Calibration of tape measures

By Mikeqc1 (****)

Date 11-05-2009 16:40

I was thinking about purchasing a 100’ tape with calibration to nist and using that to check the tapes in the Qc Dept and Shop.
But that still leaves the question of accuracy, if the tape is divided up in 1/16 ths could I say +/- 1/32.
I was never asked about tape accuracy in AISC audits, I just verified that the tape read what it need to and that’s all if not I tossed it.
This is for our nuclear program we are working on.

By CWI555

Date 11-05-2009 16:55

Are you a structural or vessel shop?

By Mikeqc1 (****)

Date 11-05-2009 16:57 Edited 11-05-2009 17:01

Vessel shop.
What would you advise.
I will be using tapes on piple lengths, assemblies, ECT.

By CWI555

Date 11-06-2009 01:27

I am assuming since your a vessel shop with pipe lengths, assemblies, etc, that your producing N stamp, or NPT stamp. If this is the case, then you need to follow your QA manual. If you are preparing for an audit for the N stamp, remember that you will have to stick to the program after you get the stamp and don't paint yourself in a corner with non required elements. If you can find no requirement for NIST tape's then don't put one in.

By jwright650 (*****)

Date 11-05-2009 16:41

Not familiar with the requirements for nuclear, but the AISC wants you to verify all tapes against a calibrated tapeline traceable back to a NIST. I purchased a 100'er from Lufkin. It comes with paperwork stating that it is within .001" @ 50' and .002" @ 100' supported throughout with 10# tension @ 68°F. You will need a pull/tension handle and a way to support the entire length of the tape plus some way to anchor it so you can pull against it to achieve the proper tension. I use the shop floor for support and have a plate with half of a c-clamp welded to it anchored to the floor...this clamps the tapeline and holds it while I tension it. I use masking tape on the floor at intervals along the tapeline to mark on, then pull the other inspection tapelines in the same manner and verify that they read the same at the same tension.

By Mikeqc1 (****)

Date 11-05-2009 16:53

Thank you, thats about what i did for AISC.....never used a pull/tension handle nor was i ever called on it (learn sumthin new daily).

By jwright650 (*****)

Date 11-05-2009 18:28

Another thing, we used to verify every tape in the shop...I stopped that, and now only verify the inspector's tapes. Cut my time handling all of that paperwork and tapelines down by a bunch.

By jrw159

Date 11-05-2009 18:43

John,
That is one of the "perks" of AISC as opposed to IAS. AISC only requires the final inspection items to be verified where IAS requires all production and inspection items to be verified.

John

By welderbrent (*****)

Date 11-05-2009 19:40

John, oh, and John, sounds kind of like a Presidential election ??

Anyway, one of the shops we regularly do inspections at has a Fabricators Certification from one of the organizations, I believe AISC but am not positive. They ask their floor guys to regularly check their tapes against a 'Certified, Calibrated, and/or Approved' in some fashion, alum 4 ft straight edge hanging on the tool room wall. When they do so they put a sticker on their tape and date it. This helps insure they have not bent the end of the tape. If the first 4 ft are good, they figure the whole thing is close enough for 'FABRICATION'.

I believe they do a more complete calibration for their QC tapes. They were preparing for an audit last time I was there and told all floor personnel to make sure their tapes had current stickers.

While organizations have different standards as a base line, doesn't part of this also come down to the type of work the shop does, the type of certification it has, and how their QC program is set up, administered, and approved by the agency that certified them?

Just a thought from observations made.

Have a Great Day, Brent

By jrw159

Date 11-05-2009 20:14

Brent,
Yes indeed the QC program may actually set higher standards than are required by, say IAS or AISC. Much like safety programs will often say they "Meet or exceed OSHA requirements".

Under higher usage environments the stickers may end up worn off completely or have the ink rubbed off so I found it more effective to engrave the employee # on when it is issued and keep a log. The log will reflect when a new tape is issued. Of course for some situations this is not necessary.

"While organizations have different standards as a base line, doesn't part of this also come down to the type of work the shop does, the type of certification it has, and how their QC program is set up, administered, and approved by the agency that certified them?"

That a big 10-4. :-)

If the first 4 ft are good, they figure the whole thing is close enough for 'FABRICATION'. This is generally what I do as well and sometimes only the first 2'.

As long as the verification procedure is written out and the agency that one is accredited through (IAS AISC) approves it, it is fine.

jrw159

By bozaktwo1 (***)

Date 11-05-2009 17:49

I just learned something from my ISO audit. If you don't have to (no customer/code requirement), then don't do it. :) I just changed all my calibration requirements for tape measures into verification requirements.

By eekpod

Date 11-05-2009 20:32

I have to do my as well, just like John.

I have a 25' w/ NIST calibration and a 100'. For the average shop tape I use the easier shorter 25' and for the long ones I use the 100'.

I also trimmed down the amount of tapes that were required to be done to make life easy for myself.

Also to make things even more tracable, I purchased a 6" scale tracable to NIST so that I can measure the differance up to 1/64" of my calibration tape vs the shop tape. When it comes down to what side of the line each increment get's at, I use the scale to say let's say "at 6" location + 1/32", at 5' +1/64""or whatever. Yes it's picky and does it need to be that close maybe not but my AISC tolerance is +/- 1/16" so I need to be able to measure at least half of that which is 1/32". How can you measure down to 1/32" of an inch with a 1/16" tape, you can't, you can guess but I didn't want to get nailed during an audit so I made it so I could prove to within 1/64" tracable to NIST all the way around.

Chris

By bozaktwo1 (***)

Date 11-05-2009 21:33

Well I also have a 25' Lufkin calibrated to NIST, but I like the idea of calibrating the inspectors' tapes only. As for the fabricators, it's a verification check using colored stickers. We'll check it for fitness for use. slap a label on it, or turn it in for new. Monthly. The calibration was eating too much time. Not to mention calibration labels.

By eekpod

Date 11-05-2009 23:19

Dont forget to check the little clip thingy on the end, that usually wears out first.