Is field welding really that expensive?
Is field welding really that expensive?
(OP)
I've always been taught that it is and to minimize field welding on the documents. What confuses me, however, is that if it's really that much extra cost to the erector why is so much unnecessary weld laid in the field?
I obviously only have a few years under my belt, but I've seen so muh extra field welding done that it makes me question the premise that it's cost prohibitive. On one recent project we had HSS shear connections thy consisted of a seat with a top angle. The top angle was for stability only so we called out for only the tips to be welded to the HSS. When on a site visit, however, they had everything welded up! The angle was welded all the way around ( to HSS and to the column) and the HSS
was welded all around directly to the column!
This happened in quite a few places. Why would they lay weld that is not called for if it's that expensive and coming out of their own pocket?
I obviously only have a few years under my belt, but I've seen so muh extra field welding done that it makes me question the premise that it's cost prohibitive. On one recent project we had HSS shear connections thy consisted of a seat with a top angle. The top angle was for stability only so we called out for only the tips to be welded to the HSS. When on a site visit, however, they had everything welded up! The angle was welded all the way around ( to HSS and to the column) and the HSS
was welded all around directly to the column!
This happened in quite a few places. Why would they lay weld that is not called for if it's that expensive and coming out of their own pocket?






RE: Is field welding really that expensive?
In some geographical areas field welding is questionable and expensive due to a lack of experience in the trades. For example it's probably very common to see good quality welds laid in port area or areas where petro-chemical facilities are common. Many welders would AWS certified but probably certified in welds that the civil building industry just don't do. Since there is experience and an abundance of good welders price is probably good.
In areas where little field welding is ever done, the quality is poor and the price for good welders is high.
Aside from that, field welding is also differientiated by industry. Buildings and other structures with little fatigue concerns are welded on without too much concern. In bridges, there is virtually no field welding. This is due, again, largely to the poor quality and experience and difficult NDE testing that are required to be done in the field.
Mind you I'm not saying that field welding doesn't or shouldn't exist. Just pointing out that to get good experience, good welders and provide for apporpriate testing it's expensive.
Regards,
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RE: Is field welding really that expensive?
In the field, the welding will often be done "out of position" meaning vertical and overhead welds will be necessary. These are the most difficult positions for welding, they take longer to put in properly and the failure rate of tested welds is much higher. Further, the testing is more difficult because of access, particularly if using radiographic testing on complete penetration welds.
So yes, field welding is more expensive for those reasons, among others.
RE: Is field welding really that expensive?
And many times you'll have to touch-up paint after the field welds.
I don't know much about statistics, but I do know that if something has a 50-50 chance of going wrong, 9 times out of 10 it will.
RE: Is field welding really that expensive?
Field welding is much slower, has many more quality problems, requires more complex inspections and possible repairs, more qualified labour and involves more complex set up than bolted connections.
Having said that, sometimes you have to do what you have to do.
RE: Is field welding really that expensive?
Regards,
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RE: Is field welding really that expensive?
RE: Is field welding really that expensive?
Drawings I made for marine exhaust fabrication had few/no weld symbols because the default was 'weld everything'. I tried on a few occasions to get partial welds on particular special articles; couldn't be done.
There are probably other places where 'all around' is customary.
Mike Halloran
Pembroke Pines, FL, USA
RE: Is field welding really that expensive?
It was mentioned that in some applications, "all around" welding is common due to corrosion. If I recall correctly, the Structural Welding Code prohibits this in certain geometries, so per that particular code, more weld is not necessarily better.
RE: Is field welding really that expensive?
In rsponse to your comment aout the HSS Tube connection, you should ask. It could have been a mistake. Or they may have increased the weld as they needed a guying point and did not think the weld would hold for that. Or they may have had problems with that type of connection in the past.Find out and let us know.
RE: Is field welding really that expensive?
In those cases where field welding is absolutely necessary, I have always insisted upon thorough welding inspection.
BA
RE: Is field welding really that expensive?
In the field of preenginered steel buildings in which I am involved, field welding is very minimized.It is not easily reliable versus shop welding which is done indoor under controlled conditions.
