Cooling and Hydrostatic Test Water in a Pipe Mill

Q, What is time frame of cracking observed? Location of cracking in relation to weld?What indicators have convinced you its corrosion related cracking? What evidence of bacteria? How have you ruled out hydrogen ? Have you closely confirnmed residual elements in your skelp? milo

Milo,

The "cracks" are in the actual weld seam. I have found one mill that cannot identify them and calls the "mill cracks" to give the condition a name.

We have identified the skelp reasons, isolated the hydrogen reasons, but are finding some hidden indications that are found by running UT on a very hot setting (above and beyond the production norm).

Evidence of cracking is happening before installation (see above)

In light of some pipeline failures in the field, that after root cause analysis, no reason can be determined using conventional wisdom.

I hope this clears up a bit of the questions, this is not a condition of concern for all customers, but something that the Quality Dept and I seen and felt needed addressed.

Thanks for the input.

The location in the seam indicts the process, not bacteria. Cracking to me in competently crafted welded products is either inclusion related, hydrogen related, or martensite related. Based on your assessment, and that the mill ain't convinced its hydrogen and aint seeing exogenous inclusions, I'd be working my @ss off to understand if I am creating untempered martensite in the weld. One way is to really look at the residuals and see if you are getting a DI that is amenable to martensite. And to review if the mill has an adequate post weld 'temper" cycle. My guess is you will say"what post weld temper process?" I suspect you are creating untempered martensite in the weld, with aggressive water quenching and higher than usual chem residuals. I'll be on a plane all day but if you go to my blog and search for carbon equivalent it will give you two formulas to evaluate. I think you may have a fruitful path of investigating. http://pmpaspeakingofprecision.com Milo"apologizing in advance for the run on paragraph- im using macbook and safari"

Post weld is performed by induction methods at approximately 1750 F. immediately after the weld followed by normalizing at ambient temperature.

Some of the best consultants in the business, including one from England are working on this also.

Both CE formulas have been used to determine such early in the process.

Metallography has also been performed and analyzed by outside labs in addition to the Mills.

I guess back to the original question, do you think contaminated water could have an effect.

Years ago, Inspection concentrated on Final UT and Visual, but the trend today is skelp sizing, forming, welding, tempering, normalizing, sizing, and straightening.

email me off line for the particular mill and the other consultants working on this.

This started out, for me, strictly as a UT analysis and grew after My findings revealed a pattern of indications and a quantity of indications thrice the expected.

We are talking about API grade X70.

I've been out of office in LA for a week. I'll look up the X70 spec and get back to you. As far as water contamination, I'm very skeptical. I'd be more inclined to believe no wood blocking between pipe during transport- It was an early case study I had At USS Management training on problemsolving. I'll get back to you in the Am offline. Now if you had a gun to the head of my wifes dog, and I wasn't aggravated by my wife that day, I'd tell you that over a very very very long time I might consider some kind of electrochemical reaction, But as soon as you reassert that it is in the weld bead itself I'd say "shoot the dog." The location of the cracking os a clear voice of the process. We just dont know which language its shouting- metalographic, (martensite) crystallographic(hydrogen) and what the hell the root cause (causa sine qua non)is. 'll hook up in the Am and look at whatever data you can share. Have you created an is /is not matrix, or a KWL diagram for this? milo

http://www.corrosionlab.com/failureanalysis/c2/mic-piping.htm

http://www.onepetro.org/mslib/servlet/onepetropreview?id=NACE-02556&soc=NACE&speAppNameCookie=ONEPETRO

http://www.ias.ac.in/sadhana/Pdf2003JunAug/Pe1101.pdf

BTW: the bacteria has a speciall appetite for weld joints.

Did you also check the water chemistry?