Why leave a brether hole when welding structural tubing? - Page 2
Close
Login to Your Account
Page 2 of 2 FirstFirst 12
Results 21 to 39 of 39
  1. #21
    Join Date
    Oct 2005
    Location
    erie,pa
    Posts
    8,429
    Post Thanks / Like
    Likes (Given)
    15309
    Likes (Received)
    4122

    Default

    Quote Originally Posted by Pete Deal View Post
    True but the typical in building systems (no freeze risk) that I am familiar with are full of water.


    Also true but for the sake of this discussion I would assume someone would not weld the thing up with a bunch of water in it.
    Note pix I posted of water spraying out of column. I snapped that myself, local gas station
    canopy, e-mailed company....they put some sillycone over that hole...

    Everyone thinks they welded it up air tight, however, unless tested as an air tank, many times
    (as shown by various accidents and lawsuits from failing structures) there is a small leak.

    As far as a building column inside, many times the heat is off, building is off rent, shut down, etc.

    Assumptions get innocent people killed.

    "Water always wins, that's why there is a Grand Canyon"

  2. Likes Pete Deal liked this post
  3. #22
    Join Date
    May 2012
    Location
    Pittsford, NY
    Posts
    746
    Post Thanks / Like
    Likes (Given)
    510
    Likes (Received)
    499

    Default

    Some of those gas station canopies use the structural tube as the roof drain line. They'll have fittings near the bottom to evacuate the water. And often, quite a bit of corrosion.

  4. Likes digger doug liked this post
  5. #23
    Join Date
    Jun 2015
    Country
    CANADA
    State/Province
    Ontario
    Posts
    297
    Post Thanks / Like
    Likes (Given)
    621
    Likes (Received)
    164

    Default

    Just because you can't see where water gets in, doesn't mean it's waterproof.

    It's easy to let it out.

    Structural Safety :: Confidential Reporting on Structural Safety

    The barrier structures were only 4-5 years old and made of RHS sections with fully welded joints and end plates.

    Visual inspection of the barriers showed no sign of any openings that would allow ingress of water (see photo).

    It appears that water can be drawn into tubular steel structures of this type by capillary action. The phenomenon has been experienced in other structures; such as roof trusses made from hollow steel sections, and welded box girders. Although the structural elements are manufactured as 'sealed units', continuous welding does not necessarily produce a complete seal and water may accumulate inside where the units are exposed to the weather. Research into the phenomenon in Canada has shown that a partial vacuum caused when a relatively warm, imperfectly sealed steel tube is rapidly cooled by rainwater, can draw in water through very small cracks and holes. Over a period of time this can result in a considerable build-up of water trapped inside. Where such a steel tube forms a structural element that is exposed to the weather, the trapped water may freeze in winter. The element may thus be damaged as it fails to restrain the expansive action of ice formation. The resulting bulging and/or splitting may reduce the load-carrying capacity of the element substantially, thereby undermining the safety of the structure

  6. Likes digger doug, alexhawker liked this post
  7. #24
    Join Date
    Dec 2004
    Location
    uk
    Posts
    11,998
    Post Thanks / Like
    Likes (Given)
    3243
    Likes (Received)
    5261

    Default

    Quote Originally Posted by digger doug View Post
    On that one I would have drilled small holes at each intersection, then
    pressurized the whole frame with nitrogen, put a pressure gage
    where you can check it (seen this done before, not my idea)
    No disrespect, but you clearly have never ever done any work for the funfair crowd! There a very unique bread of customer, the reasons for damn near certain there was no rust bleed through or tell tail signs on that ride is because most of the rides get repainted every few years during the off season its a incredibly tough life on equipment. There std approach to a low pressure gauge would just be to pump it back up and get the ride open again assuming it was not simply broken and never replaced! Rides not open there not making money! Thats not to say they will run a intentionally dangerous ride, they won't but there not going to notice subtle clues like that.