Also in bridge construction ( as also already mentioned above ) is almost prohibited.
Of course in other works it can be of wider application provided that experienced and certified welders are easily available..
That as far as quality is concerned.
Besides,when a lot of welding work is to be done, the cost of field welding is clearly higher than shop welding.
RE: Is field welding really that expensive?
I am presently working on a project that is nearly completely field welded. The fabricator that was selected does not have the equipment, CNC beam lines, etc. to accurately located and provided bolt holes. They selected and negotiated with the erector to field welded nearly everything. In this rare case things are proceeding smoothly. As connection designers we have tried to provide connection flexibility and field adjustment where ever possible. Structurally connection flexibility is a significant concern. For the erector, fit-up, column plumbness, and stability during erection can be a nightmare. In this case the project is a large commercial design with cantilever trusses and large axial loads. Many of the axial members required complete penetration welds of the flanges and/or webs. Due to welding considerations, preheating, weld shrinkage, etc. welding sequences had to be considered to maintain the structure geometry.
There are also additional costs related to the types of field welds chosen. There are additional cost for qualified welders. There is additional time and labor associated with with preheat, interpass temperatures, NDT testing, inspection, and repairs. These costs are also increased relative to similar shop procedures in a controlled environment.
Welding in general is more expensive than bolting, whether in the shop or field for most structural steel fabrication. With automated beam lines the fabricator can cut and drill all three surfaces of a wide-flange shape without physically touching the piece. The beam can be cut to length and drilled for connection angles and holes for filler beams. Most AISC certified fabricators will chose to shop bolt as much connection material as possible.
The most obvious exception to this are moment connections. Fabrication and mill tolerances can make flange bolted connections problematic in the field. And endplate moment connections can be limited by capacity. Erection stability is provided by field bolted web connections for shear. But there are exceptions, in some areas of the country qualified welders/iron workers are a premium and the fabricator may find field bolting an alternative.
With regard to providing more weld than required. This is primarily where fillet welds are required. Depending on the setup of the equipment, there is little additional time required for various sizes of single pass fillets. Welding in a vertical position, general deposits more weld metal depending on the welder's experience. In the field the welders prefer the largest diameter electrode allowed, where this may be useful in multipass welds, it is excessive when a 3/16 fillet is noted on the erection drawings. Remember welders know nothing about connection flexibility or ductility. Unless specifically instructed, they will weld till they run out of room. To the iron worker a little too much weld is better than having to come back to an area and overlay or continue a weld.
I can go on and on... Sorry
http://www.FerrellEngineering.com
RE: Is field welding really that expensive?
I would say it really depends on how common it is in your area and section of the industry.
RE: Is field welding really that expensive?
www.PeirceEngineering.com
RE: Is field welding really that expensive?
RE: Is field welding really that expensive?
Frankly, its so hard to keep up with every economic consideration in steel detailing that I try to keep as many rules of thumbs as I can and then do what works and makes common sense. And good communication with your fabricator during the shop drawing process is extremely important.
OVERWELDING- keep in mind with some connections this is BAD. The one that jumps to mind is angle shear connections, bolted to the beam and welded to the supporting member. AISC places a limit on the return weld at the top of 2*weld thickness to retain flexibility, so that your simple shear connection can be modeled as a pin-pin.
Everyone else had great stories, many of which I have experienced. Having done specialty engineering for a steel fabricator for about 5 years now, we still get surprised. A couple of months ago they wanted to do all bolted connections, angles to girder webs, in the SHOP. Still not sure why, and they paid us to engineer it because it was not detailed that way by the EOR, and is not a standard AISC table either. Maybe a manpower and machine issue at the time they needed to go to production...
My one advice is on big projects with lots of steel connections, try if you can to get a steel fab on board before you do the connections, or give them as many options as economically feasible on your drawings (tables/schedules and typical details help), or defer them to the fabricator's specialty engineer.
And make friends with a good AISC certified steel fabricator. You can always pick up the phone for a second opinion and invite them to do the same. I have really enjoyed this experience...
HTH,
Andrew Kester, PE
Florida