Adjusting Calibration Intervals for Welding related Gages

[AimzF]

I've got some questions re: calibration intervals, in part because our last Nadcap auditor advised us that we didn't need to have our radius gauges, fillet weld gauges or go/no-go pin gauges calibrated annually, that we could go a longer interval (when we asked for details he said we could hire him as a consultant, but then he couldn't audit us in the future? ).

I've looked in both the AWS D17.1 inspection section, AWS B1.11M on visual inspection of welds, and both choose not to define recommended/required intervals (and neither does Nadcap AC7004 AQS). Our customer's supplier quality manual requires that we have a calibration plan and 'regular calibration intervals.'

We're a 2-person Nadcap welding job shop. About 85% of our work is AWS D17.1 class C welding work that requires alignment of 2 holes to clear a 0.190 diameter bolt (thus the go/no-go gauges) with a square groove weld that's a glorified tack weld. The rest of the work is 1G and 1F class B & C welds, maybe 1-3 times a month (qtys are usually 50-500 parts). I'm the only person inspecting parts, and I try to take very good care of all of our inspection equipment.

We've been blindly getting everything calibrated annually, out of a generalized fear of auditors. At the same time, we're up for 2-year merit, and we've had zero non-conforming product in 10+ years from our customer. Should/can we extend our calibration intervals? I've seen a few posts about risk management etc, just would like to hear opinions on if/how we should word our procedures to reflect this.

Thanks for your time,

-Amy

 

[Jen Kirley]

Welcome to the Cove!

Your auditor correctly stated that he wouldn't be able to audit you if he gave you "details" (that is, specific advice for your processes) he would not be able to come back and audit you. But rather than pay him out the wazoo for said details, I am happy you came here.

What he was referring to is the fact that your gages would likely be undergoing a minimum of wear from use, your tolerances are probably not very tight and that there is no adjustment involved. Therefore, the cost of calibration (most of us would call it verification, but I've seen the terms used interchangeably) at a one-year interval would very possibly soon exceed the cost of buying new...

I wonder: what documentation, if any, comes with the gages to provide confidence in their accuracy? I once had a tape measure that was seriously off. Really. I wish I'd kept it.

I had a client with the same issue as you, faithfully sending out a steel rule yearly; the thing was like an I-beam, so I told him what your auditor told you (minus the bit about being hired as a consultant). The thermal expansion coefficient won't apply to gages like these, so your frequency, when not called out by customer or relevant specification, can be set up based on risk considerations, including:

• The amount of use
• The handling during use
• The storage when not in use
• The tolerances
• The cost of getting it wrong

I hope this helps!

 

[hogheavenfarm]

As Jennifer said, with particular attention to "the cost of getting it wrong", which really governs the other factors. I have 'validated' our radius gauges with our Faro Arm, so we 'calibrate' them on an extended schedule, but it is done in house. Because I am pretty much the only one using them, they are on a "5 year or GUD" schedule (Good Unless Damaged).

 

[AimzF]

Jen:
Thanks for the warm welcome to the cove, and the confirmation that we're likely spending more than we have to given the risk. Even if new equipment comes with certs we feel better if we get it calibrated initially, in case it was off in shipment/storage prior to shipping/etc. We should document the extension and have "management" list justifications for the risks you cited, correct?

hogheavenfarm:
I've browsed through the forums and seen enough that it's not likely cost-effective for us given our size to calibrate in-house (I looked up a Faro Arm and just about did a spit take on ebay pricing ), but thanks for concurring. I get why there's flexibility involved, but especially when audit failure means no work for 6 months, I get a little squirrely when it comes to flexibility.

 

[Jen Kirley]

Jen:
Thanks for the warm welcome to the cove, and the confirmation that we're likely spending more than we have to given the risk. Even if new equipment comes with certs we feel better if we get it calibrated initially, in case it was off in shipment/storage prior to shipping/etc. We should document the extension and have "management" list justifications for the risks you cited, correct?

My guess is you have some record for each gage calibration, yes? What are you using?

Also, what tolerances are you keeping to for these measurements?

What make and model are they?

Some people make a table to include all their instruments, and set out tolerances, frequency, etc. in there for the purposes of evaluating impact if the instrument comes back out-of-tolerance at time of calibration. Anyway, this table could have a Notes section that can include justification of extending calibration frequency. Software such as Gage Trak (I am not affiliated) can do this too.