    Over here i doubt the fault would have been picked up either, yeah the rides very much get tested and inspected, but the testers skill level leaves a lot to be desired. Pins and key frame locations will get magneticialy crack tested. Which to be fair does pick up a lot, but its only done once a year. If you have ever been around large moving structures you know how fast fatigue cracks can go from appearing to failing. Most of the rides use nasty oscillating motions with often surprisingly large forces. Its the perfect opportunity for fatigue to happen. From a structural stand point nearly all fun fair rides will fall apart from fatigue and there own motions, just a case of when!

    Big part of the problem is being outdoors, the day - night temp swings condense the moisture out inside structural elements and electric motors! Have now replaced over a half dozen motors on there rides with some over 3/4 full of water from simple condensation build up. Trust me when i say a 1/8" hole is not a drain, it will get plugged up in no time by a few bugs setting up home. You need more like 3/8" at a minimum.

  8. #25
    Join Date
    Oct 2005
    Location
    erie,pa
    Posts
    8,429
    Post Thanks / Like
    Likes (Given)
    15309
    Likes (Received)
    4122

    Default

    Quote Originally Posted by adama View Post
    No disrespect, but you clearly have never ever done any work for the funfair crowd! There a very unique bread of customer, the reasons for damn near certain there was no rust bleed through or tell tail signs on that ride is because most of the rides get repainted every few years during the off season its a incredibly tough life on equipment. There std approach to a low pressure gauge would just be to pump it back up and get the ride open again assuming it was not simply broken and never replaced! Rides not open there not making money! Thats not to say they will run a intentionally dangerous ride, they won't but there not going to notice subtle clues like that.

    Over here i doubt the fault would have been picked up either, yeah the rides very much get tested and inspected, but the testers skill level leaves a lot to be desired. Pins and key frame locations will get magneticialy crack tested. Which to be fair does pick up a lot, but its only done once a year. If you have ever been around large moving structures you know how fast fatigue cracks can go from appearing to failing. Most of the rides use nasty oscillating motions with often surprisingly large forces. Its the perfect opportunity for fatigue to happen. From a structural stand point nearly all fun fair rides will fall apart from fatigue and there own motions, just a case of when!

    Big part of the problem is being outdoors, the day - night temp swings condense the moisture out inside structural elements and electric motors! Have now replaced over a half dozen motors on there rides with some over 3/4 full of water from simple condensation build up. Trust me when i say a 1/8" hole is not a drain, it will get plugged up in no time by a few bugs setting up home. You need more like 3/8" at a minimum.
    Where did I say I worked on any funfair stuff ?
    The nitrogen technique I noted, is used on HIGH END stuff.....Duh.

    And your snarky comments on hole size ?
    I suggested that I use 1/2" minimum, that's what I have found out in the field doesn't rust shut as easily.

  9. #26
    Join Date
    Dec 2004
    Location
    uk
    Posts
    11,998
    Post Thanks / Like
    Likes (Given)
    3243
    Likes (Received)
    5261

    Default

    Not all my post was addressed at you, read some of the comments further up, just trying to save others the problems i have seen. As to high end stuff, you probably don't want to know what those rides go for, but its a lot more than most people expect! Makeing FUNFAIR rides is very much a high end product, you would not praphs think so but they hold value way way better than machine tools too. 20 year rides will oftern change hands for near 3/4 of new price if they have been well maintained Its a very small very bespoke high end market.

  10. #27
    Join Date
    Feb 2014
    Location
    Midlands UK
    Posts
    374
    Post Thanks / Like
    Likes (Given)
    154
    Likes (Received)
    413

    Default

    Never did much hole drilling.
    I have often filled tubes with argon to prevent weld contamination, some of which would remain inside afterwards as an inert corrosion limiter, although that was not the primary purpose.
    Never done it but using holes it does not seem to be beyond the wit of man to plan to finish with an inert interior.

    I got the labourer to put a small nick in the tube end where I intended to finish the welding, to minimise blowouts and gas inclusions.

    If you are welding rectangular tube to rectangular tube saw it at 89 degrees/44 degrees etc. Start with the gaps to get full penetration on cold tube, finish towards the no gap end of hot tube.
    Fine on stick and MIG, does not really help on TIG.

