I agree with you. The code is specific about storage of low hydrogen electrodes after the container has been opened. I have also found that most welders don't agree or don't understand what you are trying to accomplish with the oven.
Respectfully,
Mike Sherman
Shermans Welding
Let's make some reasoning.
If the oven is hermetically sealed, it means that it doesn't exchange air with the surrounding atmosphere. In other words, the air within the oven is not pushed away from it, nor is the surrounding air pulled in into the oven. Agree? OK let's go on.
Now you turn the oven on until it reaches the LH rods storage temperature, which is above water boiling point. At this moment, all the moisture contained in the rods coating has evaporated and is WITHIN THE OVEN ATMOSPHERE, for the oven is hermetically sealed.
Now you turn the oven off, as stated by your friend. What will happen? The temperature will drop below the water boiling point and the relative humidity within the oven will increase and be absorbed by the electrodes coating. When the temperature into the oven has finally reached room one, things will be exactly as they were in the beginning, for the simple reason that the oven is hermetical and there was no exchange of air and moisture with the exterior.
Conclusion: this oven can not be turned off, as hermetical as it may be.
Giovanni S. Crisi
Sao Paulo - Brazil
Sounds like a smooth talking welder to me.
Good point Professor. I did mention that to the welder and he had no defense.
So just for argument say that the oven is purged with dry nitrogen while hot- now the moisture is gone- can you then seal the oven and turn it off and have the rods retain thier quality? Would the code be happy?
Bill
Seems to me it would be much more simple just to leave the oven plugged in.
Kpauly, yes it would be much easier to just leave the oven plugged in. But the problem I have seen with most of the smaller jobs is the only storage trailer on site belongs to the General Contractor and they just dont want a rod oven radiating heat in their office. And thats even if the erectors have a oven. So my solution is to just write up the improper storage of electrodes. It's kinda funny how the engineers specify Low-Hydrogen electrodes but do not care how they are stored.
The answer to Bill is yes, the rods will retain their quality. Now, about the Code, I don't think the Code has gone that far so as to regulate the use of nitrogen purged ovens.
Giovanni S. Crisi
Yes i would have to agree that the over has to stay within the required oven temps at all times...another thing i have heard is that some people neglect to keep thier LH in ovens (or just leave them lying around) I have been in the navy the last 5 years and have been to jobsites that have ovens that dont work...and thus the LH are not fit to weld with, but they make us use them anyway..i just dont see how a welder can use these electrodes in this manner and not even care...i had no choice but to use them...and the welds were spattery and tended to get a lot of porosity in them...in my mind i would never use them on my jobsite in the future...but....i guess some people dont care...
Dave, your information leaves me astonished.
Back in my days of erector engineer I had a hard time trying to convince the welders (and even the welding foremen), to use only LH electrodes which were recently taken off the oven, and, if they saw some electrode laying around, not use it but take it to the tool room to be put again into the oven.
I thought their atitude was because they were Third World, underdeveloped welders. Now I learn to my surprise that American, First World, highly developed welders do the same .............
Giovanni S. Crisi
Well since we are on the subject. You are allowed to use rods right out of a fresh opened can. Does anyone know what the manufactures do to prevent moisture from being in the hermitically sealed containers before shipping? And are the low-hydrogen electrodes shipped in the cardboard box with plastic wrap just as good as the ones in the metal can?
In my experience there are two primary circumstances that perpetuate this type of thinking and I’ve had it run on me many times.
One is by welders and companies that use welding rigs. The rod oven is onboard and plugged in but power is supplied only when the welding machine is running. At the end of the shift until the next morning, that rod oven is cold.
Secondly, is when the job site only allows electrical tools to be used under a “Hot Work Permit” for a specified period of time or shift. Once the shift is done, all electrical tools (rod ovens included) are shut down at the job site. This was a very common practice in my old plant. Rod ovens were kept off the actual job site and in marshalling areas or designated areas, which were not included under the HWP and had fulltime power. As with the rigs, the welders/supervision seemed to always try to keep ovens in their fab shanties regardless of the power being shut down for sixteen hours between shifts.
As pertaining to your most recent question, nope, as long as the container wasn’t damaged to allow contamination and it met the project specs. My concern was what happened after the container was opened not before. Of course, I worked in a chemical plant, which isn’t as finite as a nuke!
