7018 not in rod oven 6

[Downhand]

I understand that 7018 can not be out of a rod oven for more than 4 hours before it needs to be rebaked, however, if the rod is out of the oven say for 2 hours and doesn't get used I am told that it must go back in the oven for 4 hours before it can be used again. Is this true? Please reference the any of the U.S. codes that refer to this.

 

[Ron]

The procedure you've outlined is overly restrictive and can cause problems with the electrode coating. The following link is to Lincoln, giving its recommendation for drying and storage. Most costs require adherence to the manufacturer's recommendations.

http://www.lincolnelectric.com/knowledge/articles/content/storing.asp

 

[HgTX]

Lincoln's recommendations do not override codes.

AWS D1.1 clause 5.3.2.2:
"...electrode exposure to the atmosphere shall not exceed the values shown in Column A, Table 5.1...Electrodes exposed to the atmosphere for periods less than those allowed by column A, Table 5.1 may be returned to a holding oven maintained at 250°F [120°C] min.; after a minimum hold period of four hours at 250°F [120°C] min. the electrodes may be reissued."

Lincoln says one hour, D1.1 says four hours. If D1.1 is referenced in your contract, D1.1 wins.

At holding rather than baking temperatures, you're not hurting the electrode by keeping it in longer.


But I'm kind of confused about your scenario. The table gives you 4 hours. You've had the electrode out for 2 hours. If you want to use it now, you can still use it because it hasn't been out for 4 hours yet.

If you put it back in the holding oven after 2 hours and go to lunch for an hour, you don't get another 4-hour period on that electrode when you get back. (Code doesn't say what you do get; me, I'd probably say you get the remaining 2 hours but that's just off the top of my head. More realistically, I'd say your electrode control procedure should require that once it goes back into the oven it stays for 4 hours so that we don't have to get into that sort of question. Use another electrode in the meantime. You shouldn't be down to your last electrode.)

On the other hand, if you put it back in the holding oven after 2 hours and leave it there for at least 4 hours, now (as far as the code is concerned) it's like you never had it out before and when you take it out again, you have 4 more hours.

At least that's the way I see it.

Hg

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[Ron]

Sorry..."costs" should have been "codes"...not good at typing!

 

[Downhand]

Thanks HgTX, your posts the last couple days have been valuable. To clarify I am under the understanding that if an electrode is under the storage temperature of 120 celcius that it should not be used even if it is under the 4 hours before rebaking is required. Therefore, if this is correct, in my scenario if the rod oven has been unplugged for a couple of hours and the rods are cold the welder cannot just pick up the rods and start welding because it is still under the 4 hour time period. So my question was if the rods have been out of the oven for a couple of hours and have not exceeded the 4 hour time limit, how long do they have to go back into the storage oven for before they can be used again? The AWS clause that you referenced has answered this question nicely. The rods need to go back into the storage oven for 4 hours before they can be used again. Thank you for this reference.

 

[HgTX]

I don't really see a practical difference between the rod oven being unplugged for 2 hours (assuming you really do know exactly when the rod oven was unplugged and didn't just come in this morning to find it unplugged and you are hypothesizing that it happened when the janitor did their 5 AM vacuuming) and having taken the rod out of the oven on purpose for 2 hours.

Either way, the rod has been out of its mandated storage conditions for 2 hours and it has 2 hours left to go. IF you are completely sure about when the oven got unplugged.

Hg

Eng-Tips policies: faq731-376

 

[racookpe1978]

Get your welders to use a take-along local 120 volt portable rod box.

They won't lose temp, break apart the rod coating, or get wet. (As much as unprotected rods in a back pocket.)

 

[Downhand]

Am I correct in saying 7018 rod should never be used unless it is up to the mandated storage temperature? In other words, if the rod has only been out of the rod oven for an hour and it is no longer up to temperature, it should not be used. This is how I interpret what both Lincoln and AWS are saying.

 

[Ron]

Downhand...technically, yes. Practically, E7018 electrode are used routinely without rod ovens, particularly on construction sites. It is more critical for fatigue or fracture critical structures.

 

[racookpe1978]

No. Your interpretation isn't correct.

What the regs require is that a 7018 rod not be out of the oven (left to cool down towards room temp - in the case of an oven being turned off) for more than 4 hours before use.

