drill pipe - pitting on threads

Question

drill pipe - pitting on threads

MMR Advisor (Materials)

(OP)

21 Aug 06 14:03

I work for a land-based drilling company. Recently, we've had a lot of drill pipe rejected as unservicable during routine inspections due to pitting on the threads. Our drilling mud chemistry is usually oil based, with a ph of about 9-10. We haven't observed any H2S (not that we know of anyway). The joints are lubed every time we make a connection. I just found out about this and have not been able to send anything to a lab yet. Any ideas on what could be causing this? Simple mechanical wear? Galvanic corrosion? H2 cracking? I can email a photo of the threads if needed.

BigInch (Petroleum) · Answer 1 · 2006-08-21 14:22:27

Have you changed pipe suppliers or do you have a new inspector?

Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

MMR Advisor (Materials) · Answer 2 · 2006-08-21 14:39:53

I'm not sure if I can mention companies by name on here, so I won't. Most of the time we go with one of the larger inspection companies, but occasionally we have to go with a mom-n-pop, as in this case.

I'm sure I know where you're going with that, and I agree, vendors in this business like to create work for themselves. However, based on the couple of photos emailed to me, it is legit if they are representative of the entire lot (116 out of 120).

BigInch (Petroleum) · Answer 3 · 2006-08-21 17:46:04

Not only that. I hear drill string is getting pretty hard to find these days (and expensive). I'm sure that there is probably a lot stored for years somewhere out on an old drill pad in south Texas that is making its way out to the market these days.

Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

MMR Advisor (Materials) · Answer 4 · 2006-08-22 14:30:41

I've uploaded a photo at the following link:

http://www.photo.net/photodb/member-photos?user_id=2222172

Note the abrasive wear on the threads in addition to the pitting.

The initial concern was galling, but most examples I've seen before have a much more jagged fracture surface.  Let me know if you think there is galling (def.-A condition whereby excessive friction between high spots results in localized welding with subsequent splitting and a further roughening of rubbing surfaces of one or both of two mating parts).

Also, could under-torqing during make up contribute?

We use Jet-lube Koprkote pipe dope (http://www.jetlube.com/NewFiles/eng.html).

I don't see anything to support ringworm corrosion.

After some research, we found out that this lot of pipe was stacked for a while 2004, which leads me to believe there was some corrsion due to moisture.  It has been in continuous use for the last year or so.

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drill pipe - pitting on threads