TPi September 2015

Horn – A tool manufacturer with API certification

positive locking and leak-proof. Not only that, but in the case of directional boring (when the vertical path of the bore moves in the horizontal plane), high levels of bending stress are exerted on the threaded connection. Stationary or rotating tool Machining with a stationary tool on two- and four-axis machines can involve either one or two supports. Aside from this, there is another machining concept that relies on a rotating tool head and six individually controllable slides. The key issue here is to master the centrifugal forces of the tool slides and tools. Thread machining on a finishing line must satisfy several boundary conditions: the concentricity of the pipes that are being screwed together, a high level of torque transmission, and high-quality centring during screwing operations to prevent cold welding of the threaded connection. This does not really pose a problem in the case of welded pipes with the same wall thickness. However, greater machining effort is required for rolled pipes with diameter tolerances, different wall thicknesses and out-of-roundness deviations. In addition, rolled pipes generally have a rolling skin, which affects the tool life. If the threads are machined while the pipe rotates, vibrations may be generated as a result of the mass, and this could affect the precision, the surface quality and, once again, the life of the tools.

The pipes used in exploration and producing wells range from 2 3 / 8 " to 28" in diameter. They can be longitudinally welded, spiral welded, rolled, hot rolled or pilgered. A distinction is drawn between delivery pipes, casing and tubing. The materials used include chromium steel, stainless steels, carbon steels (hot-rolled and high-strength), chromium-nickel steel pipes for acidic environments or, in the case of extreme applications, round-forged and longitudinally bored drill rods made from nickel-based alloys. Pipes with API round/buttress threads, which are referred to as standard pipes, must feature screwed connections that are both positive and non-positive locking. In the case of integral connections, one end of the pipe has an external thread while the other end has been widened and has an internal thread. These pipes are screwed together without using sockets. In the case of standard socket connections, both ends of the pipe have an external thread and the pipes are connected via a threaded socket. Threads approved for oilfields must meet the requirements of the API standard (American Petroleum Institute) and are subdivided into API round and buttress threads. In addition to these, there is a whole range of premium threads for the most stringent requirements. The threaded connections have to withstand extreme levels of stress due to the high temperatures and pressures that prevail deep underground. The connections have to be positive/non- The fact that pipes measuring eight to twelve metres in length have to be screwed together to create the strings means that threads are required every eight to twelve metres as well. In the case of socket joints, it is every four metres. This is a mammoth production task, and finding a production method that is cost-effective, precise and fast is a major challenge for tool manufacturers. Horn in Tübingen, Germany, decided to take on this challenge by developing a system that would allow precision manufacturing of oilfield pipe threads. I f you were to line up the oil and gas drill strings of all the production derricks and platforms that are currently in use, you would end up with a total length far in excess of one million kilometres. That is long enough to circle the equator at least 25 times. Given that these strings constantly have to be replaced due to wear and the creation of new extraction sites, there is a huge market for these products.

Combination cartridge for peeling and thread cutting

57

www.read-tpi.com

september 2015 Tube ProducTs InTernaTIonal