I can't keep a rod constantly that hot up at the weld site without a local 120 v heater), but I am not required to either.

 

[gtaw]

Electrodes removed from a hermetically seal tin can be used directly from the tin can provided there is no evidence the can was breached or damaged (the can is no longer hermetically sealed).

Once the electrodes are removed from the tin, they should be:
a) Used immediately, exposure limited by your code requirements, i.e., D1.1 4-hours, before being placed into a "holding oven" set to 250 degrees F for reconditioning.
b) Placed directly into the "holding oven" and maintained at 250 degrees F until needed for production, subject to the exposure limitations of the applicable welding code.
c) Electrodes exposed less than the maximum time allowed by the applicable code can be placed back into the oven and reconditioned.
d) Electrodes exposed for more than the time permitted by the applicable code can be reconditioned if they are rebaked at elevated temperatures (700 degrees F per AWS D1.1) for the required time (1 hour per AWS D1.1). Electrodes can be rebaked once per AWS D1.1, other codes may have more or less restrictive requirements.

This is a synopsis of AWS D1.1; the actual requirements should be verified for detailed information.

Different welding standards have different requirements or recommendations. ASME provides little direction regarding the subject, whereas NAVSEA welding standards are more restrictive.


Best regards - Al

 

[Downhand]

In the case of "C" how long is the reconditioning period?

 

[Ron]

Same as (d).

 

[Downhand]

(D) is talking about reconditioning electrodes that have been exposed for over 4 hours and therefore are reconditioned by rebaking. (C) is talking about reconditioning electrodes in a holding oven that have been exposed for less than 4 hours and therefore do not need to be rebaked as in the case of (D). Therefore, in the case of (C) how long to the electrodes need to be reconditioned in the holding oven before use?

 

[gtaw]

Condition C) exposed for less than 4 hours; return to the holding oven for 4 hours at 250 degrees F. Reference AWS D1.1-2006 clause 5.3.2.2.

Condition D) A5.1 electrodes exposed for more time than that permitted; Baked for two hours at temperatures between 500 and 800 degrees F. Reference AWS D1.1-2006 clause 5.3.2.4 (1)

A5.5 electrodes exposed for more time than that permitted; Baked for one hour at temperatures between 700 and 800 degrees F. Reference AWS D1.1-2006 clause 5.3.2.4 (2)

Electrodes shall be rebaked no more than once.Reference AWS D1.1-2006 clause 5.3.2.1

Best regards - Al

 

[Downhand]

Gtaw, another good post. I interpret the code the same as you. The code seems to be clear that when the rods come out of a hermetically sealed container that they need to be used within 4 hours or put into a rod oven at 250 degrees. I don't think the code is as clear as to what happens when the rods come out of the rod oven. Does the welder have another 4 hours to use the rods and if so can the 4 hours in the rod oven and 4 hours out of the rod oven be repeated indefinitaely? Here is a scenario that I have come across more than once: A welder takes rods out of the hermetically sealed container and doesn't burn them all within the 4 hour time period so he puts the rods into a portable rod oven that heats the rods to 250 degrees and this is the temperature the rods are maintained at. At lunch time the welder shuts off his welding machine (which is running the rod oven) and goes for a 1 hour lunch. When he comes back the rods have dropped in temperature from 250 degrees to say -20 degrees (I live in northern Canada). At this point does the welder still have 3 hours to burn the rods (the rods have already been unplugged for 1 hour for lunch) or would the rods be considered to have been "exposed" and therefore they need to be brought back up to 250 degrees for 4 hours before burning them?

 

[gtaw]

A rebake (high temperature) is limited to once. There is no such restriction on "reconditioning" (my words) that I can see. So, as long as the electrodes are not out of the oven for a time period that exceeds the allowable time limit, the number of times they can be returned to the oven (at lower temperature) is unlimited per D1.1.

Lets not forget that the exposure limits are dependent on the tensile strength of the electrode, i.e., 4-hours for E7018, 2-hours for E8018, 1-hour for E9018, etc.

Best regards - Al

 

[HgTX]

You've asked a variation of this question before, and I still don't understand the difference between having the rod out of the oven for 4 hours or having the rod in a cold oven for 1 hour and subsequently being out of the oven for 3 more hours. How is being in a cold oven any worse than being out of the oven completely? Either way, you've started your exposure timeclock running, and you have 4 hours to do as you please, unless the thing actually gets wet (someone sweats on it, or the extreme humidity that another poster described).

