Densitometer Calibration

By Mikeqc1 (****)

Date 06-03-2009 17:28

T-262.1 Densitometers shall be calibrated every 90 days…..
(a) A national standard step tablet or a step wedge calibration film, traceable to a national standard step tablet having at least 5 steps with densities 1.0 thru 4.0 shall be used.
The step wedge calibration film shall have been verified within the last year by comparison with a national standard step tablet unless……………

My questions are
National standard step tablet ,Is this something that can be purchased or is this something that only a lab would have access too.
And, If I purchase a Calibrated step tablet would this be considered a national standard step tablet and do I need to have this verified yearly (The step wedge calibration film shall have been verified within the last year by comparison with a national standard step tablet).
Any input on this would help
MDK

By CWI555

Date 06-03-2009 18:01

It is something you can purchase.

Most density strips are traceable to an NIST standard. What you need to do is download a copy of ASTM E 1079 latest rev. It will have all the info you need.
As for the step wedge itself, they do have a shelf life. Usually the there is a statement of expiration after 12 months of initial use. or when physical abuse is noted, or three years from the date of certification. The 1 year part is dependant on the step manufacture. Structurix is 2 years.
All step tablets should state (paraphrased) verified against NIST S.R.M. 1001: xxxxxxxx (the ID number) etc. You will see that same statement in E1079

Regards,
Gerald

By Mikeqc1 (****)

Date 06-03-2009 18:28

So you say i can purchase a national standard step tablet?
I purchase a calibrated step tablet every 3 years tracible NIST( although i think i must change to every year to be compliant with ASME SEC V T-262.1 )
As it says ..."The step wedge calibration film shall have been verified within the last year by comparison with a national standard prior to 1st use blah blah

Do you use ASME?
MDK

By CWI555

Date 06-03-2009 19:26 Edited 06-03-2009 19:30

As for buying the actual NIST standard, no. Buying something traceable to it, yes.
If it's good enough for section III and XI I would find it hard to believe it wouldn't work for you.

T-262.1 Densitometers. Densitometers shall be calibrated
at least every 90 days during use as follows:
(a) A national standard step tablet or a step wedge calibration
film, traceable to a national standard step tablet
and having at least 5 steps with neutral densities

By michael kniolek (***)

Date 06-03-2009 21:47

buying a Calibrated step tablet every 3 years ( opening it right away and its one year longer than Manufacturers recomendation )and using it to calibrate the densitometer would not be in accordance with ASME correct?
I only stumbled accross this issue because im calibrating the equipment.Today the calibrated step wedge came up for renewal. when reading the proceedure there was an out dated spec referenced. i read the code for the new spec i came to the conclusion that 3 years is too long and now im asking to see if anyone can correct me if im wrong. the last thing i want to do recomend a change thats not needed.
Any1 disagree that i need a change?
MDK

By Mikeqc1 (****)

Date 06-08-2009 13:37

What do you do get a new one each year

By CWI555

Date 06-08-2009 13:54

Given the low cost of them, I'll open one a year. It's very very hard to argue that on anyone's part. I believe the last 3 I req'd were 50 bucks as I recall. Their expiration is in 2012 unopened. So I keep them in the fireproof until needed. I just opened my second one today.

By Mikeqc1 (****)

Date 06-08-2009 13:56

do you have a supplier # ans contact?
im paying 300+ for 1 step wedge.
MDK