If you are drilling deep with a mud rotary or perhaps drilling 5,000 feet for natural gas, then you are familiar with the term “upset”. Sometimes elevator shouldered drill pipe, where the tool joints are larger in diameter than the tubes, are referred to as upset drill pipe. In reality, drill pipe is considered upset when the tubes are upset prior to welding.
Upsetting is a forging process that makes for a thicker wall on the tube ends. The tube ends are heated to a near liquid state. The heated end is then placed in the upsetter machine and held in a clamp. The machine is engaged and it strikes the end of the tube with so much force that the metal to flows backwards a few inches. The exact new wall thickness and the location of this extra metal is set depending on which die and punch are placed in the upsetter.
If all the extra material is on the outside, it is an External Upset (EU). If all the extra metal is on the inside, it is called an Internal Upset (IU), or it can be on both the OD & ID or an Internal-External Upset (IEU). Sometimes it takes two hits (strikes) to form the IEU.
Once upset, the tubes should be full body heat treated to grade.
So, upsetting provides for a thicker tube at the tube ends.
Fact: Statistically speaking, whether a drill pipe is upset or not has no bearing on the tube’s ultimate tensile or yield strengths. These are still determined by the the body. So why bother?
Upsetting provides two main advantages. It provides for a thicker, stronger weld area. And it provides a better transition from the stiffer tool joints to the more flexible tubes. It moves the stressed areas away from the weld zone.
So why aren’t all drill rods upset? It comes down to need and cost. Upsetting is not only expensive to operate but typically not a fun thing for manufacturers. Upsetters can weight over 250,000 pounds. They are expensive to fix. Having in-house heat treating to process the tubes after upsetting is also really expensive. So, a lot of manufacturers will outsource these operations.
I personally like the upset for all elevator shouldered drill pipe for depths over 1,000 feet or in difficult drilling situations. In this design, tool joints are much larger , stronger & stiffer than the tubes & all those drilling stresses are pushed back to the tube & weld areas.
In my opinion for flush joint drill pipe, the IU should be considered when drilling over 2,000 feet in depth, Strongly considered over 3,000 feet , and a definite need for over 4,000 ft. Although non upset flush joint drill pipe, sometimes referred to a plain end welded, has successfully drilled over 5,000 feet, the risks increase as the demands on the drill pipe increase. Drilling conditions are also important as difficult conditions can add stress to the drill pipe.
If a product description of drill pipe does not say upset (IU, EU, IEU) then it probably is not. When seeking pricing & you think you might want an upset., ask for it or ask for both an upset & Plain End (PE) product.