Once the heat of the oven is no longer applied to your electrode, it doesn't matter which side of the oven door it's on. Sitting outside at your workstation, or in the unplugged oven, what's the difference? Time in an unplugged oven is exactly the same as time in an open box placed near the welder's workstation.

So if the electrode spends an hour outside the oven and two hours in a cold oven, that's three hours of "exposure" and you still have an hour to play with before the electrode has to be baked. If instead it spends an hour outside the oven, one hour in the holding oven at holding temperature, and one hour in the cold oven, you're no worse off than you were before. You still have that hour left of the four hours since the electrode was first issued. You haven't gained anything either, though, since the hour in the holding oven wasn't long enough to reset the clock and let you start your four hours all over again.

One might think that the one hour spent in the holding oven might suspend the 4-hour exposure clock, but there's no provision for that in the code, so for the sake of code compliance and conservatism we'll let the exposure clock keep running even during short stays in the holding oven.

Here's how I see it:

8 AM: Welder takes rods from big oven, puts in little oven.
8 AM - noon: Rods live in little oven unless they're taken out one at a time and used immediately. No worries about 4-hour exposure limit except for the electrode being used at that moment, which will soon cease to be an electrode.
noon - 1 PM: Oven turned off. 4-hour exposure clock starts for all remaining electrodes.
1 PM: Welder returns. 3 hours of available exposure time remains for all electrodes.

Scenario 1, for the sake of discussion: Oven stays off.
1 - 3:55 PM: Welder welds. Exposure clock keeps ticking.
3:55 PM: Allowable exposure period almost done. Welder puts electrodes back in holding oven. Reconditioning clock starts. Electrodes will be available for use at 8 PM.

Scenario 2, closer to reality: Oven turns back on.
1 - 3:55 PM: Welder welds. Since the code does not provide for suspension of the exposure limit for short times in the oven, as opposed to a complete 4-hour reconditioning, the exposure clock keeps ticking even while the electrodes sit in the oven, counting down from 3 hours remaining at 1 PM to 5 minutes remaining at 3:55 PM.
1:15 PM: Oven reaches proper holding temperature. Reconditioning clock starts, and the 4-hour reconditioning period will be over at 5:15 PM.
3:55 PM: Everything in the rod oven is very close to its exposure limit and can no longer be used right now for welding until it goes in for reconditioning. However, since all those electrodes have been sitting in the oven at holding temperature since 1:15 PM, they can be considered to be reconditioned at 5:15 PM instead of 8 PM.

That's how I see it. Am I missing something?

If the schedule can't be arranged so that lunch ends only 3 hours before the end of the shift (at which point the rods can go in for a leisurely conditioning), you could segregate your ovens into A & B regions. "A" electrodes go into the welder's holding oven when he starts his shift and are returned to the main oven when he goes to lunch. When he comes back from lunch, he gets some "B" electrodes, and puts those back into the main oven when he's done with his shift. The "A" electrodes will be ready for use the next morning, or for the beginning of the second shift. "B" electrodes will be ready the next day, or for the second half of the second shift.

Hg

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[gtaw]

I've been on several large projects where they maintained two electrode ovens.

At the beginning of the shift the electrodes were distributed from oven A. At lunch the welders returned any unused electrodes and the electrodes were returned to oven A. After lunch the welders were issued electrodes from oven B. At the end of the afternoon shift the electrodes were returned to oven B.

The next morning the process was repeated with the reconditioned electrodes from oven A being distributed first with the idea they would be consumed and not returned to the oven for a second time. Additional fresh electrode was also distributed from oven A for the morning "session".

After lunch the electrodes from oven B were distributed using the same logic as the morning.

It seemed to work, most of the welders consumed most of the electrodes handed out in the morning and in the afternoon. The amount of electrodes returned at lunch and at the end of the day were few. Distributing the electrodes twice during the day was not a major issue since most welders had used their alottments anyway, i.e., they would have had to return to get more electrodes just after or just before lunch anyway. Rather than walking back for more electrodes they would simply take some electrodes form one of their buddies to finish the ""session".

Best regards - Al

 

[Ron]

Al...good solution!

Ron