevel. When you get to the end of the tack stop your arc and do notpull out your filler wire! Wait a second for the tack to cool and then break off the filler wire from the tack. This is done toavoid creating a keyhole that would later create a lump in the root when you try to tie in the root into the tack. Once all ofthe tacks are in you should feather the tacks before putting in the root. If the tacks are not perfect dont worry becauseyou will go over them when you put in the root. When you go over them on the root pass they will smooth out and be

www.wahdatalnimr.com


2/3/2014


3/4

barely noticeable. After each tack make sure you cut off the end of you filler wire to get rid of any contamination.

After each tack make sure you cut off the end of you filler wire to get rid of any contamination. A contaminated filler rod willcause problems with the weld and at the same time make the tack or weld difficult to do. When it comes to TIG welding thetrick is to have everything clean. That means the joint, filler wire and the tungsten must all be extremely clean. The pictureof the tungsten electrode below is a perfect example of a contaminated electrode that needs reshaping!

Pipe Weld ing Techniques for an Open Root

When it comes to the techniques used for TIG welding an open root there are two ways to do it. It comes down to whereyou learned to weld. In America the southern states weld different then the northern states. The northern states just laythe filler rod in the bevel and walk over it. Thats me the Yankee! In the southern states, mostly on the Gulf of Mexico, theyuse a smaller diameter wire then the root opening. What they do is feed the wire from the opposite side of the pipe byleaning it on a tack. The filler wire is literally being feed from the inside of the pipe! Its not easy but knowing how to do thatis really good if your pipe has a bad fit-up. Personally just running over the wire works for me and is a lot easier thenfeeding the filler rod!

The welding technique used will depend on the thickness of the pipe. On thin wall pipe you can either ratchet or wobble thecup. This is because you will have a shallow bevel that you can walk on with the cup. If it is heavy wall pipe you will wanta cup size that is small enough to fit between the groves and slide easily.

Before starting to weld you need to cut your filler wire on an angle to match the feathered tacks. Then place the wire onthe feathered tack and strike an arc in the middle of the tack. Wait for the tack to start melting and slowly walk the cup

toward the filler rod. When you get close to the filler wire you will want to keep the wire pressed into the root and slowlyapproach it. Move slowly enough that the filler wire becomes fluid and sucks itself into the tack. At this point the travelspeed is picked up and you keep walking the cup. When walking the cup do not wash the root too far onto the sides of thebevel. If you do you will get suck back or a concave root surface. Once the weld is ready to tie into the next tack, start toslow your travel speed down. Approach the tack slowly while pressing the filler rod into the tack. Once the filler wirereaches the tack start to press and lift the filler wire to at least a 45 degrees or more when tying into the tack. If you donot lift the filler wire and create a steep angle you will likely create a hole before the tack is tied in properly. Breaking thearc off of the tack needs to be done by quickly increasing your travel speed and long arcing off. This is done to prevent afisheye. The finished root pass should be smooth all around. The tie-ins should be barely noticeable and the root surfaceshould be flat to convex. A flat root surface is not a big deal because it will push in more on the hot pass.

Troub le Shooti ng an Open Root TIG Weld

When it comes to open root TIG welds there are some common problems but all of them are easy to fix. TIG welding is avery forgiving process! Here are some common problems with open root welds and there solutions:

Concave Root Surface or Suck Back

Increase your travel speed

Lower the amperage

Filler wire is to large

Shielding gas flow is to low


2/3/2014


4/4

Dont wash to far onto the bevel

Increase the TIG torch angle

Increase the angle of the filler wire

Pipe Weld ing Techniques for the Hot Pass and Fill er Passes

When it comes to the hot pass and filler passes they are just like to root passbut require a higher heat setting. For example if you are welding a 2 schedule160 pipe the root pass will require about 90 amps and the hot pass will require125 amps. On heavy wall pipe the technique used is sliding the cup. On thin wallpipe the technique used is walking the cup. This is because the bevel is shallowenough to allow the cup to walk on the edges of the bevel.

The general rule for these passes is keeping them under 3/4 of an inch wide.After that, start doing multiple passes. The hot pass is also where you will beable to push the root pass in to fix a flat or concave root surface. On the hot andfiller passes you want to wash into the bevel very well. Unlike the root passwhere you a focusing on pushing the filler wire into to grove here the main focusis on washing the filler wire onto the sides of the bevel. The fill pass does gettricky if you are almost done filling a heavy wall pipe. This is an area that willrequire compromise when it comes to the welding technique used. It typicallytakes half the motion of sliding the cup and the other half walking the cup.

When selecting a cup size for heavy wall pipe it is very common to use multiple cups depending on the thickness of the

grove. Most times you start with a smaller cup and work your way up to larger cup sizes depending on how much if thegrove is filled. The idea is to use a large enough cup that will slide in the grove above the weld without touching the weld.Once the pipe is almost filled up you go back to a smaller cup so that you can build a shelf of weld and start the transitionto walking the cup.

Pipe Weld ing Techniques for the Cap

Welding the cap on a pipe is no different than walking the cup on any other surface. Ideally you want to ratchet the cup butif you are not there yet just wobble the cup. The cap weld does have some common problems that are easily solved. Themost common problem with the cap is undercut. Undercut is typically solved by cleaning the weld area before each passwith a sanding disk or file. What happens is each pass that you weld creates a heat affected zone. What needs to becleaned is the surface of the pipe that is going to be welded. This area typically has a blue tint to it that shows you theheat affected area. Just remove the surface metal with a file or fine sanding disk! This applies to all restarts and stringerbeads. After that the weld should flow smoothly again. When it comes to TIG welding pipe or anything else the key to goodweld quality is cleanliness!

Go Welding.Org. 2008 - 2014 All rights reserved.


2/3/2014

TIG Welding Pipe – Weld Techniques and How to Walk the Cup

Documents

Transcript of TIG Welding Pipe – Weld Techniques and How to Walk the Cup