random radiography in pipe line

[balaji srinivasan]

Dear all,
in my project we are performing random radiography as per as per ASME 31.8 and cliend specification(saudiaramco). now the issue is when we performing random inspection which means radiography.
the following additional requirements also we need to follow as per saudi aramco.

16.7.1.4
When random radiography or ultrasonic testing is permitted
for onshore lines the percentage of radiography must be
increased if the repair rate is not below an acceptable level.
The extent of coverage (RAD) listed means the percentage
of welds completed that day that shall be inspected over
their entire length. The joints to be inspected shall be
selected to include a representative selection from all
welders. Additional emphasis may be placed on welders
with repair rates higher than the current job average.

16.7.1.5
The minimum extent of Radiographic or Ultrasonic testing
shall be in accordance with ASME B31.4 or ASME B31.8
as applicable. An increased percentage is required if a
higher percentage of coverage is established by either of the
following methods listed in 16.7.1.5.1 or 16.7.1.5.2 (both
methods shall be calculated and the higher percentage rate
shall govern).
16.7.1.5.1
Linear Basis
% RAD =
(N x D)
(318 x L)
(1)
where:
% RAD is the percent minimum radiographic
or ultrasonic coverage to be applied to the
production the following day.
L = total length of repairs, mm
N = total number of joints welded in one day
D = pipe diameter, mm

16.7.1.5.2
Joint Basis
The following repair rates are calculated on a
joint basis, i.e., the number of joints requiring
repairs divided by the total number of joints
inspected for that day’s welds.
a) An increase to 50% RAD is required when
the repair rate exceeds 30%. This increase
shall be required for both the same day's
(i.e., additional joints must be inspected to
increase the RAD for that day to 50%) and
the next day's production.
b) An increase to 100% RAD is required
when the repair rate exceeds 50%.
This increase shall be required for both
the same day's (i.e., all other joints for
that day must be inspected) and the next
day's production.

now as per my under standing the above mentioned classes are if the repair percentage is not in acceptable level. then only we need to follow  as per class 16.7.1.4.

please give your valuable suggection.

Regards,
balaji

[Sunil Jared]

Dear balaji 

According to Asme 31.8, the required NDT is based on the class. The criteria tO select the class please refer SAES-A-064. 

Now the case of %RAD. 

First, see the definition: % RAD is the percent minimum radiographic or ultrasonic coverage to be applied to the production the following day. Consider only joint basis as we follow random NDT. 

For example take the case of, minimum NDT required from DAILY PRODUCTION is 10% according to ASME B31.8   

Repair rate to evaluate on daily basis and accordingly the required NDT will be applied for next day. 

Consider below cases:

Case1 : repair rate is 18% for a particular day. Then NDT requirement to be applied to next day production is 18%, not 10%. Required penalty as per the standard is applicable. 

Case 2 : repair  rate is 5% for a particular day. Then NDT requirement to be applied to next day production is 10%, as that is minimum requirements . Penalty applicable. 

If the repair is more than 30 %or 50 %, the NDT requirement to be applied as per SAES W 012.

Hope it is clarified now. 

Regards

Sunil Javed paramban 

Sent from my iPhone

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