Weld repairs after draining glycol/water mixture

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Hello, My name is Edward. I work in the specialty chemicals bussiness and have a question on weld repairs.We are in the final stages of a project in Asia and will start hydrotesting and commissioning the unit (with water) within several months. We have looked at the risks of these two activities as the temperatures will drop to -20°C/-4°F at the construction site and damage due to freezing is inherrent at these temperatures. We will start using a 50% Glycol mixture to prevent freezing of the test and commissioning water. However, we expect several welds to be faulty which need to be repaired. Normal procedure is to rinse with water and or steam and dry with (hot) air. As rinsing with water or steaming out at these arctic temperatures will be impossible, we are looking if it is possible to repair the weld with just draining the water/Glycol mixture and drying with cloths.Does anybody done this before? Is there a risk for the weld quality or a fire/health risk?I hope you can help me.
Reply:I installed fire sprinkler system and we used a non flamable, non toxic anti freeze..so if you use that welding with it in the sysytem will be fine as far as a fire hazzard.... weld quality you would have to clean the area tobe welded with what ever method will work in that enviroment.Of all the things I lost I miss my mind the most...I know just enough about everything to be dangerous......You cant cure stupid..only kill it...
Reply:I would think that you could dry out the system using hot air, but I have not seen a system diagram.   That might depend on whether or not you have drain points in the system, how many different places you could inject hot air, how hot you could get the air, etc.  This would of course work better on a warm day than a cold day.   If you use hot air, heat the air electrically, not with fuel, as water is a fuel combustion product, defeating the purpose of the hot air.   (If the air line is sealed relative to the combustion, then you could use fuel to heat an air line).Note that in extreme conditions, it is not unusual to build a temporary enclosure to heat the entire project above freezing, so that is another approach, but perhaps unsuitable for large projects.Note that the pipeline industry uses "pigs" to clean their lines, you might look into a pig small enough to fit your pipes.It will be interesting to see who has actual experience with this kind of project, and what their experience has been.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:More details might be useful; some metals like Nickel can be damaged by picking up trace elements like lead from contaminants like lubricants, although I wouldn't expect glycols to be a problem except from the carbon (which could theoretically cause trouble with some stainless alloys).Why not use a mix of alcohol and water for the final rinse of the area needing rework? That won't freeze and can be removed by dry air and gentle heat before welding;  here's a table of Freezing Point Depression for Ethanol/water mixes:http://www.engineeringtoolbox.com/et...ter-d_989.htmlAnd for Methanol/water:http://www.engineeringtoolbox.com/me...ter-d_987.html
Reply:There is Food Grade Propylene Glycol that is the stuff to use if you are worried about freezing and poisoning people or getting into water lines like a fire sprinkler system. But is their something else? Is there a problem that could react with chemicals later that is need for good removal?Miller thunderbolt 250Decastar 135ERecovering tool-o-holic ESAB OAI have been interested or involved in Electrical, Fire Alarm, Auto, Marine, Welding, Electronics ETC to name a just a few. So YES you can own too many tools.
Reply:Another option, considering that I know nothing about your application, to completely dry a confined space is to use a vacuum pump.  This will be very dependent on your unit of course - size, fitting types etc.Any leaks found while testing with water can be soft patched (rubber boots, hammered lead etc) then pull 30 inches of mercury.  Any water will evaporate or freeze then evaporate.   Adding heat to low points using either open flame torch or heating blankets will speed the process significantly.When any government, or any church for that matter, undertakes to say to its subjects, "This you may not read, this you must not see, this you are forbidden to know," the end result is tyranny and oppression, no matter how holy the motives.
Reply:The vacuum pump is an interesting idea.   However, the vapor pressure of ice at -20C is less than 1 mm of mercury    So you would need to be able to hold a very high degree of vacuum to get ice in the pipes to sublime into a gas.     My guess is that you might not be able to obtain and hold such a high vacuum, especially in a piping system that was not designed for vacuum.If I thought it through correctly, you would need to be able to get the absolute pressure in the pipes down to 0.01 psi or so to even start to convert ice to gas.   (Yeah, I know that most gauges read relative pressure, such as 950 milimeters of mercury, not absolute pressure, but the laws of thermodynamics work based on the absolute pressure and temperature.)   And at that temperature, the sublimation process might be pretty slow.......  The other problem that you could get into would be that the glycol may have a much higher vapor pressure than water at those temperatures, which means that the glycol might be removed, but not the water.     That could cause freezing, when most of the glycol is gone but the water is still there......   I did not look up the vapor pressure of glycol, because I was not sure which form of glycol (or alcohol) that might be used.If you could get the piping system up above freezing, the vapor pressure would be 5 or 10 times as high, making the vacuum approach more reasonable.However, a different approach might work.     Let's assume that there are a small number of leaks in the system.    If you could heat the area around the leaks, and use the vacuum pump, you could drive all the moisture away from that area.   Much of that moisture might recondense in a cold section of piping, but that might be just fine.   So you could use hot air to blow out as much of the fluid as you could, and then apply vacuum as well as heat to the leak area.     The moisture would tend to leave the leak area, perhaps recondense somewhere else, but the leak area would be dry, or dry enough.   The vacuum might not even be required, the heat alone might drive the moisture elsewhere, and the cold would lock the moisture in place as fluid or ice in a different location.  To make that work, I would apply heat to a large enough section of pipe that water/glycol condensing elsewhere could not migrate back to the repair area.  That also goes back to the question of where the drain points are relative to the repair.You can see the condensing of water vapor in a compressed air piping system.    If the pipes are cold, the air coming out is pretty dry.   If the pipes are warm, the piping does not trap as much of the moisture.  (I only have 25 feet of pipe in my shop, so I see this a lot).  Really cold pipes would be very effective in condensing moisture, whether water or glycol.This strategy uses the very cold temperatures, which you thought were a big problem, as an advantage, allowing the selective use of heat to move fluid away from the repair areas.   Always good to turn a disadvantage into an advantage.   ;-)Of course, this strategy would not help you remove all the moisture from the piping system, but it would allow you to relocate it away from the work area.   You still would have the problem of flushing out any water/glycol mix in the piping and replacing it with the actual fluid to be used in production.Interesting problem.RichardSculptures in copper and other metalshttp://www.fergusonsculpture.comSyncrowave 200 Millermatic 211Readywelder spoolgunHypertherm 600 plasma cutterThermal Arc GMS300 Victor OA torchHomemade Blacksmith propane forge
Reply:glycol doesnt evaporate so it needs tobe cleaned out either with chemicalor mechanical means.., if it will affect the weld qualityOf all the things I lost I miss my mind the most...I know just enough about everything to be dangerous......You cant cure stupid..only kill it...