for you stainless guru's

Date 08-16-2012 00:14

Which direction is the pitting going? Inside to outside or outside to inside? What grade stainless is it? Where is the pitting occurring, weld metal, base metal or at the HAZ?

By hojopens3 (**)

Date 08-16-2012 00:21

picks are to large to upload, stainless is 304 tubing, not leaking at welds, cleaned the rust off and found small pits in tubing, almost like it was shot with birdshot, lots of the piping is showing rust on here

By Cactusthewelder (*****)

Date 08-16-2012 00:57

Just Cut it out, sell it for scrap, and have a party

By fbrieden (***)

Date 08-16-2012 01:09

Possible cross contamination with CS, or exposure to chlorine. What type of environment?

By Stringer (***)

Date 08-16-2012 01:45

+1 on Chlorine or CS contamination. What is a new build drillship?

By ssbn727 (*****)

Date 08-16-2012 03:47

It's a ship that's used to drill for oil, natural gas out in the oceans or seas of this world...

To the OP... Could you please provide us with more information in order for us to give you some better possibilities as to why this is happening?

First problem I have to mention is no mention of any specific quality controls taken into account... in order to prevent for the possibility of different types of corrosion you have so far encountered...

Now, is this vessel completed as of yet, or is this still an ongoing build that has reached whatever stage it's currently @??? Because if it's still an ongoing build, then it's not too late for a corrosion review or audit to be performed in order to mitigate the current situation but since I'm going by what little information you so far have provided, then I can only guess what details are involved with this specific project, and I don't guess too well so I'm just going to defer to you providing us with much more details than presently available.

Respectfully,
Henry

By Superflux (****)

Date 08-16-2012 06:05

See if you can resize the fotos down to around 2Kb and then post.
Sure sounds like some errant Air Arc or 6010 spark contamination.

By Lawrence (*****)

Date 08-16-2012 07:41

*this*

By Tommyjoking (****)

Date 08-17-2012 04:10

HI HENRY!!!! Get er done!!!! Glad to see you on the forum!!!!!

By 803056

Date 08-16-2012 09:45

I will agree with many of the "guesses" listed already.

Free iron and chloride ions do not play well with austenitic stainless steel. The contamination along the length of the pipe could come from any number of sources. I can easily imagine the stainless pipe stored in a carbon steel pipe rack alongside carbon steel pipe. It is just as easy to imagine the pipe stored in such a way that it could get contaminated with iron from grinding grit in a shop that fabricates both carbon steel and stainless piping. I can imagine the stainless spools being stored and dragged across a steel deck awaiting installation. The sources of iron contamination are nearly endless unless the fabricator and the installers take special care in fabrication, handling, storing, and installing the stainless pipe. From what I've seen over the last, well let's just say based on experience, it is doubtful the proper procedures were followed.

I have seen ASTM A240 type 316L stainless perforated in as little as three months in an installation where brackish sea water was involved. The thickness of the stainless plate was 3/16 inch. The source of contamination: the plates were stored on a pallet on the shop floor for several weeks. They were fabricating carbon steel tanks in the same work space. The grinding grit from the carbon steel settled on the stainless before it was fabricated.

Best regards - Al

By Tommyjoking (****)

Date 08-17-2012 04:19

Al I have seen extreme care taken with SS in a shop environment because of exactly what you spoke of....simple carbon grinding dust contaminating it. It is amazing that a swath of particles can start rusting, embed and eat out entire wall thickness of in service pipe...but that is the story they gave me whilst I was in charge of building some new service heater coils. I reckon with the costs involved a few simple precautions are not really as crazy as they sound. Different saw blades, new grinding blades on everything, environment separation and the like.