Gio, I hope you didnt interpret that i just use any old LH that i can find, i hated using room temp LH rods..i always stressed to my supervisors for a rod oven that worked...i knew this was wrong to use these rods...and i have been on jobsites and shops where the ovens work fine, and in turn i use hot fresh LH rods religously and wouldnt do otherwise. But being a E-5 in the military and knowing how to store LH rods. Im still wrong when an E-6 or above or money tells them differently. This is why im getting out. :)
Not a clue Wild Turkey, understanding that "Hermetic" in this context refers to being airtight, and "sealed" meaning... well..sealed, this is a question worthy of some explanation. Though it seems the last time I questioned the pocess by which electrodes were manufactured I found that the procedures were developed around and mainly for military use, basically froget about us showing you how we make our tanks faster than you can. But this could be old news and manufacturers of electrodes might be more willing to share this information. would love to hear more on the subject.
I've found that for site work, where this problem comes up alot, we solved the problem by requiring the contractors to purchase vacuum containers. These can be had with 3.5 kgs., enough for part of a shift.
The codes are very clear on moisture pickup, and the electrode manufacurers are even clearer regarding the subject.
You should be aware that standard cardboard packaging with plastic around it is not hermetically sealed. hermetically sealed has the electrodes sitting in a padded plastic tray, surrounded by aluminum foil of some type, and has all the air sucked out it. The packaging and storage has to be precise or the packaging will be damaged, a pinhole is all thats required. Then you must go through the baking process.
Daon,
I ran into a problem once when a Mechanical Contractor showed up at a power plant with a case of E-7018 electrodes packaged in cardboard boxes with plastic wrap. The contractor found a deal on these rods at a local hardware store and since the rods were packaged with about 5 pounds of rods to a box the welders could open a new box and never need a rod oven. Needless to say my client was not happy about this. So I did some research and come to find out the electrodes were considered hermetically sealed (kind of like a pack of cigarettes) and met the code requirements. The contractor decided not to use the electrodes to keep the client happy, but it did raise quite a few questions.
About 12 years ago I spent a lot of time making unannounced spot inspections on steel fabricating shops. The issue of rod ovens was always interesting, especially in the mornings. Before lunch I frequently found the LH rods in a pile on the floor next to the oven and the oven full of burritos. After lunch the rods went back into the oven but, without any concern by the shop foreman, it was always a hassle to get them to to comply. One even said, "So come after lunch instead of before and you won't have a problem." That guy got his accredation put on probation.
Worst case I had was a shop where the foreman got a "deal" on some electrodes that had been salvaged from the leaky hold of a ship. Hermetically sealed doesn't last long in salt water. I told him to throw away all the electrodes. Later I saw his crew scavenging them for the uncertified shop across the alley where they built trailer hitches and dumpsters.
Yes Giovanni, the technologically advanced US does do some stupid stuff.
I don't know what "burritos" are, but I guess they're something to eat which should be kept warm for lunchtime.
Giovanni
We must never stand in the path of the thirst for knowledge!
This link will take you to an excellent example of *American Knowhow*, an amazing demonstration of the Great Melting Pot of America, Taking a good Idea from another culture to unheard of extreems.
http://www.luszcz.com/burrito-all.html
Mixing metaphors :)
Lar.
Very Nice, Wheres the Electrode oven??
Nice picture Lawrence. After seeing those it give me an idea. From now on when I see some of the common stuff on the job sites like ovens with corn and baked potatoes in them and ovens made out of an old refrigerator or a wood box with a 100-150 watt light bulb in them. I'm going to take a few pictures and post them as "not what a oven is used for".
I would just like to get back to the "Sealed" Rod oven once more. Wouldn't a rod oven that was airtight need some sort of pop off valve or vent to keep it from blowing up? Sounds more like they had a hermeticly sealed pressure vessel than a rod oven! Oh yeah, Cooks great BBQ too! Nothing like some low hydrogen chicken to keep you hitting the Jiffy John all afternoon! Not to mention every time you make a weld someone will ask "Who's cooking ?"
According to the D1.1-2002 edition, you can only store rods in a vented oven and yes it has to stay plugged in. As for the card board box thing, those rods were never baked, so they have to be baked first 700° to 800° for about 2 hrs. The ones in the can have been baked, therefore they can be put right into the oven. Now, are they moisture resistant rods? If not they can only be out of the oven for 4 hr's, if they are M.R., then they can be out as long as 9-10 hr's. If they are out longer then that they have to be rebaked, now, you can only rebake rods 1 time, so my advise would be keep them in the oven till needed, and only take out what you will use in a 4 hr. period, and hold the BBQ, and pizza.
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