Pipe End Forging API 5DP

[Pipeman23]

Our plant forges drill pipe (seamless rolled tube) ends to make and upset ready for friction welding to a connector that joins several pipes. The forged upset has to meet specific dimensions and have generous tapers and radii from the upset to the the original pipe body. See attachment. The question has come up by a 3rd party surveillance engineer about our machining of the external transition area. He says that this are should be as forged because it will have a detrimental effect on the grain flow if we machine it. The API spec does not address this issue at all. My question is can anyone identify what the grain flow would typically look like in a forged pipe end. Secondly, would machining have any effect on the grain flow. Surely machining of forged pieces is very common.
Any feedback, support or comments would be helpful. Thanks.

 

[blacksmith37]

In the '80s (and before) there was a problem with fatigue (washouts) at the end of the taper. It was most common from the ID where it was not as easy to examine. Tuboscope did a lot of data collection and likely published. I don't recall problem discussions in 5D committee regarding grain flow. Full body HT after upsetting would remove most grain flow patterns.
Generally, oil companys did not own the drill pipe, so did not put as much effort into 5D as the other specs. That is why most data available will be from 3rd Parties like Tubo.

 

[Pipeman23]

Hi Blacksmith37, many thanks for your reply. I agree with your answer, the Miu taper and radius are the most important features of the upset. The external upset is very small. Also Quench and Temper does change the grain to a fine martensite structure. However today we have many 3rd parties out there who are not engineers and oil companies tend to listen to them....

 

[frankm461]

Pipeman23,

Turning of the od and boring the id is common. How else do you remove scale and yield (unless your upsetting to the exact od/id dimension and use a descaler prior to upsetting).

When I design a tool, I work from the finished pipe dimensions (that will go to the friction welder)and determine the yeild I will build-in for the as-forged upset to be machined.

Do you design the upset tools? It would be very interesting to compare notes- without compromising trade secrets

 

[salmon2]

pipeman23, the 3rd party engineer is "right" and you can check out the below link where you can peek grain structures of cold/hot forging, vs machining:

http://www.google.com/imgres?imgurl...39&bih=586&tbm=isch&ei=e4IrTtfCJcqpsAKawdSGCw

So it is abosolutely right that formed parts has favorable grain patterns vs. machined, but I believe a lof of industry standards accepts both machined or formed (such as forged or rolled) parts because forming usually means very high tooling investment, only justified for high volume of production, or lengthy turnaround time if done it outside.

 

[redpicker]

Not only is the 3rd party "right", he may also be (knowingly or unknowingly) revealing "trade secrets" from other manufacturers he has witnessed prior to your operation.

Yes, API is silent on this issue. Some manufacturers have practices in place that prevent machining in this area. Unless the purchase specification forbids this, however, the 3rd party should remain silent, even though he may believe it is not good practice. The 3rd party's function is to make sure the manufacture is in accordance with the prescribed specifications, not to make all manufacturers obey what he believes is "best practice". The particular 3rd party could land himself (and his employer) in considerable legal trouble if the right (or wrong) people learn the details of this.

In my opinion, you should tell the 3rd party to bugger-off. It is not his place to tell you how to run your manufacturing; only to make sure you are conforming to the purchase order requirements. If the 3rd party decides to escalate the issue, the more likely the revelation of "trade secrets" will come out, which is where the 3rd party firm will back down and pretend nothing ever happened (if they are smart).

The actual effect this has on the life of the pipe is little to none. While, in theory there may be a difference, in practice the effects of wear of the pipe in service will out-weigh this small effect as to make it inconsequential (ever see what drill pipe slips do to the OD of the pipe? And he is worried about flow lines on the ID? This is so obvious that he is trying to impose another manufacturer's in-house requirements on you that I would be surprised if it is even mentioned on Monday morning).

Ask him what other manufacturers he has been a 3rd party on. Document it. Then tell him that if he wants to make anything of it, you will tell his boss that you will contact these other manufacturers and tell them what you are asking of them. If you do that, you will see the faster "crawfishing" than they've ever seen in southern Louisiana.

rp

 

[salmon2]

So actually the 3rd party engineer is helping pipeman23, maybe unknowingly

But unless the so called "3rd part" is actually a certification authority and they have their preference against machining upset. I have noticed a trend that those certification authorities are reluncent to adopt new technology and their codes are lagging even further compared with industry standards.

 

[frankm461]

Redpicker and salom2,

I don't beleive you two are touching on the subject as initially described.

Machining the Meu/Leu, Liu/Mi and facing off is well established in the drill pipe industry. I would say that 9 out 10 companies perform the turn and bore operations on a daily basis without negative consequences. The machining of the yield is okay, it is not affecting the grain structure of the upset since your removing less that .100" of material. The balance should have a fine grain structure since it has gone through austenitizing, work hardening and slow cool.

 

[redpicker]

I don't beleive you two are touching on the subject as initially described.

frankm461, you are correct. I misread the OP. I thought he was talking about machining the internal transition, not the external transition. In the case described in the OP, the 3rd party is just plain bonkers (not an uncommon situation, unfortunately). In fact, I believe 5DP does specifically address this issue be saying that defects in this area may be removed by machining and/or grinding. Now, the 3rd party expert may argue that this only allows machining to remove defects, not for dimensional control, but I'd argue that just the fact that it permits machining in this area (for any reason) proves there is no prohibition, explicit or implied. And, I'd be right.

I would say that 9 out 10 companies perform the turn and bore operations on a daily basis without negative consequences.

I'd have to doubt this one, but only because I think you would have a hard time finding 10 companies that upset and process drill pipe. But, you are right, those that do will machine this area without ill effect.


rp