periodically calibration of densitometer ASME BPV

[jamNauman]

dear folks
Assalam O alaikum And GOOD NOON
PLZ INTERPRET THE CODE ASME BPV SEC V ARTICLE262
CZ I M CONFUSED DURING READING


FOR HOW MUCH PERIOD after DENSITOMETER SHOULD BE RE CALIBRATED FROM LAB?


T-262 Densitometer and Step Wedge
Comparison Film
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

(It mean after 90 Days)


T-262.3 Periodic Verification
(a) Densitometers. Periodic cablibration verification
checks shall be performed as described in T-262.1 at the
beginning of each shift, after 8 hr of continuous use, or
after change of apertures, whichever comes first.
(b) Step Wedge Comparison Films. Verification checks
shall be performed annually per T-262.2.

(now what ? after 8 hrs or 90 days or 1 year)
when will due the nxt calibration ?


regards

Jam Nauman

 

[BigInch]

I don't have specific knowledge of this, however just simplifying the clauses you have provided,

(1) You must always calibrate sometime between 0 and a maximum of 90 days, regardless of use.

Step wedges must be checked at least once per year. Sometime between 1 to 365 days. After checked, you can not go more than 364 days without another calibration.

(2) Calibrate at the start of every work shift, or when restarting after it has been stopped.

The following calibrations depend on the time of use,

(3) Calibrate within every 8 hours of continuous use. You cannot exceed 8 hours of use without a calibration.

(4) Calibrate after each change of aperature.






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[cloa]

Equally I don't have experience of them but my reading is that these are different types of calibrations. The yearly calibration is through and naturally expensive probably using an outside agency and 90day less expensive and shift wise test merely a simple check.

 

[JR97]

jamNauman,

There are two types of calibrations/verfications required for densitometers. A formal calibration is performed at a period of no more than 90 days (T-262.1). This calibration requires the use of a currently certified national standard step tablet. Most people purchase a step tablet and only get it out of storage once every 90 days. Otherwise it is maintained away from light and extreme temperature and humidity to preserve it's accuracy.

The second verification is a daily check (T-262.3). It is not a formal calibration. This check is peformed using a reference strip which is a step tablet that does not need to be currently certified. Some people use expired national standard step tablets from T262.1 above or make up their own by Xraying a step block. This reference strip is kept in the reading room to be used daily. At least once a year, the densities of this strip are re-measured against the national standard step tablet and the recorded values adjusted as necessary.

During the daily check, if the readings from the densitometer do not match the recorded densities from the reference strip, then you get the national standard step tablet and verify the accuracy of the densitometer. You do not need to maintain any records of the daily check, as opposed to the 90 day calibration which requires before and after adjustment values for the different steps like any other calibration.

I agree the requirement can be confusing. Hope this helps.

JR97

 

[jamNauman]

thanks to all for prompt responce and time spent on my query specially JR97 whaich was too much help full


regards

Jam Nauman Anjum

Moody International