    Blowing out moisture with compressed air? I assume this was dry compressed air.

    I used to do mostly piece work on aluminium and stainless steel. Nothing I welded went into submarines or into space.
    It did go through the door PDQ though.

  11. #28
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    7,979
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2111

    Default

    plated stuff often has a drain hole cause i have seen plated stuff weep out plating chemicals over the next few years. leave a bigger hole it comes out faster

  12. #29
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    7,979
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2111

    Default

    working on fire escapes i often loosened a 3/4" dia bolt going through the wall and it twists off and you see its rusted down to less than 3/8 dia.
    .
    the cold air goes through the wall hole and moisture condenses and rod wet in the wall in the winter. kind of scary. i replace all bolts with galvanized rod. old rods were not even painted. any fire escape over 40 years old i would not trust

  13. #30
    Join Date
    May 2002
    Location
    South Central PA
    Posts
    12,439
    Post Thanks / Like
    Likes (Given)
    1509
    Likes (Received)
    2624

    Default

    Quote Originally Posted by DMF_TomB View Post
    working on fire escapes i often loosened a 3/4" dia bolt going through the wall and it twists off and you see its rusted down to less than 3/8 dia.
    .
    I see that on heavy equipment too, bolts rusted down to half their size or less in critical locations. I try not to think about this when on or under bridges bolted or riveted together.

  14. #31
    Join Date
    Jan 2008
    Location
    Fl. west coast USA
    Posts
    103
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3

    Default

    Quote Originally Posted by Kiwi2wheels View Post
    Your post made me search ( as I was curious about how repairs were made on an oil preserved structure ) and I found this ;

    Corrosion Protection Method for Welded Steel Tube Structures - Aircraft engineering - Eng-Tips

    One advantage of drilling breather holes in TIG welded tube structures for motorsport ( and probably aircraft as well ) is the elimination of blow out at the end of a weld with cluster joints or a chambered area, which is mandatory for any components to be heat treated.

    Plus it's far easier and quicker to just plug weld one breather hole if the component is to be sealed, rather than waiting for the part to cool before finish welding a joint with a small unwelded area.

    More here; anti corrosion oil for tubular aircraft structures - Google Search
    I build aluminum trail doors for jeeps from .125 wall tubing. If I don't make provision for venting I sometimes have the last 1/8 of a finish weld blow up like a little volcano, and it can be a blank to fix. I dont think this applies to larger jobs with steel though.

  15. Likes Fabworks, PlasmaOnTheBrain liked this post
  16. #32
    Join Date
    Jul 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    4
    Post Thanks / Like

    Default

    Someone asked about an oil for the insides of tube structures. From what I gather it is common practice in light aircraft tubular structures to drill vent holes such that there are no captured volumes and there is one (at least) exterior access hole for stuff like this: http://www.aircraftspruce.com/catalo...clickkey=80768
    In my experience with race car chassis (drag, road race, & off-road) it is hit or miss whether such holes are present. Except in plated weldments, they always have them. Some sanctioning bodies have tube wall thickness requirements for some or all of the tubular structure and the way those are checked is with a hole that is usually not in a logical place for a vent hole.

  17. #33
    Join Date
    Feb 2014
    Location
    westmoreland city pa
    Posts
    6
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2

    Default vent hole

    Quote Originally Posted by Gos View Post
    The title says it all.
    I know there's a practice of leaving a breather hole at the lowest part of a welded structural tubing for venting out moisture. What I wanting to know is which is the better from a longevity point of view. Welding a structural tubing with a vent hole, or welding it with no vent hole and pressure testing?

    The tubing in in this question is 6x6x.25 square tubing, 12' long sections vertical mount to cement pad. The interior of the tubing will not be coated, just paint on the outside with all season weather contact. These are exposed beams.

    Thanks all.
    i was taught the reason to have vent holes in welded structures was to prevent pressure build up from blowing out the arc when you get to the end of the welde.

