Is it necessary to calibrate and certify the portable electrode quivers, rated for 250W @ 48 - 75VDC and fed from the welding power, used for the SMAW applications, as one of our clients is insisting for it?
We have about 1,500 quivers and being used for the last 25 years without any such calibration/ certification, considering that it is a tool for the welders to keep the processed/ hot electrodes transferred from the nearby holding ovens and to retain its temperature by adding certain heat input. The double wall type quiver has no thermal insulation, the heating element is attached into the bottom plate with a heat sink, the thermostat rated for 30 - 120 Deg.C is controlling the heat sink temperature and the heat is transferring by conduction. It cannot provide a stable temperature, as a result of ambient variation, voltage variation (ARC voltage and OCV) and quantity & temperature of the electrode being stored.
Considering their design, application and our experience, we think, there is no meaning in spending extra efforts for calibration/ certification activities other than inspection/ maintenance for ensuring the physical integrity and functionality.
Please review the above and comment. If calibration is required, what will be the acceptance criteria for the subject quivers used to handle the carbon steel low hydrogen electrodes (E 7018-1, E7018, E7018-1, E7028 etc.), transferring from the nearby holding ovens at 120 - 150 Deg.C?
The primary code that we used is AWS D1.1. The table 5.1 gives the exposure limits and stating that the heated quivers are not mandatory. however, it does not state the minimum temperature (or the temperature to be maintained above the ambient) that the electrode can expose before the welding.
As I understand it the rod ovens are not necessarily to pre-heat the electrode but to drive the moisture absorbed from the atmosphere from the electrode to prevent the hydrogen molecules from becoming entraped in the weld pool.
As for the temperature of the portable quivers, unless they are to only source of drying the electrodes after exposure there is not much need for them to be calibrated. 10 years ago an old refrigerator with a 40 watt bulb was ok as was a leather quiver to take a few rods at a time to the work area. Too many "experts" are getting hung up on technical criteria instead of understanding why the standard was established in the first place.
Have your client review the section on electrode conditioning in the Welding Handbook or in Jefferson's Welding Encyclopedia under Low-Hydrogen Electrodes. Both refer to the electrode manufacturer's specifications for temperature and time limits. Lincoln's Procedure Handbook of Arc Welding has a good commentary under Low-Hydrogen electrodes. When in doubt, you can always check the commentaries in the back of D1.1 C5.3.2.1 for a start
This subject was discussed in earlier posts but I don't recall what the consensus was.
This is basically repeating what you have stated...........Per D1.1 , as long as you issue your rods from factory sealed containers, or from heated storage ovens, you have 4 hours maximum allowed to use the rods you listed or return them to a heated oven.
(Section 5.3.2.3 gives you an alternative to that if you need to extend the limit.)
If you want to extend the allowable exposure time based on electrodes being heated in your quivers, then you need some way to prove the quivers were hot enough and that minimum required temperature is continuous, not intermittant.
If you use your heated quivers simply to ensure the rods are dry during the time limit, then I cannot see why calibration is needed. You could have the rods inside an old welding glove and still be OK as long as the rods are dry and not beyond time limits.
The rod ovens themselves are easy enough to verify minimum temperature. I place a small piece of metal inside the oven and leave it long enough to come up to temperature. Then I use a 250 F Tempil stick to check the metal- if the tempstick melts, the oven is hot enough. If it doesn't melt, there is a problem. I use a piece of scrap metal because some people feel the tempstick will contaminate the electrodes. Whether it will or not, I can't say, but with this method there isn't an argument.
Your quivers would not be easy to calibrate without some kind of temperature logger.
Hope this helps,
Chet Guilford
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