Acceptable field hardness testing of weld

[engr2GW]

Hi all,

I have conducted hardness testing on etched samples as stated in the NACE MR0175 traverse for shop testing to test the Metal, HAZ, and weld. Is there a way to test in the field on production weld to verify that the weld is not too hard or to excuse certain construction from Post weld heat treatment.
1. how is the test done is it is possible
2. can it be used to test HAZ also, I assume the weld (cap) and base metal will not be a problem
3. If this test (if possible) is done, how dependent is the hardness number derived this way...
4. how easy/difficult is it to conduct

Thanks for your help.

As much as possible, do it right the first time...

 

[SnTMan]

http://www.worldoftest.com/telebrineller.htm

 

[metengr]

You can test production welds using a portable hardness tester - Equotip or Microdur, see below

http://www.kutlultd.com.tr/files/downloads/pdf/hardness/mobile/Mic10.pdf

Without knowing your capabilities and equipment, the real fun begins;

1. You can test the weld cap and surrounding base material, away from the weld region. The HAZ will be a problem because of location in relation to surrounding base material.

2. You should have personnel qualified to use a portable hardness tester with a hardness testing procedure to assure consistency in the field.

3. Surface preparation will be critical for portable hardness testing. Your procedure should detail field metallographic grinding/polishing methods and a suitable chemical etchant to delineate the weld heat affected zone in the base material.

3. I would hire this service out in lieu of trying to so this in-house unless you have lots of production welds and it is worth a dedicated team of technicians to qualify and perform polishing, etching and hardness testing.

Here is some background information that may help you;

http://www.wtia.com.au/pdf/TGN-PE-01 Hardness testing of Welds.pdf

 

[stanweld]

You can also test with tellebrineller or pin brineller. Hardness testing of the process side of the joint may prove impossible depending on accessibility. Accurate testing of the HAZ is not possible with these methods.

 

[Duwe6]

Even marginally accurate hardness readings are not possible on fieldwelds using Equotip or other rebound type hardness testers. You don't have to believe me, just try it on an actual weld coupon that can be put in a brinnell or rockwell hardness device. The spread in results is amazing and nauseating.

On the other hand, if a FLAT area is ground or filed on the weld, the previously mentioned telebrineller or pin-brinnell device will give very accurate measurements. These are the only devices that have proven themselves to me to actually work on in-situ pipe welds. Yes it is OLD technology, but it actually works.

 

[stanweld]

Adding to Duwe6 comments, a recent study by EPRI and past studies by ARAMCO and another independent lab confirmed the poor accuracy of the rebound test method in field testing of pipe and pipe welds. We recently compared Equotip field results with bench test from coupons removed from the same tube locations tested with Equotip and the results from the Equotip were consistently lower (approximately 30 points BHN) than the laboratory bench test hardness results.

 

[metengr]

As a basic quality control check, hardness testing of production welds can and is used with noted cautions regarding limitation of equipment AND expertise in using such equipment.

 

[engr2GW]

Thanksa lot for your replies...

Yes, if we will do it, it'll have to be done by a third party. I'm asking because we are planning to say, "test for hardness and if the material is soft enough, then forgo PWHT, but if it's hard, just PWHT"
from what I'm hearing, does it sound like the testing might be just as much work as the PWHT? to where we might just go ahear and PWHT and not worry about hardness testing...
THIS IS FOR SOUR AREAS ONLY

thanks again.

As much as possible, do it right the first time...

 

[stanweld]

If you cannot tset the sour, process side of the weld joint, you will need to hardness test qualify the welding procedure(s). One of the greatest catastrophic events due to SCC occurred at the Unocal refinery out side Chicago. Hardness testing was done by the field contractor responsible for making the field alteration of the vessel but it was done on the OD meeting the Unocal requirements but not the process side, which was readily accessible. Hardness of the HAZ on the process side was considerably > than permitted by Unocal or by NACE recommendations at the time.

 

[engr2GW]

All the welding procedures in this welding are NACE qualified, meaning, they hardness values for all of them passed...

As much as possible, do it right the first time...

 

[weld7777]

Gentlemen, We qualify our procedures with and without PWHT to ASME, with that being said, we have had no problems with any welds, but we have stuck to the parameters of the procedure. And I agree no accuracy testing pipe.

 

[Guest102023]

Stanweld,

Can you provide any references that discuss the Unocal failure?

I regularly encounter cases of poorly trained NDE techs playing Russian Roulette with refinery vessels and exotic boiler alloys. The deficiencies typically include any number of the following:

- No metallurgical training,
- Inappropriate test method,
- No task-specific procedure,
- No knowledge of applicable ASTM testing standard,
- No/wrong calibration,
- No surface preparation,
- Permitting heat treaters to check their own work,
- Repeating tests until happy results are found,
- and a few more that don't come immediately to mind

The most recent horror show was two techs getting double overtime to test the HAZ of fillet welds(!!) One was a level 2 visual inspector. I earned less performing a related failure analysis than they got to generate a sheet with random numbers which naturally were lower than realistically possible ... and presumably a PE oversaw the task from his desk.

Even with the appropriate equipment, I believe that more than 4/5 of field hardness testing is done wrong.

 

[stanweld]

The blast killed 17 and injured over 20 at the Lemont Refinery.
The involved vessel was altered by adding at least one shell course. The R-Stamp holder made the welds with the SAW process, first (primarily) on the OD side and subsequently on the process side. A monel liner was attached as well by fillet welding to the carbon steel shell using the GMAW process. The liner weld terminated adjacent to the shell course, circumferential weld addition which failed in the HAZ. Hardness in the HAZ was > 260 BHN (determined during the failure analysis).

I believe that this failure was the first failure attributed to SOHIC but don't quote me on that. My involvement was during the discovery phase at the initial law suits. The failure prompted examination of numerous vessels in similar service at other refineries; a number of refiner's found similarly cracked welds some nearly 1/2 wall.

 

[Guest102023]

wtanweld,

Ever arm-wrestle with a shop foreman who thought your suggested sequence was irrelevant? Just one of a long list of reasons I no longer inhale fumes on a daily basis (and the callous on my forehead has nearly faded away).

I shall see what I can discover in the vast googleverse.