  18. Likes Ries, PlasmaOnTheBrain liked this post
  19. #34
    Join Date
    Jun 2011
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    12
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    1

    Default Vent holes in welded tubing

    In the mid 1970’s, just out of high school, I worked as a draftsman-detailer for an engineering service firm. Occasionally we would be drawing large structural tubing bases for machine tools. We were always taught to add a note on the drawing to “Vent all tubing before welding”. Rarely did we spec the hole size for the vent hole. Not sure what the purpose of the vent holes was, don’t think I ever ever asked any of the designers or checkers (these were usually the “old timers” with years of experience). I was always under the impression that reason for the vent holes was due to the heat of the welding process heating the air inside the tubing. The vent holes would let the weldment “breathe” and allow any pressure or vacuum that occurred inside the tubing to relieve itself. I do recall an experiment in elementary school science class where the teacher took an empty sealed gallon steel container (like the “tin” cans paint thinner used to come in), can was set on a hot plate, heated for a few minutes, then allowed to cool. As it cooled, the can would eventually crumple. I assume that was because since the can was sealed, heating it heated the air inside the can causing the air to expand, then as the can and air inside of it cooled off, the air contracted, creating a vacuum which caused the can to crumple. Of course, cans such as that are made of thin metal. But would that happen to a closed and sealed structural steel tube with a wall thickness of 1/8”, 3/16”, 1/4”, or thicker wall as the welds were completed on the final end?

  20. #35
    Join Date
    Oct 2017
    Country
    UNITED STATES
    State/Province
    Tennessee
    Posts
    16
    Post Thanks / Like
    Likes (Given)
    3
    Likes (Received)
    0

    Default

    Can't have oxidation without oxygen,

  21. #36
    Join Date
    Mar 2004
    Location
    Edison Washington USA
    Posts
    10,055
    Post Thanks / Like
    Likes (Given)
    804
    Likes (Received)
    4506

    Default

    Quote Originally Posted by larryr View Post
    i was taught the reason to have vent holes in welded structures was to prevent pressure build up from blowing out the arc when you get to the end of the welde.
    we drilled vent holes in some tubing this week for exactly this reason. Sealed square tube, after a bit of welding, the air inside gets hot. it expands. no vent hole, and, when you tig weld a seam, the heat of the arc softens the steel, the air pressure inside pushes it out, and it gets molten steel on your tungsten.
    Its not a structural problem, its just annoying, because you have to stop and regrind your tungsten.
    When you are doing quality tig welds that have to look good, its common practice to have a vent hole, and seal that last, and sand it out so it disappears.

    For mig, or stick, not needed. For stuff that is expected to be ugly, not needed.

  22. Likes PlasmaOnTheBrain, Fabworks liked this post
  23. #37
    Join Date
    Nov 2015
    Country
    POLAND
    Posts
    68
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    9

    Default

    The cause was structural tubing rusting from the inside, it looked perfect on the outside.

  24. #38
    Join Date
    Oct 2005
    Location
    erie,pa
    Posts
    8,429
    Post Thanks / Like
    Likes (Given)
    15309
    Likes (Received)
    4122

    Default

    I try to always detail a hole in any column I specify for outside, you cannot control what happens after install.

    I have had those %$#@! pesky electricians drill holes into the columns for mounting hardware etc.

  25. #39
    Join Date
    Mar 2014
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    185
    Post Thanks / Like
    Likes (Given)
    47
    Likes (Received)
    81

    Default

    Quote Originally Posted by digger doug View Post
    Note pix I posted of water spraying out of column. I snapped that myself, local gas station
    canopy, e-mailed company....they put some sillycone over that hole...
    At this Shell gas station, the foot of the columns was completely rusted away. The reporter and inspector have over-emphasized the role of the wind. That structure is supposed to easily handle those winds. It wasn't that windy.

    Looking at those bases is something to do while you're passing time at the pump.

    Wind, corrosion toppled Ann Arbor gas station canopy, official says | MLive.com



    Note the condition of the lamp pole.


  26. Likes digger doug liked this post

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •