Hardness Test - How many readings should be performed per welded pipe diameter?

[Eduardo1982]

Dear Sirs.
I would appreciate your help or advice regarding readings of hardness to be performed in a welded pipe in a HRSG.
I've found some information of the vendor that indicates that in a welded pipe (if the diameter is above 6 inches) it must be carried out 3 readings at 0º - 120º - 240º.
I was searching on ASME I or B31.1 and there dont mention about mínimum of readings to be performed. that is why I ask for some help to you guys.
I think that if vendor approves that just 2 readings are enough, so there is not a problem.
Readings of hardness are within material's requirements.

 

[metengr]

I always like to use minimum of 3 hardness readings per location, this way a low value or high value can be discarded, if necessary resulting in two values. For pipe, I typically require 3 locations for each butt weld at 120 degree locations.

 

[Eduardo1982]

Thanks Metengr for your help. This procedure that you have been following up (3 locations for each butt Weld) is mentioned in some standard, code or recommended practise?

 

[metengr]

Internal company specification.

 

[EdStainless]

We use five readings, but again just out of internal practice. We always discard the outlier.

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P.E. Metallurgy, Plymouth Tube

 

[r6155]

for information see ASME IX, ASME B31.3, API 1104, etc...etc.

Regards
r6155

 

[Eduardo1982]

Dear Metengr..
do you have any docs or recommended practice that indicates 3 readings per welded joint?
I've searched on website and I cannnot find any recommended practice that specified this quantity.
In my opinion 3 tests seems good

 

[weldstan]

There is no requirement in B31.1 or ASME I. Hardness locations and number of tests per location are requirements of the Owner, Engineer and even the Constructor. Ours were based on empirical testing of installed pipe systems some years ago. Low hardness and high hardness areas can be obtained due to a number of welding factors; such as, inadequate preheat both too low and highly excessive especially when using flame methods, too low or too high PWHT due to improper T/C placement, furnace hot and cold spots Slow too slow a cooling rate from the normalizing temp, etc.

 

[r6155]

See more in NACE Standards RP 0472: " For piping welds, a percentage of butt welds shall be
hardness tested. A minimum of 5% should be hardness tested, unless otherwise specified by the user.

Regards
r6155